List of publications

@article{2091,

title = {Physics design, construction and commissioning of the ICRH system for the stellarator Wendelstein 7-X},

author = {J. Ongena and D. Castano-Bardawil and K. Crombé and Y. O. Kazakov and B. Schweer and I. Stepanov and M. Van Schoor and M. Vervier and A. Krämer-Flecken and O. Neubauer and D. Nicolai and G. Satheeswaran and G. Offermanns and K. P. Hollfeld and A. Benndorf and A. Dinklage and D. Hartmann and J. P. Kallmeyer and R. C. Wolf and TEC},

url = {https://www.sciencedirect.com/science/article/pii/S0920379623002119},

doi = {https://doi.org/10.1016/j.fusengdes.2023.113627},

issn = {0920-3796},

year  = {2023},

date = {2023-07-01},

journal = {Fusion Engineering and Design},

volume = {192},

pages = {113627},

abstract = {The ICRH antenna for the stellarator Wendelstein 7-X (W7-X) aims at delivering RF power levels up to about 1.5 MW in the frequency range 25–38 MHz with pulse lengths up to 10 s. The antenna was constructed and tested in the institute IEK-4 of the Research Centre Jülich, and subsequently installed at W7-X. The paper will review the physics design, the construction and installation in W7-X, and the commissioning plans for the ICRH system in the coming months.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{2090,

title = {Recent modeling for the ITER ion cyclotron range of frequency antennas with the TOPICA code},

author = {D. Milanesio and W. Helou and V. Polli and F. Durodié and P. U. Lamalle and V. Maquet and A. Messiaen and W. Tierens and W. Zhang},

url = {https://dx.doi.org/10.1088/1741-4326/acb785},

doi = {10.1088/1741-4326/acb785},

year  = {2023},

date = {2023-04-01},

journal = {Nuclear Fusion},

volume = {63},

number = {4},

pages = {046010},

publisher = {IOP Publishing},

abstract = {This paper documents the analysis of the ITER ion cyclotron resonance heating (ICRF) launcher using the TOPICA code, throughout recent years' design activities. The ability to simulate the detailed geometry of an ICRF antenna in front of a realistic plasma and to obtain the antenna input parameters, the electric currents on conductors and the radiated field distribution next to the antenna is of significant importance to evaluate and predict the overall system performances. Starting from a reference geometry, we first investigated the impact of some geometrical and numerical factors, such as the Faraday Screen geometry or the mesh quality. Then a final geometry was the object of a comprehensive analysis, varying the working frequency, the plasma conditions and the poloidal and toroidal phasings between the feeding lines. The performance of the antenna has been documented in terms of input parameters, power coupled to plasma and electric fields. Eventually, the four-port junction has also been included in TOPICA models.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{2089,

title = {Analysis of high frequency Alfvén eigenmodes observed in ASDEX Upgrade plasmas in the presence of RF-accelerated NBI ions},

author = {R. Ochoukov and S. Sipilä and R. Bilato and V. Bobkov and M. Dreval and M. Weiland and R. Dendy and H. Faugel and T. Johnson and A. Kappatou and Y. O. Kazakov and K. G. McClements and D. Moseev and M. Salewski and P. Schneider and ASDEX Upgrade Team and EUROfusion MST1 Team},

url = {https://dx.doi.org/10.1088/1741-4326/acb831},

doi = {10.1088/1741-4326/acb831},

year  = {2023},

date = {2023-04-01},

journal = {Nuclear Fusion},

volume = {63},

number = {4},

pages = {046001},

publisher = {IOP Publishing},

abstract = {High frequency Alfvén eigenmodes in the ion cyclotron frequency range are actively researched on the ASDEX Upgrade tokamak (AUG). The general properties of this particular mode type are: (a) the mode is beam-driven and, if excited, can persist for the entire duration of the beam-on time window; (b) the mode is sub-cyclotron with the frequency ω ∼0.5ω ci, where ωci corresponds to the on-axis cyclotron frequency of the beam ions; (c) the mode propagates in the counter-current/counter-injection direction; and (d) the field-aligned (∼toroidal) mode number is large: |n //| ∼50. It has been observed on AUG that radio frequency- (RF)-acceleration of beam-injected ions at the 3rd cyclotron harmonic significantly expands the number of excited modes. In this work we demonstrate how this observation is consistent with the global Alfvén eigenmode (GAE) behavior. The RF-driven fast ion population is modeled using a combination of an orbit-following Monte Carlo code (ASCOT-RFOF) and an electro-magnetic wave code (TORIC). The application of this code combination is a first to model beam-ion RF-acceleration at the 3rd cyclotron harmonic. The RF-accelerated fast ion distributions are then used to analytically calculate anisotropy-driven mode growth rates. We see that the region of positive (unstable) growth rates is expanded by RF-accelerated fast ions in both the frequency and the mode number directions for the GAEs, consistent with the measurements. Although the compressional Alfvén eigenmode growth rates are also positive for our particular fast ion distributions, the growth rate values are ∼3 orders of magnitude lower. The plasma conditions on AUG are more destabilizing to the GAEs. Overall, our results are consistent with the observation of similar modes on other conventional tokamaks, namely JT-60U and DIII-D.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{2088,

title = {Parameter dependencies of the separatrix density in low triangularity L-mode and H-mode JET-ILW plasmas},

author = {B. Lomanowski and G. Rubino and A. Uccello and M. Dunne and N. Vianello and S. Aleiferis and J. Canik and I. Carvalho and G. Corrigan and L. Frassinetti and D. Frigione and L. Garzotti and M. Groth and A. Meigs and M. Maslov and C. Perez Thun and F. Rimini and P. A. Schneider and G. Sergienko and J. Simpson and D. Van Eester and JET Contributors},

url = {https://dx.doi.org/10.1088/1741-4326/aca9de},

doi = {10.1088/1741-4326/aca9de},

year  = {2023},

date = {2023-03-01},

journal = {Nuclear Fusion},

volume = {63},

number = {3},

pages = {036019},

publisher = {IOP Publishing},

abstract = {The midplane electron separatrix density, n e,sep, in JET-ILW L-mode and H-mode low triangularity deuterium fuelled plasmas exhibits a strong explicit dependence on the averaged outer divertor target electron temperature, n e,sep ∼ T e,ot −1/2. This dependence is reproduced by analytic reversed two point model (rev-2PM), and arises from parallel pressure balance, as well as the ratio of the power and momentum volumetric loss factors, (1 − f cooling)/(1 − f mom-loss). Quantifying the influence of the (1 − f cooling) and (1 − f mom-loss) loss factors on n e,sep has been enabled by measurement estimates of these quantities from L-mode density (fueling) ramps in the outer horizontal, VH(C), and vertical target, VV, divertor configurations. Rev-2PM n e,sep estimates from the extended H-mode and more limited L-mode datasets are recovered to within $±$25% of the measurements, with a scaling factor applied to account for use of , an averaged quantity, rather than flux tube resolved target values. Both the (1 − f cooling) and (1 − f mom-loss) trends and recovery of n e,sep using the rev-2PM formatting are reproduced in EDGE2D-EIRENE L-mode-like and H-mode-like density scan simulations. The general lack of a divertor configuration effect in the JET-ILW n e,sep trends can be attributed to a significant influence of main chamber recycling, which has been shown in the EDGE2D-EIRENE results to moderate n e,sep with respect to changes in divertor neutral leakage imposed by changes in the divertor configuration. The unified n e,sep vs trends can, however, be broken if large modifications to the divertor geometry (e.g. complete removal of the outer divertor baffle structure) are introduced in the model. The more pronounced high-field side high density region formation in the VH(C) configuration with reduced clearance to the separatrix does not appear to have a significant influence on the outer midplane separatrix and pedestal parameters when mapped to , although conditions at the inner midplane could not be assessed.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{2087,

title = {Parametric study of midplane gas puffing to maximize ICRF power coupling in ITER},

author = {W. Zhang and A. Messiaen and W. Helou and V. Bobkov and P. U. Lamalle and R. A. Pitts and W. Tierens},

url = {https://dx.doi.org/10.1088/1741-4326/acb4ad},

doi = {10.1088/1741-4326/acb4ad},

year  = {2023},

date = {2023-03-01},

journal = {Nuclear Fusion},

volume = {63},

number = {3},

pages = {036008},

publisher = {IOP Publishing},

abstract = {Midplane gas puffing close to the ion cyclotron range of frequencies (ICRF) antennae has been demonstrated to be robust in improving ICRF power coupling in current tokamaks. It is also shown in a previous study (Zhang 2019 Nucl. Mater. Energy 19 364–71) that in ITER, midplane gas puffing with a puff rate of ∼4.5 × 1022 electrons s−1 can increase the antenna loading/coupling resistance by about a factor of two. In this paper, a comprehensive parametric study has been carried out to characterize the influence of midplane gas puffing on ICRF power coupling in additional and broader range of parameter scans. The new parameter scans include the gas puff rate, the poloidal location of the gas pipe orifices (GPOs), the separatrix density, the particle perpendicular diffusion coefficient, the radial distance between the plasma and antenna as well as the antenna phasing. The 3D edge plasma fluid and neutral transport code EMC3-EIRENE code has been used to simulate the 3D distributions of plasma density in the presence of gas puffing, which are then used in the antenna code ANTITER II to calculate the antenna coupling. The simulation results indicate that the ITER ICRF local midplane gas injection layout (with the GPOs located on one side of each antenna port) increases the ICRF power coupling significantly in all studied plasma scenarios and antenna parameters. We are hence confident that the chosen layout for the ICRF local gas injection on ITER is appropriate. We are also confident that the ITER local gas injection will allow boosting the ICRF coupling with all studied plasma conditions and antenna phasings.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{2085,

title = {Investigation of Te measurements discrepancies between ECE and Thomson diagnostics in high-performance plasmas in JET},

author = {M. Fontana and G. Giruzzi and F. P. Orsitto and E. Luna and R. Dumont and L. Figini and D. Kos and M. Maslov and S. Schmuck and C. Sozzi and C. D. Challis and D. Frigione and J. Garcia and L. Garzotti and J. Hobirk and A. Kappatou and D. Keeling and E. Lerche and C. Maggi and J. Maillous and F. Rimini and D. Van Eester and JET Contributors},

year  = {2023},

date = {2023-02-01},

journal = {EPJ Web Confenrece},

volume = {277},

pages = {03006},

abstract = {For high-temperature JET and TFTR discharges, electron cyclotron emission (ECE) measurements of central electron temperature were systematically found to be up to 20% higher than those taken with Thom- son scattering. In recent high-performance JET discharges, central Te measurements, performed with LIDAR Thomson scattering and the X-mode ECE interferometer, have been studied in a large database, including deuterium (DD), and deuterium-tritium plasmas (DT). Discrepancies between Te measurements have been ob- served outside of the experimental uncertainties. ECE measurements, at high Te, have been found to be higher or lower than those of LIDAR, depending on the specific plasma scenario. In addition, discrepancies between the peaks of the second and third harmonic ranges of the ECE spectrum have been interpreted as evidence for the presence of non-Maxwellian features in the electron distribution function. These comparisons seem to suggest that such features can be found in most of the high-performance scenarios selected in this JET database.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{2084,

title = {A model of non-Maxwellian electron distribution function for the analysis of ECE data in JET discharges},

author = {G. Giruzzi and M. Fontana and F. P. Orsitto and E. Luna and R. Dumont and L. Figini and M. Maslov and S. Mazzi and S. Schmuck and L. Senna and C. Sozzi and C. Challis and D. Frigione and J. Garcia and L. Garzotti and J. Hobirk and A. Kappatou and D. Keeling and E. Lerche and C. Maggi and J. Mailloux and F. Rimini and D. Van Eester and JET Contributors},

year  = {2023},

date = {2023-02-01},

journal = {EPJ Web Conference},

volume = {277},

pages = {03005},

abstract = {Recent experiments performed in JET at high level of plasma heating, in preparation of, and during the DT campaign have shown significant discrepancies between electron temperature measurements by Thomson Scattering (TS) and Electron Cyclotron Emission (ECE). In order to perform a systematic analysis of this phenomenon, a simple model of bipolar distortion of the electron distribution function has been developed, allowing analytic calculation of the EC emission and absorption coefficients. Extensive comparisons of the modelled ECE spectra (at both the 2nd and the 3rd harmonic extraordinary mode) with experimental measurements display good agreement when bulk electron distribution distortions around 1-2 times the electron thermal velocity are used and prove useful for a first level of analysis of this effect.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{2086,

title = {Overview of TOMAS plasma diagnostics},

author = {Yu. Kovtun and A. Goriaev and D. López-Rodríguez and L. Dittrich and P. Petersson and S. Moon and T. Wauters and K. Crombé and S. Möller and J. Buermans and M. Verstraeten and S. Brezinsek},

url = {https://dx.doi.org/10.1088/1748-0221/18/02/C02034},

doi = {10.1088/1748-0221/18/02/C02034},

year  = {2023},

date = {2023-02-01},

journal = {Journal of Instrumentation},

volume = {18},

number = {02},

pages = {C02034},

publisher = {IOP Publishing},

abstract = {This paper presents an overview of the TOMAS plasma diagnostics. The Langmuir probe method is employed to measure electron temperature, density and floating potential distributions.Two triple probes (horizontal and vertical distributions) and a single probe (horizontal distribution) are used. The measured plasma parameters by the triple and single probes are compared. The ion and neutral atom flux and energy distribution is respectively characterized with a Residual Field Energy Analyzer and a Time-of-Flight Neutral Particle Analyzer. To determine the elemental/charge content of the plasma, the passive method of time-resolved optical emission spectroscopy is used. The time dependence of the integral flow of plasma emission from the discharge is registered by a photodetector. Using a filter allows the photodetector to measure spectral line intensities. To record a wide variety of plasma events several video diagnostics are used. It includes slow video cameras and one high-speed camera in the visible range including Hα.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{2083,

title = {Development of ECRH-based methods for assisted discharge burn-through: Experiment and simulation},

author = {D. Ricci and J. Stober and R. Dux and L. Figini and T. Wauters and E. Lerche and G. Granucci and ASDEX Upgrade Team and EUROfusion WPTE Team},

year  = {2023},

date = {2023-02-01},

journal = {EPJ Web Confenrece},

volume = {277},

pages = {02001},

abstract = {Electron Cyclotron (EC) waves will be routinely used in future reactors not only for plasma heating and/or non-inductive current drive during the flat top but also to assist the plasma start-up phase in large tokamaks with superconductive coils. In ITER, for example, EC start-up is foreseen since first plasma operation. To limit the level of stray radiation, ECRH can be used after ohmic breakdown, as a robust solution to successfully sustain the plasma burn-through in the presence of pre-filling gas and impurity influx from the wall. 

On ASDEX Upgrade (AUG), a series of dedicated experiments have been performed using EC heating (X2) with a controlled Ne impurity injection in the prefill phase, to mimic non-favourable burn-through conditions such as would be expected in a discharge following a disruption event. The time for EC heating onset has been optimised to assist the early burn-through and a scan of the Ne concentration has been performed to find the threshold for successful burn-through conditions for two ECH power levels (0.7 and 1.4 MW). The toroidal magnetic field flexibility has been also documented, with the cold resonance position being shifted up to 13% in major radius to match the ITER condition. These experiments showed that optimised settings of ECH power (onset and duration of the pulse) have a key role in making feasible the early Ne burn-through (with Ne concentration up to 14% and EC power of 1.4 MW). Successful pulses will be extended to study stationarity and clean up properties. 

For an efficient and robust use of such a technique, it is essential to develop appropriate models capable of describing present experiments and of extrapolating (or predicting) to future scenarios. In this work, the predictive 0D model for the burn-though phase BKD0 [1] has been used to reproduce experimental results and estimate the power required for a successful burn-through as a function of the impurity concentration, finding that ECH power of 1.4 MW is required to sustain burn-through with more than 20% of Ne. The scalability of the model has been also tested on TCV [2] and its implication for ITER will be discussed.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{2079,

title = {The Impact of Radio Frequency Waves on the Plasma Density in the Tokamak Edge},

author = {D. Van Eester and N. Tournay},

year  = {2023},

date = {2023-01-01},

journal = {Physics},

volume = {5},

number = {1},

pages = {116-130},

abstract = {A simple model is presented to describe how the radio frequency electromagnetic field modifies the plasma density the antenna faces in tokamaks. Aside from ``off-the-shelf'' equations standardly used to describe wave-plasma interaction relying on the quasilinear approach, it invokes the ponderomotive force in presence of the confining static magnetic field. The focus is on dynamics perpendicular to the Bo magnetic field. Stronger fields result in density being pushed further away from the launcher and in stronger density asymmetry along the antenna.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{2081,

title = {Peripheral temperature gradient screening of high-Z impurities in optimised `hybrid' scenario H-mode plasmas in JET-ILW},

author = {A. R. Field and F. J. Casson and D. Fajardo and C. Angioni and C. D. Challis and J. Hobirk and A. Kappatou and Hyun-Tae Kim and E. Lerche and A. Loarte and J. Mailloux and JET Contributors},

url = {https://dx.doi.org/10.1088/1741-4326/aca54e},

doi = {10.1088/1741-4326/aca54e},

year  = {2023},

date = {2023-01-01},

journal = {Nuclear Fusion},

volume = {63},

number = {1},

pages = {016028},

publisher = {IOP Publishing},

abstract = {Screening of high-Z (W) impurities from the confined plasma by the temperature gradient at the plasma periphery of fusion-grade H-mode plasmas has been demonstrated in the JET-ILW (ITER-like wall) tokamak. Through careful optimisation of the hybrid-scenario, deuterium plasmas with sufficient heating power ( 32 MW), high enough ion temperature gradients at the H-mode pedestal top can be achieved for the collisional, neo-classical convection of the W impurities to be directed outwards, expelling them from the confined plasma. Measurements of the W impurity fluxes between and during edge-localised modes (ELMs) based on fast bolometry measurements show that in such plasmas there is a net efflux (loss) between ELMs but that ELMs often allow some W back into the confined plasma. Provided steady, high-power heating is maintained, this mechanism allows such plasmas to sustain high performance, with an average D–D neutron rate of s−1 over a period of ∼3 s, after an initial overshoot (equivalent to a D–T fusion power of ∼9.4 MW), without an uncontrolled rise in W impurity radiation, giving added confidence that impurity screening by the pedestal may also occur in ITER, as has previously been predicted (Dux et al 2017 Nucl. Mater. Energy 12 28–35).},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{2080,

title = {The broadening of SOL profiles in JET tritium plasma and its impact on machine operation},

author = {H. J. Sun and S. A. Silburn and I. S. Carvalho and D. B. King and C. Giroud and G. Fishpool and G. F. Matthews and R. B. Henriques and D. L. Keeling and F. G. Rimini and L. Garzotti and D. Frigione and D. Van Eester and M. Groth and J. Flanagan and D. Kos and B. Viola and A. Boboc and P. Shi and M. -L. Mayoral and J. Mailloux and C. Maggi and A. Huber and D. Douai and N. Vianello and P. J. Lomas and M. Lennholm and M. Maslov and K. Kirov and P. Jacquet and C. G. Lowry and M. Baruzzo and C. Stuart and J. Mitchell and L. Horvath and D. C. McDonald and JET Contributors},

url = {https://dx.doi.org/10.1088/1741-4326/aca48f},

doi = {10.1088/1741-4326/aca48f},

year  = {2023},

date = {2023-01-01},

journal = {Nuclear Fusion},

volume = {63},

number = {1},

pages = {016021},

publisher = {IOP Publishing},

abstract = {Unusually high power loads on the beryllium limiter caused by neutral beam re-ionisation, and much cooler divertor target surfaces were observed during the recent JET tokamak tritium campaign. As both phenomena are driven by scrape-off layer (SOL) physics, the SOL features of 72 tritium H-mode discharges and their deuterium references have been studied. The majority (70) of tritium H-mode discharges had exponentially decaying SOL profiles. The tritium plasmas are observed to have increased separatrix density and collisionality compared to their deuterium references. This is associated with times broader SOL width for both density and temperature profiles. This is consistent with previous observations in highly collisional deuterium H-mode plasma on the ASDEX Upgrade tokamak (Sun et al 2015 Plasma Phys. Control. Fusion 57 125011) and interpreted as high collisionality enhancing cross-field transport across the separatrix and resulting in the broadening of near SOL above a critical value. The other two tritium H-mode discharges had near flat SOL density profiles, similar to the so-called `density shoulder formation' observed in L-mode plasma. The SOL collisionality of these two pulses lies within the range of T pulses without density shoulder formation. This supports the conclusion of previous studies (Vianello et al 2017 Nucl. Fusion 57 116014; Wynn et al 2018 Nucl. Fusion 58 056001) that increased collisionality is not sufficient for the formation of a `density shoulder' and additional factors, likely divertor condition or interaction with neutrals, are required. JET tritium plasma provides evidence of favourable and unfavourable effects of enhanced cross-field SOL transport on machine operation. The larger limiter power loads due to re-ionisation of neutral beam injection observed in the T pulses relative to their D references has been shown to be consistent with the combined effects of the broadening of the SOL profile and larger beam ion Larmor radius. The enhanced cross-field particle transport and the resulting broader SOL width provides more particles to ionize the fast Beam neutrals, causing the unfavourable power load issue on the beryllium limiter. The broader near SOL profiles of the T plasma spreads the heat load over a larger area and, together with the increased separatrix density, results in a favourably cooler divertor target surface.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{2077,

title = {Prediction of ICRF minority heating schemes for JET D–T experiments},

author = {D Gallart and M J Mantsinen and J Manyer and E Planas and D M A Taylor and J Garcia and D Frigione and L Garzotti and Hyun-Tae Kim and M Nocente and F Rimini and D. Van Eester and JET Contributors},

url = {https://dx.doi.org/10.1088/1361-6587/ac9925},

doi = {10.1088/1361-6587/ac9925},

year  = {2022},

date = {2022-12-01},

journal = {Plasma Physics and Controlled Fusion},

volume = {64},

number = {12},

pages = {125006},

publisher = {IOP Publishing},

abstract = {Achieving high-performance conditions and maximizing the fusion yield of plasma discharges have been one of the main goals of recent Joint European Torus (JET) campaigns in preparation for its second deuterium–tritium (D–T) campaign. The simulations shown in this work delve into the role of external heating using neutral beam injection (NBI) and radio-frequency waves in the ion cyclotron range of frequencies (ICRF) in order to optimise high fusion performance in the JET tokamak. A baseline discharge with record neutron rate is used as a reference in order to perform a D–T prediction, which considers the NBI+RF synergy. In this work, our focus is on JET's two main minority schemes, H and 3He. This study tackles the heating mechanisms by which these schemes reach high-performance conditions. The H scheme typically boosts the ICRF fusion enhancement through the second D harmonic heating, whereas 3He minority is characterised by its strong bulk ion heating. Both features are beneficial for increasing the fusion yield. Nevertheless, the minority concentration is a relevant parameter, which needs to be assessed to understand in which concentration ranges the benefits of each particular minority scheme are met. Therefore, the main objective of this work is to assess in which concentration range the ICRF fusion enhancement and bulk ion heating are optimal, for H and 3He, respectively. Under these conditions, our prediction suggests 3He concentration should stay above 1.2% and H should remain below 2.2%.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{2076,

title = {Developing high performance RF heating scenarios on the WEST tokamak},

author = {M. Goniche and V. Ostuni and C. Bourdelle and P. Maget and J. F. Artaud and J. M. Bernard and V. Bobkov and J. Bucalossi and F. Clairet and L. Colas and C. Desgranges and L. Delpech and P. Devynck and R. Dumont and A. Ekedahl and N. Fedorczak and J. Garcia and J. Gaspar and C. Gil and C. Guillemaut and J. Gunn and J. Hillairet and C. Klepper and C. Lau and E. Lerche and G. Lombard and P. Manas and E. H. Martin and D. Mazon and O. Meyer and J. Morales and Ph. Moreau and E. Nardon and R. Nouailletas and B. Pegourié and M. Peret and Y. Peysson and X. Regal-Mezin and R. Sabot and S. Shiraiwa and G. Urbanczyk and L. Vermare and D. Vezinet and G. M. Wallace and WEST Team},

url = {https://dx.doi.org/10.1088/1741-4326/ac9691},

doi = {10.1088/1741-4326/ac9691},

year  = {2022},

date = {2022-12-01},

journal = {Nuclear Fusion},

volume = {62},

number = {12},

pages = {126058},

publisher = {IOP Publishing},

abstract = {High power experiments, up to 9.2 MW with LHCD and ICRH, have been carried out in the full tungsten tokamak WEST. Quasi non inductive discharges have been achieved allowing to extend the plasma duration to 53 s with stationary conditions in particular with respect to tungsten contamination. Transitions to H mode are observed, and H-modes lasting up to 4 s have been obtained. The increase in stored energy is weak since the power crossing the separatrix is close to the L–H threshold. Hot L mode plasmas (central temperature exceeding 3 keV) with a confinement time following the ITER L96 scaling law are routinely obtained. The weak aspect ratio dependence of this scaling law is confirmed. Tungsten accumulation is generally not an operational issue on WEST. Difficulty of burning through tungsten can prevent the discharge from accessing to a hot core plasma in the ramp-up phase, or can lead to rapid collapse of the central temperature when radiation is enhanced by a slight decrease of the temperature. Except a few pulses post-boronization, the plasma radiation is rather high (P rad/ P tot ∼ 50%) and is dominated by tungsten. This fraction does not vary as the RF power is ramped up and is quite similar in ICRH and/or LHCD heated plasmas. An estimate of the contribution of the RF antennas to the plasma contamination in tungsten is given.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{2075,

title = {Assessment of the potential of ion cyclotron resonance heating and current drive in STEP},

author = {D. Van Eester},

year  = {2022},

date = {2022-11-01},

journal = {Lab Report},

number = {147},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{2074,

title = {The JET Baseline scenario: an overview of recent findings in DTE2 and its preparations},

author = {D. Van Eester and D. Frigione and L. Garzotti and P. Lomas and C. Lowry and F. Rimini and S. Aleiferis and A. Alessi and F. Auriemma and M. Baruzzo and A. Boboc and I. Carvalho and A. Chomiczewska and E. Luna and M. Dreval and D. Ferreira and J.Ferreira and A. R. Field and L. Frassinetti and J. Garcia and L. Horvath and Ph. Huynh and P. Jacquet and T. Johnson and D. King and V. Kimtily and K. Kirov and M. Lennholm and E. LErche and C. Maggi and J. Mailloux and S. Menmuir and I. Monakhov and S. Novak and R. Otin and A Patel and L. Piron and E. Solano and Z. Stancar and G. Stankunas and C. Stuart and H. J. Sun and G. Telesca and D. Valcarcel and M. Valovic and V. Zotta and JET contribtors and EUROfusion-IM team},

year  = {2022},

date = {2022-11-01},

journal = {Lab Report},

number = {146},

abstract = {The present set of notes offers a brief summary of the Baseline experiments performed during the recent 2021 JET DT campaign as well as its preparations.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{2070,

title = {Fast-ion orbit sensitivity of neutron and gamma-ray diagnostics for one-step fusion reactions},

author = {H. Järleblad and L. Stagner and M. Salewski and J. Eriksson and M. Nocente and J. Rasmussen and Ž. Štancar and Y. O. Kazakov and B. Simmendefeldt and JET Contributors},

url = {https://doi.org/10.1088/1741-4326/ac63d3},

doi = {10.1088/1741-4326/ac63d3},

year  = {2022},

date = {2022-11-01},

journal = {Nuclear Fusion},

volume = {62},

number = {11},

pages = {112005},

publisher = {IOP Publishing},

abstract = {Fast ions in the MeV-range can be diagnosed by neutron emission spectroscopy (NES) and gamma-ray spectroscopy (GRS). In this work, we present orbit weight functions for one-step fusion reactions, using NES and GRS diagnostics on perpendicular and oblique lines-of-sight (LOS) at Joint European Torus (JET) as examples. The orbit weight functions allow us to express the sensitivities of the diagnostics in terms of fast-ion (FI) orbits and can be used to swiftly reproduce synthetic signals that have been computed by established codes. For diagnostically relevant neutron energies for the D(D, n)3He reaction, the orbit sensitivities of the NES diagnostics follow a predictable pattern. As the neutron energy of interest increases, the pattern shifts upwards in FI energy. For the GRS diagnostic and the T(p,γ)4He reaction, the orbit sensitivity is shown to be qualitatively different for red-shifted, blue-shifted and nominal gamma birth energies. Finally, we demonstrate how orbit weight functions can be used to decompose diagnostic signals into the contributions from different orbit types. For a TRANSP simulation of the JET discharge (a three-ion ICRF scenario) considered in this work, the NES signals for both the perpendicular and oblique LOS are shown to originate mostly from co-passing orbits. In addition, a significant fraction of the NES signal for the oblique LOS is shown to originate from stagnation orbits.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{2072,

title = {Gyrokinetic study of transport suppression in JET plasmas with MeV-ions and toroidal Alfvén eigenmodes},

author = {S Mazzi and J Garcia and D Zarzoso and Y. O. Kazakov and J. Ongena and M Dreval and M Nocente and Ž Štancar and G Szepesi},

url = {https://doi.org/10.1088/1361-6587/ac91f3},

doi = {10.1088/1361-6587/ac91f3},

year  = {2022},

date = {2022-11-01},

journal = {Plasma Physics and Controlled Fusion},

volume = {64},

number = {11},

pages = {114001},

publisher = {IOP Publishing},

abstract = {The impact of fast ions, generated in the MeV-range through the efficient application of the three-ion scheme in JET plasmas, on the turbulence properties is presented through complex numerical simulations. The suppression of the ion-scale turbulent transport is studied by means of in-depth gyrokinetic numerical analyses. Such a suppression is demonstrated to be achieved in the presence of toroidal Alfvén eigenmodes (TAEs) destabilized by the highly energetic ions. Details on the TAE excitation are also provided with a multi-code analysis. The inherently nonlinear and multi-scale mechanism triggered by the fast ions, also involving the high-frequency modes and the large-scale zonal flows, is deeply analyzed. Such mechanism is thus demonstrated, with experimental validating studies, to be the main cause of turbulence suppression and improvement of ion thermal confinement. Additional simulations address the implications of reversed shear magnetic equilibrium on the turbulent transport.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{2073,

title = {A high-resolution neutron spectroscopic camera for the SPARC tokamak based on the Jet European Torus deuterium–tritium experience},

author = {M. Tardocchi and M. Rebai and D. Rigamonti and R. A. Tinguely and F. Caruggi and A. Dal Molin and Z. Ghani and L. Giacomelli and M. Girolami and G. Grosso and M. Kushoro and G. Marcer and M. Mastellone and A. Muraro and M. Nocente and E. Perelli Cippo and M. Petruzzo and O. Putignano and J. Scionti and V. Serpente and D. M. Trucchi and S. Mackie and A. A. Saltos and E. De Marchi and M. Parisi and A. Trotta and E. Luna and J. Garcia and Y. O. Kazakov and M. Maslov and Z. Stancar and G. Gorini and JET contributors},

year  = {2022},

date = {2022-11-01},

journal = {Review of Scientific Instruments},

volume = {93},

pages = {113512},

abstract = {Dedicated nuclear diagnostics have been designed, developed, and built within EUROFUSION enhancement programs in the last ten years for installation at the Joint European Torus and capable of operation in high power Deuterium–Tritium (DT) plasmas. The recent DT Experiment campaign, called DTE2, has been successfully carried out in the second half of 2021 and provides a unique opportunity to evaluate the performance of the new nuclear diagnostics and for an understanding of their behavior in the record high 14 MeV neutron yields (up to 4.7 × 1018 n/s) and total number of neutrons (up to 2 × 1019 n) achieved on a tokamak. In this work, we will focus on the 14 MeV high resolution neutron spectrometers based on artificial diamonds which, for the first time, have extensively been used to measure 14 MeV DT neutron spectra with unprecedented energy resolution (Full Width at Half Maximum of ≈1% at 14 MeV). The work will describe their long-term stability and operation over the DTE2 campaign as well as their performance as neutron spectrometers in terms of achieved energy resolution and high rate capability. This important experience will be used to outline the concept of a spectroscopic neutron camera for the SPARC tokamak. The proposed neutron camera will be the first one to feature the dual capability to measure (i) the 2.5 and 14 MeV neutron emissivity profile via the conventional neutron detectors based on liquid or plastics scintillators and (ii) the 14 MeV neutron spectral emission via the use of high-resolution diamond-based spectrometers. The new opportunities opened by the spectroscopic neutron camera to measure plasma parameters will be discussed.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{2071,

title = {Simultaneous measurements of unstable and stable Alfvén eigenmodes in JET},

author = {R. A. Tinguely and J. Gonzalez-Martin and P. G. Puglia and N. Fil and S. Dowson and M. Porkolab and I. Kumar and M. Podestà and M. Baruzzo and A. Fasoli and Y. O. Kazakov and M. F. F. Nave and M. Nocente and J. Ongena and Ž. Štancar and JET Contributors},

url = {https://doi.org/10.1088/1741-4326/ac899e},

doi = {10.1088/1741-4326/ac899e},

year  = {2022},

date = {2022-11-01},

journal = {Nuclear Fusion},

volume = {62},

number = {11},

pages = {112008},

publisher = {IOP Publishing},

abstract = {In this paper, we report the novel experimental observation of both unstable and stable toroidicity-induced Alfvén eigenmodes (TAEs) measured simultaneously in a JET tokamak plasma. The three-ion-heating scheme (D-DNBI-3He) is employed to accelerate deuterons to MeV energies, thereby destabilizing TAEs with toroidal mode numbers n = 3–5, each decreasing in mode amplitude. At the same time, the Alfvén eigenmode active diagnostic resonantly excites a stable n = 6 TAE with total normalized damping rate −γ/ω 0 ≈ 1%–4%. Hybrid kinetic-MHD modeling with codes NOVA-K and MEGA both find eigenmodes with similar frequencies, mode structures, and radial locations as in experiment. NOVA-K demonstrates good agreement with the n = 3, 4, and 6 TAEs, matching the damping rate of the n = 6 mode within uncertainties and identifying radiative damping as the dominant contribution. Improved agreement is found with MEGA for all modes: the unstable n = 3–5 and stable n = 2, 6 modes, with the latter two stabilized by higher intrinsic damping and lower fast ion drive, respectively. While some discrepancies remain to be resolved, this unique validation effort gives us confidence in TAE stability predictions for future fusion devices.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{2069,

title = {Lost alpha Faraday cup foil noise characterization during Joint European Torus plasma post-processing analysis},

author = {P. J. Bonofiglo and V. Goloborodko and Z. Stancar and M. Podestà and F. E. Cecil and C. D. Challis and J. Hobirk and A. Kappatou and E. Lerche and I. S. Carvalho and J. Garcia and J. Mailloux and C. F. Maggi and A. G. Meigs and JET Contributors},

year  = {2022},

date = {2022-09-01},

journal = {Review of Scientific Instruments},

volume = {93},

number = {09},

pages = {093527},

abstract = {Capacitive plasma pickup is a well-known and difficult problem for plasma-facing edge diagnostics. This problem must be addressed to ensure an accurate and robust interpretation of the real signal measurements vs noise. The Faraday cup fast ion loss detector array of the Joint European Torus (JET) is particularly prone to this issue and can be used as a testbed to prototype solutions. The issue of separation and distinction between warranted fast ion signal and electromagnetic plasma noise has traditionally been solved with hardware modifications, but a more versatile post-processing approach is of great interest. This work presents post-processing techniques to characterize the signal noise. While hardware changes and advancements may be limited, the combination with post-processing procedures allows for more rapid and robust analysis of measurements. The characterization of plasma pickup noise is examined for alpha losses in a discharge from JET's tritium campaign. In addition to highlighting the post-processing methodology, the spatial sensitivity of the detector array is also examined, which presents significant advantages for the physical interpretation of fast ion losses.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{2068,

title = {A new dedicated signal processing system for gamma-ray spectrometers in high power deuterium–tritium plasma scenarios in tokamaks},

author = {G. Marcerer and E. Khilkevitch and A. Shevelev and G. Croci and A. Dal Molin and G. Gorini and G. Grosso and A. Muraro and M. Nocente and E. Perelli Cippo and O. Putignano and M. Rebai and D. Rigamonti and E. Luna and J. Garcia and Y. O. Kazakov and V. Kiptily and M. Maslov and M. F. F. Nave and J. Ongena and M. Tardocchi and JET Contributors},

year  = {2022},

date = {2022-09-01},

journal = {Review of Scientific Instruments},

volume = {93},

number = {9},

pages = {093525},

abstract = {The most performant deuterium–tritium (DT) plasma discharges realized by the Joint European Torus (JET) tokamak in the recent DT campaign have produced neutron yields on the order of 1018 n/s. At such high neutron yields, gamma-ray spectroscopy measurements with scintillators are challenging as events from the neutron-induced background often dominate over the signal, leading to a significant fraction of pileup events and instability of the photodetector gain along with the consequent degradation of the reconstructed spectrum. Here, we describe the solutions adopted for the tangential lanthanum bromide spectrometer installed at JET. A data acquisition system with free streaming mode digitization capabilities for the entire duration of the discharge has been used to solve dead-time related issues and a data reconstruction code with pileup recovery and photodetector gain drift restoration has been implemented for off-line analysis of the data. This work focuses on the acquired data storage and parsing, with a detailed explanation of the pileup recovery and gain drift restoration algorithms.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{2066,

title = {Effects of the parallel flow shear on the ITG-driven turbulent transport in tokamak plasmas},

author = {S. Mazzi and Y. Camenen and J. Garcia and D. Zarzoso and D. Frigione and L. Garzotti and F. Rimini and D. Van Eester and JET Contributors},

url = {https://doi.org/10.1088/1741-4326/ac7ac2},

doi = {10.1088/1741-4326/ac7ac2},

year  = {2022},

date = {2022-09-01},

journal = {Nuclear Fusion},

volume = {62},

number = {9},

pages = {096024},

publisher = {IOP Publishing},

abstract = {The impact of the parallel flow shear on the tokamak plasma stability and turbulent transport driven by the ion temperature gradient (ITG) modes is analyzed by means of local gyrokinetic numerical analyses. It is shown that the parallel flow shear increases the ITG growth rate in the linear regime, and induces a broadening and shift of the radial spectrum. Then, the different effects of the finite parallel shear on the ITG turbulence characteristics are deeply analyzed in the nonlinear regime. These studies highlight that a reduction of the thermal-ion turbulent heat flux is induced by a complex mechanism involving the nonlinear generation of an enhanced zonal flow activity. Indeed, the turbulent sources of the zonal flows are increased by the introduction of the finite parallel flow shear in the system, beneficially acting on the saturation level of the ITG turbulence. The study has been carried out for the Waltz standard case below the critical threshold of the destabilization of the parallel velocity gradient instability, and then generalized to a selected pulse of a recent JET scenario with substantial toroidal rotation in the edge plasma region. It is, thus, suggested that the investigated complex mechanism triggered by the finite parallel flow shear reducing the ITG turbulent heat fluxes could be complementary to the well-established perpendicular flow shear in a region with sufficiently large plasma toroidal rotation.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{2067,

title = {Fusion product measurements by nuclear diagnostics in the Joint European Torus deuterium-tritium 2 campaign},

author = {M. Nocente and V. Kiptily and M. Tardocchi and P. J. Bonofiglo and T. Craciunescu and A. Dal Molin and E. De La Luna and J. Eriksson and J. Garcia and Z. Ghani and G. Gorini and L. Hägg and Y. O. Kazakov and E. Lerche and C. F. Maggi and P. Mantica and G. Marcer and M. Maslov and O. Putignano and D. Rigamonti and M. Salewski and S. Sharapov and P. Siren and Z. Stancar and A. Zohar and P. Beaumont and K. Crombé and G. Ericsson and M. Garcia-Munoz and D. Keeling and D. King and K. Kirov and M. F. F. Nave and J. Ongena and A. Patel and C. Perez Thun and JET Contributors},

year  = {2022},

date = {2022-09-01},

journal = {Review of Scientific Instruments},

volume = {93},

number = {9},

pages = {093520},

abstract = {A new deuterium–tritium experimental, DTE2, campaign has been conducted at the Joint European Torus (JET) between August 2021 and late December 2021. Motivated by significant enhancements in the past decade at JET, such as the ITER-like wall and enhanced auxiliary heating power, the campaign achieved a new fusion energy world record and performed a broad range of fundamental experiments to inform ITER physics scenarios and operations. New capabilities in the area of fusion product measurements by nuclear diagnostics were available as a result of a decade long enhancement program. These have been tested for the first time in DTE2 and a concise overview is provided here. Confined alpha particle measurements by gamma-ray spectroscopy were successfully demonstrated, albeit with limitations at neutron rates higher than some 1017 n/s. High resolution neutron spectroscopy measurements with the magnetic proton recoil instrument were complemented by novel data from a set of synthetic diamond detectors, which enabled studies of the supra-thermal contributions to the neutron emission. In the area of escaping fast ion diagnostics, a lost fast ion detector and a set of Faraday cups made it possible to determine information on the velocity space and poloidal distribution of the lost alpha particles for the first time. This extensive set of data provides unique information for fundamental physics studies and validation of the numerical models, which are key to inform the physics and scenarios of ITER.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{2064,

title = {The power threshold of H-mode access in mixed hydrogen-tritium and pure tritium plasmas at JET with ITER-like wall},

author = {G. Birkenmeier and E. R. Solano and E. Lerche and D. Taylor and D. Gallart and M. J. Mantsinen and E. Delabie and I. S. Carvalho and P. Carvalho and E. Pawelec and J. C. Hillesheim and F. Parra Diaz and C. Silva and S. Aleiferis and J. Bernardo and A. Boboc and D. Douai and E. Litherland-Smith and R. Henriques and K. K. Kirov and C. F. Maggi and J. Mailloux and M. Maslov and F. G. Rimini and S. A. Silburn and P. Sirén and H. Weisen},

url = {https://doi.org/10.1088/1741-4326/ac6d6b},

doi = {10.1088/1741-4326/ac6d6b},

year  = {2022},

date = {2022-08-01},

journal = {Nuclear Fusion},

volume = {62},

number = {8},

pages = {086005},

publisher = {IOP Publishing},

abstract = {The heating power to access the high confinement mode (H-mode), P LH, scales approximately inversely with the isotope mass of the main ion plasma species as found in (protonic) hydrogen, deuterium and tritium plasmas in many fusion facilities over the last decades. In first dedicated L–H transition experiments at the Joint European Torus (JET) tokamak facility with the ITER-like wall (ILW), the power threshold, P LH, was studied systematically in plasmas of pure tritium and hydrogen–tritium mixtures at a magnetic field of 1.8 T and a plasma current of 1.7 MA in order to assess whether this scaling still holds in a metallic wall device. The measured power thresholds, P LH, in Ohmically heated tritium plasmas agree well with the expected isotope scaling for metallic walls and the lowest power threshold was found in Ohmic phases at low density. The measured power thresholds in ion cyclotron heated plasmas of pure tritium or hydrogen–tritium mixtures are significantly higher than the expected isotope mass scaling due to higher radiation levels. However, when the radiated power is taken into account, the ion cyclotron heated plasmas exhibit similar power thresholds as a neutral beam heated plasma, and are close to the scaling. The tritium plasmas in this study tended to higher electron heating fractions and, when heated with ion cyclotron waves, to relatively higher radiation fractions compared to other isotopes potentially impeding access to sustained H-modes.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{2065,

title = {Conditional recurrence plots for the investigation of sawteeth pacing with RF modulation},

author = {Emmanuele Peluso and Andrea Murari and Teddy Craciunescu and E. Lerche and Pasquale Gaudio and Michela Gelfusa and Daniel Gallart and David Taylor},

url = {https://doi.org/10.1088/1361-6587/ac757c},

doi = {10.1088/1361-6587/ac757c},

year  = {2022},

date = {2022-08-01},

journal = {Plasma Physics and Controlled Fusion},

volume = {64},

number = {8},

pages = {084002},

publisher = {IOP Publishing},

abstract = {In many areas of research, from neurobiology to nuclear fusion, which investigate complex dynamical systems involving numerous, different and interconnected physical quantities, the application of advanced analysis tools based on Chaos theory and Information theory has provided significant improvements both by supporting theoretical models and by highlighting hidden relationships between quantities characterizing the observed phenomena. The present article is therefore devoted to the analysis of synchronization experiments in magnetically controlled plasmas at JET, involving a `target' quantity (sawteeth) and a `driver' (modulated injected radio frequency) one. The typical approach to such analysis would start from assuming that the coupling between driver and target is free from external influences. However, since sawteeth can occur naturally and constitute a confounding factor in the analysis, by relaxing such an assumption a more realistic description of the system can emerge. The use of the conditional joint recurrence plots, complemented by the conditional transfer entropy, has provided further evidences supporting the effective influence of the pacing on the fast ions populations of both the minority and of the main plasma species in H-mode plasmas. The results highlight specific physical factors affecting the efficiency of the pacing and are in agreement with modelling estimates. The analysis performed then paves the way for future studies on more recent DT pulses performed at JET, and on data from other synchronization experiments.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{2063,

title = {Energy-selective confinement of fusion-born alpha particles during internal relaxations in a tokamak plasma},

author = {A. Bierwage and K. Shinohara and Y. O. Kazakov and V. G. Kiptily and Ph. Lauber and M. Nocente and Z. Stancar and S. Sumida and M. Yagi and J. Garcia and S. Ide and JET contributors},

year  = {2022},

date = {2022-07-01},

journal = {Nature Communications},

volume = {13},

number = {3941},

abstract = {Long-pulse operation of a self-sustained fusion reactor using toroidal magnetic containment requires control over the content of alpha particles produced by D-T fusion reactions. On the one hand, MeV-class alpha particles must stay confined to heat the plasma. On the other hand, decelerated helium ash must be expelled before diluting the fusion fuel. Here, we report results of kinetic-magnetohydrodynamic hybrid simulations of a large tokamak plasma that confirm the existence of a parameter window where such energy-selective confinement can be accomplished by exploiting internal relaxation events known as sawtooth crashes. The physical picture — a synergy between magnetic geometry, optimal crash duration and rapid particle motion — is completed by clarifying the role of magnetic drifts. Besides causing asymmetry between co- and counter-going particle populations, magnetic drifts determine the size of the confinement window by dictating where and how much reconnection occurs in particle orbit topology.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{2060,

title = {Recent progress in L-H transition studies at JET: tritium, helium, hydrogen and deuterium},

author = {E. R. Solano and E. Delabie and G. Birkenmeier and C. Silva and J. C. Hillesheim and P. Vincenzi and A. H. Nielsen and J. Juul Rasmussen and A. Baciero and S. Aleiferis and I. Balboa and A. Boboc and C. Bourdelle and I. S. Carvalho and P. Carvalho and M. Chernyshova and R. Coelho and T. Craciunescu and R. Dumont and P. Dumortier and E. de Luna and J. Flanagan and M. Fontana and J. M. Fontdecaba and L. Frassinetti and D. Gallart and J. Garcia and E. Giovannozzi and C. Giroud and W. Gromelski and R. Henriques and L. Horvath and P. Jacquet and I. Jepu and A. Kappatou and D. L. Keeling and D. King and E. Kowalska-Strzęciwilk and M. Lennholm and E. Lerche and E. Litherland-Smith and V. Kiptily and K. Kirov and A. Loarte and B. Lomanowski and C. F. Maggi and M. J. Mantsinen and A. Manzanares and M. Maslov and A. G. Meigs and I. Monakhov and R. B. Morales and D. Nina and C. Noble and V. Parail and F. Parra Diaz and E. Pawelec and G. Pucella and D. Réfy and E. Righi-Steele and F. G. Rimini and T. Robinson and S. Saarelma and M. Sertoli and A. Shaw and S. Silburn and P. Sirén and Ž. Štancar and H. Sun and G. Szepesi and D. Taylor and E. Tholerus and S. Vartanian and G. Verdoolaege and B. Viola and H. Weisen and T. Wilson and JET Contributors},

url = {https://doi.org/10.1088/1741-4326/ac4ed8},

doi = {10.1088/1741-4326/ac4ed8},

year  = {2022},

date = {2022-07-01},

journal = {Nuclear Fusion},

volume = {62},

number = {7},

pages = {076026},

publisher = {IOP Publishing},

abstract = {We present an overview of results from a series of L–H transition experiments undertaken at JET since the installation of the ITER-like-wall (JET-ILW), with beryllium wall tiles and a tungsten divertor. Tritium, helium and deuterium plasmas have been investigated. Initial results in tritium show ohmic L–H transitions at low density and the power threshold for the L–H transition (P LH) is lower in tritium plasmas than in deuterium ones at low densities, while we still lack contrasted data to provide a scaling at high densities. In helium plasmas there is a notable shift of the density at which the power threshold is minimum () to higher values relative to deuterium and hydrogen references. Above (He) the L–H power threshold at high densities is similar for D and He plasmas. Transport modelling in slab geometry shows that in helium neoclassical transport competes with interchange-driven transport, unlike in hydrogen isotopes. Measurements of the radial electric field in deuterium plasmas show that E r shear is not a good indicator of proximity to the L–H transition. Transport analysis of ion heat flux in deuterium plasmas show a non-linearity as density is decreased below . Lastly, a regression of the JET-ILW deuterium data is compared to the 2008 ITPA scaling law.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{2058,

title = {A novel measurement of marginal Alfvén eigenmode stability during high power auxiliary heating in JET},

author = {R. A. Tinguely and N. Fil and P. G. Puglia and S. Dowson and M. Porkolab and V. Guillemot and M. Podesta and M. Baruzzo and R. Dumont and A. Fasoli and M. Fitzgerald and Y. O. Kazakov and M. F. F. Nave and M. Nocente and J. Ongena and S. E. Sharapov and Ž. Štancar and JET Contributors},

url = {https://doi.org/10.1088/1741-4326/ac3c84},

doi = {10.1088/1741-4326/ac3c84},

year  = {2022},

date = {2022-07-01},

journal = {Nuclear Fusion},

volume = {62},

number = {7},

pages = {076001},

publisher = {IOP Publishing},

abstract = {The interaction of Alfvén eigenmodes (AEs) and energetic particles is one of many important factors determining the success of future tokamaks. In JET, eight in-vessel antennas were installed to actively probe stable AEs with frequencies ranging 25–250 kHz and toroidal mode numbers |n| < 20. During the 2019–2020 deuterium campaign, almost 7500 resonances and their frequencies f 0, net damping rates γ < 0, and toroidal mode numbers were measured in almost 800 plasma discharges. From a statistical analysis of this database, continuum and radiative damping are inferred to increase with edge safety factor, edge magnetic shear, and when including non-ideal effects. Both stable AE observations and their associated damping rates are found to decrease with |n|. Active antenna excitation is also found to be ineffective in H-mode as opposed to L-mode; this is likely due to the increased edge density gradient's effect on accessibility and ELM-related noise's impact on mode identification. A novel measurement is reported of a marginally stable, edge-localized ellipticity-induced AE probed by the antennas during high-power auxiliary heating (ion cyclotron resonance heating and neutral beam injection) up to 25 MW. NOVA-K kinetic-MHD simulations show good agreement with experimental measurements of f 0, γ, and n, indicating the dominance of continuum and electron Landau damping in this case. Similar experimental and computational studies are planned for the recent hydrogen and ongoing tritium campaigns, in preparation for the upcoming DT campaign.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{2062,

title = {Status and future development of Heating and Current Drive for the EU DEMO},

author = {M. Q. Tran and P. Agostinetti and G. Aiello and K. Avramidis and B. Baiocchi and M. Barbisan and V. Bobkov and S. Briefi and A. Bruschi and R. Chavan and I. Chelis and Ch. Day and R. Delogu and B. Ell and F. Fanale and A. Fassina and U. Fantz and H. Faugel and L. Figini and D. Fiorucci and R. Friedl and Th. Franke and G. Gantenbein and S. Garavaglia and G. Granucci and S. Hanke and J. -P. Hogge and C. Hopf and A. Kostic and S. Illy and Z. Ioannidis and J. Jelonnek and J. Jin and G. Latsas and F. Louche and V. Maquet and R. Maggiora and A. Messiaen and D. Milanesio and A. Mimo and A. Moro and R. Ochoukov and J. Ongena and I. G. Pagonakis and D. Peponis and A. Pimazzoni and R. Ragona and N. Rispoli and T. Ruess and T. Rzesnicki and T. Scherer and P. Spaeh and G. Starnella and D. Strauss and M. Thumm and W. Tierens and I. Tigelis and C. Tsironis and M. Usoltceva and D. Van Eester and F. Veronese and P. Vincenzi and F. Wagner and C. Wu and F. Zeus and W. Zhang},

url = {https://www.sciencedirect.com/science/article/pii/S0920379622001557},

doi = {https://doi.org/10.1016/j.fusengdes.2022.113159},

issn = {0920-3796},

year  = {2022},

date = {2022-07-01},

journal = {Fusion Engineering and Design},

volume = {180},

pages = {113159},

abstract = {The European DEMO is a pulsed device with pulse length of 2 hours. The functions devoted to the heating and current drive system are: plasma breakdown, plasma ramp-up to the flat-top where fusion reactions occur, the control of the plasma during the flat-top phase, and finally the plasma ramp-down. The EU-DEMO project was in a Pre-Concept Design Phase during 2014-2020, meaning that in some cases, the design values of the device and the precise requirements from the physics point of view were not yet frozen. A total of 130 MW was considered for the all phases of the plasma: in the flat top, 30 MW is required for neoclassical tearing modes (NTM) control, 30 MW for burn control, and 70 MW for the control of thermal instability (TI), without any specific functions requested from each system, Electron Cyclotron (EC), Ion Cyclotron (IC), or Neutral Beam (NB) Injection. At the beginning of 2020, a strategic decision was taken, to consider EC as the baseline for the next phase (in 2021 and beyond). R&D on IC and NB will be risk mitigation measures. In parallel with progresses in Physics modelling, a decision point on the heating strategy will be taken by 2024. This paper describes the status of the R&D development during the period 2014-2020. It assumes that the 3 systems EC, IC and NB will be needed. For integration studies, they are assumed to be implemented at a power level of at least 50 MW. This paper describes in detail the status reached by the EC, IC and NB at the end of 2020. It will be used in the future for further development of the baseline heating method EC, and serves as starting point to further develop IC and NB in areas needed for these systems to be considered for DEMO.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{2061,

title = {Investigation of plasma wall interactions between tungsten plasma facing components and helium plasmas in the WEST tokamak},

author = {E. Tsitrone and B. Pegourie and J. P. Gunn and E. Bernard and V. Bruno and Y. Corre and L. Delpech and M. Diez and D. Douai and A. Ekedahl and N. Fedorczak and A. Gallo and T. Loarer and S. Vartanian and J. Gaspar and M. Le Bohec and F. Rigollet and R. Bisson and S. Brezinsek and T. Dittmar and G. De Temmerman and A. Hakola and T. Wauters and M. Balden and M. Mayer and WEST Team},

url = {https://doi.org/10.1088/1741-4326/ac2ef3},

doi = {10.1088/1741-4326/ac2ef3},

year  = {2022},

date = {2022-07-01},

journal = {Nuclear Fusion},

volume = {62},

number = {7},

pages = {076028},

publisher = {IOP Publishing},

abstract = {ITER will operate with a tungsten divertor, a material featuring surface morphology changes when exposed to helium plasmas, in particular the formation of the so called tungsten fuzz under specific conditions. Investigating interactions between tungsten plasma facing components and helium plasmas in a tokamak environment is therefore a key point to consolidate predictions for the ITER divertor performance and lifetime. To this end, a dedicated helium campaign was performed in the full tungsten WEST tokamak, cumulating ∼2000 s of repetitive L mode discharges. It is shown that conditions for tungsten fuzz formation, as derived from linear devices experiments (incident helium energy E inc > 20 eV, helium fluence >1024 He/m2, surface temperature T surf > 700 $,^circ$C), were met in the outer strike point (OSP) area of the inertially cooled tungsten divertor elements of WEST. Preliminary inspection of the components after the campaign did not show visible signs of surface modification, but points to significant net erosion in the OSP area. An extensive post mortem analysis is now ongoing to confirm these first indications. These results underline that the complex balance between erosion/redeposition (in particular linked to impurities) and tungsten fuzz formation needs to be taken into account in tokamak conditions.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{2057,

title = {Recent progress in modeling ICRF-edge plasma interactions with application to ASDEX Upgrade},

author = {W. Zhang and R. Bilato and V. Bobkov and A. Cathey and A. Di Siena and M. Hoelzl and A. Messiaen and J. R. Myra and G. Suárez López and W. Tierens and M. Usoltceva and J. C. Wright and ASDEX Upgrade Team and EUROfusion MST1 Team},

url = {https://doi.org/10.1088/1741-4326/ac38c8},

doi = {10.1088/1741-4326/ac38c8},

year  = {2022},

date = {2022-07-01},

journal = {Nuclear Fusion},

volume = {62},

number = {7},

pages = {075001},

publisher = {IOP Publishing},

abstract = {This paper summarizes recent progress in modeling the interaction between ion cyclotron range of frequency (ICRF) waves and edge plasma with application to ASDEX Upgrade. The basic theories, the development of ICRF and edge plasma codes, the integrated modeling methods and some key results are reviewed. In particular, the following physical aspects are discussed: (1) ICRF power coupling; (2) slow wave propagation; (3) ICRF-rectified sheath; (4) ICRF-induced convection; (5) ICRF-edge turbulence interaction. Moreover, comprehensive integrated modeling strategies by including all necessary codes in one package and solving multiple physical issues self-consistently are discussed.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{2059,

title = {Fusion power predictions for βN ≈ 1.8 baseline scenario with 50-50 D-T fuel mix and NBI injection in preparation to D-T operations at JET},

author = {V. K. Zotta and L. Garzotti and F. J. Casson and D. Frigione and F. Köchl and E. Lerche and P. Lomas and F. Rimini and M. Sertoli and D. Van Eester and R. Gatto and C. Mazzotta and G. Pucella and JET Contributors},

url = {https://doi.org/10.1088/1741-4326/ac5f19},

doi = {10.1088/1741-4326/ac5f19},

year  = {2022},

date = {2022-07-01},

journal = {Nuclear Fusion},

volume = {62},

number = {7},

pages = {076024},

publisher = {IOP Publishing},

abstract = {The fusion performance of ELMy H-mode 50–50 deuterium–tritium (DT) plasmas with 50–50 DT NBI injection and q 95 ≈ 3 and β N ≈ 1.8 (also referred to as medium-β N baseline scenario in the rest of this paper) are predicted with the JINTRAC suite of codes and the QuaLiKiZ transport model. The predictions are based on the analysis of plasmas from the first DT campaign on JET in 1997 (DTE1) and pure deuterium plasmas developed at JET in preparation for the DT experimental campaign in 2021 (DTE2), after the installation of a Be/W ITER-like wall in 2011. The sensitivity of the predictions to plasma parameters such as current, toroidal field, pedestal confinement and impurity content are analysed together with the sensitivity to the amount of auxiliary heating power available. The simulations indicate that a fusion power of 10 MW should be achievable under a fairly wide range of assumptions, provided that the auxiliary heating power is around or above 38 MW. Higher fusion power approaching 15 MW could be achievable for this value of β N only for particularly pure plasmas and with 40 MW of additional heating power.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{2052,

title = {Influence of the impurities in the hybrid discharges with high power in JET ILW},

author = {I. Ivanova-Stanik and C. D. Challis and A. Chomiczewska and J. Hobirk and A. Huber and A. Kappatou and E. Lerche and G. Telesca and R. Zagórski and JET Contributors},

url = {https://doi.org/10.1088/1741-4326/ac2a89},

doi = {10.1088/1741-4326/ac2a89},

year  = {2022},

date = {2022-06-01},

journal = {Nuclear Fusion},

volume = {62},

number = {6},

pages = {066010},

publisher = {IOP Publishing},

abstract = {The aim of this paper is to numerically study the influences of the impurities on the high power hybrid discharges in the JET ITER-like wall (ILW) configuration in the DD and deuterium–tritium (DT) scenarios. Numerical simulations with the COREDIV code of hybrid discharges with 32 MW auxiliary heating, 2.2 MA plasma current and 2.8 T toroidal magnetic field in the ILW corner configuration are presented. In the simulations five impurity species are used: intrinsic: beryllium (Be) and nickel (Ni) from the side walls, helium (He) from DT reaction, tungsten (W) from divertor and extrinsic neon (Ne) or argon (Ar) by gas puff. The extrapolation of the DD discharges to DT plasmas at the original input power of 32 MW and taking into account only the thermal component of the alpha-power, does not show any significant difference regarding the power to the target with respect to the DD case. Simulations show that sputtering due to D and T is negligible. In contrast, the simulations at auxiliary heating 39 MW show that the power to the target is possibly too high to be sustained for about 5 s by strike-point sweeping alone without any control by Ne seeding. The tungsten is produced mainly by Ni, Be and seeded impurities.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{2054,

title = {Excitation of Alfvén eigenmodes by fusion-born alpha-particles in D-3 He plasmas on JET},

author = {V G Kiptily and Y. O. Kazakov and M Nocente and J. Ongena and F Belli and M Dreval and T Craciunescu and J Eriksson and M Fitzgerald and L Giacomelli and V Goloborodko and M V Iliasova and E M Khilkevitch and D Rigamonti and A Sahlberg and M Salewski and A E Shevelev and J Garcia and H J C Oliver and S E Sharapov and Z Stancar and H Weisen},

url = {https://doi.org/10.1088/1361-6587/ac5d9e},

doi = {10.1088/1361-6587/ac5d9e},

year  = {2022},

date = {2022-06-01},

journal = {Plasma Physics and Controlled Fusion},

volume = {64},

number = {6},

pages = {064001},

publisher = {IOP Publishing},

abstract = {Alfvén eigenmode (AE) instabilities driven by alpha-particles have been observed in D-3He fusion experiments on the Joint European Torus (JET) with the ITER-like wall. For the efficient generation of fusion alpha-particles from D-3He fusion reaction, the three-ion radio frequency scenario was used to accelerate the neutral beam injection 100 keV deuterons to higher energies in the core of mixed D-3He plasmas at high concentrations of 3He. A large variety of fast-ion driven magnetohydrodynamic modes were observed, including the elliptical Alfvén eigenmodes (EAEs) with mode numbers n = −1 and axisymmetric modes with n = 0 in the frequency range of EAEs. The simultaneous observation of these modes indicates the presence of rather strong alpha-particle population in the plasma with a `bump-on-tail' shaped velocity distribution. Linear stability analysis and Fokker–Planck calculations support the observations. Experimental evidence of the AEs excitation by fusion-born alpha-particles in the D-3He plasma is provided by neutron and gamma-ray diagnostics as well as fast-ion loss measurements. We discuss an experimental proposal for the planned full-scale D-T plasma experiments on JET based on the physics insights gained from these experiments.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{2053,

title = {Experimental study on the role of the target electron temperature as a key parameter linking recycling to plasma performance in JET-ILWast},

author = {B. Lomanowski and M. Dunne and N. Vianello and S. Aleiferis and M. Brix and J. Canik and I. S. Carvalho and L. Frassinetti and D. Frigione and L. Garzotti and M. Groth and A. Meigs and S. Menmuir and M. Maslov and T. Pereira and C. Perez Thun and M. Reinke and D. Refy and F. Rimini and G. Rubino and P. A. Schneider and G. Sergienko and A. Uccello and D. Van Eester and JET Contributors},

url = {https://doi.org/10.1088/1741-4326/ac5668},

doi = {10.1088/1741-4326/ac5668},

year  = {2022},

date = {2022-06-01},

journal = {Nuclear Fusion},

volume = {62},

number = {6},

pages = {066030},

publisher = {IOP Publishing},

abstract = {Changes in global and edge plasma parameters (H 98(y,2), dimensionless collisionality ν *, core density peaking, separatrix density n e,sep) with variations in the D2 fueling rate and divertor configuration are unified into a single trend when mapped to ⟨T e,ot⟩, the spatially averaged spectroscopically derived outer target electron temperature. Dedicated JET with the ITER-like wall (JET-ILW) experiments in combination with an extended JET-ILW database of unseeded low-triangularity H-mode plasmas spanning a wide range of D2 fueling rates, I p, B t and heating power have demonstrated the importance of ⟨T e,ot⟩ as a key physics parameter linking the recycling particle source and detachment with plasma performance. The remarkably robust H 98(y,2) trend with ⟨T e,ot⟩ is connected to a strong inverse correlation between ⟨T e,ot⟩, n e,sep and ν *, thus directly linking changes in the divertor recycling moderated by ⟨T e,ot⟩ with the previously established relationship between ν *, core density peaking and core pressure resulting in a degradation in core plasma performance with decreasing ⟨T e,ot⟩ (increasing ν *). A strong inverse correlation between the separatrix to pedestal density ratio, n e,sep/n e,ped, and ⟨T e,ot⟩ is also established, with the rise in n e,sep/n e,ped saturating at ⟨T e,ot⟩ > 10 eV. A strong reduction in H 98(y,2) is observed as ⟨T e,ot⟩ is driven from 30 to 10 eV via additional D2 gas fueling, while the divertor remains attached. Consequently, the pronounced performance degradation in attached divertor conditions has implications for impurity seeding radiative divertor scenarios, in which H 98(y,2) is already low (∼0.7) before impurities are injected into the plasma since moderate gas fueling rates are required to promote high divertor neutral pressure. A favorable pedestal pressure, p e,ped, dependence on I p has also been observed, with an overall increase in p e,ped at I p = 3.4 MA as ⟨T e,ot⟩ is driven down from attached to high-recycling divertor conditions. In contrast, p e,ped is reduced with decreasing ⟨T e,ot⟩ in the lower I p branches. Further work is needed to (i) clarify the potential role of edge opacity on the observed favorable pedestal pressure I p scaling; as well as to (ii) project the global and edge plasma performance trends with ⟨T e,ot⟩ to reactor-scale devices to improve predictive capability of the coupling between recycling and confined plasma fueling in what are foreseen to be more opaque edge plasma conditions.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{2055,

title = {Enhanced performance in fusion plasmas through turbulence suppression by megaelectronvolt ions},

author = {S. Mazzi and J. Garcia and D. Zarzoso and Y. O. Kazakov and J. Ongena and M. Dreval and M. Nocente and Z. Stancar and G. Szepesi and J. Eriksson and A. Sahlberg and S. Benkadda and JET Contributors},

year  = {2022},

date = {2022-06-01},

journal = {Nature Physics},

volume = {18},

pages = {776-788},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{2051,

title = {Role of NBI fuelling in contributing to density peaking between the ICRH and NBI identity plasmas on JET},

author = {T. Tala and F. Eriksson and P. Mantica and A. Mariani and A. Salmi and E. R. Solano and I. S. Carvalho and A. Chomiczewska and E. Delabie and J. Ferreira and E. Fransson and L. Horvath and P. Jacquet and D. King and A. Kirjasuo and S. Leerink and E. Lerche and C. Maggi and M. Marin and M. Maslov and S. Menmuir and R. B. Morales and V. Naulin and M. F. F. Nave and H. Nordman and C. Perez Thun and P. A. Schneider and M. Sertoli and K. Tanaka and JET Contributors},

url = {https://doi.org/10.1088/1741-4326/ac5667},

doi = {10.1088/1741-4326/ac5667},

year  = {2022},

date = {2022-06-01},

journal = {Nuclear Fusion},

volume = {62},

number = {6},

pages = {066008},

publisher = {IOP Publishing},

abstract = {Density peaking has been studied between an ICRH and NBI identity plasma in JET. The comparison shows that 8 MW of NBI heating/fueling increases the density peaking by a factor of two, being R/L n = 0.45 for the ICRH pulse and R/L n = 0.93 for the NBI one averaged radially over ρ tor = 0.4, 0.8. The dimensionless profiles of q, ρ *, υ *, β n and T i/T e ≈ 1 were matched within 5% difference except in the central part of the plasma (ρ tor < 0.3). The difference in the curvature pinch (same q-profile) and thermo-pinch (T i = T e) between the ICRH and NBI discharges is virtually zero. Both the gyro-kinetic simulations and integrated modelling strongly support the experimental result where the NBI fuelling is the main contributor to the density peaking for this identity pair. It is to be noted here that the integrated modeling does not reproduce the measured electron density profiles, but approximately reproduces the difference in the density profiles between the ICRH and NBI discharge. Based on these modelling results and the analyses, the differences between the two pulses in impurities, fast ions (FIs), toroidal rotation and radiation do not cause any such changes in the background transport that would invalidate the experimental result where the NBI fuelling is the main contributor to the density peaking. This result of R/L n increasing by a factor of 2 per 8 MW of NBI power is valid for the ion temperature gradient dominated low power H-mode plasmas. However, some of the physics processes influencing particle transport, like rotation, turbulence and FI content scale with power, and therefore, the simple scaling on the role of the NBI fuelling in JET is not necessarily the same under higher power conditions or in larger devices.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{2050,

title = {Validation of realistic Monte Carlo plasma gamma-ray source on JET discharges},

author = {A. Zohar and M. Nocente and B. Kos and Z. Stancar and M. Rebai and D. Rigamonti and T. Craciunescu and M. Gorelenkova and Y. O. Kazakov and V. G. Kiptily and L. Snoj and M. Tardocchi and I. Lengar and JET Contributors},

url = {https://doi.org/10.1088/1741-4326/ac50c0},

doi = {10.1088/1741-4326/ac50c0},

year  = {2022},

date = {2022-06-01},

journal = {Nuclear Fusion},

volume = {62},

number = {6},

pages = {066004},

publisher = {IOP Publishing},

abstract = {A novel modelling methodology has been developed for the creation of a realistic plasma gamma-ray source for Monte Carlo transport simulations in the tokamak JET. The methodology couples the TRANSP code for plasma transport calculations with the MCNP Monte Carlo particle transport code, thus connecting plasma physics with gamma-ray transport. This paper presents the validation of the developed source methodology by comparing calculated gamma-ray spectra with measurements performed at JET. The validation focuses on gamma-ray spectra measured by the tangential gamma-ray spectrometer during two JET three ion RF scenario discharges, performed in the JET 2019 deuterium experimental campaign. For validation the calculated plasma gamma-ray spectrum was combined with the neutron induced prompt gamma-ray background, originating in the vacuum vessel, and scaled to absolute values calculating the total number of plasma gamma-ray and neutron emitting reactions. The comparison between calculated and measured gamma-ray spectra shows good agreement with the shape of the calculated gamma-ray spectra matching that of measurements for both studied discharges. Moreover, the calculated absolute values of the gamma-ray spectra were of the same order of magnitude at the position of the gamma-ray detector located at the end of a long line-of-sight in a biological shield. The comparison has validated the developed plasma gamma-ray source methodology for MCNP photon transport calculations at JET. The validation provides a basis for the developed plasma gamma-ray source to be used as a support for the development of future tokamaks such as DEMO.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{2047,

title = {Alfvén cascade eigenmodes above the TAE-frequency and localization of Alfvén modes in D–3 He plasmas on JET},

author = {M. Dreval and S. E. Sharapov and Y. O. Kazakov and J. Ongena and M. Nocente and R. Calado and R. Coelho and J. Ferreira and A. Figueiredo and M. Fitzgerald and J. Garcia and C. Giroud and N. C. Hawkes and V. G. Kiptily and F. Nabais and M. F. F. Nave and H. Weisen and T. Craciunescu and M. Salewski and Ž. Štancar and JET Contributors},

url = {https://doi.org/10.1088/1741-4326/ac45a4},

doi = {10.1088/1741-4326/ac45a4},

year  = {2022},

date = {2022-05-01},

journal = {Nuclear Fusion},

volume = {62},

number = {5},

pages = {056001},

publisher = {IOP Publishing},

abstract = {Various types of Alfvén eigenmodes (AEs) have been destabilized by fast ions over a broad frequency range from ∼80 kHz to ∼700 kHz in a series of JET experiments in mixed D–3He plasmas heated with the three-ion ICRF scenario (2020 Nocente et al Nucl. Fusion 60 124006). In this paper, we identify the radial localization of AEs using an X-mode reflectometer, a multiline interferometer and soft x-ray diagnostics. The analysis is focused on the most representative example of these measurements in JET pulse #95691, where two different types of Alfvén cascade (AC) eigenmodes were observed. These modes originate from the presence of a local minimum of the safety factor q min. In addition to ACs with frequencies below the frequency of toroidal Alfvén eigenmodes (TAEs), ACs with frequencies above the TAE frequency were destabilized by energetic ions. Both low- (f ≈ 80–180 kHz) and high-frequency (f ≈ 330–450 kHz) ACs were localized in the central regions of the plasma. The characteristics of the high-frequency ACs are investigated in detail numerically using HELENA, CSCAS and MISHKA codes. The resonant conditions for the mode excitation are found to be determined by passing ions of rather high energy of several hundred keV and similar to those established in JT-60U with negative-ion-based NBI (2005 Takechi et al Phys. Plasmas 12 082509). The computed radial mode structure is found to be consistent with the experimental measurements. In contrast to low-frequency ACs observed most often, the frequency of the high-frequency ACs decreases with time as the value of q min decreases. This feature is in a qualitative agreement with the analytical model of the high-frequency ACs in Breizman et al (2003 Phys. Plasmas 10 3649). The high-frequency AC could be highly relevant for future ITER and fusion reactor plasmas dominated by ∼MeV energetic ions, including a significant population of passing fast ions.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{2049,

title = {Maximising DT fusion power by optimising the plasma composition and beam choice in JET},

author = {D. Van Eester and E. Lerche and P Huynh and T Johnson and D Yadikin and Z. Stancar and S Aleiferis and D Frigione and L Garzotti and P Lomas and C Lowry and M Maslov},

url = {https://doi.org/10.1088/1361-6587/ac5a09},

doi = {10.1088/1361-6587/ac5a09},

year  = {2022},

date = {2022-05-01},

journal = {Plasma Physics and Controlled Fusion},

volume = {64},

number = {5},

pages = {055014},

publisher = {IOP Publishing},

abstract = {JET has a neutral beam injection as well as a radio frequency (RF) system for bringing plasmas to fusion-relevant temperatures. The former allows D as well as T birth energies of the order of 100–120 keV while the latter has the flexibility to heat a variety of populations by adjusting the antenna frequency. In this paper it is illustrated that—when the JET plasma is heated—the power harvested from D − T fusion reactions favours operating away from the 50–50 D − T balance and that exploiting pure D beams is more beneficial than combined D and T beams as well as pure T beams. Although beam heating dominates the overall behaviour in JET—as much more beam power than wave power can be coupled to the plasma—RF heating allows efficient heating of the very core.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{2048,

title = {Plasma physics and control studies planned in JT-60SA for ITER and DEMO operations and risk mitigation},

author = {M Yoshida and G Giruzzi and N Aiba and J F Artaud and J Ayllon-Guerola and L Balbinot and O Beeke and E Belonohy and P Bettini and W Bin and A Bierwage and T Bolzonella and M Bonotto and C Boulbe and J Buermans and M Chernyshova and S Coda and R Coelho and S Davis and C Day and G De Tommasi and M Dibon and A Ejiri and G Falchetto and A Fassina and B Faugeras and L Figini and M Fukumoto and S Futatani and K Galazka and J Garcia and M Garcia-Muñoz and L Garzotti and L Giacomelli and L Giudicotti and S Hall and N Hayashi and C Hoa and M Honda and K Hoshino and M Iafrati and A Iantchenko and S Ide and S Iio and R Imazawa and S Inoue and A Isayama and E Joffrin and K Kamiya and Y Ko and M Kobayashi and T Kobayashi and G Kocsis and A Kovacsik and T Kurki-Suonio and B Lacroix and P Lang and Ph Lauber and A Louzguiti and E Luna and G Marchiori and M Mattei and A Matsuyama and S Mazzi and A Mele and F Michel and Y Miyata and J Morales and P Moreau and A Moro and T Nakano and M Nakata and E Narita and R Neu and S Nicollet and M Nocente and S Nowak and F P Orsitto and V Ostuni and Y Ohtani and N Oyama and R Pasqualotto and B Pégourié and E Perelli and L Pigatto and C Piccinni and A Pironti and P Platania and B Ploeckl and D Ricci and P Roussel and G Rubino and R Sano and K Särkimäki and K Shinohara and S Soare and C Sozzi and S Sumida and T Suzuki and Y Suzuki and T Szabolics and T Szepesi and Y Takase and M Takech and N Tamura and K Tanaka and H Tanaka and M Tardocchi and A Terakado and H Tojo and T Tokuzawa and A Torre and N Tsujii and H Tsutsui and Y Ueda and H Urano and M Valisa and M Vallar and J Vega and F Villone and T Wakatsuki and T. Wauters and M Wischmeier and S Yamoto and L Zani},

url = {https://doi.org/10.1088/1361-6587/ac57a0},

doi = {10.1088/1361-6587/ac57a0},

year  = {2022},

date = {2022-05-01},

journal = {Plasma Physics and Controlled Fusion},

volume = {64},

number = {5},

pages = {054004},

publisher = {IOP Publishing},

abstract = {A large superconducting machine, JT-60SA has been constructed to provide major contributions to the ITER program and DEMO design. For the success of the ITER project and fusion reactor, understanding and development of plasma controllability in ITER and DEMO relevant higher beta regimes are essential. JT-60SA has focused the program on the plasma controllability for scenario development and risk mitigation in ITER as well as on investigating DEMO relevant regimes. This paper summarizes the high research priorities and strategy for the JT-60SA project. Recent works on simulation studies to prepare the plasma physics and control experiments are presented, such as plasma breakdown and equilibrium controls, hybrid and steady-state scenario development, and risk mitigation techniques. Contributions of JT-60SA to ITER and DEMO have been clarified through those studies.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{2043,

title = {Beta-induced Alfvén eigenmodes and geodesic acoustic modes in the presence of strong tearing activity during the current ramp-down on JET},

author = {G Pucella and E Alessi and F Auriemma and P Buratti and M V Falessi and E Giovannozzi and F Zonca and M Baruzzo and C D Challis and R Dumont and D Frigione and L Garzotti and J Hobirk and A Kappatou and D L Keeling and D King and V G Kiptily and E. Lerche and P J Lomas and M Maslov and I Nunes and F Rimini and P Sirén and C Sozzi and M F Stamp and Z Stancar and H Sun and D. Van Eester and M Zerbini},

url = {https://doi.org/10.1088/1361-6587/ac4ade},

doi = {10.1088/1361-6587/ac4ade},

year  = {2022},

date = {2022-04-01},

journal = {Plasma Physics and Controlled Fusion},

volume = {64},

number = {4},

pages = {045023},

publisher = {IOP Publishing},

abstract = {The analysis of the current ramp-down phase of JET plasmas has revealed the occurrence of additional magnetic oscillations in pulses characterized by large magnetic islands. The frequencies of these oscillations range from 5 to , being well below the toroidal gap in the Alfvén continuum and of the same order as the low-frequency gap opened by plasma compressibility. The additional oscillations only appear when the magnetic island width exceeds a critical threshold, suggesting that the oscillations could tap their energy from the tearing mode (TM) by a non-linear coupling mechanism. A possible role of fast ions in the excitation process can be excluded, being the pulse phase considered in the observations characterized by very low additional heating. The calculation of the coupled Alfvén–acoustic continuum in toroidal geometry suggests the possibility of beta-induced Alfvén eigenmodes (BAEs) rather than beta-induced Alfvén–acoustic eigenmodes. As a main novelty compared to previous work, the analysis of the electron temperature profiles from electron cyclotron emission has shown the simultaneous presence of magnetic islands on different rational surfaces in pulses with multiple magnetic oscillations in the low-frequency gap of the Alfvén continuum. This observation supports the hypothesis of different BAE with toroidal mode number n = 1 associated with different magnetic islands. As another novelty, the observation of magnetic oscillations with n = 2 in the BAE range is reported for the first time in this work. Some pulses, characterized by slowly rotating magnetic islands, exhibit additional oscillations with n = 0, likely associated with geodesic acoustic modes (GAMs), and a cross-spectral bicoherence analysis has confirmed a non-linear interaction between TM, BAE and GAM, with the novelty of the observation of multiple triplets (twin BAEs plus GAM), due to the simultaneous presence of several magnetic islands in the plasma.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{2044,

title = {Isotope removal experiment in JET-ILW in view of T-removal after the 2nd DT campaign at JET},

author = {T. Wauters and D Matveev and D Douai and J Banks and R Buckingham and I S Carvalho and E Cal and E Delabie and T Dittmar and J Gaspar and A Huber and I Jepu and J Karhunen and S Knipe and M Maslov and A Meigs and I Monakhov and V S Neverov and C Noble and G Papadopoulos and E Pawelec and S Romanelli and A Shaw and H Sheikh and S Silburn and A Widdowson and P Abreu and S Aleiferis and J Bernardo and D Borodin and S Brezinsek and J Buermans and P Card and P Carvalho and K. Crombé and S Dalley and L Dittrich and C Elsmore and M Groth and S Hacquin and R Henriques and V Huber and P Jacquet and X Jiang and G Jones and D Keeling and D Kinna and K Kirov and M Kovari and E Kowalska-Strzeciwilk and A B Kukushkin and H Kumpulainen and E Litherland-Smith and P Lomas and T Loarer and C Lowry and A Manzanares and A Patel and A Peacock and P Petersson and N Petrella and R A Pitts and J Romazanov and M Rubel and P Siren and T Smart and E R Solano and Ž Štancar and J Varje and A Whitehead and S Wiesen and M Zerbini and M Zlobinski},

url = {https://doi.org/10.1088/1402-4896/ac5856},

doi = {10.1088/1402-4896/ac5856},

year  = {2022},

date = {2022-04-01},

journal = {Physica Scripta},

volume = {97},

number = {4},

pages = {044001},

publisher = {IOP Publishing},

abstract = {A sequence of fuel recovery methods was tested in JET, equipped with the ITER-like beryllium main chamber wall and tungsten divertor, to reduce the plasma deuterium concentration to less than 1% in preparation for operation with tritium. This was also a key activity with regard to refining the clean-up strategy to be implemented at the end of the 2nd DT campaign in JET (DTE2) and to assess the tools that are envisaged to mitigate the tritium inventory build-up in ITER. The sequence began with 4 days of main chamber baking at 320 $,^circ$C, followed by a further 4 days in which Ion Cyclotron Wall Conditioning (ICWC) and Glow Discharge Conditioning (GDC) were applied with hydrogen fuelling, still at 320 $,^circ$C, followed by more ICWC while the vessel cooled gradually from 320 $,^circ$C to 225 $,^circ$C on the 4th day. While baking alone is very efficient at recovering fuel from the main chamber, the ICWC and GDC sessions at 320 $,^circ$C still removed slightly higher amounts of fuel than found previously in isotopic changeover experiments at 200 $,^circ$C in JET. Finally, GDC and ICWC are found to have similar removal efficiency per unit of discharge energy. The baking week with ICWC and GDC was followed by plasma discharges to remove deposited fuel from the divertor. Raising the inner divertor strike point up to the uppermost accessible point allowed local heating of the surfaces to at least 800 $,^circ$C for the duration of this discharge configuration (typically 18 s), according to infra-red thermography measurements. In laboratory thermal desorption measurements, maintaining this temperature level for several minutes depletes thick co-deposit samples of fuel. The fuel removal by 14 diverted plasma discharges is analysed, of which 9, for 160 s in total, with raised inner strike point. The initial D content in these discharges started at the low value of 3%–5%, due to the preceding baking and conditioning sequence, and reduced further to 1%, depending on the applied configuration, thus meeting the experimental target.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{2039,

title = {Status of the WEST travelling wave array antenna design and results from the high power mock-up},

author = {R. Ragona and F. Durodie and A. Messiaen and J. Ongena and M. Van Schoor and S. Agzaf and T. Batal and J. -M. Bernard and X. Courtois and J. -M. Delaplanche and R. Dumont and F. Durand and F. Faisse and M. Firdaouss and L. Gargiulo and P. Garibaldi and J. Hillairet and T. Hoang and G. Lombard and P. Mollard and Z. Chen and Y. Song and H. Xu and Q. Yang and C. Yu},

url = {https://doi.org/10.1088/1741-4326/ac4467},

doi = {10.1088/1741-4326/ac4467},

year  = {2022},

date = {2022-02-01},

journal = {Nuclear Fusion},

volume = {62},

number = {2},

pages = {026046},

publisher = {IOP Publishing},

abstract = {This paper presents the current status of the WEST TWA antenna, its mock-up and a possible extrapolation to DEMO. The updated WEST TWA design has a reduced antenna length and features feeding and mechanical support from a single vessel port. A mock-up of the WEST TWA antenna was designed in 2019, manufactured during 2020 and installed in the TITAN test facility at the beginning of 2021. The results of the mock-up at low and high power, its diagnostic system and the prospects are explained. Extensions towards a TWA antenna for WEST and a possible TWA system for the future DEMO tokamak reactor are briefly discussed.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{2037,

title = {Plasma-surface interaction in the stellarator W7-X: conclusions drawn from operation with graphite plasma-facing components},

author = {S. BrezƖnsek and C. P. Dhard and M. Jakubowski and R. König and S. Masuzaki and M. Mayer and D. Naujoks and J. Romazanov and K. Schmid and O. Schmitz and D. Zhao and M. Balden and R. Brakel and B. Butterschoen and T. Dittmar and P. Drews and F. Effenberg and S. Elgeti and O. Ford and E. Fortuna-Zalesna and G. Fuchert and Y. Gao and A. Goriaev and A. Hakola and T. Kremeyer and M. Krychowiak and Y. Liang and Ch. Linsmeier and R. Lunsford and G. Motojima and R. Neu and O. Neubauer and J. Oelmann and P. Petersson and M. Rasinski and M. Rubel and S. Sereda and G. Sergienko and T. Sunn Pedersen and T. Vuoriheimo and E. Wang and T. Wauters and V. Winters and M. Zhao and R. Yi and W7-X Team},

url = {https://doi.org/10.1088/1741-4326/ac3508},

doi = {10.1088/1741-4326/ac3508},

year  = {2022},

date = {2022-01-01},

journal = {Nuclear Fusion},

volume = {62},

number = {1},

pages = {016006},

publisher = {IOP Publishing},

abstract = {W7-X completed its plasma operation in hydrogen with island divertor and inertially cooled test divertor unit (TDU) made of graphite. A substantial set of plasma-facing components (PFCs), including in particular marker target elements, were extracted from the W7-X vessel and analysed post-mortem. The analysis provided key information about underlying plasma–surface interactions (PSI) processes, namely erosion, transport, and deposition as well as fuel retention in the graphite components. The net carbon (C) erosion and deposition distribution on the horizontal target (HT) and vertical target (VT) plates were quantified and related to the plasma time in standard divertor configuration with edge transform ι = 5/5, the dominant magnetic configuration of the two operational phases (OP) with TDU. The operation resulted in integrated high net C erosion rate of 2.8 mg s−1 in OP1.2B over 4809 plasma seconds. Boronisations reduced the net erosion on the HT by about a factor 5.4 with respect to OP1.2A owing to the suppression of oxygen (O). In the case of the VT, high peak net C erosion of 11 μm at the strike line was measured during OP1.2B which converts to 2.5 nm s−1 or 1.4 mg s−1 when related to the exposed area of the target plate and the operational time in standard divertor configuration. PSI modelling with ERO2.0 and WallDYN-3D is applied in an interpretative manner and reproduces the net C erosion and deposition pattern at the target plates determined by different post-mortem analysis techniques. This includes also the 13C tracer deposition from the last experiment of OP1.2B with local 13CH4 injection through a magnetic island in one half module. The experimental findings are used to predict the C erosion, transport, and deposition in the next campaigns aiming in long-pulse operation up to 1800 s and utilising the actively cooled carbon-fibre composite (CFC) divertor currently being installed. The CFC divertor has the same geometrical design as the TDU and extrapolation depends mainly on the applied plasma boundary. Extrapolation from campaign averaged information obtained in OP1.2B reveals a net erosion of 7.6 g per 1800 s for a typical W7-X attached divertor plasma in hydrogen.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{2038,

title = {The geometry of the ICRF-induced wave-SOL interaction. A multi-machine experimental review in view of the ITER operation},

author = {L. Colas and G. Urbanczyk and M. Goniche and J. Hillairet and J. -M. Bernard and C. Bourdelle and N. Fedorczak and C. Guillemaut and W. Helou and V. Bobkov and R. Ochoukov and Ph. Jacquet and E. Lerche and X. Zhang and C. Qin and C. C. Klepper and C. Lau and B. Van Compernolle and S. J. Wukitch and Y. Lin and M. Ono and JET Contributors and ASDEX Upgrade Team and EAST Team and WEST Team and ITPA IOS},

url = {https://doi.org/10.1088/1741-4326/ac35f9},

doi = {10.1088/1741-4326/ac35f9},

year  = {2022},

date = {2022-01-01},

journal = {Nuclear Fusion},

volume = {62},

number = {1},

pages = {016014},

publisher = {IOP Publishing},

abstract = {As part of ITPA-Integrated Operational Scenario activities, this contribution reviews recent experimental characterizations of radio-frequency (RF)-induced scrape-off layer (SOL) modifications of various tokamaks worldwide and of the LArge Plasma Device at UCLA. The phenomenology, as observed using a large variety of measurement techniques, is consistent with expectations from RF sheath rectification. Emphasis is then put on the complex three-dimensional (3D) spatial patterns of the RF–SOL interaction, in relation to the magnetic topology and the spatial distribution of RF currents over the metallic structures surrounding the RF wave launchers. Dependence on the local plasma parameters in the antenna vicinity is also briefly addressed. The final part discusses implications for future devices.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{2032,

title = {Plasma-wall interaction studies in W7-X: main results from the recent divertor operations},

author = {C P Dhard and S Brezinsek and M Mayer and D Naujoks and S Masuzaki and D Zhao and R Yi and J Oelmann and K Schmid and J Romazanov and C Pardanaud and M Kandler and A K Kharwandikar and G Schlisio and O Volzke and H Grote and Y Gao and L Rudischhauser and A. Goriaev and T. Wauters and A Kirschner and S Sereda and E Wang and M Rasinski and T Dittmar and G Motojima and D Hwangbo and S Kajita and M Balden and V V Burwitz and R Neu and Ch Linsmeier and W7-X Team},

url = {https://doi.org/10.1088/1402-4896/ac35c0},

doi = {10.1088/1402-4896/ac35c0},

year  = {2021},

date = {2021-12-01},

journal = {Physica Scripta},

volume = {96},

number = {12},

pages = {124059},

publisher = {IOP Publishing},

abstract = {Wendelstein 7-X (W7-X) is an optimized stellarator with a 3-dimensional five-fold modular geometry. The plasma-wall-interaction (PWI) investigations in the complex 3D geometry of W7-X were carried out by in situ spectroscopic observations, exhaust gas analysis and post-mortem measurements on a large number of plasma-facing components extracted after campaigns. The investigations showed that the divertor strike line areas on the divertor targets appeared to be the major source of carbon impurities. After multistep erosion and deposition events, carbon was found to be deposited largely at the first wall components, with thick deposits of >1 μm on some baffle tiles, moderate deposits on toroidal closure tiles and thin deposits at the heat shield tiles and the outer wall panels. Some amount of the eroded carbon was pumped out via the vacuum pumps as volatile hydrocarbons and carbon oxides (CO, CO2) formed due to the chemical processes. Boron was introduced by three boronizations and one boron powder injection experiment. Thin boron-dominated layers were found on the inner heat shield and the outer wall panels, some boron was also found at the test divertor unit and in redeposited layers together with carbon. Local erosion/deposition and global migration processes were studied using field-line transport simulations, analytical estimations, 3D-WallDYN and ERO2.0 modeling in standard magnetic field configuration.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}