Jef Ongena’s personal page

@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{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{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{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{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{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{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{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{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{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{2027,

title = {First experiments on plasma production using field-aligned ICRF fast wave antennas in the large helical device},

author = {S. Kamio and V. E. Moiseenko and Yu. V. Kovtun and H. Kasahara and K. Saito and R. Seki and M. Kanda and G. Nomura and T. Seki and Y. Takemura and T. Wauters and R. Brakel and A. Dinklage and D. Hartmann and H. Laqua and T. Stange and A. Alonso and S. Lazerson and R. Ragona and J. Ongena and H. Thomsen and G. Fuchert and I. E. Garkusha},

url = {https://doi.org/10.1088/1741-4326/ac277b},

doi = {10.1088/1741-4326/ac277b},

year  = {2021},

date = {2021-11-01},

journal = {Nuclear Fusion},

volume = {61},

number = {11},

pages = {114004},

publisher = {IOP Publishing},

abstract = {The results of the first experimental series to produce a plasma using the ion cyclotron range of frequency (ICRF) in the large helical device (LHD) within the minority scenario developed at Uragan-2M (U-2M) are presented. The motivation of this study is to provide plasma creation in conditions when an electron cyclotron resonance heating start-up is not possible, and in this way widen the operational frame of helical machines. The major constraint of the experiments is the low RF power to reduce the possibility of arcing. No dangerous voltage increase at the radio-frequency (RF) system elements and no arcing has been detected. As a result, a low plasma density is obtained and the antenna-plasma coupling is not optimal. However, such plasmas are sufficient to be used as targets for further neutral beam injection (NBI) heating. This will open possibilities to explore new regimes of operation at LHD and Wendelstein 7-X (W7-X) stellarator. The successful RF plasma production in LHD in this experimental series stimulates the planning of further studies of ICRF plasma production aimed at increasing plasma density and temperature within the ICRF minority scenario as well as investigating the plasma prolongation by NBI heating.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{2028,

title = {Evidence for Alfvén eigenmodes driven by alpha particles in D-3He fusion experiments on JET},

author = {V. G. Kiptily and M. Fitzgerald and Y. O. Kazakov and J. Ongena and M. Nocente and S. E. Sharapov and M. Dreval and Ž. Štancar and T. Craciunescu and J. Garcia and L. Giacomelli and V. Goloborodko and H. J. C. Oliver and H. Weisen and JET Contributors},

url = {https://doi.org/10.1088/1741-4326/ac26a2},

doi = {10.1088/1741-4326/ac26a2},

year  = {2021},

date = {2021-11-01},

journal = {Nuclear Fusion},

volume = {61},

number = {11},

pages = {114006},

publisher = {IOP Publishing},

abstract = {Alfvén eigenmodes (AEs) driven by energetic alpha particles can lead to enhanced fast ion transport and losses, thereby degrading the plasma performance in ITER and future magnetic confinement fusion reactors. Unexpectedly, AEs with negative toroidal mode numbers, which are currently not considered for ITER, were observed in dedicated experiments with fusion-born alpha particles on the tokamak Joint European Torus (JET). The paper provides evidence for a complex interplay between fast ions, monster sawtooth crashes and AEs. Our results highlight the need for an improved description of the synergies between different fast ion phenomena in future burning plasmas.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{2029,

title = {Fast ion transport by sawtooth instability in the presence of ICRF–NBI synergy in JET plasmas},

author = {A. A. Teplukhina and M. Podesta and F. M. Poli and G. Szepesi and Y. O. Kazakov and P. J. Bonofiglo and M. Gorelenkova and M. Nocente and J. Ongena and Z. Stancar and JET Contributors},

url = {https://doi.org/10.1088/1741-4326/ac2524},

doi = {10.1088/1741-4326/ac2524},

year  = {2021},

date = {2021-11-01},

journal = {Nuclear Fusion},

volume = {61},

number = {11},

pages = {116056},

publisher = {IOP Publishing},

abstract = {JET experiments have shown that the three-ion scenarios using waves in the ion cyclotron range of frequencies (ICRF) is an efficient way to build fast ion population through beam ion acceleration by radio frequency (RF) waves. Such a heating scheme is applied to plasmas with at least two thermal ion species. Analysis of mixed discharges with complex heating schemes requires a workflow that allows to model thermal and fast ion transport consistently. This paper is dedicated to modelling of a mixed plasma discharge with significant fraction of fast ions and contributes to development of fast ion transport models. For interpretive analysis with the TRANSP code a JET hydrogen–deuterium plasma discharge with neutral beam injection (NBI) and ICRF heating has been chosen. The task is complicated by NBI–ICRF synergy and plasma magnetohydrodynamic activity, like sawtooth crashes. D beam ions accelerated by RF waves form a high energy tail in fast ion distribution. Significant difference between the neutron rate computed by TRANSP and measured one is observed if the same diffusivity for electrons and ions is assumed. Sensitivity studies show that uncertainties in input plasma parameters and thermal ion transport models are crucial for modelling mixed plasma discharges and increased D transport is required to reach the plasma composition consistent with diagnostic measurements at the plasma edge. Fast ion redistribution by a sawtooth instability is characterised by non-resonant transport due to reconnection of magnetic field lines and resonant transport caused by resonance interaction between the instability and fast ions. With ORBIT simulations it has been shown that resonant interaction strongly affects fast ions of high energies, like beam ions accelerated by RF waves and fusion products. For the considered case, fast ion profiles simulated by ORBIT remain peaked after the sawtooth crashes.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{2006,

title = {Ion cyclotron resonance heating fast and slow wave excitation and power deposition in edge plasmas with application to ITER},

author = {A. Messiaen and V. Maquet and J. Ongena},

url = {https://doi.org/10.1088/1361-6587/abdf2b},

doi = {10.1088/1361-6587/abdf2b},

year  = {2021},

date = {2021-04-01},

journal = {Plasma Physics and Controlled Fusion},

volume = {63},

number = {4},

pages = {045021},

publisher = {IOP Publishing},

abstract = {The antenna power coupling to the plasma centre and its possible deleterious coupling to the plasma edge are key parameters in an ion cyclotron resonance heating system. The influence on these parameters by the confluence between the slow and the fast magnetosonic waves is studied for the case of large machines. Until now, the modelling of the scrape off layer region has been calculated by ANTITER II, which contains only the fast wave description and where the confluence with the slow wave (S wave) is approximated by the Alfvén resonance. In the present study, a complete modelling of the slow and fast waves is made by ANTITER IV. The modelling by the two codes is compared and shows the important role of the Alfvén and the lower hybrid resonances for the excitation of large fields and associated power deposition at the edge of the plasma even far from the antenna location. The ANTITER IV modelling is thereafter applied to the case of the ITER antenna with a reference density profile and heating parameters. A comparative study is made for the edge power deposition and the excitation of large fields for different toroidal phasing cases of the antenna. This study also takes into account the tilting of the antenna array with respect to the total magnetic field in front of the antenna. If the Faraday screen is field-aligned, the excitation of the S wave occurs at the wave confluence; however, in the case of non-alignment the antenna directly excites the S wave. This effect is studied and quantified. All edge effects, even the direct excitation of S waves, can be strongly reduced by tailoring the current distribution in the straps of the antenna array. Resulting cases for the minimisation of edge power deposition in ITER and the reactor are studied.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{2000,

title = {Physics and applications of three-ion ICRF scenarios for fusion research},

author = {Y. O. Kazakov and J. Ongena and J. C. Wright and S. J. Wukitch and V. Bobkov and J. Garcia and V. G. Kiptily and M. J. Mantsinen and M. Nocente and M. Schneider and H. Weisen and Y. Barakov and M. Baruzzo and R. Bilato and A. Chomiczewska and R. Coelho and T. Craciunescu and K. Crombé and M. Dreval and E. Dumont and P. Dumortier and F. Durodié and J. Eriksson and M. Fitzgerald and J. Galdon-Quiroga and D. Gallart and M. Garcia-Munoz and L. Giacomelli and C. Giroud and J. Gonzalez Martin and A. Hakola and P. Jacquet and T. Johnson and A. Kappatou and D. Keeling and D. King and K. K. Kirov and P. U. Lamalle and M. Lennholm and E. Lerche and M. Maslov and S. Mazzi and S. Menmuir and I. Monakhov and F. Nabais and M. F. F. Nave and R. Ochoukov and A. R. Polevoi and S. D. Pinches and U. Plank and D. Rigamonti and M. Salewski and P. A. Schneider and S. E. Sharapov and Z. Stancar and A. Thorman and D. Valcarcel and D. Van Eester and M. Van Schoor and J. Varje and M. Weiland and N. Wendler and JET Contributors and ASDEX Upgrade Team and EUROfusion MST1 Team and Alcator C-Mod Team},

year  = {2021},

date = {2021-02-01},

journal = {Physics of Plasmas},

volume = {28},

number = {2},

pages = {020501},

abstract = {This paper summarizes the physical principles behind the novel three-ion scenarios using radio frequency waves in the ion cyclotron range of frequencies (ICRF). We discuss how to transform mode conversion electron heating into a new flexible ICRF technique for ion cyclotron heating and fast-ion generation in multi-ion species plasmas. The theoretical section provides practical recipes for selecting the plasma composition to realize three-ion ICRF scenarios, including two equivalent possibilities for the choice of resonant absorbers that have been identified. The theoretical findings have been convincingly confirmed by the proof-of-principle experiments in mixed H–D plasmas on the Alcator C-Mod and JET tokamaks, using thermal 3He and fast D ions from neutral beam injection as resonant absorbers. Since 2018, significant progress has been made on the ASDEX Upgrade and JET tokamaks in H–4He and H–D plasmas, guided by the ITER needs. Furthermore, the scenario was also successfully applied in JET D–3He plasmas as a technique to generate fusion-born alpha particles and study effects of fast ions on plasma confinement under ITER-relevant plasma heating conditions. Tuned for the central deposition of ICRF power in a small region in the plasma core of large devices such as JET, three-ion ICRF scenarios are efficient in generating large populations of passing fast ions and modifying the q-profile. Recent experimental and modeling developments have expanded the use of three-ion scenarios from dedicated ICRF studies to a flexible tool with a broad range of different applications in fusion research.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{1994,

title = {Generation and observation of fast deuterium ions and fusion-born alpha particles in JET D - 3He plasmas with the 3-ion radio-frequency heating scenario},

author = {M Nocente and Y. O. Kazakov and J Garcia and V G Kiptily and J. Ongena and M Dreval and M Fitzgerald and S E Sharapov and Z Stancar and H Weisen and Y Baranov and A Bierwage and T Craciunescu and Dal A Molin and E Luna and R Dumont and P. Dumortier and J Eriksson and L Giacomelli and C Giroud and V Goloborodko and G Gorini and E Khilkevitch and K K Kirov and M Iliasova and P Jacquet and P Lauber and E. Lerche and M J Mantsinen and A Mariani and S Mazzi and F Nabais and M F F Nave and J Oliver and E Panontin and D Rigamonti and A Sahlberg and M Salewski and A Shevelev and K Shinohara and P Siren and S Sumida and M Tardocchi and D. Van Eester and J Varje and A Zohar and JET Contributors},

url = {https://doi.org/10.1088%2F1741-4326%2Fabb95d},

doi = {10.1088/1741-4326/abb95d},

year  = {2020},

date = {2020-12-01},

journal = {Nuclear Fusion},

volume = {60},

number = {12},

pages = {124006},

publisher = {IOP Publishing},

abstract = {Dedicated experiments to generate energetic D ions and fusion-born alpha particles were performed at the Joint European Torus (JET) with the ITER-like wall (ILW). Using the 3-ion radio frequency (RF) heating scenario, deuterium ions from neutral beam injection (NBI) were accelerated in the core of mixed plasmas to higher energies with ion cyclotron resonance frequency (ICRF) waves, in turn leading to a core-localized source of alpha particles. The fast-ion distribution of RF-accelerated D-NBI ions was controlled by varying the ICRF and NBI power ( 4–6 MW, 3–20 MW), resulting in rather high D-D neutron (≈ 1 × 1016 s−1) and alpha rates (≈ 2 × 1016 s−1) at moderate input heating power. Theory and TRANSP analysis shows that large populations of co-passing MeV-range D ions were generated using the 3-ion ICRF scenario. This important result is corroborated by several experimental observations, in particular gamma-ray measurements. The developed experimental scenario at JET provides unique conditions for probing several aspects of future burning plasmas, such as the contribution from MeV range ions to global confinement, but without introducing tritium. Dominant fast-ion core electron heating with and a rich variety of fast-ion driven Alfvén eigenmodes (AEs) were observed in these plasmas. The observed AE activities do not have a detrimental effect on the thermal confinement and, in some cases, may be driven by the fusion born alpha particles. A strong continuous increase in neutron rate was observed during long-period sawteeth (1 s), accompanied by the observation of reversed shear AEs, which implies that a non monotonic q profile was systematically developed in these plasmas, sustained by the large fast-ion populations generated by the 3-ion ICRF scenario.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{1992,

title = {Plasma heating and generation of energetic D ions with the 3-ion ICRF +NBI scenario in mixed H-D plasmas at JET-ILW},

author = {Y. O. Kazakov and M Nocente and M J Mantsinen and J. Ongena and Y Baranov and T Craciunescu and M Dreval and R Dumont and J Eriksson and J Garcia and L Giacomelli and V G Kiptily and K K Kirov and L Meneses and F Nabais and M F F Nave and M Salewski and S E Sharapov and Ž Š and J Varje and Weisen H and},

url = {https://doi.org/10.1088%2F1741-4326%2Fab9256},

doi = {10.1088/1741-4326/ab9256},

year  = {2020},

date = {2020-11-01},

journal = {Nuclear Fusion},

volume = {60},

number = {11},

pages = {112013},

publisher = {IOP Publishing},

abstract = {Dedicated experiments were conducted in mixed H-D plasmas in JET to demonstrate the efficiency of the 3-ion ICRF scenario for plasma heating, relying on injected fast NBI ions as the resonant ion component. Strong core localization of the RF power deposition in the close vicinity of the ion-ion hybrid layer was achieved, resulting in an efficient plasma heating, generation of energetic D ions, strong enhancement of the neutron rate and observation of Alfvénic modes. A consistent physical picture that emerged from a range of fast-ion measurements at JET, including neutron and gamma-ray measurements, a high-energy neutral particle analyzer and MHD mode localization analysis, is presented. The possibility to moderate the fast-ion energies with the ratio P 

ICRF/P 

NBI and the choice of the NBI injectors is demonstrated. An outlook of possible applications of the 3-ion scenarios, including a recent example of its use in mixed D-3He plasmas in JET and promising scenarios for D-T plasmas, are presented.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{1991,

title = {Excitation of elliptical and toroidal Alfvén eigenmodes by 3He-ions of the MeV-energy range in hydrogen-rich JET plasmas},

author = {V G Kiptily and Y. O. Kazakov and M Fitzgerald and M Nocente and M Iliasova and E Khilkevich and M J Mantsinen and M F F Nave and J. Ongena and S E Sharapov and A E Shevelev and Ž Š and G Szepesi and D M A Taylor and Yu. V. Yakovenko and},

url = {https://doi.org/10.1088%2F1741-4326%2Fab79cb},

doi = {10.1088/1741-4326/ab79cb},

year  = {2020},

date = {2020-11-01},

journal = {Nuclear Fusion},

volume = {60},

number = {11},

pages = {112003},

publisher = {IOP Publishing},

abstract = {Elliptical (EAE) and toroidal Alfvén eigenmode (TAE) instabilities have been observed in hydrogen-rich JET discharges of the D-(3He)-H ion cyclotron resonance heating (ICRH) scenario, which is characterized by strong absorption of radio frequency waves at very low concentrations of the resonant 3He-ions. In the experiments, core localized TAEs with a frequency f TAE ≈ 280 kHz with mode numbers n= 3, 4, 5 and 6 were detected. Following the phase with TAE excitation, EAE modes at higher frequencies f EAE ≈ 550–580 kHz with mode numbers n = 1, 3, 5 were seen. These high frequency modes indicate that a MeV range population of trapped energetic ions was present in the plasma. The experimental evidence of existence of the MeV-energy 3He-ions able to excite the AEs is provided by neutron and gamma-ray diagnostics as well as fast ion loss measurements. The ICRH modelling code calculations confirm the acceleration of 3He-ions to MeV energies. The magnetohydrodynamic (MHD) analysis results are consistent with the experimental data showing that the MeV 3He ions satisfy to resonant conditions interacting with TAE and EAE modes. This experiment demonstrates the efficient plasma heating mimicking the conditions representative for the ITER plasmas and contribute to the understanding of fast-ion interaction with MHD wave modes.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{1990,

title = {First experiments on ICRF discharge generation by a W7-X-like antenna in the Uragan-2M stellarator},

author = {V E Moiseenko and Yu. V Kovtun and T. Wauters and A. Goriaev and A. I. Lyssoivan and A V Lozin and R O Pavlichenko and A N Shapoval and S M Maznichenko and V B Korovin and E D Kramskoy and M M Kozulya and N V Zamanov and Y V Siusko and Yu. A Krasiuk and V S Romanov and A Alonso and R Brakel and A Dinklage and D Hartmann and Y. O. Kazakov and H Laqua and J. Ongena and T Stange},

year  = {2020},

date = {2020-10-01},

journal = {Journal of Plasma Physics},

volume = {86},

number = {5},

pages = {905860517},

keywords = {},

pubstate = {published},

tppubtype = {article}

}