List of publications

@article{1860,

title = {A quantitative comparison between confined fast ion data and models from radio frequency heating experiments with the three ion scenarios at JET},

author = {M Nocente and Y. O. Kazakov and V Kiptily and T Craciunescu and J Eriksson and J Faustin and L Giacomelli and G Gorini and C Hellesen and E. Lerche and M Mantsinen and J. Ongena and M Salewski and S Sharapov and M Tardocchi and D. Van Eester and JET Contributors},

year  = {2018},

date = {2018-07-01},

journal = {Europhysics Conference Abstracts},

volume = {42A},

pages = {O5.103},

abstract = {45th EPS Conference on Plasma Physics, Prage (Czech Republic), 02 - 06 July 2018},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{1851,

title = {Wall conditioning by ECRH discharges and He-GDC in the limiter phase of Wendelstein 7-X},

author = {T. Wauters and R Brakel and S Brezinsek and A Dinklage and A. Goriaev and H P Laqua and S Marsen and D Moseev and T Stange and G Schlisio and Sunn T Pedersen and O Volzke and U Wenzel and W7-X Team},

url = {http://stacks.iop.org/0029-5515/58/i=6/a=066013},

year  = {2018},

date = {2018-06-01},

journal = {Nuclear Fusion},

volume = {58},

number = {6},

pages = {066013},

abstract = {Wendelstein 7-X (W7-X) relies on wall conditioning to control the density and the impurity content of the plasma. Wall conditioning in the first operation campaign of W7-X consisted of baking at 150 $,^circ$C during 1 week prior to operation, glow discharge conditioning (GDC) in helium (He) and electron cyclotron resonance heating (ECRH) discharges. Additionally, the usage of He-GDC was limited to avoid sputtering and migration of metallic plasma facing components. This presented a unique opportunity for studying the applicability of ECRH discharges for initial wall conditioning on a stellarator, albeit in the carbon limiter configuration. A single envelope curve is observed in the normalised outgassing data that takes into account all ECRH discharges. This illustrates that the majority of discharges operates at the limits of a radiative collapse. Hydrogen recycling dominated the fuelling of ECRH discharges throughout while CO outgassing was found strongest at the start of the campaign. A reduction of recycling was observed throughout the campaign. Temporarily depleting the walls from H and impurities was possible by He-GDC. It was shown that the recycling coefficient in ##IMG## [http://ej.iop.org/images/0029-5515/58/6/066013/nfaab2c9ieqn001.gif] -ECRH plasmas could be reduced and the pulse duration significantly extended by He-'recovery' ECRH plasmas. Good wall conditions were defined by normalised outgassing values below ##IMG## [http://ej.iop.org/images/0029-5515/58/6/066013/nfaab2c9ieqn002.gif] mbar kJ −1 . In absence of ##IMG## [http://ej.iop.org/images/0029-5515/58/6/066013/nfaab2c9ieqn003.gif] -GDC, more than 311 cumulated discharge seconds of ECRH discharges are needed for obtaining lasting low outgassing levels. A release model with two trapping reservoirs could reproduce the normalised outgassing trend, including ECRH and GDC plasma wall interactions.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{1825,

title = {Development of an ICRH antenna system at W7-X for plasma heating and wall conditioning},

author = {B Schweer and J. Ongena and F. Durodié and A. Krivska and F. Louche and A. Messiaen and M. Van Schoor and M. Vervier},

url = {http://www.sciencedirect.com/science/article/pii/S0920379617305641},

doi = {https://doi.org/10.1016/j.fusengdes.2017.05.019},

issn = {0920-3796},

year  = {2017},

date = {2017-11-01},

journal = {Fusion Engineering and Design},

volume = {123},

pages = {303 - 308},

note = {Proceedings of the 29th Symposium on Fusion Technology (SOFT-29) Prague, Czech Republic, September 5-9, 2016},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{1826,

title = {Design of an ICRF system for plasma-wall interactions and RF plasma production studies on TOMAS},

author = {F. Louche and T. Wauters and R. Ragona and F. Durodié and A. I. Lyssoivan and A. Messiaen and J. Ongena and M. Van Schoor},

url = {http://www.sciencedirect.com/science/article/pii/S0920379617305264},

doi = {https://doi.org/10.1016/j.fusengdes.2017.04.123},

issn = {0920-3796},

year  = {2017},

date = {2017-11-01},

journal = {Fusion Engineering and Design},

volume = {123},

pages = {317 - 320},

note = {Proceedings of the 29th Symposium on Fusion Technology (SOFT-29) Prague, Czech Republic, September 5-9, 2016},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{1797,

title = {Major results from the first plasma campaign of the Wendelstein 7-X stellarator},

author = {R C Wolf and T. Wauters and F. Durodié and A. Goriaev and J. Ongena and M. Vergote},

url = {http://stacks.iop.org/0029-5515/57/i=10/a=102020},

year  = {2017},

date = {2017-10-01},

journal = {Nuclear Fusion},

volume = {57},

number = {10},

pages = {102020},

abstract = {After completing the main construction phase of Wendelstein 7-X (W7-X) and successfully commissioning the device, first plasma operation started at the end of 2015. Integral commissioning of plasma start-up and operation using electron cyclotron resonance heating (ECRH) and an extensive set of plasma diagnostics have been completed, allowing initial physics studies during the first operational campaign. Both in helium and hydrogen, plasma breakdown was easily achieved. Gaining experience with plasma vessel conditioning, discharge lengths could be extended gradually. Eventually, discharges lasted up to 6 s, reaching an injected energy of 4 MJ, which is twice the limit originally agreed for the limiter configuration employed during the first operational campaign. At power levels of 4 MW central electron densities reached 3 × 10 19 m −3 , central electron temperatures reached values of 7 keV and ion temperatures reached just above 2 keV. Important physics studies during this first operational phase include a first assessment of power balance and energy confinement, ECRH power deposition experiments, 2nd harmonic O-mode ECRH using multi-pass absorption, and current drive experiments using electron cyclotron current drive. As in many plasma discharges the electron temperature exceeds the ion temperature significantly, these plasmas are governed by core electron root confinement showing a strong positive electric field in the plasma centre.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{1762,

title = {Contribution of LPP/ERM-KMS to the modern developments of ICRH antenna systems},

author = {A. Messiaen and J. Ongena and P. Dumortier and F. Durodié and F. Louche and R. Ragona and M. Vervier},

url = {http://dx.doi.org/10.1016/j.fusengdes.2016.06.035},

doi = {10.1016/j.fusengdes.2016.06.035},

issn = {09203796},

year  = {2016},

date = {2016-11-01},

journal = {Fusion Engineering and Design},

volume = {112},

pages = {21-35},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{1718,

title = {Study of the choice of the decoupling layout for the ITER ICRH system},

author = {M. Vervier and A. Messiaen and J. Ongena and F. Durodié},

url = {http://dx.doi.org/10.1063/1.4936519},

doi = {10.1063/1.4936519},

issn = {0094-243X},

year  = {2015},

date = {2015-12-10},

journal = {AIP Conference Proceedings},

volume = {1689},

number = {1},

pages = {070012+},

abstract = {10 decouplers are used to neutralize the mutual coupling effects and to control the current amplitude of the 24 straps array of the ITER ICRH antenna in the case of current drive phasing. In the case of heating phasing only 4 decouplers are active and the array current control needs to act on the ratio between the power delivered by the 4 generators. This ratio is very sensitive to the precise adjustment of the antenna array phasing. The maximum total radiated power capability is then limited when the power of one generator reaches its maximum value. With the addition of four switches all 10 installed decouplers are made active and can act on all mutual coupling effects with equal source power from the 4 generators. With four more switches the current drive phasing could work with a reduced poloidal phasing resulting in a 35% increase of its coupling to the plasma.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{1717,

title = {Analysis of the phase control of the ITER ICRH antenna array. Influence on the load resilience and radiated power spectrum},

author = {A. Messiaen and D Swain and J. Ongena and M. Vervier},

url = {http://dx.doi.org/10.1063/1.4936518},

doi = {10.1063/1.4936518},

issn = {0094-243X},

year  = {2015},

date = {2015-12-10},

journal = {AIP Conference Proceedings},

volume = {1689},

number = {1},

pages = {070011},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{1702,

title = {Fast ion generation and bulk plasma heating with three-ion ICRF scenarios},

author = {Y. O. Kazakov and D. Van Eester and R Dumont and J. Ongena and E. Lerche and A. Messiaen},

url = {http://dx.doi.org/10.1063/1.4936473},

doi = {10.1063/1.4936473},

issn = {0094-243X},

year  = {2015},

date = {2015-12-10},

journal = {AIP Conference Proceedings},

volume = {1689},

number = {1},

pages = {030008+},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{1698,

title = {ICRH for core impurity mitigation in JET-ILW},

author = {E. Lerche and M Goniche and P Jacquet and D. Van Eester and V Bobkov and L Colas and I Monakhov and F Rimini and A Czarnecka and K. Crombé and R Dumont and J Hobirk and Y. O. Kazakov and M L Mayoral and L Meneses and J Mlynar and C Noble and I Nunes and J. Ongena and V Petrzilka and M Reich and M Santala and A Shaw and M Tsalas and Contributors},

url = {http://dx.doi.org/10.1063/1.4936467},

doi = {10.1063/1.4936467},

issn = {0094-243X},

year  = {2015},

date = {2015-12-10},

journal = {AIP Conference Proceedings},

volume = {1689},

number = {1},

pages = {030002+},

abstract = {Ion cyclotron resonance frequency (ICRF) heating has been an essential component in the development of high power H-mode scenarios in JET-ILW. The steps that were taken for the successful use of ICRF heating in terms of enhancing the power capabilities and optimizing the heating performance in view of core impurity mitigation in these experiments will be reviewed.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{1690,

title = {Three-dimensional modelling and numerical optimisation of the W7-X ICRH antenna},

author = {F. Louche and A. Křivská and A. Messiaen and J. Ongena and V Borsuk and F. Durodié and B Schweer},

url = {http://dx.doi.org/10.1016/j.fusengdes.2015.01.039},

doi = {10.1016/j.fusengdes.2015.01.039},

issn = {09203796},

year  = {2015},

date = {2015-10-01},

journal = {Fusion Engineering and Design},

volume = {96-97},

pages = {508-511},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{1689,

title = {Validation of the electrical design of the W7-X ICRF antenna on a reduced-scale mock-up},

author = {P. Dumortier and A. Křivská and A. Messiaen and M. Vervier and F. Louche and J. Ongena},

url = {http://dx.doi.org/10.1016/j.fusengdes.2015.02.022},

doi = {10.1016/j.fusengdes.2015.02.022},

issn = {09203796},

year  = {2015},

date = {2015-10-01},

journal = {Fusion Engineering and Design},

volume = {96-97},

pages = {463-467},

abstract = {The electrical design of the W7X ICRF antenna is validated on a reduced-scale mock-up. High dieletric constant materials are needed for the dummy load to mimic the plasma load. Salted water and a mix of ferroelectric BaTiO3 and salted water are used as loads. A comparison is made between experimental measurements and numerical simulations by 3 codes: Antiter II, CST MWS and Topica. The best agreement is obtained with the BaTiO3 mix load for all phasings. The dependence of the coupled power estimate on the dielectric load properties is given. A scaled mock-up (1/4) of the proposed W7-X ICRF antenna has been constructed and placed in front of dielectric dummy loads. It allows comparing measured and predicted coupling performances and hence validating the electrical design of the antenna. High dielectric constant materials are needed for the dummy load to mimic the plasma. Salted water and a mix of the ferroelectric BaTiO3 and salted water are used. The measurements are compared with the expectations of 3 codes: ANTITER II, MWS and TOPICA. The best agreement is obtained with the BaTiO3 load for all phasings.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{1729,

title = {Fusion: A true challenge for an enormous reward},

author = {J. Ongena},

editor = {L Cifarelli and Wagner F (Eds.)},

url = {https://doi.org/10.1051/epjconf/20159805004},

doi = {10.1051/epjconf/20159805004},

year  = {2015},

date = {2015-08-01},

journal = {EPJ Web of Conferences},

volume = {98},

pages = {05004},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{1687,

title = {A new ion cyclotron range of frequency scenario for bulk ion heating in deuterium-tritium plasmas: How to utilize intrinsic impurities in our favour},

author = {Y. O. Kazakov and J. Ongena and D. Van Eester and R Bilato and R Dumont and E. Lerche and M Mantsinen and A. Messiaen},

url = {http://dx.doi.org/10.1063/1.4928880},

doi = {10.1063/1.4928880},

issn = {1070-664X},

year  = {2015},

date = {2015-08-01},

journal = {Physics of Plasmas (1994-present)},

volume = {22},

number = {8},

pages = {082511+},

abstract = {A fusion reactor requires plasma pre-heating before the rate of deuterium-tritium fusion reactions becomes significant. In ITER, radio frequency (RF) 

heating of 3He ions, additionally puffed into the plasma, is one of the main options considered for increasing bulk ion temperature during the ramp-up phase of the pulse. In this paper, we propose an alternative scenario for bulk ion heating with RF 

waves, which requires no extra 3He puff and profits from the presence of intrinsic Beryllium impurities in the plasma. The discussed method to heat Be impurities in D-T 

plasmas is shown to provide an even larger fraction of fuel ion heating.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{1665,

title = {On resonant ICRF absorption in three-ion component plasmas: a new promising tool for fast ion generation},

author = {Y. O. Kazakov and D. Van Eester and R Dumont and J. Ongena},

url = {http://dx.doi.org/10.1088/0029-5515/55/3/032001},

doi = {10.1088/0029-5515/55/3/032001},

issn = {0029-5515},

year  = {2015},

date = {2015-03-01},

journal = {Nuclear Fusion},

volume = {55},

number = {3},

pages = {032001+},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{1724,

title = {Potential of ion cyclotron resonance frequency current drive via fast waves in DEMO},

author = {Y. O. Kazakov and D. Van Eester and T. Wauters and E. Lerche and J. Ongena},

url = {http://stacks.iop.org/0741-3335/57/i=2/a=025014},

year  = {2015},

date = {2015-02-01},

journal = {Plasma Physics and Controlled Fusion},

volume = {57},

number = {2},

pages = {025014},

abstract = {For the continuous operation of future tokamak-reactors like DEMO, non-inductively driven toroidal plasma current is needed. Bootstrap current, due to the pressure gradient, and current driven by auxiliary heating systems are currently considered as the two main options. This paper addresses the current drive (CD) potential of the ion cyclotron resonance frequency (ICRF) heating system in DEMO-like plasmas. Fast wave CD scenarios are evaluated for both the standard midplane launch and an alternative case of exciting the waves from the top of the machine. Optimal ICRF frequencies and parallel wave numbers are identified to maximize the CD efficiency. Limitations of the high frequency ICRF CD operation are discussed. A simplified analytical method to estimate the fast wave CD efficiency is presented, complemented with the discussion of its dependencies on plasma parameters. The calculated CD efficiency for the ICRF system is shown to be similar to those for the negative neutral beam injection and electron cyclotron resonance heating.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{1603,

title = {Study and design of the ion cyclotron resonance heating system for the stellarator Wendelstein 7-X},

author = {J. Ongena and A. Messiaen and D. Van Eester and B Schweer and P. Dumortier and F. Durodié and Y. O. Kazakov and F. Louche and M. Vervier and R. Koch and A. Krivska and A. I. Lyssoivan and M. Van Schoor and T. Wauters and V Borsuk and O Neubauer and O Schmitz and G Offermans and Y Altenburg and C Baylard and D Birus and S Bozhenkov and D A Hartmann and J P Kallmeyer and S Renard and R C Wolf and T Fülöp},

url = {http://dx.doi.org/10.1063/1.4884377},

doi = {10.1063/1.4884377},

issn = {1070-664X},

year  = {2014},

date = {2014-06-01},

journal = {Physics of Plasmas (1994-present)},

volume = {21},

number = {6},

pages = {061514+},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{1596,

title = {On the challenge of plasma heating with the JET metallic wall},

author = {M L Mayoral and V Bobkov and A Czarnecka and I Day and A Ekedahl and P Jacquet and M Goniche and R King and K Kirov and E. Lerche and J Mailloux and D. Van Eester and O Asunta and C Challis and D Ciric and J W Coenen and L Colas and C Giroud and M Graham and I Jenkins and E Joffrin and T Jones and D King and V Kiptily and C C Klepper and C Maggi and R Maggiora and F Marcotte and G Matthews and D Milanesio and I Monakhov and M Nightingale and R Neu and J. Ongena and T Pütterich and V Riccardo and F Rimini and J Strachan and E Surrey and V Thompson and G. Van Rooij and contributors},

url = {http://dx.doi.org/10.1088/0029-5515/54/3/033002},

doi = {10.1088/0029-5515/54/3/033002},

issn = {0029-5515},

year  = {2014},

date = {2014-03-01},

journal = {Nuclear Fusion},

volume = {54},

number = {3},

pages = {033002+},

abstract = {The major aspects linked to the use of the JET auxiliary heating systems: NBI, ICRF and LHCD, in the new JET ITER-like wall are presented. We show that although there were issues related to the operation of each system, efficient and safe plasma heating was obtained with room for higher power. For the NBI up to 25.7 MW was safely injected; issues that had to be tackled were mainly the beam shine-through and beam re-ionization before its entrance into the plasma. For the ICRF system, 5 MW were coupled in L-mode and 4 MW in H-mode; the main areas of concern were RF sheaths related heat loads and impurities production. For the LH, 2.5 MW were delivered without problems; arcing and generation of fast electron beams in front of the launcher that can lead to high heat loads were the keys issues. For each system, an overview will be given of: the main modifications implemented for safe use, their compatibility with the new metallic wall, the differences in behaviour compared with the previous carbon wall, with emphasis on heat loads and impurity content in the plasma.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{1589,

title = {Coupling and matching study of the ICRF antenna for W7-X},

author = {A. Messiaen and A. Krivska and F. Louche and J. Ongena and P. Dumortier and F. Durodié and D. Van Eester and M. Vervier},

url = {http://dx.doi.org/10.1063/1.4864561},

doi = {10.1063/1.4864561},

issn = {0094-243X},

year  = {2014},

date = {2014-02-12},

journal = {AIP Conference Proceedings},

volume = {1580},

number = {1},

pages = {354–357},

abstract = {A tight antenna plug consisting in a pair of straps with strong pre-matching covers the first selected frequency band (25-38MHz) for W7-X and provides the toroidal phasings for heating, current drive and wall conditioning. Another plug-in with two short strap triplets is devoted for operation around 76MHz. The antenna coupling to a reference plasma profile is first analyzed by means of the coupling code ANTITER II. It shows the radiation power spectra for the different phasing cases and indicates the problem of the edge power deposition through the Alfven resonance occurring when the operating frequency is lower than the majority cyclotron frequency. Matrices provided by the TOPICA code are used for the matching-decoupling study of the first antenna plug. The large mutual coupling between the 2 straps is counterbalanced by the use of a decoupler. Finally the tunable 5-port junction used to feed in parallel each triplet of the second plug-in is analyzed by means of MWS simulation together with its decoupling-matching system.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{1588,

title = {Modelling of the ion cyclotron resonance heating scenarios for W7-X stellarator},

author = {Y. O. Kazakov and D. Van Eester and J. Ongena and T Fülöp},

url = {http://dx.doi.org/10.1063/1.4864558},

doi = {10.1063/1.4864558},

issn = {0094-243X},

year  = {2014},

date = {2014-02-12},

journal = {AIP Conference Proceedings},

volume = {1580},

number = {1},

pages = {342–345},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{1576,

title = {Effect of the minority concentration on ion cyclotron resonance heating in presence of the ITER-like wall in JET},

author = {D. Van Eester and E. Lerche and P Jacquet and V Bobkov and A Czarnecka and J W Coenen and L Colas and K. Crombé and M Graham and S. Jachmich and E Joffrin and C C Klepper and V Kiptily and M Lehnen and C Maggi and F Marcotte and G Matthews and M L Mayoral and K Mc Cormick and I Monakhov and M F F Nave and R Neu and C Noble and J. Ongena and T Pütterich and F Rimini and E R Solano and G. Van Rooij and contributors},

url = {http://dx.doi.org/10.1063/1.4864528},

doi = {10.1063/1.4864528},

issn = {0094-243X},

year  = {2014},

date = {2014-02-12},

journal = {AIP Conference Proceedings},

volume = {1580},

number = {1},

pages = {223–226},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{1562,

title = {Operation and coupling of LH waves with the ITER-like wall at JET},

author = {K K Kirov and J Mailloux and A Ekedahl and V Petrzilka and G Arnoux and Yu Baranov and M Brix and M Goniche and S. Jachmich and M L Mayoral and J. Ongena and F Rimini and M Stamp and Jet-Efda Contributors},

url = {http://dx.doi.org/10.1088/0741-3335/55/11/115008},

doi = {10.1088/0741-3335/55/11/115008},

issn = {0741-3335},

year  = {2013},

date = {2013-11-01},

journal = {Plasma Physics and Controlled Fusion},

volume = {55},

number = {11},

pages = {115008+},

abstract = {In this paper important aspects of the lower hybrid (LH) operation with the ITER-like wall (ILW) [1] at JET are reported. Impurity release during LH operation was investigated and it was found that there is no significant Be increase with LH power. The concentration of W was analysed in more detail and it was concluded that LH negligibly contributes to its increase. No cases of W accumulation in LH-only heating experiments were observed so far. LH wave coupling was studied and optimised to achieve the level of system performance similar to before ILW installation. Measurements by Li-beam were used to study systematic dependencies of the scrape-off layer (SOL) density on the gas injection rate from a dedicated gas introduction module and the LH power and launcher position. Experimental results are supported by SOL transport modelling. Observations of arcs in front of the LH launcher and hotspots on magnetically connected sections of the vessel are reported. Overall, a relatively trouble-free operation of the LH system up to 2.5 MW of coupled radio frequency power in L-mode plasma was achieved with no indication that the power cannot be increased further.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{1502,

title = {Usage of three-halfturn antenna at the uragan-3m Device},

author = {A V Lozin and V E Moiseenko and L I Grigor'eva and M M Kozulya and A. Yu Krasyuk and A E Kulaga and E D Kramskoy and A. I. Lyssoivan and S M Maznichenko and Yu. K. Mironov and R O Pavlichenko and N V Zamanov and V S Romanov and V. Ya. Chernyshenko and V V Chechkin and URAGAN-3M Team},

year  = {2013},

date = {2013-06-01},

journal = {Problems of Atomic Science and Technology, Series},

volume = {83},

number = {1},

pages = {27-29},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{1494,

title = {Physical meaning of one-machine and multimachine tokamak scalings},

author = {Yu Dnestrovskij and A V Danilov and Dnestrovskij and S E Lysenko and J. Ongena},

url = {http://dx.doi.org/10.1134/s1063780x13040016},

doi = {10.1134/s1063780x13040016},

year  = {2013},

date = {2013-04-01},

booktitle = {Plasma Physics Reports},

journal = {Plasma Physics Reports},

volume = {39},

number = {4},

pages = {263–271},

publisher = {SP MAIK Nauka/Interperiodica},

abstract = {Specific features of energy confinement scalings constructed using different experimental databases for tokamak plasmas are considered. In the multimachine database, some pairs of engineering variables are collinear; e.g., the current I and the input power P both increase with increasing minor radius a. As a result, scalings derived from this database are reliable only for discharges in which such ratios as I/a 2 or P/a 2 are close to their values averaged over the database. The collinearity of variables allows one to exclude the normalized Debye radius d* from the scaling expressed in a nondimensional form. In one-machine databases, the dimensionless variables are functionally dependent, which allow one to cast a scaling without d*. In a database combined from two devices, the collinearity may be absent, so the Debye radius cannot generally be excluded from the scaling. It is shown that the experiments performed in support of the absence of d* in the two-machine scaling are unconvincing. Transformation expressions are given that allow one to compare experiments for the determination of scaling in any set of independent variables.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}