Hydrogen plasmas with ICRF inverted minority and mode conversion heating regimes in the JET tokamak

Mayoral, M.‐L.; Lamalle, P.; Eester, D. Van; Lerche, E.; Beaumont, P.; Luna, E. de la; Vries, P. de; Gowers, C.; Felton, R.; Harling, J.; Kiptily, V.; Lawson, K.; Laxåbäck, Martin; Lomas, P. J.; Mantsinen, M.; Méo, F.; Noterdaeme, J.-M.; Nunes, I.; Piazza, G.; Santala, M.; Contributors, Jet

doi:10.1088/0029-5515/46/7/s14

Cited by 39 publications

(138 citation statements)

References 37 publications

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“…For the H majority plasmas, maximum absorption occurs at lower 3 He concentrations X3 He ≈ 2 − 3%. This is consistent with the fact that ( 3 He)-H heating is an inverted ICRF scenario and the transition from minority heating to mode conversion (MC) occurs at lower 3 He concentrations [14,15,16]. Three-ion ICRF heating corresponds to the conditions highlighted in Fig.…”

Section: Introductionsupporting

confidence: 82%

Fast ion generation and bulk plasma heating with three-ion ICRF scenarios

Kazakov¹,

Eester²,

Dümont³

et al. 2015

AIP Conference Proceedings

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A new ion cyclotron range of frequency scenario for bulk ion heating in deuterium-tritium plasmas: How to utilize intrinsic impurities in our favour Physics of Plasmas 22, 082511 (2015) Abstract. Launching electromagnetic waves in the ion cyclotron range of frequencies (ICRF) is an efficient method of plasma heating, actively employed in most of fusion machines. ICRF has a number of important supplementary applications, including the generation of high-energy ions. In this paper, we discuss a new set of three-ion ICRF scenarios and the prospect of their use as a dedicated tool for fast ion generation in tokamaks and stellarators. A distinct feature of these scenarios is a strong absorption efficiency possible at very low concentrations of resonant minority ions (∼ 1% or even below). Such concentration levels are typical for impurities contaminating fusion plasmas. An alternative ICRF scenario for maximizing the efficiency of bulk D-T ion heating is suggested for JET and ITER tokamaks, which is based on three-ion ICRF heating of intrinsic Beryllium impurities. a) Corresponding author: yevgen.kazakov@rma.ac.be

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Section: Introductionsupporting

confidence: 82%

Fast ion generation and bulk plasma heating with three-ion ICRF scenarios

Kazakov¹,

Eester²,

Dümont³

et al. 2015

AIP Conference Proceedings

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“…On the one hand, this is related to the low heating efficiency of this heating scheme, since only a small fraction of the RF power coupled to the plasma is actually absorbed by the 3 He ions. On the other hand, the restricted 3 He RF acceleration observed in these experiments comes from the fact that in most of the pulses discussed here, the 3 He concentration was above 8%, which is considerably higher than the concentrations used in typical minority 3 He-H ICRH experiments (1-2%), where significant 3 He tails were observed [23,24]. Furthermore, in contrast to the fundamental ion cyclotron acceleration which exhibits a relatively flat response in phase space, the second harmonic heating is usually more efficient at higher energies and the fact that the bulk plasma temperatures were relatively low in these pulses 'limits' this process.…”

Section: Fast Particlesmentioning

confidence: 55%

Experimental investigation of ion cyclotron range of frequencies heating scenarios for ITER's half-field hydrogen phase performed in JET

Lerche¹,

Eester²,

Johnson³

et al. 2012

Plasma Phys. Control. Fusion

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Two ion cyclotron range of frequencies (ICRF) heating schemes proposed for the half-field operation phase of ITER in hydrogen plasmas-fundamental H majority and second harmonic 3 He ICRF heating-were recently investigated in JET. Although the same magnetic field and RF frequencies (f ≈ 42 MHz and f ≈ 52 MHz, respectively) were used, the density and particularly the plasma temperature were lower than those expected in the initial phase of ITER. Unlike for the well-performing H minority heating scheme to be used in 4 He plasmas, modest heating efficiencies (η = P absorbed /P launched < 40%) with dominant electron heating were found in both H plasma scenarios studied, and enhanced plasma-wall interaction manifested by high radiation losses and relatively large impurity content in the plasma was observed. This effect was stronger in the 3 He ICRF heating case than in the H majority heating experiments and it was verified that concentrations as high as ∼20% are necessary to observe significant ion heating in this case. The RF acceleration of the heated ions was modest in both cases, although a small fraction of the 3 He ions reached about 260 keV in the second harmonic 3 He heating experiments when 11 Romanelli F et al 2010 Proc. 23rd IAEA Fusion Energy Conf. (Daejeon, Korea, 2010 5 MW of ICRF power was applied. Considerable RF acceleration of deuterium beam ions was also observed in some discharges of the 3 He heating experiments (where both the second and third harmonic ion cyclotron resonance layers of the D ions are inside the plasma) whilst it was practically absent in the majority hydrogen heating scenario. While hints of improved RF heating efficiency as a function of the plasma temperature and plasma dilution (with 4 He) were confirmed in the H majority case, the 3 He concentration was the main handle on the heating efficiency in the second harmonic 3 He heating scenario.

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“…A comprehensive account of the ICRF heating experiments in hydrogen plasmas summarized in this section can be found in [14] and [15].…”

Section: Icrf Heating In Hydrogen Plasmasmentioning

confidence: 99%

Expanding the operating space of ICRF on JET with a view to ITER

et al. 2006

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This paper reports on ITER-relevant ICRF physics investigated on JET in 2003 and early 2004.Minority heating of helium three in hydrogen plasmas -( 3 He)H -was systematically explored by varying the 3 He concentration and the toroidal phasing of the antenna arrays. The best heating performance (a maximum electron temperature of 6.2keV with 5MW of ICRF power) was obtained with a preferential wave launch in the direction of the plasma current. A clear experimental demonstration was made of the sharp and reproducible transition to the mode conversion heating regime when the 3 He concentration increases above ~2%. In the latter regime the best heating performance (a maximum electron temperature of 8keV with 5MW of ICRF power) was achieved with dipole array phasing, i.e. a symmetric antenna power spectrum. Minority heating of deuterium in hydrogen plasmas -(D)H -was also investigated but was found inaccessible, because this scenario is too sensitive to impurity ions with Z/A=1/2 such as C 6+ , small amounts of which directly lead into the mode conversion regime. Minority heating of up to 3% of tritium in deuterium plasmas was systematically investigated during the JET Trace Tritium experimental campaign (TTE). This required operating JET at its highest possible magnetic field (3.9 to 4T) and the ICRF system at its lowest frequency (23MHz). The interest of this scenario for ICRF heating at these low concentrations and its efficiency at boosting the suprathermal neutron yield were confirmed, and the measured neutron and gammay ray spectra permit interesting comparisons with advanced ICRF code simulations.Investigations of finite Larmor radius effects on the RF-induced high-energy tails during second harmonic (ω=2 ω c ) heating of a hydrogen minority in D plasmas clearly demonstrated a strong decrease of the RF diffusion coefficient at proton energies ~1MeV, in agreement with theoretical 4 expectations. Fast wave heating and current drive experiments in deuterium plasmas showed effective direct electron heating with dipole phasing of the antennas, but only small changes of the central plasma current density were observed with the directive phasings, in particular at low single pass damping. New investigations of the heating efficiency of ICRF antennas confirmed its strong dependence on the parallel wavenumber spectrum. Advances i n topics of a more technological nature are also summarized: ELM studies using fast RF measurements, the successful experimental demonstration of a new ELM-tolerant antenna matching scheme, and technical enhancements planned on the JET ICRF system for 2006, themselves equally strongly driven by the preparation for ITER.5

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Hydrogen plasmas with ICRF inverted minority and mode conversion heating regimes in the JET tokamak

Cited by 39 publications

References 37 publications

Fast ion generation and bulk plasma heating with three-ion ICRF scenarios

Fast ion generation and bulk plasma heating with three-ion ICRF scenarios

Experimental investigation of ion cyclotron range of frequencies heating scenarios for ITER's half-field hydrogen phase performed in JET

Expanding the operating space of ICRF on JET with a view to ITER

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