On the parasitic absorption in FWCD experiments in JET ITB plasmas

Hellsten, T.; Laxåbäck, Martin; Bergkvist, Tommy; Johnson, T.; Méo, F.; Nguyen, Frédéric; Petty, C. C.; Mantsinen, M.; Matthews, G. F.; Noterdaeme, Jean-Marie; Tala, T.; Eester, D. Van; Andrew, P.; Beaumont, P.; Bobkov, V.; Brix, M.; Brzozowski, J.; Eriksson, L.‐G.; Giroud, C.; Joffrin, E.; Kiptily, V.; Mailloux, J.; Mayoral, M.‐L.; Monakhov, I.; Sartori, R.; Staebler, A.; Rachlew, Elisabeth; Tennfors, E.; Tuccillo, A. A.; Walden, A.; Zastrow, K.‐D.; Contributors, Jet‐Efda

doi:10.1088/0029-5515/45/7/020

Cited by 13 publications

(11 citation statements)

References 51 publications

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“…In the FWHCD experiments reported in Section 5 [30], η(0π0π) was similar to that of hydrogen minority heating in +90°. The heating efficiencies for ±90° FWCD phasings were η(+90°)~0.6 η(0π0π) and η(-90°)~0.5 η(0π0π), with a difference attributed to 3 He orbit pinch effects.…”

Section: New Investigations Of the Icrf Heating Efficiencysupporting

confidence: 56%

“…This is the same f/B 0 ratio as planned for ITER, at which the hydrogen and deuterium fundamental cyclotron layers are both outside the plasma, respectively on the low and high magnetic field sides of the discharge. This section only provides a brief summary of the experiments, and we refer the reader to [30] for a comprehensive account. Traces of residual and electron Landau damping (ELD).…”

Section: Fast Wave Heating and Current Drive (Fwhcd) Experimentsmentioning

confidence: 99%

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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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Section: New Investigations Of the Icrf Heating Efficiencysupporting

confidence: 56%

Section: Fast Wave Heating and Current Drive (Fwhcd) Experimentsmentioning

confidence: 99%

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

et al. 2006

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“…Owing to the absence of stringent accessibility limitations for the FW, and to the availability of reliable RF generators in the ICRF, this method is attractive for next-step fusion reactors, including during H-mode operation [5][6][7]. On the other hand, FW current drive (FWCD) is known to be experimentally challenging due to low absorptivity of the FW electron damping mechanisms and/or to parasitic damping of the wave by ions, even at rather high harmonics of the cyclotron resonance [8]. In ITER, the situation is different compared with most past experiments [9], as no 'pure' FWCD scheme is readily available.…”

Section: Introductionmentioning

confidence: 99%

Heating and current drive by ion cyclotron waves in the activated phase of ITER

Dümont

Zarzoso

2012

Nucl. Fusion

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Waves in the ion cyclotron range of frequency (ICRF) are expected to play a central role in the heating of ITER plasmas during deuterium (D)–tritium (T) operation. These waves can also be used to drive current by direct electron damping of the fast wave, provided an appropriate antenna phasing is used. The corresponding current profile is peaked near the magnetic axis, and can have a beneficial effect on the discharge stability and performance. In this paper, two scenarios applicable during the activated phase of ITER operation are compared: second harmonic tritium heating and minority helium-3 heating, which differ in the addition of a small fraction of 3He ions (2%) in the DT mixture for the latter. The resulting change of the dominant ICRF heating scheme causes the discharge properties to differ appreciably. In this paper, a full-wave code is coupled to a Fokker–Planck solver and a current drive module to investigate in detail the effect of ICRF waves on the discharge. The impact of phasing on the scenario in terms of plasma heating and current drive efficiency is studied by simulating ICRF heating with various antenna toroidal spectra. It is found that despite a lower current drive efficiency, the addition of 3He in the discharge increases the single-pass absorption rate, the ion heating fraction, and makes the scenario essentially immune to details in the toroidal phasing and fast ion properties.

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“…Owing to the robustness of the underlying technologies and to their versatility, waves in the ion cyclotron range of frequencies (ICRFs) are routinely employed in magnetic fusion devices and, as such, constitute one of the key elements for the success of future reactors [1]. Although plasma ion heating through minority fundamental absorption or harmonic damping is currently the most widespread scenario and is therefore favoured in plans for next-step experiments, ICRF waves also offer other possibilities, such as electron heating and/or non-inductive current drive either by direct damping of the fast magnetosonic wave excited by the antenna [2] or by damping of mode converted short wavelength kinetic waves [3], sawtooth stabilization by ion cyclotron current drive [4], and may even be used to generate plasma rotation [5]. Alfvén waves propagate at frequencies below the lowest ion cyclotron frequency.…”

Section: Introductionmentioning

confidence: 99%

“…(nres)part,s = − 0 d 3 rω2 ps |A| 2 − (2π)Since the equilibrium distribution function is independent of the generalized angles, it is possible to use the Parseval identity for the Hamiltonian:N |δh N | 2 = 1 (2π) 3 d 3 Φ |δH s | 2 . (B.9)In accordance with equation (50), the particle unperturbed velocity is given by v s,0 ≡ v ⊥ [cos(φ c )e ⊥1 − sin(φ c )e ⊥2 ]+v e with φ c the gyro-angle.…”

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confidence: 99%

Variational approach to radiofrequency waves in magnetic fusion devices

Dümont¹

2009

Nucl. Fusion

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Magnetic fusion plasmas feature two major classes of low frequency electromagnetic oscillations: waves in the ion cyclotron range of frequencies (ICRFs) constitute a well established method employed for plasma heating and current drive, whereas waves in the Alfvén range of frequencies naturally occur in the form of modes in close interaction with fast particles. The propagation of these waves is characterized by significant space-dispersion, making it necessary to incorporate non-local effects in the global kinetic full-wave codes which are often employed for their simulation. We present here a variational approach to this problem, which has the advantage of providing a common framework to the wave calculation and to the quasilinear response description. Two important points are discussed: firstly, we show that the irreversible part of the power transferred from the wave to the plasma particles is directly available and does not require an explicit evaluation of the kinetic flux; secondly, it is demonstrated that the symmetry of the obtained plasma functional ensures that these energy transfers are described in a consistent fashion, regardless of the level of approximation employed to evaluate the particle Hamiltonian. Finally, quasi-local, finite Larmor radius expressions are derived in the framework of this formalism and implemented in a new multi-dimensional full-wave code, named EVE, which is employed to analyse two ICRF heating scenarios for ITER.

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On the parasitic absorption in FWCD experiments in JET ITB plasmas

Cited by 13 publications

References 51 publications

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

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

Heating and current drive by ion cyclotron waves in the activated phase of ITER

Variational approach to radiofrequency waves in magnetic fusion devices

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