Present and future JET ICRF antennae

Kaye, A.; Brown, T.; Bhatnagar, V.P.; Crawley, P.; Jacquinot, J.; Lobel, Ruben; Plancoulaine, J.; Rebut, P.H.; Wade, T.; Walker, C.

doi:10.1016/0920-3796(94)90034-5

Cited by 83 publications

(99 citation statements)

References 10 publications

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“…This layer resides in the hot plasma core when using f=32.5MHz, a frequency in reach both for the A2 [6] and the ILA antenna [7,8]. Up to 7.6MW was launched into the plasma.…”

Section: Resultsmentioning

confidence: 99%

Recent H majority inverted radio frequency heating scheme experiments in JET-ILW

Eester¹,

Lerche²,

Kazakov³

et al. 2017

EPJ Web Conf.

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Abstract. Inverted 3 He and D ion cyclotron minority heating scenarios were recently tested in JET-ILW. They confirm the good heating efficiency at low concentrations of ~3%. The 3 He minority heating scheme is only modestly affected by the change from a carbon (JET-C) to a Beryllium (JET-ILW) wall but unlike what was the case in JET-C, the intrinsic Be ions D-like particles in terms of charge-over-mass ratio do not prevent the D (or 4 He) minority regime from being exploited. Direct and indirect evidence of the existence of fast particle subpopulations was found in both cases.

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“…This layer resides in the hot plasma core when using f=32.5MHz, a frequency in reach both for the A2 [6] and the ILA antenna [7,8]. Up to 7.6MW was launched into the plasma.…”

Section: Resultsmentioning

confidence: 99%

Recent H majority inverted radio frequency heating scheme experiments in JET-ILW

Eester¹,

Lerche²,

Kazakov³

et al. 2017

EPJ Web Conf.

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“…1 shows three discharges with [ 3 He]<1% and 5MW of ICRF, each of them using a different toroidal phasing of the JET antenna arrays. The design of these four four-strap ICRF antennas, known as "A2", is described in detail in reference [8]. In dipole (0π0π) phasing of the strap currents they launch waves with a symmetric toroidal spectrum and dominant peak at toroidal modes n≈±27, which corresponds to dominant toroidal wavenumbers k ϕ ≈±6.4 m -1 at the antennas.…”

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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“…In all them, the ICRF power was coupled using the four A2 antennae [13], known as antennas A, B, C, and D. In pulses performed in 2009, additional power was provided by the JET ICRF ITER-Like antenna (ILA) [14]. The antennae layout is illustrated in figure 1.…”

mentioning

confidence: 99%

JET intrinsic rotation studies in plasmas with a high normalized beta and varying toroidal field ripple

Nave

Eriksson

Giroud

et al. 2012

Plasma Phys. Control. Fusion

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Understanding the origin of rotation in Ion Cyclotron Resonance Frequency (ICRF) heated plasmas is important for predictions for burning plasmas sustained by alpha particles, being characterized by a large population of fast ions and no external momentum input. The angular velocity of the plasma column has been measured in JET H-mode plasmas with pure ICRF heating for both the standard low toroidal magnetic ripple configuration, of about ~ 0.08% and, for increased ripple values up to 1.5 % [1]. These new JET rotation data were compared with the multi-machine scaling of ref. [2] for the Alfven-Mach number and with the scaling for the velocity change from L-mode into H-mode. The JET data do not fit well any of these scalings that were derived for plasmas that are co-rotating with respect to the plasma-current.With the standard low ripple configuration, JET plasmas with large ICRF heating power and normalized beta, βN ≈1.3, have a very small co-current rotation, with Alfven-Mach numbers significantly below those given by the rotation scaling of ref. [2]. In some cases the plasmas are actually counter-rotating. No significant difference between the H-mode and L-mode rotation is observed. Typically the H-mode velocities near the edge are lower than in Lmodes. With ripple values larger than the standard JET value, between 1% and 1.5%, H-mode plasmas were obtained where both the edge and the core counter rotated. I -IntroductionIntrinsic rotation can play a key role in the performance of future tokamak power plants where the momentum input will be small [3]. In present day tokamak experiments, rotation is mostly driven by the torque coming from the neutral beam injection (NBI). However, in reactors with high NBI power at high beam energy, the torque is expected to be small. The central toroidal rotation velocity for ITER H-mode plasmas with NBI power of 34 MW, was predicted to be in the range of 10-170 km/s [4]. This is lower than currently observed at JET for the same Prandtl number (ratio between momentum and ion heat diffusivity) and with NBI power less than 20 MW [5]. It is important to note that ITER simulations depend on options of momentum transport whose theory is still evolving. For instance, the ITER simulations of ref.[4] do not include any contribution from a momentum pinch which is found to exist in JET NBI discharges [6,7] and other tokamaks [8,9]. This inward pinch will modify the rotation profile in ITER, in particular the peaking of the rotation profile will increase. Understanding of momentum transport is crucial in order to reliably model rotation profiles in ITER and other future devices, however, this is not the scope of this paper. A good overview of momentum transport theory, covering also aspects like residual stress and up-down asymmetry that may affect significantly the rotation profile in ITER, is given in reference [10].As the NBI driven rotation in future machines is presumed to be small, the intrinsic plasma rotation, which occurs in the absence of momentum sources such as NBI, has...

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Present and future JET ICRF antennae

Cited by 83 publications

References 10 publications

Recent H majority inverted radio frequency heating scheme experiments in JET-ILW

Recent H majority inverted radio frequency heating scheme experiments in JET-ILW

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

JET intrinsic rotation studies in plasmas with a high normalized beta and varying toroidal field ripple

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