This paper reports on ITER-relevant ion cyclotron resonance frequency (ICRF) physics investigated on JET in 2003 and early 2004. Minority heating of helium three in hydrogen plasmas—(3He)H—was systematically explored by varying the 3He concentration and the toroidal phasing of the antenna arrays. The best heating performance (a maximum electron temperature of 6.2 keV with 5 MW 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 3He concentration increased above ∼2%. In the latter regime the best heating performance (a maximum electron temperature of 8 keV with 5 MW 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 C6+, 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 4 T) and the ICRF system at its lowest frequency (23 MHz). 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 = 2ωc) heating of a hydrogen minority in D plasmas clearly demonstrated a strong decrease in the RF diffusion coefficient at proton energies ∼ 1 MeV, in agreement with theoretical 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 in 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, they being equally strongly driven by the preparation for ITER.
本论文报告了2003年及2004年初在JET上开展的与ITER相关的离子回旋共振频率（ICRF）物理研究。通过改变氦-3浓度和天线环向相位，系统研究了氢等离子体中的氦-3少数加热——(³He)H。最佳加热性能（电子温度最高达6.2 keV，ICRF功率为5 MW）是在沿等离子体电流方向优先发射波时获得的。实验明确展示了当氦-3浓度增加到约2%以上时，向模式转换加热机制的尖锐且可重复的转变。在后一种机制下，最佳加热性能（电子温度最高达8 keV，ICRF功率为5 MW）是通过偶极子阵列相位（即对称天线功率谱）实现的。还研究了氘等离子体中的氢少数加热——(D)H，但发现该方案不可行，因为该方案对Z/A = 1/2的杂质离子（如C⁶⁺）过于敏感，少量此类杂质就会直接导致进入模式转换机制。在JET痕量氚实验（TTE）期间，系统研究了氘等离子体中高达3%的氚少数加热。这要求JET在其可能的最高磁场（3.9至4 T）下运行，且ICRF系统在其最低频率（23 MHz）下工作。该方案在低浓度下用于ICRF加热的兴趣及其提高超热中子产额的效率得到了证实，所测量的中子和伽马射线谱可与先进的ICRF代码模拟进行有意义的比较。对氢少数在D等离子体中二次谐波（ω = 2ωc）加热期间射频诱导高能尾部的有限拉莫尔半径效应的研究明确表明，在质子能量约1 MeV时射频扩散系数显著降低，这与理论预期一致。在氘等离子体中的快波加热和电流驱动实验表明，使用偶极子相位时能有效直接加热电子，但在低单程阻尼条件下，使用定向相位时等离子体中心电流密度仅发生微小变化。对ICRF天线加热效率的新研究证实了其与平行波数谱的强依赖性。此外还总结了更具技术性质的进展：利用快速射频测量进行ELM研究、新型耐ELM天线匹配方案的成功实验演示，以及为2006年计划在JET ICRF系统上进行的技术改进，这些均同样受到为ITER做准备的强烈驱动。