Ion cyclotron emission (ICE) driven by perpendicular neutral beam-injected (NBI) deuterons, together with the distinctive ICE driven by tangential NBI, have been observed from heliotron–stellarator plasmas in the large helical device (LHD). Radio frequency radiation in the lower hybrid range has also been observed Saito K. etal (2018 Plasma Fusion Res. 13 3402043), with frequency dependent on plasma density. Here we focus on recent measurements of ICE from deuterium plasmas in LHD, which show substantial variation in spectral character, between otherwise similar plasmas that have different local density in the emitting region. We analyse this variation by means of first principles simulations, carried out using a particle-in-cell (PIC) kinetic approach. We show, first, that this ICE is driven by perpendicular NBI deuterons, freshly ionised near their injection point in the outer midplane edge of LHD. We find that these NBI deuterons undergo collective sub-Alfvnic relaxation, which we follow deep into the nonlinear phase of the magnetoacoustic cyclotron instability (MCI). The frequency and wavenumber dependence of the saturated amplitudes of the excited fields determine our simulated ICE spectra, and these spectra are obtained for different local densities corresponding to the different LHD ICE-emitting plasmas. The variation with density of the spectral character of the simulated ICE corresponds well with that of the observed ICE from LHD. These results from heliotron–stellarator plasmas complement recent studies of density-dependent ICE from tokamak plasmas in KSTAR Thatipamula S.G. etal (2016 Plasma Phys. Control. Fusion 58 065003); Chapman B. etal (2017 Nucl. Fusion 57 124004), where the spectra vary on sub-microsecond timescales after an ELM crash. Taken together, these results confirm the strongly spatially localised character of ICE physics, and reinforce the potential of ICE as a diagnostic of energetic ion populations and of the ambient plasma.

已从大型螺旋装置 (LHD) 中的日光加速器-仿星器等离子体观察到由垂直中性束注入 (NBI) 氘核驱动的离子回旋加速器发射 (ICE)，以及由切向 NBI 驱动的独特 ICE。Saito K. et al (2018 Plasma Fusion Res. 13)3402043)，频率取决于等离子体密度。在这里，我们重点关注 LHD 中氘等离子体的 ICE 的最近测量，这些测量显示光谱特征的显着变化，在发射区域具有不同局部密度的其他相似等离子体之间。我们通过第一性原理模拟来分析这种变化，该模拟使用细胞内粒子 (PIC) 动力学方法进行。我们首先表明，这个 ICE 是由垂直的 NBI 氘核驱动的，在 LHD 的外中平面边缘的注入点附近新鲜电离。我们发现这些 NBI 氘核经历了集体亚 Alfvnic 弛豫，我们深入研究了磁声回旋不稳定性 (MCI) 的非线性阶段。激发场饱和振幅的频率和波数依赖性决定了我们模拟的 ICE 光谱，这些光谱是针对不同的局部密度获得的，对应于不同的 LHD ICE 发射等离子体。模拟 ICE 的光谱特征随密度的变化与从 LHD 观察到的 ICE 的变化很好地对应。这些来自日光加速器-仿星器等离子体的结果补充了最近对 KSTAR Thatipamula SG 中托卡马克等离子体密度依赖性 ICE 的研究等（2016 Plasma Phys. Control. Fusion 58 065003）；Chapman B.等人(2017 Nucl. Fusion 57 124004)，其中在 ELM 崩溃后，光谱在亚微秒时间尺度上变化。总之，这些结果证实了 ICE 物理学的强烈空间局部化特征，并加强了 ICE 作为高能离子群和环境等离子体诊断的潜力。