In DIII-D, it has been observed that ELM frequency decreases by 40% and ELM spacing becomes more regular in time when heating is changed from pure neutral beam injection (NBI) to predominantly electron cyclotron heating (ECH) in ITER similar shape plasmas. In comparison with the pure NBI discharges, pedestal fluctuations in magnetics and density increase in the ECH-dominated discharges. Recovery of the pedestal profiles like electron density (n _e), temperature (T _e) and pressure (p _e) shows marked differences for these two heating schemes. Average profiles in the last 30% of the ELM cycle show higher T _e, lower n _e, and similar p _e at the pedestal top for the ECH discharge when compared to the NBI discharge. The gradient of T _e (∇T _e) is also steeper at the pedestal in the ECH discharge. Magnetic fluctuations show three distinct modes at 13–116 kHz in the ECH discharges only. n _e fluctuations show two modes evolving in the inter-ELM period of the ECH discharge, a low-frequency (400 kHz) quasi-coherent mode (LFQC) and high-frequency (∼2MHz) broadband (HFB) fluctuations. Evolution of these modes has marked correspondence with the inter-ELM ∇T _e recovery. A sharp decrease in the D _α baseline is observed whenever the LFQC weakens and the HFB grows, prior to each large ELM. Transport coefficients obtained from TRANSP show that MTM and/or TEM are plausible candidates for the observed fluctuations. Linear gyrofluid simulation (TGLF) corroborates this characterization. TGLF shows that the linear growth rate of the most dominant mode peaks at ion-scale (k _θ ρ _s ∼ 0.4) at the pedestal steep gradient and the frequency is in the electron diamagnetic direction. It is proposed that increased fluctuations in the ECH-dominated case, due to increased ∇T _e, caused an increase in fluctuation-driven transport in the pedestal and slowed the pedestal recovery between ELMs, leading to a reduction in the ELM frequency.

在 DIII-D 中，当加热从纯中性束注入 (NBI) 变为 ITER 类似形状等离子体中主要的电子回旋加速器加热 (ECH) 时，ELM 频率降低了 40%，ELM 间距在时间上变得更加规律。与纯 NBI 放电相比，以 ECH 为主的放电中磁学和密度的基座波动增加。电子密度 ( n _e )、温度 ( T _e ) 和压力 ( p _e )等基座轮廓的恢复显示这两种加热方案的显着差异。ELM 周期最后 30% 的平均曲线显示更高的T _e、更低的n _e和类似的p _{与 NBI 放电相比，ECH 放电的e}在基座顶部。T _e (∇ T _e )的梯度在 ECH 放电的基座处也更陡峭。磁波动仅在 ECH 放电中显示 13-116 kHz 的三种不同模式。n _e波动显示在 ECH 放电的 ELM 间期演变的两种模式，低频（400 kHz）准相干模式（LFQC）和高频（~2MHz）宽带（HFB）波动。这些模式的演变与 ELM 间的 ∇ T _e恢复具有显着的对应关系。D _α急剧下降 在每个大型 ELM 之前，只要 LFQC 减弱且 HFB 增长，就会观察到基线。从 TRANSP 获得的传输系数表明，MTM 和/或 TEM 是观察到的波动的合理候选者。线性陀螺流体模拟 (TGLF) 证实了这一特征。TGLF 表明，主要模式的线性增长率在离子尺度（k _θ ρ _s ∼ 0.4）处在基座陡峭梯度处达到峰值，并且频率在电子反磁方向上。有人提出，在以 ECH 为主的情况下，由于 ∇ T _e增加，波动增加会导致基座中波动驱动的传输增加，并减慢 ELM 之间的基座恢复，从而导致 ELM 频率降低。