Simulation of the Ohkawa-mechanism- dominated current drive of electron cyclotron waves using linear and quasi-linear models,Plasma Physics and Controlled Fusion

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Simulation of the Ohkawa-mechanism- dominated current drive of electron cyclotron waves using linear and quasi-linear models
Plasma Physics and Controlled Fusion ( IF 2.2 ) Pub Date : 2021-01-05 , DOI: 10.1088/1361-6587/abce8e
P W Zheng ₁ , L H He ₁ , L Yin ₁ , X Q Lu _{1,

2} , Q H Huang ₁ , Y J Zhong ₁ , S Deng ₁ , X C Jiang ₁ , X Y Gong ₁

Affiliation

Simulation on the Ohkawa-mechanism-dominated current drive (OKCD) of electron cyclotron (EC) waves is performed using TORAY-GA linear code, and the results are compared with those calculated by CQL3D quasi-linear code. It is found that the radial location of the OKCD profile is almost identical between the linear and the quasi-linear calculations. However, there are significant differences in the calculation of the total driven current ${I_{\, ec}}$ and the peak value of the driven current profile $j_{ec}^{\, peak}$ between the two models. The ${I_{ec}}$ calculated by the CQL3D code is at least 1.4 times larger than the results from the TORAY-GA code. For the calculation of $j_{ec}^{\, peak}$ , the results from CQL3D are at least 1.6 times larger than that calculated by TORAY-GA. With increasing electron temperature, the two models further enlarge the total driven current scaling factor ${F_I}$ and the peak driven current density scaling factor ${F_j}$ . This is mainly because the collision operator in TORAY-GA code adopts a high-speed model and does not retain the first-order Legendre expansion term for momentum conservation of electron self-collision. The quasi-linear effect does not have a significant influence on the total driven current of OKCD when the EC power level does not meet $\frac{{{P_{rf}}\left( {{\text{MW}}\;{{\text{m}}^{ - 3}}} \right)}}{{{n_e}\left( {{{10}^{19}}{{\text{m}}^{ - 3}}} \right)}}$ > 0.5. Therefore, in practical engineering, the TORAY-GA code can be used to calculate OKCD quickly and accurately by multiplying with appropriate scaling factors. The effect of momentum conservation is very important for OKCD and on-axis EC current drive (ECCD), but this effect is not important for off-axis ECCD. The results from this study show that the effects of electron trapping and the collision between resonant passing electrons and trapped electrons are responsible for the decrease in off-axis ECCD efficiency.

中文翻译：

使用线性和准线性模型模拟电子回旋波的大川机制控制的电流驱动

使用TORAY-GA线性代码对电子回旋加速器（EC）波的大川机制主导的电流驱动（OKCD）进行仿真，并将结果与CQL3D准线性代码计算的结果进行比较。发现在线性和准线性计算之间，OKCD轮廓的径向位置几乎相同。但是，在两个模型之间，总驱动电流 ${I _ {\，ec}}$ 和驱动电流曲线的峰值的计算存在很大差异 $j_ {ec} ^ {\，峰值}$ 。在 ${I_ {ec}}$ 由CQL3D代码计算比从TORAY-GA代码的结果大至少1.4倍。用于计算 $j_ {ec} ^ {\，峰值}$ ，CQL3D的结果至少比TORAY-GA计算的结果大1.6倍。随着电子温度的升高，两个模型进一步扩大了总驱动电流比例因子 ${F_I}$ 和峰值驱动电流密度比例因子 ${F_j}$ 。这主要是因为TORAY-GA代码中的碰撞算子采用了高速模型，并且没有保留电子自碰撞动量守恒的一阶Legendre展开项。当EC功率电平不满足时，准线性效应对OKCD的总驱动电流没有重大影响 $\ frac {{{P_ {rf}} \ left（{{\ text {MW}} \; {{\ text {m}} ^ {-3}}} \ right）}} {{{n_e} \ left（{{{10} ^ {19}} {{\ text {m}} ^ {-3}}} \ right）}}$ > 0.5。因此，在实际工程中，通过乘以适当的比例因子，可以使用TORAY-GA代码快速而准确地计算OKCD。动量守恒的效果对OKCD和轴上EC电流驱动（ECCD）非常重要，但对离轴ECCD而言不重要。这项研究的结果表明，电子俘获的影响以及共振通过的电子与被俘获的电子之间的碰撞是导致离轴ECCD效率下降的原因。

更新日期：2021-01-05

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