Global electromagnetic gyrokinetic simulations are performed with the particle-in-cell code ORB5 for an ITER pre-fusion-power-operation plasma scenario, with half-field (2.65 T) and half-current (7.5 MA). We report on a 'multi-scale' analysis of the discharge, considering eigenmodes and instabilities across three scale-lengths (n < 35, 45 < n < 70, n > 100). Although the scenario will nominally have neutral beam heating with particles injected with 1 MeV, Alfvén eigenmodes are investigated in the absence of such source, and reversed shear, toroidal and elliptical Alfvén eigenmodes are found with weak damping for moderately low toroidal mode numbers (10 ⩽ n ⩽ 35). At higher toroidal mode numbers (40 ⩽ n ⩽ 70), unstable Alfvénic modes have been observed close to rational surfaces and are labelled as beta-induced Alfvén eigenmodes (BAEs)/Alfvénic ion temperature gradient modes, since their frequency is associated with the BAE gap and they are driven by the bulk plasma on the Alfvénic continuum. These modes are unstable in the absence of energetic particles (EPs), and adding a species of EPs (with an isotropic 1 MeV slowing down distribution) has negligible impact on their growth rate. At higher toroidal mode numbers (n ⪅ 200), low frequency microscale instabilities are observed.
全球电磁回旋动理学模拟采用粒子网格法代码ORB5，针对ITER预聚变功率运行方案，在半磁场（2.65 T）和半电流（7.5 MA）条件下进行。我们报告了对该放电的“多尺度”分析，考虑了三个尺度范围（n < 45、45 < n < 70、n > 100）内的本征模和不稳定性。尽管该方案名义上具有以1 MeV能量注入粒子的中性束加热，但阿尔文本征模是在无此类源的情况下研究的，并在中等低环向模数（10 ⩽ n ⩽ 35）下发现了具有弱阻尼的反转剪切、环形和椭圆形阿尔文本征模。在较高环向模数（40 ⩽ n ⩽ 70）下，在有理面附近观测到了不稳定的阿尔文模，并将其归类为β诱导阿尔文本征模（BAEs）/阿尔文离子温度梯度模，因为其频率与BAE间隙相关，且由体等离子体在阿尔文连续谱上驱动。这些模在无高能粒子（EPs）的情况下是不稳定的，而加入具有各向同性1 MeV慢化分布的高能粒子种类对其增长率的影响可忽略不计。在更高环向模数（n ⪅ 200）下，观测到了低频微观不稳定性。