100 s negative ion accelerations for the JT-60SA negative-ion-based neutral beam injector
100 s negative ion accelerations for the JT-60SA negative-ion-based neutral beam injector
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JT-60SA 负离子中性束注入器的 100 秒负离子加速
DOI：
10.1088/1741-4326/ac388a
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发表时间：
2021
期刊：
影响因子：
3.3
通讯作者：
L. Grisham
中科院分区：
文献类型：
--
作者：
M. Kashiwagi;J. Hiratsuka;M. Ichikawa;G. Saquilayan;A. Kojima;H. Tobari;N. Umeda;K. Watanabe;M. Yoshida;L. Grisham
在JT-60 SA的负离子中性束注入器（N-NBI）中，成功演示了能量为500 keV、电流密度为154 A m−2、持续时间为118 s的氢负离子束。这一成就首次超过了要求（500 keV，130 A m−2，100 s）。为了在长脉冲下保持稳定的负离子产生，分析了腔室壁和等离子体栅极的最佳温度，并进行了实验验证。经确认，在射束脉冲期间，腔室壁的温度应<50 °C，等离子体栅格的温度应>200 °C。由于异常放电（即所谓的电弧放电）对灯丝阴极造成的损坏，已通过开发电弧放电后约100 μs的电弧电流快速切断系统来减轻。为了保持足够的电压保持能力，并减少电网的热负荷，由于在加速器中的束，技术开发的束加速已被应用到这个测试。由于这些技术的集成，一个稳定的光束超过100秒已被成功地证明。这是第一个超过100 s的稳定光束，强度大于75 MW m−2，这是N-NBI所需的实际水平。这些结果将为ITER和DEMO的NBI系统提供参考。
In the negative-ion-based neutral beam injector (N-NBI) of JT-60SA, a hydrogen negative ion beam with energy of 500 keV and a current density of 154 A m−2 for 118 s has been successfully demonstrated. This achievement exceeds the requirements (500 keV, 130 A m−2, 100 s) for the first time. To maintain stable negative ion production for a long pulse, the optimal temperatures of the chamber wall and plasma grid were analytically examined and were experimentally demonstrated. It was confirmed that the temperature during the beam pulse should be <50 °C for the chamber wall and >200 °C for the plasma grid. Damage to the filament cathode due to an abnormal discharge, so-called arcing, has been mitigated by developing a fast cut-off system of the arc current for around 100 μs after the arcing. To maintain sufficient voltage holding capability and to reduce the grid heat load due to the beam in the accelerator, techniques developed for the beam acceleration have been applied to this test. As a result of the integration of these techniques, a stable beam over 100 s has been demonstrated successfully. This is the first achievement over a 100 s stable beam with intensity of >75 MW m−2, which is the required practical level in the N-NBI. These results contribute to the coming NBI system for ITER and DEMO.