Improvement of beam performance in the negative-ion based NBI system for JT-60U
Improvement of beam performance in the negative-ion based NBI system for JT-60U
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JT-60U 负离子 NBI 系统光束性能的改进
DOI：
10.1088/0029-5515/43/7/302
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发表时间：
2003
期刊：
影响因子：
3.3
通讯作者：
T. Takayanagi
中科院分区：
文献类型：
--
作者：
N. Umeda;L. Grisham;Takumi Yamamoto;M. Kuriyama;M. Kawai;T. Ohga;K. Mogaki;N. Akino;H. Yamazaki;K. Usui;A. Honda;L. Guang;Kazuhiro Watanabe;T. Inoue;M. Hanada;M. Kashiwagi;T. Morishita;M. Dairaku;T. Takayanagi
为了改善JT-60 U负离子束注入系统的注入性能，对负离子束偏转进行了修正，提高了负离子产生的空间均匀性。由于在提取器底部的扭曲电场的网格段的外围区域的小束偏转已被观察到。通过修改提取器处的表面几何形状以形成平坦电场来校正这一点。此外，通过挤压底部提取器的边缘，还补偿了由于空间电荷引起的小束-小束排斥而导致的小束偏转。这导致NBI端口限制器上的热负荷减少。作为上述改进的结果，在355 keV的2.6 MW H 0束流的连续注入已经实现了10秒。因此，长脉冲注入高达标称脉冲持续时间的JT-60 U被证明。这为稳态托卡马克堆负离子束注入系统的长脉冲运行开辟了前景。到目前为止，在JT-60 U N-NBI中，氘束在400 keV下的最大注入功率为5.8 MW，氢束在381 keV下的最大注入功率为6.2 MW。通过调节灯丝发射电流，使更多的电弧功率进入负离子电流提取较少的区域，从而改善负离子产生的均匀性。
The injection performance of the negative-ion based NBI (N-NBI) system for JT-60U has been improved by correcting beamlet deflection and improving spatial uniformity of negative ion production. Beamlet deflection at the peripheral region of the grid segment due to the distorted electric field at the bottom of the extractor has been observed. This was corrected by modifying the surface geometry at the extractor to form a flat electric field. Moreover, beamlet deflection due to beamlet–beamlet repulsion caused by space charge was also compensated for by extruding the edge of the bottom extractor. This resulted in a reduction of the heat loading on the NBI port limiter. As a result of the improvement above, continuous injection of a 2.6 MW H0 beam at 355 keV has been achieved for 10 s. Thus, long pulse injection up to the nominal pulse duration of JT-60U was demonstrated. This has opened up the prospect of long pulse operation of the negative-ion based NBI system for a steady-state tokamak reactor. So far, a maximum injection power of 5.8 MW at 400 keV, with a deuterium beam, and 6.2 MW at 381 keV, with a hydrogen beam, have been achieved in the JT-60U N-NBI. Uniformity of negative ion production was improved by tuning the filament emission current so as to direct more arc power into the region where less negative ion current was extracted.