Experimental study on spatial uniformity of H- ion beam in a large negative ion source
Experimental study on spatial uniformity of H- ion beam in a large negative ion source
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大型负离子源H离子束空间均匀性实验研究
DOI：
10.1016/j.fusengdes.2005.06.259
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发表时间：
2005
期刊：
影响因子：
--
通讯作者：
Kazuhiro Watanabe
中科院分区：
文献类型：
--
作者：
M. Hanada;T. Seki;N. Takado;T. Inoue;T. Morishita;T. Mizuno;A. Hatayama;T. Imai;M. Kashiwagi;K. Sakamoto;M. Taniguchi;Kazuhiro Watanabe
通过测量JAERI 10 A负离子源中的H−离子束强度与等离子体参数（例如电子温度和等离子体密度）之间的相关性，对JT-60负离子源中的关键问题之一的束不均匀性的起源进行了实验研究。离子源在没有铯的情况下操作。虽然施加了均匀的滤波场，但在纵向上半区，等离子体栅极（PG）附近的电子温度高于1 eV，空间束流强度迅速下降。这表明束流的不均匀性是由电子温度高于1 eV引起的，即高能电子向PG泄漏引起的。为了研究高能电子泄漏到PG的路径，在等离子体中放置了一个50 mm × 50 mm的金属板。通过将板放置在<30 G的弱磁场中，导致上壁附近的驱动区，PG附近的电子温度在上半区中充分降低到1 eV，其中束流强度同时增加。结果，获得了20%的束流增益。此外，通过改变相对于上壁的灯丝位置，检查了向PG泄漏的高能电子的来源。发现最靠近上壁的细丝，即，距上壁80 mm处是高能电子漏入PG的源之一。
The origin of the beam non-uniformity, that is one of the key issues in JT-60 negative ion sources, was experimentally examined by measuring correlations between the intensity of the H−ion beam and plasma parameters, such as an electron temperature and plasma density in the JAERI 10 A negative ion source. The ion source was operated without cesium. Although a uniform filter field was applied, the electron temperature near plasma grid (PG) was higher than 1eV in the upper half region of the longitudinal direction, where the spatial beam intensity decreased rapidly. This indicates that the beam non-uniformity is caused by a higher electron temperature than 1eV, namely, by a leakage of the high-energy electrons toward the PG. To investigate the path of high-energy electrons leaking into the PG, a metal plate of 50mm×50mm was placed in the plasma. By placing the plate in a weak magnetic field of <30G leading to a driver region near the upper wall, the electron temperature near the PG was sufficiently reduced to 1eV in the upper half region, where the beam intensity was simultaneously increased. As a result, a 20% gain of the beam current was obtained. Further, the source of the high-energy electrons leaking toward the PG was examined by changing the relative filament position to the upper wall. It is found that the filaments closest to the upper wall, i.e., at 80mm from the upper wall is one of the sources of the high-energy electrons leaking into the PG.