Taniguchi M, Inoue T, Umeda N, Kashiwagi M, Watanabe K, Tobari H, Dairaku M, Sakamoto K
Fusion Research and Development Directorate, Japan Atomic Energy Agency, Naka, Japan.
Rev Sci Instrum. 2008 Feb;79(2 Pt 2):02C110. doi: 10.1063/1.2816839.
The H(-) ion accelerator R&D to realize the international thermonuclear experimental reactor neutral beam is ongoing at Japan Atomic Energy Agency (JAEA). The required performance for the prototype MeV accelerator developed at JAEA is 1 MeV, 500 mA (current density of 200 A/m(2)) H(-) ion beam at the beamlet divergence angle of less than 7 mrad. Up to 2005, 836 keV, 146 A/m(2) H(-) ion beam was successfully accelerated as the highest record of the current density at MeV class energy beams. In the present work, high current negative ion beam acceleration test was performed by increasing the beam extraction apertures from 3 x 3 (9 apertures) to 3 x 5 (15 apertures). By fixing the air leak at the source chamber due to backstream ions as well as the improvement of voltage holding capability by a new fiber reinforced plastic insulator ring, the performance of the MeV accelerator was improved. So far, H(-) ion beam of 320 mA was successfully accelerated up to 796 keV with the beam divergence angle of 5.5 mrad. The accelerated drain current including the electron reaches close to the power supply limit for the MeV test facility. The heat flux by the backstream ion during the above beam acceleration was estimated to be 360 W/cm(2). The Cs leakage to the accelerator during the test campaign (Cs total input of 5.0 g) was 0.26 mg (7.0 microg/cm(2)). This is considered to be the allowable level from the viewpoint of voltage holding.
日本原子能机构（JAEA）正在进行用于实现国际热核聚变实验堆中性束的H(-)离子加速器的研发工作。JAEA研发的原型兆电子伏加速器所需性能为：1兆电子伏、500毫安（电流密度为200安/米²）的H(-)离子束，束斑发散角小于7毫弧度。截至2005年，成功加速出了836千电子伏、146安/米²的H(-)离子束，这是兆电子伏级能量束流中电流密度的最高记录。在当前工作中，通过将束流引出孔径从3×3（9个孔）增加到3×5（15个孔），进行了高电流负离子束加速测试。通过固定源室因反流离子导致的空气泄漏以及采用新型纤维增强塑料绝缘环提高耐压能力，兆电子伏加速器的性能得到了提升。到目前为止，已成功加速出320毫安的H(-)离子束，能量达到796千电子伏，束发散角为5.5毫弧度。包括电子在内的加速漏电流接近兆电子伏测试设施的电源极限。上述束流加速过程中反流离子产生的热流估计为360瓦/厘米²。测试期间（铯总输入量为5.0克）铯向加速器的泄漏量为0.26毫克（7.0微克/厘米²）。从耐压角度来看，这被认为是可接受的水平。
