Development of MeV Range Heavy Ion Beam Probe

该合作项目的目的是为安装在大型螺旋装置(LHD)上的6 MeV重离子束探测器的设计奠定基础。主要研究内容包括以下三个方面：(1)低纹波6 MeV加速器设计；(2)三维束流轨迹控制系统设计；(3)DE/E&lt；10^&lt；-5&gt；高分辨率能量分析仪设计。重离子束加速器在传统的重离子探头中使用热离子源和单端加速器，但对于LHD实验大厅来说，它太大了。我们已经决定使用负离子源和串列加速器。这是基于这样一个事实，即能量扩散小于10 eV的负金离子源的研制是在范围内的，并且可以通过JIPPT-IIU HIBP所使用的射频衍生电源实现纹波小于10^-5的高电压。在束流轨迹控制方面，束流轨迹完全是三维的，二维势能分布测量的数据精度可能会降低。我们设计了一种新的束线布置，在分析器侧放置二次扫描电极来控制二次束流轨迹，从而使能量分析器可以放置在远离环面的位置，并将在CHS HIBP上进行测试。这将需要复杂的计算机控制系统。能量分析仪我们研制了一种新型的无保护环电极平行板分析仪，该分析仪不受电场干扰，并成功地在JIPPT-IIU HIBZP上进行了测试。此外，还提出了一种消除电势剖面测量误差的新方法。然而，这种类型的分析仪对于6 MeV HIBP用于LHD是不现实的。有必要引入新的观念。

The purpose of this collaboration program is to establish foundations for the design of 6 MeV heavy ion beam probe to be installed on the Large Helical Device (LHD). The critical issues are summarized in the following three items.(1) Design of 6 MeV accelerator with low ripple(2) Design of control system for three dimensional beam trajectory(3) Design of energy analyzer with high resolution of DE/E < 10^<-5> We summarize below the results of the collaboration program.1. On Heavy Ion Beam AcceleratorA thermionic ion source and single ended accelerator has been used in the conventional heavy ion beam probe, but it should be too large for the LHD experimental hall. We have decided to utilize a negative ion source and tandem accelerator. It is based on the facts that development of a negative gold ion source with energy spread less than 10 eV is within range and that high voltages with ripple less than 10^<-5> can be achieved by a RF derived power supply as is used in JIPPT-IIU HIBP.2. On Beam trajectory controlBeam trajectories are completely three dimensional and data accuracy for two dimensional potential profile measurement can be degraded. We have designed a new arrangement of the beam line in which second sweep electrodes are placed on the analyzer side to control the secondary beam trajectory so that the energy analyzer can be placed away from the torus, which will be tested with CHS HIBP. This will require sophisticated computer-controlled system.3. An Energy AnalyzerWe have constructed a new type of parallel plate analyzer with shaped electrode without guard ring, which is free from electric field disturbance in the analyzer, and successfully tested with JIPPT-IIU HIBZP. Furthermore, a new method of error elimination for the potential profile measurements has been developed. However, This type of analyzer is not a realistic for 6 MeV HIBP for LHD. New idea is necessary to be introduced.