Test construction of a large current low voltage CW ion source for ion implantation

研究了新型低压连续波霍尔加速器（HALOC）的性能特点。氢气压力、磁场和电源的漏极电流决定了HALOC的性能。实验研究了对抽提氢束电流、能量分布、V-I特性、能量效率等的影响。压力参数范围为0.93 ~ 10.6 (Pa)，磁场参数范围为0 ~ 190 (Gauss)，漏极电流参数范围为0.1 ~ 3.0 (A)。通过对中间电极施加正电压提取光束，同时对阳极和两个阴极进行接地。在600 V的加速电压下，可以在几个小时内成功地提取出约3a的光束。特别地，利用Baratron压力控制系统可以提取出非常稳定的光束。光束的点火可以仅仅通过增加压力到约0.1托而不使用灯丝来实现。目前的萃取效率为70% ~ 90%。利用多栅格分析仪对能量谱进行了分析，结果表明，当加速电压为600 V时，在300 V附近有一个非常尖锐的峰值，且半宽与峰值电压的比值小于0.1。根据操作条件，从能量剖面中获得的平均能量范围为260至360伏，从而实现30%至70%的能源效率。从以上结果可以看出，HALOC可以成功地产生3a的大氢束电流，并且非常稳定，能量谱中有一个非常尖锐的峰值，并且持续数小时。（到目前为止，总运行时间约为100小时。）30- 70%的能源效率符合HALOC的要求。进一步的研究，以进一步降低光束的能量，例如，降低到100 V，并提取其他气体离子（特别是氧气）是必要的。

The performance characteristics of the newly constructed Hall accelerator for low voltage CW operation (HALOC) were investigated. Hydrogen gas pressure, magnetic field, and drain current of the power supply determine the HALOC performance. Effects on the extracted hydrogen beam current, energy profiles, V-I characteristics, energy efficiency and so on were investigated in the experiments. Parameter ranges were from 0.93 to 10.6 (Pa) for pressure, 0 to 190 (Gauss) for magnetic field, and 0.1 to 3.0 (A) for drain current. The beam was extracted by appling positive voltage to intermediate electrodes while the anode and two cathodes were grounded. A beam of about 3 A could be extracted successfully for an acceleration voltage of 600 V, for several hours. Particularly, a very stable beam could be extracted by using a Baratron pressure control system. The ignition of the beam could be achieved merely by increasing the pressure to about 0.1 Torr without the use of filaments. Efficiency of current extraction ranges form 70 to 90%. The analyses of the energy profiles by means of a multi-grid analyzer show a very sharp peak around 300 V for an acceleration voltage of 600 V, and the ratio of half width to the peak voltage is less than 0.1. The average energy obtained from the energy profile ranges from 260 to 360 V, depending on the operation conditions, resulting in an energy efficiency between 30 to 70 %. From the above results, It can be seen that the HALOC could have successfully generated a large hydrogen beam current of 3 A, and very stably with a very sharp peak in the energy profile, and continuously for several hours. (So far total running time is about 100 hours.) The 30-70 % energy efficiency meets the requirements posed for HALOC. Further research to further decrease the beam energy, say, down to 100 V, and the extraction of other gas ions (oxygen, in particular) are needed.