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

对新研制的用于低压连续波工作的霍尔加速器的性能特性进行了研究。电源的氢气压力、磁场和漏电流决定了HALOC的性能。实验研究了氢束电流、能量分布、伏安特性、能量效率等因素对氢束电流的影响。参数范围为：压力0.93~10.6(Pa.)，磁场0~190(Gauss)，漏电流0.1~3.0(A)。当阳极和两个阴极接地时，通过在中间电极上施加正电压来引出束流。在600V的加速电压下，可以成功地引出约3A的束流，持续数小时。特别是，使用Baratron压力控制系统可以提取非常稳定的光束。在不使用灯丝的情况下，只需将压力增加到约0.1Torr，就可以实现束流的点火。电流萃取效率在70%~90%之间。用多网格分析仪对能量分布的分析表明，当加速电压为600V时，在300V附近有一个非常尖锐的峰值，半宽与峰值电压之比小于0.1。根据运行条件的不同，从能量分布获得的平均能量范围为260至360 V，能效在30%至70%之间。从上面的结果可以看出，HALOC可以成功地产生3A的大氢束电流，并且非常稳定，能量分布有非常尖锐的峰值，并且连续几个小时。(到目前为止，总运行时间约为100个小时。)30%-70%的能效满足对HALOC的要求。还需要进一步的研究，以进一步降低束流能量，例如，降至100V，并提取其他气体离子(特别是氧气)。

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.