Development of a negative hydrogen ion source for tandem proton accelerator using transformer couled plasma sources

Abstract

A negative hydrogen ion source based on the transformer coupled plasma (TCP) source has been developed for 1.75 MeV tandem proton accelerator to detect underground explosives and mines. The TCP-based ion source has been designed and constructed for H− beam currents of 10 mA at the extraction voltage of 30 kV. High-density hydrogen plasmas of 1012 cm−3 are generated by 13.56 MHz radio frequency (rf) power with the threshold power of 1 kW. Negative hydrogen beam currents of up to 0.7 mA at the extraction voltage of 30 kV are extracted with the rf power of 1.5 kW. Extracted beam currents follow the magnitudes of plasma densities which can be adjusted by changing rf power and neutral gas pressure. The e/H− ratio of down to 70 has been achieved with a simple magnetic filter.