He2+ source based on Penning-type discharge with electron cyclotron resonant heating by millimeter waves

Abstract

Electron cyclotron resonance (ECR) ion sources are particularly useful for nuclear, atomic and high energy physics, as unique high current generators of multicharged ion beams. Plasmas of gas discharges in open magnetic traps heated by pulsed high power high-frequency microwaves of gyrotrons are promising in the field of research in the development of ECR sources for high charge state ion beams. It is necessary to decrease pressure and increase plasma density to reach higher average charge of ions in the plasma. The ECR discharge could be ignited at very low gas pressure, but it takes longer time for the discharge start-up. Hence, it is impossible to realize the ECR discharge with limited microwave heating pulse duration at gas pressure below a certain threshold value. We suggest a Penning-type discharge as a trigger discharge for fast development of pulsed-ECR plasma. The Penning-type discharge glows at a low pressure as needed. Gyrotron radiation (75 GHz, 200 kW, 1 ms) was used for plasma heating. Fully striped helium ions were demonstrated, average charge of ions in the plasma was ≈2. Temporal evolution of charge state distribution as a function of helium pressure and microwave power was investigated.