Gasdynamic ECR ion source for negative ion production

Abstract

H− ion sources are needed in various areas of accelerator technology, such as beam injection into cyclotrons and storage rings and as a part of neutral beam injectors for plasma heating in experimental facilities studying thermonuclear fusion. It was recently demonstrated that gasdynamic ion source based on ECR discharge in a simple mirror trap is very efficient for proton beam production [1]. Here we use the gasdynamic plasma source as the first stage driver of volumetric negative ion production through dissociative electron attachment (DEA) [2]. Experiments were performed with a pulsed 37 GHz / up to 100 kW gyrotron radiation in a dual-trap magnetic system, which consists of two identical simple mirror traps. The first trap was used for the plasma production under ECR condition. Dense hydrogen plasma flux from the first trap flows into the second trap through a perforated plate, which prevented the propagation of microwaves into the second one. The configuration helps to separate plasma volumes with “hot” and “cold” electrons. We present recent experimental results on this topic. A negative ion current density of 80 mA/cm2 through 1 mm plasma electrode was demonstrated.