Improvements on the Stability and Operation of a Magnetron H- Ion Source

TL;DR

This paper reports on various modifications to Fermilab's magnetron H- ion sources over three years, aiming to enhance their stability, reliability, and performance through hardware improvements and operational adjustments.

Contribution

The paper introduces new hardware components and operational strategies that significantly improve the stability and efficiency of magnetron H- ion sources.

Findings

Solenoid gas valve reduces temperature dependence issues.

New cesium oven improves thermal management and tuning.

Current-regulated arc modulator stabilizes beam output.

Abstract

The magnetron H- ion sources developed in the 1970s currently in operation at Fermilab provide beam to the rest of the accelerator complex. A series of modifications to these sources have been tested in a dedicated offline test stand with the aim of improving different operational issues. The solenoid type gas valve was tested as an alternative to the piezoelectric gas valve in order to avoid its temperature dependence. A new cesium oven was designed and tested in order to avoid glass pieces that were present with the previous oven, improve thermal insulation and fine tune its temperature. A current-regulated arc modulator was developed to run the ion source at a constant arc current, providing very stable beam outputs during operations. In order to reduce beam noise, the addition of small amounts of N2 gas was explored, as well as testing different cathode shapes with increasing plasma volume. This paper summarizes the studies and modifications done in the source over the last three years with the aim of improving its stability, reliability and overall performance.