Recent Operation of the FNAL Magnetron $H^{-}$ Ion Source

TL;DR

This paper describes the operational changes and upgrades to the FNAL magnetron H- ion source, including design modifications and operational parameters, resulting in improved uptime and longer source lifetime after a system upgrade in 2012.

Contribution

It presents the redesigned ion source and operational adjustments necessary for direct extraction at 35 keV, enhancing performance and reliability.

Findings

Achieved >99% uptime for HEP operations.

Extended ion source lifetime to over 9 months.

Implemented successful redesign for direct extraction at 35 keV.

Abstract

This paper will detail changes in the operational paradigm of the Fermi National Accelerator Laboratory (FNAL) magnetron $H^{-}$ ion source due to upgrades in the accelerator system. Prior to November of 2012 the $H^{-}$ ions for High Energy Physics (HEP) experiments were extracted at ~18 keV vertically downward into a 90 degree bending magnet and accelerated through a Cockcroft-Walton accelerating column to 750 keV. Following the upgrade in the fall of 2012 the $H^{-}$ ions are now directly extracted from a magnetron at 35 keV and accelerated to 750 keV by a Radio Frequency Quadrupole (RFQ). This change in extraction energy as well as the orientation of the ion source required not only a redesign of the ion source, but an updated understanding of its operation at these new values. Discussed in detail are the changes to the ion source timing, arc discharge current, hydrogen gas pressure, and cesium delivery system that were needed to maintain consistent operation at >99% uptime for HEP, with an increased ion source lifetime of over 9 months.