Title: Recent Operation of the FNAL Magnetron $H^{-}$ Ion Source,
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.