Operation of the OPPIS H⁻ Ion Source during the RHIC Run-2024

This work provides an overview of the operation of the Optically Pumped Polarized Ion Source (OPPIS) during the polarized proton Run-24 of the Relativistic Heavy Ion Collider (RHIC). The successful performance of the source was achieved through targeted upgrades focusing on three key aspects: performance, stability, and safety. The modifications to the Na-cell optimized the collection of Na vapors, extending the operational duration of the cell to over six months without requiring refilling of the Na reservoir. Similarly,changes to the plasmatron significantly increased the lifetime of source components, ensuring consistent and uninterrupted beam current throughout the run. A novel concept was implemented for the Rb cell, which showed promising preliminary results but did not result in an increase in the average polarization. A 10 % enhancement in beam transport efficiency was achieved by the modifications of the Low Energy Beam Transport (LEBT). The upgrades enabled reliable operation throughout Run-24, delivering a mean 350 μA and 300 μs beam current with an average 80 % polarization at the output of the 200MeV linac. Finally, an extended beam width of 420 μs was successfully tested with minimal polarization losses, leading to the injection of $1\times10^{12}$ protons into the Booster.