Design of an upgraded screen monitor system for the Siam Photon Source injector linac

The Siam Photon Source (SPS) is a 1.2-GeV synchrotron facility in Thailand, operated by the Synchrotron Light Research Institute (SLRI), providing synchrotron radiation for various applications to the user community. The SPS injector linac generates 40-MeV electron bunches, which are then transported to the booster synchrotron via the Low-Energy Beam Transport line (LBT). To ensure effective beam monitoring along the injector linac and LBT, key beam diagnostics—including beam current, transverse profile, and energy profile monitoring—have been installed in the injector linac. In order to maintain full diagnostic performance, the screen monitor system is planned to be upgraded to enhance transverse beam profile monitoring, improve radiation resistance, and support injector linac optimization for higher machine performance. This paper presents the current status of the screen monitor system for the SPS injector linac and discusses the design and implementation plan for its upgrade.