Design and Test of Beam Diagnostics Equipment for the FAIR Proton Linac

A dedicated proton injector Linac (pLinac) for the Facility of Antiproton and Ion Research (FAIR) at GSI, Darmstadt, is currently under construction. It will provide a 68 MeV, up to 70 mA proton beam at a duty cycle of max. 35µs / 2.7 Hz for the SIS18/SIS100 synchrotrons, using the existing UNILAC transfer beamline. After further acceleration in SIS100, the protons are mainly used for antiproton production at the Pbar ANnihilations at DArmstadt (PANDA) experiment. The Linac will operate at 325 MHz and consists of a novel so called ‘Ladder’ RFQ type, followed by a chain of CH-cavities, partially coupled by rf-coupling cells. In this paper we present the beam diagnostics system for the pLinac with special emphasis on the Secondary Electron Emission (SEM) Grids and the Beam Position Monitor (BPM) system. We also describe design and status of our diagnostics testbench for stepwise Linac commissioning, which includes an energy spectrometer with associated optical system. The BPMs and SEM grids have been tested with proton and argon beam during several beamtimes in 2022. The results of these experiments are presented and discussed.