Beam Instrumentation for the CERN LINAC4 and PSB Half Sector Test

The construction, installation and initial commissioning of CERN's LINAC4 was completed in 2016 with H⁻ ions successfully accelerated to its top energy of 160 MeV. The accelerator is equipped with a large number of beam diagnostic systems that are essential to monitor, control and optimize the beam parameters. A general overview of the installed systems and their functional specifications will be followed by a summary of the most relevant results. This includes transverse profile monitors (wire scanners, wire grids and a laser profile monitor), beam position and phase monitors (whose ToF measurements were essential for adjusting RF cavity parameters), beam loss monitors, beam current transformers and longitudinal beam shape monitors. This contribution will also cover the beam instrumentation for the so-called PSB Half Sector Test, which has been temporarily installed in the LINAC4 transfer line to study H⁻ stripping efficiency. At this facility it was possible to test the new H⁰/H⁻ beam current monitor, designed to monitor the stripping efficiency and an essential element of the beam interlock system when the LINAC4 is connected to the PSB in 2019.