Electrical tests of power supplies to bias the CFC tiles in STRIKE

The calorimeter STRIKE has been developed to study and optimise the beam uniformity and extracted ion current density in SPIDER. The thermal image of the beamlet footprints that appea rs on the rear side of the calorimeter panels made of one - dimensional Carbon Fibre Composite (CFC) tiles is observed by thermal cameras, which permit to reconstruct the beam shape. Changing the measurement position of STRIKE allows a double characterisatio n of the beam, which results in the possibility of measuring the beam divergence and the halo. Each tile is electrically insulated to give a measure of the ion current reaching it and it is instrumented with a thermocouple array for absolute calibration of thermal camera measurements. The tiles are also polarized to pull secondary electrons back to the calorimeter surface. In fact t he voltage gradient in the vicinity of the tiles must guarantee that electrons emitted from one tile are attracted back to the same tile, so that the current profile measurement is not affected. 3D simulations of STRIKE inside the SPIDER vessel have been carried out and showed that 150V is enough to maintain the secondary electron trajectories shorter than the distance between the expected beamlet impact position and the edge of STRIKE tiles, the electrons should be re - absorbed on the same tile . The procurement of STRIKE is in the scope of the OFC - 531 contract. This includes the mechanical structure, the CFC tiles, the thermocoupl es and the electrostatic probes. Within this procurement, fou r power supplies was bought for the biasing of the tiles. This document reports the results of the functional tests carried out on these power supplies.