Design and construction of a fast ion loss Faraday cup array diagnostic for Joint European Torus

A thin foil Faraday cup array is being built to measure the loss of 3.5 MeV alpha particles and MeV ion cyclotron heating tail ions on Joint European Torus. It will consist of nine detectors spread over five different poloidal locations and three radial positions. They will measure the poloidal distribution and radial scrape off of the losses. The detectors will be comprised of four layers of thin (2.5 μm) Ni foil, giving some resolution of the lost particle energy distribution as different ranges of energies will stop in different layers of the detector. One detector will utilize eight thinner (1.0 μm) foils to obtain a better-resolved energy distribution. These detectors will accept particles incident up to 45° from the normal to the foils.