A setup for soft proton irradiation of X-ray detectors for future astronomical space missions

摘要

Protons that are trapped in the Earth's magnetic field are one of the mainthreats to astronomical X-ray observatories. Soft protons, in the range fromtens of keV up to a few MeV, impinging on silicon X-ray detectors can lead to asignificant degradation of the detector performance. Especially in low earthorbits an enhancement of the soft proton flux has been found. A setup toirradiate detectors with soft protons has been constructed at the Van-de-Graaffaccelerator of the Physikalisches Institut of the University of T\"ubingen. Keyadvantages are a high flux uniformity over a large area, to enable irradiationsof large detectors, and a monitoring system for the applied fluence, the beamuniformity, and the spectrum, that allows testing of detector prototypes inearly development phases, when readout electronics are not yet available. Twoirradiation campaigns have been performed so far with this setup. Theirradiated detectors are silicon drift detectors, designated for the useon-board the LOFT space mission. This paper gives a description of theexperimental setup and the associated monitoring system.