The response of a chromium doped alumina screen to keV and MeV ions

We have characterised the response of a chromium-doped alumina screen ‘Chromox’ to light ions (H+ and He+) accelerated to keV and MeV energies. In particular, we have determined the absolute luminosity in terms of the number of photons emitted per incident ion from the front and back faces of such a screen. This work has been motivated by the application of this material to a diagnostic for measuring fast ion losses, close to the plasma edge, from the hot plasmas in fusion devices, where its radiation hardness, compared to that of standard phosphors, makes it very attractive. We also discuss the persistent afterglow observed after removal of the ion beam in terms of its cause and possible repercussions for this diagnostic.