A diagnostic study of proton-beam irradiated water targets

A non-destructive method was developed for assessing the average density of a small-volume water target during particle beam irradiation. Due to local boiling of the target water the particle beam penetrates through the target and further through the thin back wall of the target unit. The charged particle beam excites water molecules both in the target water and in the cooling water. A light guide was inserted into the target cooling water to transfer the light emitted during de-excitation to a photodiode which produced a voltage signal when the beam entered the cooling water. Beam current and target-water temperature were recorded simultaneously with the diode voltage signal. The light emitted in the target during irradiation was photographed through a glass window on the target. Photographic views of the target medium during irradiation are presented. Formation of voids in the beam path of the target was verified with the photographic technique.