Effects of film thickness on scintillation characteristics of columnar CsI:Tl films exposed to high gamma radiation doses

• CsI:Tl films of different thicknesses deposited for γ and α detection.
• Pulse-height spectra found to degrade with increasing thickness.
• Radiation damage is found more in films than single crystal of comparable thickness.
• Detection efficiency increases for γ while it is invariant for α beyond 50 µm.

Oriented columnar films of Tl doped CsI (CsI:Tl) of varying thicknesses from 50 µm to 1000 µm have been deposited on silica glass substrates by a thermal evaporation technique. The SEM micrographs confirmed the columnar structure of the film while the powder X-ray diffraction pattern recorded for the films revealed a preferred orientation of the grown columns along the <200> direction. Effects of high energy gamma exposure up to 1000 Gy on luminescence properties of the films were investigated. Results of radio-luminescence, photo-luminescence and scintillation studies on the films are compared with those of a CsI:Tl single crystal with similar thickness. A possible correlation between the film thicknesses and radiation damage in films has been observed.