Dose rate dependence for different dosimeters and detectors: TLD, OSL, EBT films, and diamond detectors

Purpose: The use of laser accelerators in radiation therapy can perhaps increase the low number of proton and ion therapy facilities in some years due to the low investment costs and small size. The laser-based acceleration technology leads to a very high peak dose rate of about 1011 Gy/s. A first dosimetric task is the evaluation of dose rate dependence of clinical dosimeters and other detectors.
Methods: The measurements were done at ELBE, a superconductive linear electron accelerator which generates electron pulses with 5 ps length at 20 MeV. The different dose rates are reached by adjusting the number of electrons in one beam pulse. Three clinical dosimeters (TLD, OSL and EBT radiochromic films) were irradiated with four different dose rates and nearly the same dose. A faraday cup, an integrating current transformer and an ionization chamber were used to control the particle flux on the dosimeters. Furthermore two diamond detectors were testet.
Results: The dosimeters are dose rate independent up to 4•109 Gy/s within 2 % (OSL and TLD) and up to 15•109 Gy/s within 5 % (EBT films). The diamond detectors show strong dose rate dependence.
Conlusion: TLD, OSL dosimeters and EBT films are suitable for pulsed beams with a very high pulse dose rate like laser accelerated particle beams.