Ultra-Violet Annealing of Optically Stimulated Luminescent Dosimeter
K Lam*, C Lee, University of Michigan, ANN ARBOR, MISU-E-T-83 Sunday 3:00:00 PM - 6:00:00 PM Room: Exhibit Hall
Purpose: To study the effectiveness of an ultra-violet (UV) light source in releasing charges from deep traps in optically stimulated luminescent dosimeter (OSLD) for optical annealing. This potentially removes the known dependence of OSLD on the irradiation history and aids periodic re-calibration of each OSLD for accurate dosimetry.
Methods: We irradiated OSLDs at different doses using high energy photons. Then we illuminated them under two different light sources to observe the temporal development of the regenerated OSL signals after each illumination. A high power light-emitting diode (LED) was utilized to de-populate the intermediate dosimetry traps, whereas a UV light source was used to re-distribute charges among deep and intermediate dosimetry traps. The regeneration of OSL signal was observed using the microStar OSLD reader. The illumination sessions were repeated multiple times to reduce trapped charges.
Results: The regeneration rate of the OSL signal after de-population with the LED increased with irradiation dose, consistent with more charges in deep traps. During UV illumination, the population of charges in the intermediate dosimetry traps reached a transient-equilibrium state. After UV was turned off, the OSL signal increased with time for highly irradiated OSLD and decreased for un-irradiated OSLD. After repeated UV illuminations, the regeneration signal from the irradiated OSLD decreased to the level of un-irradiated OSLD.
Conclusions: UV illumination is effective in re-distributing charges among traps and can potentially be used to more thoroughly anneal irradiated OSLDs.