Signal-stabilized Al2O3:C-OSL dosimeter “checking chip” for correcting OSL reader sensitivity variation

Abstract

Since an OSL reader sensitivity varies 15% over two years, the sensitivity variation should be corrected for every measurement. Conventionally, the OSL reader sensitivity is corrected by either preparing a new reference OSL dosimeter or reusing a reference OSL dosimeter previously used for calibration with corrections for signal depletion and fading effect. To facilitate the correction of the OSL reader sensitivity, a signal-stabilized Al2O3:C-OSL dosimeter “checking chip” was developed in this study. The checking chip has small signal depletion and fading effect, and can correct the OSL reader sensitivity without any corrections. The checking chip was prepared through the following steps. (a) The commercial OSL dosimeter was irradiated with approximately 100 Gy. (b) The irradiated dosimeter was partially bleached by exposing visible light at 30 s to decrease the effect of signal depletion. (c) The partially bleached dosimeter was stored at 50 °C for 30 d to stabilize signal regeneration. To evaluate the usability of the checking chip, dose measurements in a high-energy photon beam were performed for half a year. The absorbed dose to water in a high-energy photon beam was determined by the calibrated ionization chamber and the OSL dosimeter. The sensitivity variation of the OSL reader was corrected by reading the checking chip on every measurement day. The signal stability of the checking chip related to multiple readings and day elapsing were −0.013% per reading and within ±0.5% at 100 d, respectively. The relative standard uncertainty of dose determination with the OSL reader sensitivity correction was 1.7%. The OSL signal of the checking chip was sufficiently stable as a reference signal source and the OSL reader sensitivity variation can be more easily corrected by using the checking chip with the same uncertainty as the conventional method.