Room: Stars at Night Ballroom 1
Purpose: To characterize a stemless plastic scintillation detector (SPSD) with respect to linearity and reproducibility and assess its dependence on energy, dose per pulse and direction.
Methods: An organic bulk heterojunction photodiode was fabricated on an ITO-coated glass substrate by spin coating a blend of P3HT and PCBM, and depositing aluminum top contacts. Eljen scintillators (EJ-204 or EJ-260) were placed on the opposite side of the glass. To measure linearity, the SPSD was irradiated with doses ranging from 20-1000 cGy with 6 MV photons, 10x10 cmÂ² field size, at a depth of 5 cm in solid water, and an SSD of 95 cm. Dose per pulse dependence was measured with the same setup except the SSD was varied from 75-125 cm. Energy dependence was measured by using 100, 180, and 300 kVp photon beams from an orthovoltage treatment unit (Xstrahl 300) and 6 and 18 MV photons from a Varian iX accelerator. Directional dependence was observed for a 16 MeV electron beam and compared to a diamond detector. Surface measurements were taken at an SSD of 107 cm and 3 cm of solid water was placed on top for depth measurements.
Results: The device showed excellent linearity with rÂ² of 1 over the dose range. The coefficient of variability over 10 identical measurements was 0.4%. Variation with dose per pulse was within 2.5% of the value measured at 95cm SSD. The largest change in response with energy was 3.2 times from 100 kV to 6 MV for EJ-260. The SPSD exhibited a directional dependence of less than 4% when compared to a diamond detector, however, correction for Cerenkov generated in the scintillator has not yet been evaluated.
Conclusion: A SPSD demonstrated excellent linearity, increase response with energy, and a small directional dependence without a Cerenkov correction.
Funding Support, Disclosures, and Conflict of Interest: NSERC Discovery Grant (Award # RGPIN/06113 - 2014) and NSERC PGS-D