Room: Exhibit Hall | Forum 3
Purpose: The response of plastic scintillators is intrinsically dependent upon the LET of incoming radiation, as demonstrated through Birksâ€™ law. This dependence can be tuned through doping of the scintillatorâ€™s composition with high-Z elements. This work presents the first quantification of the impact of high-Z dopants on plastic scintillator response to various medium and low LET radiation beams.
Methods: Four differently doped scintillators were obtained including: 0%, 1.0%, 1.5%, and 5.0% Pb-doped scintillators. Each scintillator was machined into a small cylinder (r=5mm) and coupled to a 400 Âµm optical fiber; scintillator light emitted was converted to electrical charge using a Hamamatsu H17201 photosensor. The response to various low LET (6, 9, 12, and 15 MeV electrons) and medium LET (100, 180, 250, and 300 kVp x-rays) was measured while keeping dose to the scintillator consistent (250 cGy). Measured results were then reproduced using Monte Carlo (MC) Geant4. In MC, each scintillator was modelled and the experimental beams used were re-created for the simulation (orthovoltage beam spectra were produced using SpekCalc). Each scintillator was irradiated in the simulation and the Birksâ€™ parameters (kB) were varied until an agreement between the measured and simulated dose-normalized scintillator response was obtained.
Results: As the concentration of lead doping increased, the sensitivity to high LET radiation increased while no significant effect was seen in the low LET region. With the 5.0%Pb-doped scintillator, the response to 100kV x-rays was 474%(+/-0.78%) more than the response to 15MeV electrons. The Birksâ€™ parameter, kB, was found to increase rapidly with the introduction of lead (0.126 to 0.27mm/MeV for the 0% and 5%-Pb doped scintillators).
Conclusion: This work presents the first quantification of the impact of lead doping on plastic scintillator response. These results allow for the intentional â€˜tuningâ€™ of plastic scintillators to various radiation energies and types.
Funding Support, Disclosures, and Conflict of Interest: NSERC; Grant No. RGPIN-435608.