Replicating the light output of scintillators using LEDs

Tracy Ann Roberts

Calibration of scintillation-based radiation detectors is typically accomplished with radioactive calibration sources. These sources, while frequently low level, present a human health risk and have regulatory requirements. Eliminating the need for these sources in calibrating radiation detectors, especially in field applications, is desirable. As an alternative, an LED-based calibration system has been developed. The system has the ability to replicate scintillation light pulses with varying amplitude, decay time, and wavelength, and frequency. The system is split into two components - pulse generation and light output - providing the user with maximum flexibility to define their synthetic scintillation pulse as well as the light output characteristics of the device. The pulse generation circuit is capable of generating an equivalent single-point energy calibration, multi-point energy calibration, or the user can upload a simulated or previously-obtained energy spectrum and allow the device to automatically adjust the light output of the LED so as to create a synthetic energy spectrum. In this regard, the light output of the LED is equivalent to the energy deposited in a scintillator by a radiation source. Applications of the device include scintillation-based radiation detector calibration, nuclear education, and radiation detection training. This thesis covers phases one and two of the Scintillator Light-Output Simulator design. Phase one is a pulse simulator that was designed to replicate single light pulses emitted by a scintillator, using an LED and specialized driver electronics to create a pulse with specific amplitude and decay time. The pulse simulator was intended to be a proof-of-concept prototype for the purpose of determining whether it was possible to replicate a scintillator pulse using an LED. In phase two of the Scintillator Light-Output Simulator, a spectrum simulator was designed to replicate the entire spectrum of light pulses emitted by a scintillator when exposed to a known radioactive source. The spectrum simulator builds on the concepts of the pulse simulator, and allows the user to automatically reproduce an entire spectrum of pulses with the flip of a switch.

Replicating the light output of scintillators using LEDs

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