Simulation of the output from a scintillator/photodiode detector using Monte Carlo techniques and Spice circuit simulation

We have developed a procedure to predict the output signal and system noise of various scintillator/photodiode detector combinations. The simulation is in three parts: 1. Monte Carlo techniques are used to model gamma ray interaction and light production in a scintillator 2. The current pulse generated from this light is then modeled, and finally 3. The simulation of photodiode and charge sensitive amplifier response and noise levels are made using a standard Spice package. To validate this procedure we have performed a series of simulations with a variety of scintillators and photodiodes. We have also built detectors in the laboratory to compare results simulated and measured results. Comparisons show good correlation between measured and simulated figures. Now this procedure has been developed and tested it will allow us to test and optimize scintillation detector designs quickly and efficiently.