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Comparing Measured Prompt Gamma Emission From the AFRODITE Detector System to Geant4-Simulated Results

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V Ramanathan

V Ramanathan1*, S Peterson1 , (1) University of Cape Town, Rondebosch,


TU-C3-GePD-JT-1 (Tuesday, August 1, 2017) 10:30 AM - 11:00 AM Room: Joint Imaging-Therapy ePoster Theater

Purpose: To investigate prompt gamma emission (measured and simulated) from the prominent elements (¹²C and ¹⁶O) found in human tissue using the AFRODITE detector system.

Methods: Prompt gamma measurements of 95 MeV protons striking thin targets of natural Carbon and Mylar (¹²C, ¹⁶O) were performed using the AFRODITE gamma-ray detector system at iThemba LABS in Cape Town, South Africa. The resulting gamma energy spectra were compared to Monte Carlo simulated results using a Geant4 (v10.1.p3) model of the AFRODITE detector system. The physics of the Geant4 AFRODITE model was tested with three standard gamma-emitting source and by evaluating various hadronic physics processes, particularly the binary cascade and precompound models. The final model results were compared to the experimentally measured spectra.

Results: An absolute comparison of the prompt gamma energy spectra for both the carbon and Mylar target showed good peak alignment and an agreement in the overall prompt gamma production. For the 4.438 MeV gammas produced by the Carbon target, the simulated peak was considerably broader than the measured peak due to an exaggerated C-11 production peak in the simulations. This also resulted in an over-estimation of the prompt gamma production. For the 6.129 MeV gammas produced by Oxygen in the Mylar target, there was no discernable simulated gamma peak to compare to the experimental peak for any of the tested hadronic physics models.

Conclusion: Prompt gamma production models in Geant4 over-estimate the 4.438 gamma peak produced by Carbon and appear to be unable to produce a 6.129 MeV gamma peak from proton-Oxygen collision.

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