PHITS code Monte Carlo simulation of a gamma chamber 5000

Area of Science:

• Medical Physics
• Radiation Dosimetry
• Computational Physics

Background:

• The Gamma Chamber 5000 (GC-5000) is a compact dry storage irradiator suitable for sample irradiation and dosimeter calibration.
• Optimizing calibration services necessitates detailed dose mapping within the GC-5000's sample chamber.
• Accurate dose distribution understanding is crucial for reliable radiation processing applications.

Purpose of the Study:

• To demonstrate the applicability of Monte Carlo (MC) simulations using the PHITS software for dose distribution analysis in the GC-5000 irradiator.
• To validate MC simulation results against experimental measurements using alanine dosimetry.
• To establish a reliable methodology for dose mapping in compact gamma irradiators.

Main Methods:

• Utilized the Proton Heavy-Ion Transport Code System (PHITS) software for MC simulations of the GC-5000 irradiator.
• Modeled the GC-5000 chamber, including 44 Co-60 pencil sources and their activities.
• Conducted experimental dose mapping using alanine dosimeters irradiated in a polymethyl methacrylate (PMMA) phantom at five defined points.

Main Results:

• MC simulations using PHITS showed good agreement with experimental dose mapping results.
• Relative differences between simulation and experiment ranged from 0.7% to 7.0%.
• The best agreement was observed at the center of the PMMA phantom.

Conclusions:

• Both MC simulation (PHITS) and alanine dosimetry are effective for precise dose rate determination in the GC-5000.
• The integrated methodology of MC modeling and alanine dosimetry provides a validated approach for dose mapping.
• This approach can be extended to optimize other industrial radiation processing facilities and serves as a reference for compact irradiators.