Neutron Contamination Detection of Medical Linear Accelerators by Thick Gas Electron Multiplier Detector in Self-Quenching Streamer Mode

The presence of neutron contamination in medical linear accelerators poses a significant challenge in radiation therapy. Numerous studies have addressed the estimation of neutron levels, often relying on electronic equipment to extract simulation results. This study introduces an innovative neutron detection method that eliminates the need for electrical system with complex circuit.

Neutron contamination arises in VARIAN linear accelerators through the interaction of energetic photons with heavier elements in the accelerator head, such as Tungsten. The primary objective of this study is to investigate neutron contamination in the VARIAN linear accelerators using a Thick Gas Electron Multiplier (THGEM) detector in the Self-Quenching Streamer (SQS) mode through Monte Carlo simulation. The detection system designed in this study involves of two main parts. 1- Conversion material to convert neutrons toprotons. 2- THGEM in SQS mode to detect protons. In this structure, the detection of protons gives an estimate of neutron contamination.

The findings indicate that, in the designed detection system, a distance of 0.5 cm from the converter is an optimal location for the THGEM. When the THGEM's minimum voltage is set at 700 volts, SQS mode occurs in most THGEM holes.

The simple structure is one of the advantages of detection system in this research. Its cost-effectiveness, featuring fewer electrical tolerances, lightweight design, and adaptability in various sizes are additional advantages, making it a viable option for neutron contamination detection.