Performance Characterization of a Plastic Scintillator Sensor for Fast Neutron, Thermal Neutron, and Gamma Ray...

Area of Science:

• Nuclear instrumentation
• Radiation detection and measurement
• Applied physics

Background:

• Mixed radiation fields pose challenges for accurate detection and discrimination.
• Existing detectors may lack compactness or the ability to differentiate between various radiation types.
• Single-photomultiplier tube (PMT) systems offer potential for miniaturization.

Purpose of the Study:

• To develop and characterize a compact composite scintillation detector for discriminating gamma rays, fast neutrons, and thermal neutrons.
• To evaluate the performance of two different scintillator materials (EJ200 and EJ276) in combination with a thermal neutron screen (EJ426).
• To assess the detector's suitability for mixed radiation field applications.

Main Methods:

• Fabrication of composite detector assemblies using EJ200/EJ276 plastic scintillators and an EJ426 thermal neutron screen, coupled to a single PMT.
• Calibration of gamma-equivalent energy response using standard gamma sources (137Cs, 22Na, 60Co) via Compton edge analysis.
• Evaluation of pulse shape discrimination using an Am-Be neutron source and varying moderator thicknesses.

Main Results:

• The EJ200+EJ426 assembly demonstrated good discrimination between thermal neutron capture and gamma events (figure of merit > 5).
• The EJ276+EJ426 assembly successfully resolved three distinct signal populations: gamma rays, fast neutrons, and thermal neutrons.
• Both assemblies showed potential for mixed-field radiation detection.

Conclusions:

• The developed composite scintillation detector architecture is a viable compact solution for mixed radiation fields.
• The EJ276+EJ426 configuration offers superior discrimination capabilities for gamma rays, fast neutrons, and thermal neutrons.
• This technology holds promise for various applications requiring precise radiation identification in complex environments.