Optimal design for a μBq/kg gamma spectrometer based on Monte Carlo simulation

Area of Science:

• Nuclear Physics
• Particle Physics
• Experimental Physics

Background:

• Rare event experiments require highly sensitive detectors for material screening.
• Existing methods face challenges in achieving the necessary low background and high efficiency.
• The China Jinping Underground Laboratory (CJPL) provides a unique low-background environment.

Purpose of the Study:

• To design and optimize a new gamma-ray spectrometer, the ARray of GermaniUm γ-ray Spectrometer (ARGUS).
• To achieve a decision threshold of 10μBq/kg for 238U/232Th decay chains.
• To enhance material screening capabilities for rare event experiments.

Main Methods:

• Utilizing Monte Carlo simulations with Geant4 for spectrometer optimization.
• Integrating five High-Purity Germanium (HPGe) detectors to increase efficiency.
• Evaluating two distinct shielding systems: liquid nitrogen and lead plus copper.

Main Results:

• The ARGUS spectrometer design was optimized for high efficiency and low background noise.
• The combination of multiple HPGe detectors significantly improved sensitivity.
• Evaluated shielding configurations demonstrated effectiveness in reducing external radiation.

Conclusions:

• The optimized ARGUS spectrometer, with its multi-detector array and advanced shielding, is well-suited for sensitive material screening.
• The proposed design can achieve the target decision threshold for 238U/232Th decay chains.
• ARGUS will be a valuable tool for rare event experiments at CJPL.