Design of a coplanar grid CZT gamma spectrometer with deep sensitive energy correction method

Background Gamma-ray radiation detection is of vital importance in fields such as inertial confinement fusion (ICF), nuclear physics, and environmental monitoring. However, the complex energy spectrum and limited diagnostic space in ICF experiments impose stringent requirements on the energy resolution, detection efficiency, and size of gamma spectrometers. Cadmium zinc telluride (CZT) detectors, especially those using coplanar grid (CPG) technology, are promising for room-temperature gamma detection but suffer from performance degradation due to electron trapping and non-ideal weighting potential distribution.

Purpose This study aims to design a miniaturized, low-power gamma spectrometer based on a CPG-CZT detector and to implement a depth-sensitive energy correction method to address energy resolution degradation caused by electron trapping and imperfect weighting potential distribution.

Methods The spectrometer integrates a 1 cm³ CPG-CZT detector with front-end analog and data processing modules. The analog module performs low-noise charge-sensitive amplification, gain adjustment, and single-ended to differential conversion for anode and cathode signals. The data processing module digitizes three signal channels at 40 MSPS with 12-bit resolution. A depth-sensitive energy correction method is applied by subtracting non-collecting anode waveforms from collecting anode waveforms to derive the anode signal, and using the cathode-to-anode amplitude ratio (CAR) to determine interaction depth. This allows for depth-dependent correction of the energy spectrum.

Results Two coplanar-grid CZT detectors were assembled into the gamma-ray spectrometers. Test results show that after the implementation of the depth-sensitive energy correction method, the energy resolution of one detector at 662 keV was optimized from 6.61% to 2.17%, while the other one was improved from 4.86% to 2.07%. These results verify the effectiveness of the proposed method.

Conclusions The developed CPG-CZT gamma spectrometer, combined with depth-sensitive energy correction, effectively compensates for electron trapping and weighting potential effects, achieving high energy resolution in a compact and portable design. The results validate the feasibility of the correction method and suggest potential for further improvement with higher-quality CZT crystals.