Author: Soo Hyun Byun, Troy Farncombe, Edcer Jerecho DC Laguda 👨🔬
Affiliation: McMaster University 🌍
Purpose: We present the adaptation of a Cadmium Zinc Telluride (CdZnTe) detector, initially designed for SPECT-MR applications, to neutron imaging. This study explores a novel technique that utilizes the superior energy resolution and high detection efficiency of CdZnTe detectors. 113Cd which is 12.2% naturally abundant exhibits a high thermal neutron capture cross-section. Through the 113Cd(n,γ)114Cd reaction, prompt gamma photons tends to make an interaction at another position or escape the detector. In contrast, conversion electrons deposit their energy locally, providing measurable signals that make them suitable for thermal neutron imaging.
Methods: The detector system consists of four CdZnTe detector arrays, each comprising 16×16 pixels with a 2.46 mm pixel pitch. These arrays are connected to a custom PCB readout board, which is powered by a 6.5 V power supply and incorporates -450 V high-voltage bias. This configuration enables efficient detection of thermal neutron flux while handling a count rate of up to 1×106 events per second, making it suitable for high-rate neutron imaging experiments.
Two neutron beamlines at the McMaster Nuclear Reactor were used: a cold neutron beam (energy range: 2.2–12.1 meV; flux: 2.5×103 n/cm2/s) and the diffracted neutron beamline, featuring a Si(111) monochromator (average energy: 17 meV; flux: 2.4×105 n/cm2/s). The detector response was characterized using cadmium and boron carbide slits for various neutron beam sizes.
Results: An initial calibration experiment was conducted using a 57Co source, producing a characteristic pulse height spectrum for gain corrections. These corrections were applied to neutron imaging data. For 2D neutron imaging, attenuation corrections were performed to improve spatial fidelity.
Conclusion: Future development will focus on extending the system's energy range and addition of neutron converters. Experimental results will also be systematically compared with GEANT4 Monte Carlo simulations to validate and refine the system design.