Design and evaluation of a unique weighted-sum-based Anger camera

Anger camera imaging technology has become widely popular for neutron diffraction imaging due to recent shortages in Helium-3 (He-3). Research into neutron diffraction optimized Anger camera by the Oak Ridge National Laboratory (ORNL) detectors group has provided an alternative to He-3 Tube-based detectors with a high-resolution Anger camera. However, the cost of these high-resolution Anger camera technology can make it less attractive than He-3 tubes when a large Field of View (FOV) is desired. Currently, there is a need for a lower-cost alternative to this high-resolution anger camera. Further applications for Anger camera have become of interest with the advent of high-flux Deuterium-Tritium (D-T) gas lab-based neutron generators. Implications of utilizing high-sensitivity Anger camera technology in use with high-flux lab-based neutron generators could lead to the development of a lab-based neutron diffraction instrument.

A novel low-cost weighted sum-based Anger-logic architecture optimized for neutron diffraction applications was developed targeting performance metrics like those demonstrated by more traditional resistor-network-based Discretized Positioning Circuits (DPC). The weighted-sum architecture proved capable of achieving 6mm ~ 4mm resolution as would be typical of resistor-network-based DPCs. The weighted sum architecture was then applied to a monolithic anger camera design. This design provided a weighted summing board interfaced to an H8500 Multi-Anode Photomultiplier Tube (MAPMT) through circuitry to correct for anode gain nonuniformity. The outputs of the weighted summing board were processed through custom-designed sampling and digital signal processing (DSP) hardware to calculate the position of incident photons on the MAPMT. Correction of anode gain nonuniformity provides for accurate pulse shape discrimination of light pulses incident on the MAPMT resultant from scintillation events.

A monolithic high-resolution Anger camera developed by the ORNL detectors group was applied to a newly developed high-flux D-T gas lab-based neutron generator by the Phoenix Nuclear instrument company. A single crystal pyrolytic graphite panel was used to acquire a neutron diffraction rocking curve. The high sensitivity and gamma rejection capability of the high-resolution anger camera facilitated improved Signal to Noise Ratio (SNR) given the low neutron flux and high gamma-ray background.