Polaris-H is a commercial portable detector system, comprised of a Compton camera which uses three-dimensional position-sensitive cadmium zinc telluride (CZT) detectors to take measurements at nuclear power plants.

“Polaris-H, a compact Compton camera designed by H3D, Inc. has been characterized and tested in field measurements at nuclear power plants. Polaris-H integrates a 3D position-sensitive pixelated CZT detector (20 mm × 20 mm × 15 mm), associated readout electronics, an embedded computer, a 5-hour battery, and an optical camera all within a portable water-resistant case. The total mass is about 4 kg. Start-up time is 2 minutes. Additionally, there is a connection for a tablet, which displays a real-time gamma-ray spectrum (near 1% FWHM at 662 keV) and isotope-specific images of the radiation distribution in all 4π in real time. The newest design of Polaris-H features the capability to control data acquisition without using a tablet interface, a higher energy dynamic range, and a higher maximum count rate. Absolute efficiency, imaging efficiency, energy resolution, and detection and identification performance are presented. Measurements are shown for applications of decontamination and detection of previously unknown contamination regions.“

-Polaris-H Measurements and Performance, Abstract

Measurement of the Residual Heat Removal Pump Room in a U.S. nuclear power plant, using Polaris-H, an imaging spectrometer from H3D, Inc. Polaris-H uses the room-temperature semiconductor CdZnTe. The spectrum of all gamma-ray events in this 10.2-minute measurement shows 1.1% FWHM energy resolution at 662 keV. The Compton image over all 4-pi directions can be obtained in real time for each peak in the spectrum in a single measurement. Here is shown the image from events in the full-energy peaks of Co-58, Co-60, and Cs-137 using a map projection of all 4-pi. For Co-58 and Co-60, no significant radiation is observed in the backward direction, so the images are cropped. The images tell the spatial distribution of each isotope, from which contamination history can be deducted. For instance, in this measurement, Cs-137 along the floor is due to a flood many years ago, while the different distributions of the two cobalt isotopes tell that at least two contamination events occurred in the pump.