Year
2003
Abstract
Sodium iodide has long been the standard for low-resolution scintillation detectors used for enrichment meters. However, its relatively low density and average atomic number makes detection of the high-energy emissions from 238U difficult without a large (~50 mm thick) crystal and a correspondingly large (and heavy) collimator. Cadmium tungstate offers high density (7.9 g/cc) and higher average atomic number and can develop a photopeak from the 1001 keV emission in a crystal only 15 mm on a side. In addition, the crystal is not hygroscopic and readily available. When coupled to a 1-inch diameter photomultiplier, this crystal makes for a compact, easily handled detector. We report here the design of, and preliminary measurements made with a CdWO4-based instrument. The instrument consists of a hand-held unit housing the detector, collimator/shield, and high-voltage electronics coupled to a battery-powered table-top unit containing a mixed-signal microcontroller (ADC, DAC, processor, ROM, and RAM on a single chip), pulse processing electronics, automatic gain adjustment, analysis algorithm, and LCD/push button user interface, battery charging circuit, and an RS-232 serial interface.