This is a NaI(Tl) 30x30x75mm probe with approximately 9.5% FWHM, part of a Bicron/Alpha Spectra portal monitor unit.

It includes a crystal encased in an aluminum housing with an optical entrance, as specified by the crystal manufacturer, Bicron.

The probe is fitted with an FEU85 photomultiplier tube (PMT) with high impedance.

Although the original PMT was defective and has been discarded, the crystal has been preserved.

This gamma probe, although not visually pristine, is a cost-effective and efficient tool for detecting gamma radiation, making it ideal for surveying or searching for uranium or thorium ores.

The probe's large crystal size ensures excellent value for your investment, prioritizing radiation detection efficiency over appearance.

This new build from my lab features:

● An enclosure made from heat-shrink tubing, ensuring the crystal within the sealed aluminum case is well-protected.

● Integration with an FEU85 photomultiplier and a mumetal shield for enhanced performance.

● An internal voltage divider with an approximate resistance of 80Mohm.

● Connections include a black wire for ground (GND) and a red wire for positive high voltage (+HV).

A bias-T circuit is required for pulse extraction.

● Compatibility with nearly any portable rate meter, including the Eberline ESP2 and Theremino systems, making it a versatile addition to any radiation detection setup.

This setup is fully operational and ready for use in a wide range of gamma radiation detection applications.