Instrument evaluation no. 4. Nuclear Enterprises gamma dose rate meter type 2604

The NE2604 is a portable battery-operated instrument which uses an internally mounted, energy-compensated, GM tube for the measurement of exposure rates from 0.1 mR/h to 200 mR/h and an external end-window Gm tube for the measurement of count rates from 1 to 1500 counts per second. The instrument is basically a type NE2602 dose rate meter that has been modified by the manufacturer to provide a ratemeter facility for an external GM tube probe connected by a flexible lead. According to the manufacturers the external probe is intended for the assessment of dose rates at awkward places. The performance of the instrument when used with the internal detector is similar to that of the NE2602, and has been reported fully in NRPB-IE1. The present evaluation is concerned exclusively with the performance of the NE2604 when used with the type BP1/1 external probe. The information is given under the following headings: facilities and controls; radiation performance; electrical characteristics; summary of performance; calibration procedure; construction; conclusions. (U.K.)