Beta-energy response of the Eberline RO-7 survey instrument

Abstract

An RO-7 radiation survey instrument was obtained from the Eberline Instrument Corporation to use in a study of the beta dose rates from the Godiva IV Critical Assembly at Los Alamos National Laboratory. A limited evaluation of the instrument was performed, and its energy dependence for beta particles was determined. The RO-7 instrument is a hand-held, cutie-pie-style survey meter with a liquid crystal digital readout. The instrument is available with three interchangeable ion chamber probes, although we used only the midrange probe (RO-7-BM) in this study. The midrange probe has a full-scale range of 199.9 R/h and a resolution of 0.1 R/h. The ion chamber has a 1-in.-diameter entry window 2 mils thick (approx. 7 mg/cm/sup 2/) of aluminized mylar. The chamber is lined with phenolic nominally 1/8 in. thick. The housing is nominally 60 mils thick. The chamber's internal dimensions are 1-in. diameter x 0.6-in. length (2.5 cm x 1.5 cm) with a sensitive volume of 7 cm/sup 3/. The beta shield is a plastic cap (approx. 1000 mg/cm/sup 2/) over the beta window and is held in place over the probe by an O-ring. The overall dimensions of the basic probe are 1.5 in. x 4.2 in. The weight of the instrument with the midrange probe is 3.2 pounds (1.5 kg). The batteries are three 9-V and two 30-V cells with an operating lifetime of 160 hours (for the 9-V cells). The overall unit is 9.5 in. high, 4.25 in. wide and 13.5 in. long when the probe is attached.