Low-level gas flow beta multicounter system for the measurement of 5 samples simultaneously.
The basic part of the Risø low-level beta multicounter system is a gas-flow unit with dimensions of 50x100x250 mm which incorporates five individual GM sample counter elements and a common guard counter.
The guard counter reduces the cosmic-ray background by using anticoincidence technique. Each sample counter element is provided with an aluminized Mylar window of density < 1 mg/cm2 and diameter 25 mm. The counters are gas-flow types designed for 99 % Ar/1 % isobutane or 99 % Ar/1% propane counter gas. A sample slide allows five samples to be inserted into the multicounter. These samples are measured simultaneously. A lift mechanism minimizes the sample-to-window distance to obtain optimal efficiency. The multicounter is normally placed inside a lead shielding of 100 mm thickness to reduce the ambient background radiation.