[Development of high-sensitivity radio gas chromatography--specific characteristics of a long path internal gas flow proportional counter (author's transl)].

A long path internal gas flow proportional counter was devised was to be used as a high sensitivity detector for radio gas chromatography, and its performance characteristics were investigated. The long path counter tube used for this detector has a sufficiently long passage in comparison with the diameter. The counter tube for general use is made of brass or copper tube 1 cm in diameter, 100 cm in length with a mirror finish on all internal surface, and the center electrode is of tungsten wire 0.05 mm in diameter. For actual use, several of these counter tubes are connected in series in assembly to hold the total volume of a gas sample in the counting system over a desired counting period. Thus this flow detector as an integral type one and gives directly a counting rate. Experiments showed that the dynamic counting efficiencies of tritium and carbon-14 were about 90% and equal to the static counting efficiencies. Furthermore, with this detector, the counting rate does not appear to be affected by minor variations of the effective inner volume of the counter tube and the flow rate of counting gas.