一、法国RA-12低水平β放射性测量装置 该仪器由β计数管、反符合屏蔽计数管、测量室、屏蔽层、换样装置、记录仪器等部分组成。 β计数管为扁平状的流气式计数管,工作气体为99％的氦气+1％的异丁烷;外壳由低放射性含量的有机玻璃制成,内涂银层;管窗是厚度约1毫克/厘米~2的塑料薄膜,两面均涂以银层,管窗直径有84和33毫米两种。 First, the French RA-12 low-level beta radioactivity measuring apparatus The instrument consists of β counter tube, anti-coincidence shielding counter tube, measuring room, shielding layer, sample change device, recording instrument and other components. The beta counter tube is a flat flow countercurrent gas, working gas is 99% helium + 1% isobutane; the outer shell is made of plexiglass with low radioactive content and is internally silver coated; the aperture is about 1 Mg / cm ~ 2 plastic film, both sides are coated with silver layer, the window diameter of 84 and 33 mm two.