ZENIT-100 low-background apparatus for measuring space distribution of beta activity

This paper describes low-background multichannel scanning apparatus for studying the beta-activity distribution in the collector of a mass separator. The detecting part of the instrument consists of 100 SI-19BG Geiger counters in a row with a length of 100 cm. Active and passive shielding reduces the background from external radiation by a factor of ca 6.5. The background per counter is 0.002 sec-1. A detachable collector of special design provides a space resolution of 3.3 mm. The apparatus is useful in experiments seeking plane-symmetric isomers of atomic nuclei when it is necessary to record the beta activity at the focal plane of the YaSNAPP mass separator