Over the last eight years, gas (filled) proportional counters (GPCs) of the HD-2(Fe) type (Davis et al., 1968, 1972; Wink et al., 1993) have been fabricated at NIST through a collaboration of the Materials Measurement Science Division, Facility for Low-Level Counting (llc), and the Fabrication Technology Division, Glassblowing and Optical Shops. This type of GPC has been used in our laboratory to detect low levels of (beta) radioactivity by internal gas counting of small atmospheric gas and aerosol samples (Currie, 2008). In the initial phase of the project, reverse engineering was used to develop robust procedures and techniques to fabricate, assemble and test counters. Counters were assembled by a team consisting of an expert technical glassblower to fuse together precision ground synthetic quartz components, an expert optical technician to optically seal tubes to the stopcock and lap the stopcock plug to precisely match the taper and roughness of the barrel, and a research scientist to prepare and assemble the internal components, i.e. inserting the cathode with its connecting electrical lead and stringing the anode wire, both leads requiring a final hermetic seal made by collapsing quartz tubing around each wire. Each GPC was certified for its performance based on an energy calibration as a function of high voltage and its background count rate using a specialized individual pulse digitizing counting system at the NIST llc Facility. To date, several GPCs have been fabricated of which few have required restoration because of accidental damages, malfunctions or simple electrical repairs.
Citation: NIST Interagency/Internal Report (NISTIR) - 7936
NIST Pub Series: NIST Interagency/Internal Report (NISTIR)
Pub Type: NIST Pubs
Gas Proportional Counter, Radioactivity, Low-Level Counting