Chalk River 4 Pi Proportional Counter (ca. 1950s)
This is a simple aluminum "pillbox" type of 4 pi proportional counter that was built at Chalk River Laboratories in Canada. One of the beauties of this particular design is that it is very easy to disassemble if decontamination should be necessary. The sample would have been deposited on a thin (e.g. 1-2 ug/cm2) plastic film that had been made conducting by coating it with metal (usually gold). A drawing of this counter can be seen on page 32 of NBS Handbook 80 (NCRP 28) "A Manual of Radioactivity Procedures."
Donated by Chalk River Laboratories.
National Bureau of Standards Handbook 80. A Manual of Radioactivity Procedures. (NCRP Report 28). 1961.