20th Century Electronics Proportional Counter (ca. 1970s)

This neutron detector was produced by 20th Century Electronics in England. The company began manufacturing BF₃ counters in the early 1950s. It is approximately 16 1/2 inches long, 2 inches in diameter, copper walled and filled with BF₃. One end (towards the right in the above photo) has a threaded cap to protect the fragile glass insulator.

The model number, marked on the wall of the tube, is 15EB70/50/G/UA0539. The EB refers to "enriched boron trifluoride." The 50 refers to the tube diameter, i.e., 50 mm. 

Donated by David Allard.