LLNL Environmental RPL Dosimeter (mid 1960s)
This is a radiophotoluminescent (RPL) glass dosimeter developed by Ron Kathren at Lawrence Livermore National Laboratory (LLNL) and used for environmental monitoring around the lab perimeter during the mid 1960s.
The case uses a slotted screw-on lid, the top of which can be seen in the photo above left. Inside is a 8 x 8 x 4.7 mm block of RPL glass. To flatten its over-response to low energy photons (a characteristic of RPL glass dosimeters), the holder acts as a graded filter. From the outside inward, it consists of a layer of lead, then brass, then Teflon. The round shape was chosen to reduce the dosimeter's angular dependence. While sensitivity of an RPL dosimeter is not quite as good as you might want in an environmental dosimeter, there is no fading of the signal and it is unaffected by humidity.
Size: 1/2" diameter and 3/8" high
Donated by Ron Kathren.
Ron Kathren, personal communication.