Prototype TLD Badge (early 1960s)
This is a prototype of a combination security credential and TLD that was produced in the early 1960s by Dr. Holden, one of the founders of RMC in the San Francisco area.
The worker's ID photo and employee number would be located in the larger of the two laminated plastic cases. In the accompanying photo, this case is on the bottom and has some blurry red printing on it. The smaller card, consisting of three layers of laminated plastic, has two hidden pockets in which LiF powder would be kept. Powder was chosen because at the time the Harshaw company was just figuring out how to produce large LiF crystals that were suitable for thermoluminescent dosimetry.
To determine the worker's exposure, the corner of the smaller card was cut open and the LiF powder was poured into a planchet for readout. A disposable dosimeter—use once and discard!
Donated by Ron Kathren.
Ron Kathren, personal communication.