e. The Thermoluminescent Dosimeter (TLD) (see Figures 1-12 and 1-13) is a
total dose device, which measures beta, x-ray, gamma, and neutron radiation. It utilizes
the thermoluminescent principle of operation. Energy or radiation is absorbed by the
detector molecules and raises them to an excited or metastable state. They remain in
this excited state until they are heated to a temperature high enough to cause the
molecules to return to a normal or ground state. When these molecules return to their
normal state, they give off the excess energy they contain, in the form of light. The
amount of light is proportional to the energy or radiation absorbed. The emitted light is
measured with a photomultiplier tube that serves to convert the light photons into an
electrical signal that can be quantified. The TLD is worn by an individual as a
personnel-monitoring instrument. The TLD, however, is not self-reading. It requires a
sensitive reader to quantify the dose. For peace-time use, the TLDs are shipped to the
Test, Measurement, and Diagnostic Equipment facility at Redstone Arsenal, Alabama
for analysis. During battlefield operations, the AN/PDR-75 Reader (see Figure 1-14) is
used for analysis of the DT-236 Dosimeter. Variations of the TLD are used quite
extensively in both military and civilian practices involving the use of radiation.
Figure 1-12. Thermoluminescent Dosimeter.
Figure 1-13. Thermoluminescent Dosimeter components.