Re: High tension power lines and X-rays

[pward@iastate.edu]

The following was posted regarding a test for soft X-rays from high tension
power lines:
> 
> The first test involved CaSO4 :Dy Thermoluminescent Dosimetry capsules
> from the Radiation Detection Company in Sunnyvale, California. As I
> understand it -- probably simplified -- this material acquires
> dislocations in the crystal structure as the gamma particles pass
> through. When gently heated, the crystal dislocations rebound and give
> off photons which may be counted to give an estimation of the radiation
> to which the detecter was subjected since last annealed. These detectors
> are normally shielded to hide their responsitivity low energy gamma
> (X-rays), but were obtained individually without shields.

In interpreting the data, one should be aware that CaSO4:Dy TLD materials
are *highly* energy dependent, mainly due to the relatively high atomic
number of the calcium component.  Any TLD which is used for radiation
measurements should be calibrated at or near the energy of the radiation
which is to be measured.  Calcium sulfate dosimeters should be expected to
vastly (about 30x) over-respond to low energy radiation as compared to a
similar dose of Co-60.

Paul Ward
pward@iastate.edu