Re: Spurious TLD results

["Sandy Perle" <sandyfl@earthlink.net>]

Tony LaMastra said:

> If the TLD is a true
> crystal, is it possible a mechanical defect in the crystal can cause a
> release of electrons on a random basis?   Or perhaps something similar to
> a piezo effect?

Tony,

The above is correct. If there is a crack in the crystal, or a 
"pulverization" of some time, there can be a high degree of 
variability within the chip itself. If there were a way to identify the 
chip, tracking of response would be enough to determine the 
problem, and, to pull it from the "used" population. The thinner the 
crystal, the more of a problem. Generally, with the 30 mil chips, 
there isn't much of a problem. But once the industry started to use 
much thinner chips, there have been many who have identified a 
significant amount of variation. Unless one is interested in doing 
some very low-energy beta measurements, I recommend that the 
thicker chips be used, where there is no effect on gamma or low 
energy x-rays, and beta response at Tl-204 is still excellent (even 
Pm-147).

------------------
Sandy Perle
Technical Director
ICN Dosimetry Division
ICN Plaza
3300 Hyland Avenue
Costa Mesa, CA 92626
Office: (800) 548-5100 x2306 
Fax:    (714) 668-3149
  
sandyfl@earthlink.net
sperle@icnpharm.com

ICN Dosimetry Website:
http://www.dosimetry.com

Personal Website:
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"The object of opening the mind, as of opening 
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              - G. K. Chesterton -

The opinions expressed are solely, absolutely, positively, definitely those of the author, and NOT my employer
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