Re: Temperature dependence of TLD response

[Bob Flood <bflood@SLAC.Stanford.EDU>]

At 03:06 PM 1/4/99 -0600, you wrote:
>LiBO is also hydroscopic, and is not the best 
>dosimeter to be in a wet environment (or high humidity area) for an 
>extended period of time.

I would take Sandy's assessment a bit further and say that lithium borate
is a poor material for an enviornmental dosimeter. Unless the user can take
truly extraordinary measures to ensure no intrusion of moisture, the
dosimeter will eventually fail. The phosphor crystals will absorb water,
which will be driven off and flash to steam when the dosimeter is heated
during processing. This results in the crystals being "blown apart," making
that reading and all subsequent readings useless. It is not a matter of
"perhaps that can happen" - this effect is inevitable.

I agree that LiF is usable as an environmental dosimeter, but the calcium
phosphors generally yield more light per mrem, making them better suited to
the low dose measurements an environmental dosimeter is expected to make.

---------
Bob Flood
Dosimetry Group Leader
Stanford Linear Accelerator Center
(650) 926-3793
bflood@slac.stanford.edu

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