Re: Individual Dose Monitoring Response

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

At 01:12 PM 10/22/97 -0500, you wrote:
>Responding to the query posed by Bill Stephany:
>TLDs are generall unaffected by envirnmental conditions except for VERY high
>temperatures which may cause some loss of signal from low temperature traps;
>possible response to visible light; and some fading of signal which
>primarily occurs right after exposure but which is usually not a practical
>problem with LiF and other commonly used TLD's.

Certain phosphors are also sensitive to moisture as well. If the phosphor
crystal is hygroscopic, prolonged exposure to a high humidity environment
(such as the southeast US) can lead absorption of water within the crystal
even for protected dosimeters. When the dosimeter is processed, most of the
heat applied to the phosphor intended to read out the radiation response is
instead consumed driving out the moisture. Because of this, the element
never reaches the expected temperature and is not correctly read. The
moisture usually flashes to steam in the heating process, physically
damaging the phosphor too much to be re-used. Thus, the reading is lost and
cannot be retrieved!


Bob Flood
Stanford Linear Accelerator Center
(415) 926-3793     bflood@slac.stanford.edu
Unless otherwise noted, all opinions are mine alone.