Re: Fading in TLD

["Sandy Perle" <sandyfl@ix.netcom.com>]

Fading is not very significant, if appropriately considered in the 
dose response algorithm .. For a TLD 600/700 the fade for a quarter 
is ~15%. The fade for 120 days + is substantially flat at ~18%.

For better environmental monitoring I recommedn that you use the CaF 
Harshaw elements.

We heat our LiF 700 chips to 600 degrees C for two days prior to 
sending out to the field. Upon receipt they are preheated at 100.2 C 
for 30 minutes. (this is for use as personnel extremity) however, the 
methodology can be used for a chip used in any manner.

The Substrates(TLD700)  that are in a teflon bubble, and are barcoded 
are annealed on the 6600 have a different TTP, one for field and one 
for QC. The QCs are preheated at 150 C for 10 sec and ramp up to 300 
C at a rate of 15 degree C/second. Total read time is 20 seconds. The 
field ramp immediately to 50 degree C, and then ramp upto 300 degree 
C at a rate of 15 degree C. Total readout time, again 20 seconds.

I would like to reiterate that if environmental monitoring is what 
you are intending to do, the use of a CaF element is more 
approproiate.

------------------
Sandy Perle
Technical Director
ICN Dosimetry Division
Costa Mesa, CA 92626
Office: (800) 548-5100 x2306 
Fax:    (714) 668-3149
  
mailto:sandyfl@ix.netcom.com
mailto:sperle@icnpharm.com

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