Re: Harshaw TLD info

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

At 05:21 PM 3/11/98 -0600, you wrote:
>The most efficient way to separate a TLD 100 from a TLD 700 is to 
>irradiate them to low energy beta (i.e., Tl-204). The TLD-100 will 
>under-respond significantly as compared to the TLD 700. A relative 
>response correction for Tl-204 is approximately 1.5 (TLD 700) 
>compared to approximately 5.5 for the TLD 100.
>
Wouldn't this beta response be mostly a function of the thickness of the
chips rather than the phosphor composition? Otherwise, it's not obvious to
me why there would be such a difference in response. If all TLD-100 chips
are made at a single thickness, and all TLD-700 are also made at a single
thickness, then the Tl-204 method would be universally applicable. But if
chips are made in different thicknesses, the beta factors would vary by
thickness and this method could result in misclassifying TLDs.

As an alternative, since any Li-based TLD is an albedo dosimeter and
responds only to thermal neutrons, try moderating the AmBe spectrum (water,
parafin, poly, etc). The dose rate will go way down, requiring longer
exposure to reach a meaningful dose, but the 100 should clearly out-respond
the 700.


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