Re: Field Instrument

[Ccja@aol.com]

I should have said, perhaps, in my earlier response to this question, that a
2x2" NaI probe will readily detect DU concentrations of 35 pCi/gm in soil. I
would strongly suggest energy-calibrating it, setting the ROI around the 63 &
93 keV lines from Th234, The disadvantage of a 2x2 probe is that, unless it's
side-shielded, the FOV is very wide. The great advantage of a FIDLER, along
with an effectively lower background, and the lack of a need to energy
calibrate, if DU is all that's present, and you don't need extremely low
backgrounds, is that, because the crystal is so thin and wide (0.063x5"), the
probe sees, for the most part, only what is directly in front of it (or
directly above). This allows one to scan at good speed, as when guiding
excavation, while retaining a high degree of confidence that nothing is being
missed.

Chris Alston