SLIDE 39
Whole-body counter. The detector chosen for field use by Brookhaven personnel
was a 28 cm diameter, 10 cm thick, sodium ifodide thallium activated
scintillation crystal NaI(Tl). It is optically coupled to three low
background magnetically shielded photomltiplier tubes connected in parallel
through a summing box with the combined output routed to an amplifier and then
to a microprocessor-based computer and pulse height analyzer (PHA). The PHA
data is stored on a magnetic discette, and results are analyzed in the field
and at BNL using a matrix reduction, minimization of the sum of squares
techniques.
207
The gamma emitting nuclides observed have been 657n, 137 G6 60G5 and
Bi.
Additionally, naturally occurring
K is present in normal amounts.
A
typical counting time is 15 minutes and a typical minimum detection limit is
100 Bq (3 nCi).
The whole-body counting system is currently standarized
against a human like phantom.