Appendix A
INSTRUMENTATION
Shelf geometries from bottom of window:
A.1 COLLECTOR IDENTIFICATION
Collector designations are shown in Figure A.1.
A.2.
Shelf
DETECTOR DATA
A.2.1 End-Window Counter.
Crystal dimensions and type: 14-inch diameter
x 4% inch thick, Nal(T1), Harshaw
Photomultiplier tube type: 6292 DuMont
Scaler types: Model 162 Nuclear Instrument Cor-
ards Branch).
Counting chamber dimensions: 54-inch diameter
Al absorber thickness: '/ inch
ings were normalized to the latter value.
Pwd
cm
1.0
2.6
4.2
5.8
7.4
Thimble dimensions: 1°4-inch inside diameter x
Ratios to Shelf 5 (most commonly used) for cen-
12 inches deep
tered Cs!9” point source:
2
3.02
3
1.88
4
1.31
5
1.00
Use of pre-
cision resistors (1 percent) eliminated scale correction
factors. )
Gas type and pressure: A ~ 600 psi
Shield dimensions: Pb ~ 19-inch outside diameter
x 22 inches high x 4 inches thick; additional 1-foot
thickness of sandbags in Site Elmer laboratory
Counting chamber dimensions: 11-inch diameter
x 14 inches high
Distance
5.87
The response of these to 100 ug
of Ra 700 x 10~* ma at 600 psi; therefore, all read-
Shelf distances from bottom of absorber:
1
0.2628
0.1559
0.0958
0.0363
0.0177
(Two newer chambers of modified de-
sign were also used.
x 4 inches high
Ratio
0.85
1.50
2.15
3.75
5.35
Correction
A.2.3 4=mn Ionization Chamber (Analytical and Stand.
thickness in Site Elmer laboratory
Shelf
1
2
3
4
5
Physical Geometry
.
rection: 3.0 x 10° counts/min
Pb shield dimensions: 8'4-inch outside diameter
x 20 inches high x 114 inches thick; additional 2-inch
5
———
Minimum count rate requiring coincidence loss cor-
poration, and Model 182 Nuclear-Chicago (in tandem)
Shelf
Distance
em
—
Useful range: ~ 217 x 107 '! ma (background) to
200 x 107* ma
Correction factors to equivalent 10° scale:
Scale
Factor
~ ohms
‘
1012
10%
0.936
0.963
108
1.000
10°
Minimum count rate requiring coincidence loss
correction: 1.0 x 10° counts/min
1.000
Response versus sample (Ra) position:
Counting procedure: ordinarily 3- to 1-minute
intervals for each sample
A.2.2 Beta Counter.
Gas proportions: 90 percent A, 10 percent CO,
Pb shield dimensions: 8%4-inch outside diameter
Distance from
Bottom of Tube
Relative
Response
in
pet
0to3
x 12 inches high x 144 inches thick; additional 2-inch
, 3.5 to 5.5
thickness in Site Elmer laboratory
100
99 to 92
Response to 100 ug Ra: 5.58 x 107° ma at ~ 600 psi
Counting chamber dimensions: 5/4-inch diameter
x 4 inches high
Efficiency factors relative to Co® for various nuclides:
Al window thickness: 0.92 mg/cm?
162