CORRECTION FACTOR FOR DETECTOR(SN: 496)
OPERATING AT LOW VOLTAGE
DOE/ERSP TECH NOTE NO, 5.0
DATED: Mareh 1978
AUTHOR: J. Giacomini, DRI
The PGT detector (SN: 496) installed on th EG&G IMP is supposed to be operated at -3000 volts. In
the first weeks of operation the detector was operated at -2000 volts which introduced an
inefficiency bias. To find a correction factor for the lower efficiency of the 241Am data already
recorded, an area on Sally was surveyed with the IMP using the detector at the -2000 voltage and
then resurveyed using the correct voltage of -3000. The list below shows the 24l1Am, in pCi/g,
with both voltages. Figure B-5-1 is a plot of the data.
The locations marked with * were not used in the analysis because the results were below the
minimum detector capability. A simple mean was used to determine a correction factor. The mean
of the nine numbers was 1.6 with a standard deviation of 0.24. This factor was used to multiply the
241 4m data surveyed with the low voltage to obtain the adjusted values.
241 Am at
241 am at
Location
-2000 V.
-3000 VY,
26-N-9
26-N-li
26-N-13
26-N-14
*25-N~10
*25-N-9
1.0
13.2
16.0
29.8
0.7
0.3
1.2
19.5
26.5
38.4
1.2
0.6
*25-N-11
24-N-13
24-N-14
26.5-N-14
26.5-N-13
26.5-N-12
0.4
4,1
11.6
25.2
17.0
25.1
(-3000 V.
Ratio (-2000 V.)
1.2
1.48
1.66
1.49
1.71
2.0
0.6
8.4
20.2
38.0
30.2
39.4
1.5
2.05
1.74
1.51
1.78
1.57
40
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3
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ist
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0
6
pe
12
18
24
241 am AT -2000 V (pCi/g)
FIGURE B-5-1. PLOT OF 741m at -3000V vs 241am AT -2000V
B-5-1
30