783620H / 1013
Energy
(keV)
123.14
591.74
723.3
873.20
1004.76
1274.45
Table 8. Geometry Correction Table.
Peak Count Rate
Case 1 Case 2
63.23
51.07
3.31
11.50
5.75
7.71
10.29
2.19
7.47
3.79
4.91
6.07
ratio
1.238
1.511
1.539
1.517
1.570
1.695
Table 9. Geometry Correction Results.
Nuclide
154
Eu
155
Eu
125
Sb
Case 1
12750
8020
2900
Activity
Case 2 no correction
7730
5180
1956
Case 2 correction
13000
6300
2840
6. ANALYSIS METHODS
6.10.6. Absorption
The absorption factor is used to correct for the absorption of gamma-rays by material between the detector and the source. The factors are stored as a function of energy in the attenuation
database,
Atd.mdb
, in
C:\User
. Materials that are always present (such as the detector end cap) will be accounted for in the efficiency calibration. Source containers will not normally be accounted for, nor will an absorbing matrix such as soil. In these cases, the absorption of the gamma-rays will cause low values for the isotopic abundances to be reported unless the absorption correction is made. One of two types of absorption correction (as defined in ASTM E181-
82)
32
can be selected. External absorption is for cases where all the source gamma-rays pass through the absorber. Internal absorption is for cases where the radioisotope is mixed with the absorber so that some of the gamma-rays go through a lot of absorber and some only go through a small amount of absorber.
32
“Standard General Methods for Detector Calibration and Analysis of Radionuclides,” ASTM E181-82, also
ANSI N42.14-1978, IEEE, NY, NY.
285
