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# Efficiency Calibration Curve

Make an efficiency calibration curve, where the counting efficiency is given as a function of γ energy. In table 1 the measured nuclei is listed with γ energy, number of counts, uncertainty in the number of counts and the counting time. The measurements was performed 27th March 2003.
table 1 : measurement data from standard γ-calibartion sources, measured 6. oct 2006.
Nuclide
Energy (keV)
Counts
Uncertainty
Real Time (s)
137Cs
661.66
161681
432
210

133Ba
80.997
99426
408
380

276.398
13284
150
380

302.853
31734
202
380

356.017
92291
322
380

241Am
59.54
407142
766
376

60Co
1173.237
14039
137
189

1332.501
12822
121
189

54Mn
834.84
317
26
1268.56

152Eu
121.78
486526
1031
1111

244.698
82174
519
1111

344.279
211766
625
1111

778.9
48601
396
1111

295.939
4076
245
1111

964.079
45298
359
1111

1408.006
47191
237
1111

A table of the γ intensities, Iγ, can be found Gamma-Energy Standards
To calculate the efficiency you need to know the amount of activity in the sources. Table 2 lists the amount of activity at the time of purchase. You must correct these number based upon the age and half life of the sources.

table 2: activety of standards
Nuclide:
activety:
Date
60Co
10.57 μCi
1. oct 1988
133Ba
6.09 μCi
1. oct 1988
54Mn
367 kBq
1. apr 1996
137Cs
11.5 μCi
1. oct 1988
241An
11.56 μCi
1. oct 1988
152Eu
3.71 μCi
1.apr 2004

# Determination of Unknown Sample

In table 3 the analysis results of the unknown, n-irradiated sample is shown. Use the results to :
• Determine which metal the sample consist of. Use the identified γ-ray energies to do this. if you need a database you can use this one
• Determine the absolute amount of the metal. Use the counts measured in table 3 and the efficiency curve you made in exercise 3B. Use at least two different γ lines to do this, we recommend Eγ = 222.08 keV and Eγ 1 MeV. The neutron flux was 105 n/(s cm2) during the irradiation, and the irradiation time was 18 days. The sample was measured directly after the irradiation.

Table 3: Results from spectroscopy of unknown sample
Photo Peak no.
Energy (keV
Net Count
Uncertainty
FWHM (keV
1
67.63
166011
1885
0.44
2
100.26
79985
902
1.00
3
152.56
34987
401
1.16
4
222.08
29011
335
1.52
5
511
210890
2385
2.24
6
1121.14
32098
391
1.67
7
1188.7
14563
173
1.17
8
1221.28
23825
265
2.01