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Various known sources of elements that emit gamma radiation over a wide range of energy are used to carry out energy calibration and efficiency calibration of gamma-ray detectors. 

An ideal radioactive source emits gamma-ray photons at discrete energies between 10 keV and 1.5 MeV, thus allowing a full spectrum to be analysed or calibrated.

Calibration sources with long half lives are usually chosen so that they can be used for many years before becoming too weak to be useful.

The energies shown below associated with the largest emission intensities (in bold) are the easiest to detect.

Source Half life Energies
(keV)
Intensity
(%)

22Na

2.6 yrs 511 g annihilation
1274.5 99.9
56Co 77.7 days 846.8 99.9
1037.9 14.1
1238.3 67.0
1360.3 4.3
1771.5 15.3
2598.6 16.7
3253.6 7.4
57Co 271.8 days 14.4 9.5
122.1 85.5
136.5 10.7
60Co 5.3 yrs 1173.2 99.9
1332.5 100.0
88Y 106.6 days 14.1 17.7
14.1 34.0
898.1 92.7
1836.1 99.4
133Ba 10.5 yrs 30.6 35.6
31.0 65.7
35.0 18.0
81.0 34.2
276.4 7.1
302.9 18.4
356.0 62.2
383.8 8.9
137Cs 30.0 yrs 31.8 2.0
32.2 3.8
36.4 1.0
661.7 85.2
152Eu 13.3 yrs 39.5 21.2
40.1 38.4
45.4 11.1
121.8 28.4
244.7 7.5
344.3 26.6
411.1 2.2
778.9 13.0
964.1 14.5
1085.9 9.9
1112.1 13.6
1408.0 20.8
241Am 432.7 yrs 13.9 13.0
17.6 20.2
59.5 35.7

 


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