Bernardes EMO, Delgado JU, Tauhata L, da Silva CJ, Iwahara A, Poledna R, Paschoa AS. 166mHo: a multi-gamma standard for the calibration of Ge spectrometers.
Appl Radiat Isot 2002;
56:157-61. [PMID:
11842800 DOI:
10.1016/s0969-8043(01)00182-8]
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Abstract
Efficiency calibration curves for germanium detectors are usually established by using a large number of standard gamma-ray sources of specific radionuclides, that decay with few gamma-rays, or radionuclides with complex decay schemes, such as 133Ba or 152Eu. But these multi-gamma radionuclides cannot be used alone, because the gamma-rays of high intensity are irregularly distributed across the energy spectrum. 166mHo is a more suitable single source for such calibrations, because this radionuclide decays by beta(-)emission to the excited states of 166Er with the subsequent emission of about 20 strong and well distributed gamma-rays ever the energy range 50-1000 keV. Moreover, with a relatively long half-life (1200 yr) and characteristic X-rays between 40 and 50 keV, this nuclide is a good standard for the calibration of germanium detectors. The X- and gamma-ray emission probabilities of their main lines need to be known with good accuracy in order to resolve the discrepancies found in the literature. A combination of 4pi beta-gamma coincidence and X- and gamma-ray spectrometric techniques have been used to determine 50 photon emission probabilities.
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