166mHo: a multi-gamma standard for the calibration of Ge spectrometers.
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.
Bernardes
Estela M O
EM
Laboratório Nacional de Metrologia das Radiações Ionizantes, Instituto de Radioproteção e Dosimetria da Comissão Nacional de Energia Nuclear, Rio de Janeiro-RJ, Brazil. estela@ird.gov.br
Delgado
José U
JU
Tauhata
Luiz
L
da Silva
Carlos J
CJ
Iwahara
Akira
A
Poledna
Roberto
R
Paschoa
Anselmo S
AS