Determination of photon emission probabilities of radionuclides using a Si(Li) detector calibrated by the primary standard source, BESSY

Abstract

BESSY is an electron storage ring which is optimized for use as a primary radiometric standard source for the infrared to X-ray region. The relative uncertainty of the spectral photon flux Φ E is less than 0.45% (1σ) in the spectral range 5 < E < 15 keV. Measurements in undispersed synchrotron radiation produced a quantum detection efficiency for a Si(Li) detector with relative uncertainties of less than 0.5%. The calibrated detector was used to measure the photon flux of radioactive standards of known activity ( 57Co, 65Zn and 88Y) in the photon energy range from 5 to 15 keV. From these measurements, the K α X-ray and gamma-ray emission probabilities p( E) of the radionuclides were deduced. Our results for the K α X-ray lines of 57Co, p(6.4 keV)=0.501(5) and 65Zn, p(8.0 keV)= 0.346(3) and for the ratio p( 57 Co; 14.4 keV)/p( 88 Y; 14.1 keV)=0.179(4) have small uncertainties and are not affected by uncertainties in the fluorescence yields. They confirm recommended data.