Absolute intensities of the γ-ray emissions originating from the electron capture decay of ¹⁵³Gd

Abstract

Abstract. 153 Gd has widespread use, in non-destructive testing, as a line source in SPECT imaging and has been recently proposed as an in-vitro interstitial rotating shield brachytherapy (I-RSBT) source. In this work, the six most intense emissions in the de-excitation of the daughter nucleus 153 Eu have been measured, with an improved accuracy and precision to γ -ray emission intensities reported previously, via two characterised HPGe spectrometers. A specific absolute activity of 512.5 (25) kBq g −1 was determined using the 4π (LS)-γ digital coincidence counting technique. This absolute activity was used to determine an absolute intensity for the 97.4 keV γ -ray emission of 30.15 (20) per 100 decays. The reported absolute emission intensity of this transition in this work has a relative difference of 4% from the currently recommended value.

Radionuclide Metrology and Standards in Nuclear Physics

“…If the specific activity (A) is pre-determined by a primary standard technique, a precise full-energy peak detection efficiency for a gamma-ray detection system can be established from the expression, = where is the background subtracted peak area, t is the measurement time (which should be small relative to the decay half-life), is the gamma emission probability per decay and  is the absolute full-energy peak detection efficiency  . Since the provision of independent primary standards allows accurate determination of fullenergy peak detection efficiencies, such measurements can establish very precise P values [12,13] which are used in subsequent secondary calibration sources (see figure 4).…”

“…Figure 5: Upper: The UK National Nuclear Array (NANA) which can be used for primary standardisations using the gamma-ray coincidence method; Lower: example of raw and angular correlation corrected primary activity values for a 60 Co standard taken using NANA [10]. 4: Absolute full-energy peak detection efficiency calibration curve and residuals for the LOKI HPGe detector at NPL used for absolute gamma-ray emission probability measurements of the decay of 153 Gd, adapted from reference [13].…”