Gamma-ray Emission Probabilities Research Articles

X- and gamma-ray standards for detector efficiency calibration

A Coordinated Research Programme (CRP) has been established by the IAEA Nuclear Data Section on the Measurement and Evaluation of X- and Gamma-ray Standards for Detector Efficiency Calibration (to generate appropriate efficiency curves). Participants in the programme are specialists in the standards field, and they are in the process of producing a recommended set of specific decay parameters for a selected number of radionuclides. These data have been judged as the most important for the calibration of equipment used to detect and quantify X- and gamma-ray emissions. Work began in 1985 with an initial meeting in Grenoble to agree upon the contents of the database, and to propose a programme of measurements and evaluations to be undertaken by the participants. Further meetings have been held in Rome (1987) and Braunschweig (1989) to monitor progress and agree upon the final recommended data set of half-lives and X- and gamma-ray emission probabilities.

Reconciliation of 237Np decay scheme data

Several authors have recently reported precise measurements of alpha-particle, gamma-ray and conversion electron emission probabilities in the decay of 237Np. However, difficulties have been encountered in attempting to reconcile these data in constructing a self-consistent decay scheme. Evidence for the existence of a few low-energy, high-intensity transitions which would help to balance the nuclear level scheme is discussed. An attempt has also been made to resolve some of the difficulties by low energy gamma-ray spectroscopy.

Measurements of 170Tm photon and electron emission probabilities

The 84.4 keV gamma-ray, K X-ray and conversion-electron emission probabilities of 170Tm have been measured. Triple-to-double coincidence ratio (TDCR) and 4πβ-γ coincidence methods were used to determined the activity of 170Tm while the emission probabilities of the photons were measured with a HPGe detector and electron spectra were obtained using a Si(Li) spectrometer. Absolute conversion coefficient data have also been determined on the basis of the measured intensity ratios. The emission probabilities were lower than previous measurements by 28%.

Selected gamma-ray energies and emission probabilities for the decay of 125Sb and 154Eu

The energies of 17 γ rays from 125Sb and 35 from 154Eu have been determined with typical uncertainties of 5–10 eV. Relative γ-ray emission rates have also been measured for 16 γ rays from 125Sb and 24 from 154Eu. These data will make more useful the mixed standard of 125Sb, 154Eu and 155Eu that is often used to calibrate Ge γ-ray detectors.

Relative gamma-ray emission probability for the decay of 207Bi

The relative emission probability has been measured for the 569- and 1063-keV γ rays from the decay of 207Bi.

Measurement of the gamma-ray emission probabilities of 75Se

The gamma-ray emission probabilities of 75Se were measured with Ge(Li) and HPGe detectors for an experimental intercomparison organized by the International Committee for Radionuclide Metrology (ICRM). The main characteristics of the measuring systems, the efficiency calibrations of the detectors, the radioactive sources, and the experimental procedures are described. A detailed analysis of the measured gamma-ray spectra was undertaken, and the associated problems are described. Part of the 75Se spectrum was simulated by 57Co and 203Hg radioactive sources (around the 136 keV line ) to assists in the resolution of spectral difficulties.

Measurement of the 46.5 keV gamma-ray emission probability of 219Pb and its application as a standard for the calibration of 129I monitors

A reverse electrode coaxial Ge detector has been used to determine the 46.5 keV gamma-ray emission rates of several sources of 210Pb. The effect of the escape peaks was carefully taken into account when determining the areas of the full-energy peaks for the calibration of the spectrometer. Source activities were measured by means of an improved 2πα counting techniques. The emission probability of the 46.5 keV gamma ray was found to be 0.0426±0.0007. This nuclide can be used as a low-energy gamma-ray standard as demonstrated in the calibration of 129I monitors.

Measurements of the gamma-ray emission probabilities of 75Se

The gamma-rays emission probabilities of 75Se have been measured with acoaxial Ge detector calibrated with a mixed 125 Sb + 154 Eu source and other standard sources. Corrections were made for coincedence and random summing to give data with estimated uncertainties of approximately 1.0%.

A 4πβ (ppc)-γ(HPGe) coincidence apparatus using a live-timed bi-dimensional data acquisition system and its application to measurement of gamma ray emission probability

Data accumulated automatically in a recently described coincidence counting system were used to calculate the photopeak efficiency of an HPGe γ ray detector simultaneously with the source activity. The system serves for the direct measurement of γ ray emission probabilities and as a check on γ ray emitting impurities in the 4 π source. The relatively short source-detector distance needed to attain acceptable counting statistics requires accurate corrections for effects due to cascade summing.

Measurement of the 59.5-keV gamma-ray emission probability in the decay of 241Am with a 4π-CsI(T1) - sandwich spectrometer

The 59.5-keV γ-ray emission rate of 241Am sources has been measured with a windowless 4 π-CsI(T1)-sandwich spectrometer. Photon attenuation by the α-particle absorbers was minimized by an optimal shape of these absorbers. The disintegration rates of the same 241Am sources were obtained by α-particle counting under defined low solid angles. The ratio of the two measured quantities, the 59.5-keV γ-ray emission probability, was found to be 0.3636 ± 0.0017 which is slightly higher than the recommended value of 0.359 ± 0.004.

Decay-scheme data for 65Ni

The gamma-ray emission probabilities of 65Ni have been measured. The activities of the sources used were determined by the 4πβ-γ coincidence technique, and the gamma-ray emission rates measured using calibrated germanium spectrometers. The half life of 65Ni was also measured, using an ionisation chamber. The result obtained was (2.51719±0.00026) hours.

The role of covariance in the analysis of gamma-ray spectra

When a gamma-ray spectrum contains a number of photopeaks originating from the same nuclide, the calculation of nuclide activity depends not only on the values of, and uncertainties in, the photopeak areas, photopeak efficiencies, gamma-ray emission probabilities and peak area correction factors, but also on the correlations that exist between these quantities. When photopeaks corresponding to a group of nuclides overlap or are unresolved, simultaneous estimation of the activities of all the nuclides present in the group is necessary if the information contained in the spectrum is to be used efficiently — a procedure which can prove important when the only prominent photopeak associated with a nuclide of interest overlaps with the photopeak of another nuclide. Two procedures for activity estimation are described: both procedures take correlations into account; one procedure deals with the special case of activity estimation for a single nuclide, where unresolved photopeaks are absent or neglected; the other procedure deals with simultaneous activity estimation using all the photopeaks associated with an interrelated group of nuclides.

Determination of x-,and gamma-ray emission probabilities in the decay of Np-239

Abstract The x-,and gamma-ray emission probabilities per decay of Np-239 are determined directly from the ratio of the emission rates and the activity. The emission rates are measured with calibrated Ge(Li) spectrometer and activity with 4лβ-r coincidence counting device. The 277.6 keV r-ray emission probability is determined as 0.1421±0.0013. The errors of the measured results are carefully discussed and compared with the data offered by the literatures.

Alpha-particle and gamma-ray emission probabilities in the decay of 242Pu

The α-particle emission probabilities in the decay of 242Pu were measured using a surface-barrier detector in connection with a small magnet which eliminated most of the conversion electrons. The γ-ray emission probabilities were deduced from the γ-ray emission rates, measured with calibrated high-purity-Ge detectors, and the 242Pu disintegration rates, determined by α-particle counting in well-defined solid angles. For some of the sources they were also calculated from the 242Pu content measured by mass-spectrometric isotope dilution. The results obtained are: P α 0 = 0.7645 ± 0.0017, P α45 = 0.2352 ± 0.0017, P α148 = (2.90 ± 0.14)10 −4, P α307 = (8.6 ± 0.7)10 −6, P γ45 = (3.72 ± 0.07)10 −4, P γ103 = (2.63 ± 0.09)10 −5, P γ159 = (2.98 ± 0.20)10 −6. These results yield a consistent set of data with uncertainties being considerably smaller than those previously adopted.

Gamma-ray emission probabilities in the decay of140Ba and140La

The decay of the fission product pair 140Ba and 140La has been studied using Ge(Li) detectors and 4 pi beta - gamma coincidence techniques. Absolute emission probabilities of six gamma rays in 140Ba and 15 in 140La have been determined.

Determination of γ-ray emission probabilities in the decay of 228Th and its daughters

Gamma-ray emission probabilities useful for the assessment of 232Th and 232U by γ-ray spectrometry have been determined very accurately. The results were deduced from γ-ray spectra measured with a Ge(Li) and a high purity Ge detector using sources of 228Th which is part of the decay chain of 232Th and 232U.

Accurate evaluation of gamma-ray spectra for the measurement of gamma-ray emission probabilities

A brief account is given of the equipment, measuring method, and data processing used for precision gamma-ray spectrometric measurements at OMH. The calculation of the peak area and the OMAN ( OM H AN ALYSIS) program package are discussed. The performance of OMAN is discussed in the context of the experimental results.

Determination of gamma-ray emission probabilities in the decay of 235U and 231Th

The emission probabilities for the most prominent γ-ray transitions in the energy range from 25 to 206 keV accompanying the decay of 235U and its radioactive daughter 231Th were determined using calibrated Si(Li)_and high purity Ge detectors. The results are: P γ (25.65) = (0.145 ± 0.003), P γ (84.16) = (0.066 ± 0.003), P γ (143.8) = (0.109 ± 0.002), P γ (163.4) = (0.050 ± 0.001), P γ (185.7) = (0.575 ± 0.009) , P γ (205.3) = (0.050 ± 0.002). The quoted uncertainties, corresponding to a 1σ confidence level, take into account random and systematic uncertainties.

Efficiency calibration of germanium-spectrometers in the energy range from 122–412 keV

The efficiency calibration of germanium spectrometers in the energy range nbelow 300 keV is generally less accurate than at higher energies. In order to improve this situation we have studied and produced suitable primary calibration sources and used them to set up efficiency calibration curves for three germanium spectrometers in the energy range from 122–412 keV. Gamma-ray emission probabilities of several secondary calibration nuclides, in particular of 75Se and 182Ta, were determined. In addition, the half-lives of 75Se, 152Eu and 182Ta were remeasured.

Gamma-ray emission probabilities and half-life of 139Ba

The emission probability of the 165 and 1420 keV γ-rays emitted in the decay of 139Ba has been measured by 4 π β- γ coincidence counting and Ge(Li) spectrometric techniques to be (23.76 ± 0.25) and (0.261 ± 0.005) γ-rays per 100 disintegrations, respectively. The half-life of 139Ba has been determined to be (83.06 ± 0.28) minutes.