Gamma-ray Emission Probabilities Research Articles

Activity standardization of two enriched 40K solutions for the determination of decay scheme parameters and the half-life

In this paper we describe experiments on two enriched 40K solutions to accurately determine decay data. The first solution was measured in 2004/2005 by means of a gamma-ray spectrometer with low background and a liquid scintillation (LS) counter to apply the CIEMAT/NIST efficiency tracing method. A combination of results yields an emission probability of the 1461 keV gamma-rays of Pγ = 0.1030(11) which is lower than current results of data evaluations.The activity concentration of the second solution was also determined by means of LS counting, but here, the CIEMAT/NIST efficiency tracing method as well as the TDCR method were applied. Again, the result was combined with that of independent gamma-ray spectrometry and the gamma-ray emission probability was found to be Pγ = 0.1029(9) in good agreement with the result obtained from the first solution. A combination of both experiments yields Pγ = 0.1029(9). The spectra of a TriCarb LS counter were carefully analyzed and a beta minus emission probability Pβ− = 0.8954(14) was determined. The new results for Pγ and Pβ− indicate that the overall probability of the decay via EC in recent data evaluations is overestimated.The LS counting efficiencies were computed with a stochastic model and up-to-date calculations of the beta spectrum and fractional EC probabilities were used. The final activity result of the second solution is combined with the outcome of a comprehensive isotopic analysis to determine the half-life of 40K which is found to be 1.2536(27) ·109 years. All above-stated uncertainties are standard uncertainties (k = 1).

Indirect measurements of neutron cross-secti at heavy-ion storage rings

Cross sections for neutron-induced reactions of short-lived nuclei are essential for nuclear astrophysics since these reactions in the stars are responsible for the production of most heavy elements in the universe. These reactions are also key in applied domains like energy production and medicine. Nevertheless, neutron-induced cross-section measurements can be extremely challenging or even impossible to perform due to the radioactivity of the targets involved. Indirect measurements through the surrogate-reaction method can help to overcome these difficulties.The surrogate-reaction method relies on the use of an alternative reaction that will lead to the formation of the same excited nucleus as in the neutron-induced reaction of interest. The decay probabilities (for fission, neutron and gamma-ray emission) of the nucleus produced via the surrogate reaction allow one to constrain models and the prediction of the desired neutron cross sections.We propose to perform surrogate reaction measurements in inverse kinematics at heavy-ion storage rings, in particular at the CRYRING@ESR of the GSI/FAIR facility. We present the conceptual idea of the most promising setup to measure for the first time simultaneously the fission, neutron and gamma-ray emission probabilities. The results of the first simulations considering the 238U(d,d’) reaction are shown, as well as new technical developments that are being carried out towards this set-up.

Measurement of the gamma-ray emission probability of 131mXe

131mXe has been standardized by means of an internal gas proportional counting system, employing a length-compensated method. The activity concentration of 131mXe was measured with a relative standard uncertainty of 0.6%. The gamma-ray emission probability of 131mXe was then determined as 0.0196(4) by measuring a standard sample of 131mXe using a high-purity germanium (HPGe) spectrometer.

Measurements of gamma-ray emission probabilities in the decay of americium-244g

ABSTRACT Accurate data of gamma-ray emission probabilities are frequently needed when one quantitatively determines the amount of isotope by gamma-ray measurements or obtains neutron capture cross-sections using them. Americium-243, one of the most important minor actinides, produces 244Am after neutron capture. The 744-keV gamma-ray decaying from the ground state of 244Am has a relatively large gamma-ray emission probability about 66%; however, its uncertainty is as large as 29%. The uncertainty of the gamma-ray emission probability leads to a major factor of the systematic uncertainty on determining an amount of isotope, and therefore the gamma-ray emission probability was measured by using an activation method and an examined level structure of 244Cm. In this study, the emission probability of 744-keV gamma-ray was derived as 66.5 ± 1.1%, and its uncertainty was improved from 29% to 2%.

Study of the 243Am decay

Gamma-ray emission probabilities for 243Am were published in 1996. Three new gamma transitions were then found: 46.84, 98.36 and 102.02keV. In the last evaluation by the Decay Data Evaluation Project, the emission probabilities of 46.84 and 102.02keV transitions were not included. Alpha-gamma coincidence measurements have been now used to check and revise the values for these two transitions and their emission probabilities. The emissions of the 31.13, 43.53, 74.66, 86.71 and 141.89keV transitions were also studied.

Disintegration rate and gamma-ray emission probability per decay measurement of Cu-64

The procedure followed by the Nuclear Metrology Laboratory (LMN) at the IPEN for the standardization of activity of 64Cu is described. The measurement was carried out in a 4π (PC) β-γ coincidence system. The activity per unit mass of the solution was determined by the extrapolation technique. The events were registered using a Time to Amplitude Converter (TAC) associated with a Multi-channel Analyzer. The gamma-ray emission probability per decay of the 1345.7keV transition of 64Cu determined with a calibrated REGe gamma-ray spectrometer was (0.472 ± 0.010) %, in agreement with the literature.

Method of self-consistent evaluation of absolute emission probabilities of particles and gamma rays

In assumption of well installed decay scheme the method provides a) exact balance relationships, b) lower (compared to the traditional techniques) uncertainties of recommended absolute emission probabilities of particles and gamma rays, c) evaluation of correlations between the recommended emission probabilities (for the same and different decay modes). Application of the method for the decay data evaluation for even curium isotopes led to paradoxical results. The multidimensional confidence regions for the probabilities of the most intensive alpha transitions constructed on the basis of present and the ENDF/B-VII.1, JEFF-3.1, DDEP evaluations are inconsistent whereas the confidence intervals for the evaluated probabilities of single transitions agree with each other.

Measurements of gamma-ray emission probabilities of 241, 243Am and 239Np

ABSTRACTGamma-ray emission probabilities of 241, 243Am and 239Np have been precisely measured with gamma- and alpha-ray spectroscopic methods. The activities of the samples were determined by measuring alpha particles using a Si semiconductor detector. Gamma rays emitted from the samples were measured with a planar type High-Purity Germanium (HPGe) detector. An efficiency curve of the HPGe detector was derived with uncertainties from 0.7% to 2.5% by combining measured efficiencies and Monte Carlo simulation. The gamma-ray emission probabilities for the major gamma rays of these nuclides were determined with uncertainties less than 1.2%.

Determination of photon emission probabilities for the main gamma-rays of 223Ra in equilibrium with its progeny

The currently published 223Ra gamma-ray emission probabilities display a wide variation in the values depending on the source of the data. The National Institute of Standards and Technology performed activity measurements on a 223Ra solution that was used to prepare several sources that were used to determine the photon emission probabilities for the main gamma-rays of 223Ra in equilibrium with its progeny. Several high purity germanium (HPGe) detectors were used to perform the gamma-ray spectrometry measurements.

Determination of gamma-ray emission probabilities per decay of Ga-68

The measurement of the gamma-ray emission probabilities per decay of 1077keV of 68Ga is presented. The standardization system consists of a gas-flow proportional counter in 4π geometry coupled to an HPGe detector for the gamma-ray detection. The gamma-ray emission probabilities per decay were measured in an HPGe gamma-ray spectrometer. The weaker gamma-ray intensities of 68Ga were measured in a relative way, making use of an uncalibrated ampoule of 68Ge–68Ga in radioactive equilibrium, and considering the absolute result from the 1077keV gamma-ray.

Disintegration rate, gamma-ray emission probabilities and metastable half-life measurements of 67Ga

The procedure for determining the 67Ga disintegration rate by a primary method is described. The proposed triple 4πβ–γ coincidence system consists of a thin window gas-flow 4π proportional counter (PC) coupled to a NaI(Tl) scintillator and a HPGe crystal. Independent pulse height and occurrence time information is provided for the three detector outputs by means of a Software Coincidence System. Separate spectrometry measurements with a n-type reversed electrode coaxial Ge detector (REGe) were performed for obtaining gamma-ray emission probabilities per decay. Accurate values of disintegration rate, gamma-ray emission probabilities and the metastable half-life were achieved.

Measurement of absolute gamma-ray emission probabilities from decay of 138Xe

The fission gaseous 138Xe products play an important role in the research of nuclear-reaction products and radioisotope applications. Therefore, precise data for emission probabilities of gamma-ray from decay of 138Xe are highly desired. However, a high precision is not achievable with a sufficient accuracy due to the limitations of the usual experimental techniques. In this paper, after the homogeneous sources of 138Xe–138Cs were prepared, the activity of 138Xe was obtained by the decay relationship between 138Xe and 138Cs using a HPGe detector. The full-energy peak efficiencies of gamma-ray for 138Xe and 138Cs were accurately calibrated using many activity standard sources and self-absorption was corrected. As a result, the absolute emission probabilities of the 258.4, 434.6 and 1768.3keV gamma-ray from decay of 138Xe were determined to be 34.9(10)%, 22.2(6)% and 18.8(5)%, respectively.

Determination of the emission probability of the principal gamma ray of 135Xe

The gamma ray emission probability is one of the most important characteristics used in quantifying radionuclides. This article describes in detail the principles and processes involved in the determination of the 135Xe gamma ray emission probability. Gaseous samples of 135Xe were generated by irradiating enriched 134Xe with a thermal neutron flux. The principal gamma ray emission probability of 135Xe was then determined to be 0.896±0.016 (k=1) by measuring the absolute activity using length-compensated internal gas proportional counters and γ-ray intensity using a high-purity germanium (HPGe) detector.

Disintegration rate and gamma ray emission probability per decay measurement of 123I

A series of 123I measurements have been carried out in a 4π(eA,X)–γ coincidence system. The experimental extrapolation curve was determined and compared to Monte Carlo simulation, performed by code ESQUEMA. From the slope of the experimental curve, the total conversion coefficient for the 159keV total gamma transition, α159, was determined. All radioactive sources were also measured in an HPGe spectrometry system, in order to determine the gamma-ray emission probability per decay for several gamma transitions. All uncertainties involved and their correlations were analyzed applying the covariance matrix methodology and the measured parameters were compared with those from the literature.

An Innovative Method to Measure the Gamma-Ray Emission Probabilities in the Decay of 238Np and 233Pa

The absolute emission probabilities of gamma rays from the decay of 238Np and 233Pa have been measured by an innovative method combining pile oscillation and neutron activation techniques. We obtained values of (24.99 ± 0.34)% and (37.79 ± 0.64)% for the 984.5- and 311.9-keV gamma rays from 238Np and 233Pa, respectively, in good agreement with the recommended values proposed by the Decay Data Evaluation Project (DDEP): (25.18 ± 0.13)% and (38.3 ± 0.5)%. The influence of gamma-ray emission probabilities from 238Np and 233Pa on neutron capture cross-section measurements of 237Np and 232Th, respectively, are discussed and tend to confirm the recommended values from the DDEP. A patent has been granted for this method.

Gamma-ray emission probabilities in the decay of 177mLu

γ-Ray emission probabilities from the decay of the long-lived (T1/2=160.44d) isomeric state in 177mLu were measured with planar (LEPS) and coaxial Ge detectors. The isomer γ-ray and β−-decay branching intensities were also determined. Measurements were carried out at low absolute efficiencies in order to minimize coincidence summing losses. The results are compared with the previous measurements.

Beta decay of the fission product 125Sb and a new complete evaluation of absolute gamma ray transition intensities

The radionuclide 125Sb is a long-lived fission product, which decays to 125Te by negative beta emission with a half-life of 1008 day. The beta decay is followed by the emission of several gamma radiations, ranging from low to medium energy, that can suitably be used for high-resolution detector calibrations, decay heat calculations and in many other applications. In this work, the beta decay of 125Sb has been studied in detail. The complete published experimental data of relative gamma ray intensities in the beta decay of the radionuclide 125Sb has been compiled. The consistency analysis was performed and discrepancies found at several gamma ray energies. Evaluation of the discrepant data was carried out using Normalized Residual and RAJEVAL methods. The decay scheme balance was carried out using beta branching ratios, internal conversion coefficients, populating and depopulating gamma transitions to 125Te levels. The work has resulted in the consistent conversion factor equal to 29.59(13) %, and determined a new evaluated set of the absolute gamma ray emission probabilities. The work has also shown 22.99% of the delayed intensity fraction as outgoing from the 58 d isomeric 144keV energy level and 77.01% of the prompt intensity fraction reaching to the ground state from the other excited states. The results are discussed and compared with previous evaluations. The present work includes additional experimental data sets which were not included in the previous evaluations. A new set of recommended relative and absolute gamma ray emission probabilities is presented.

Experimental determination of absolute gamma-ray emission probabilities for 88Kr

Through preparation of the homogeneous sources for 88Kr and 88Rb, the activity of 88Kr was determined by the decay relationship between 88Kr and 88Rb using HPGe detector. The peak efficiencies of gamma-ray for 88Kr and 88Rb were accurately calibrated. As a result, the absolute gamma-ray probabilities of the 196.3, 834.8,1529.8,2195.8 and 2392.1 keV gamma rays for 88Kr were determined to be 25.1(5)%, 12.9(2)%,10.7(2)%,13.3(2)% and 34.9(5)%, respectively.

Measurements of absolute gamma-ray emission probabilities in the decay of 233Pa

Abstract Gamma-ray emission probabilities from the β − decay of 233 Pa were measured with planar (LEPS) and coaxial Ge detectors. A 233 Pa source was produced after radiochemical separation from a 237 Np sample in which the parent ( 237 Np) and daughter ( 233 Pa) nuclides were in secular equilibrium. Absolute γ ‐ ray emission probabilities per 100 α decays of the parent nuclide 237 Np were also measured in conjunction with the α - and γ ‐ ray spectroscopy techniques.

Evaluation of the decay data of 109Cd

109Cd decays to the excited states of 109Ag through the electron capture decay mode. The evaluation of the complete decay scheme and data of 109Cd including the recent new measurements is presented in this report. The limitation of relative statistical weight method (LRSW) was applied to average numbers throughout the evaluation. The uncertainty assigned to the average value was always greater than or equal to the smallest uncertainty of the values used to calculate the average. The half-life is determined to be 462.0±0.3 days. All known measured absolute emission probabilities for gamma-ray and KX-ray have been examined. And the gamma-ray emission probability of the reference γ line of 88.0336keV is recommended to be 3.65±0.3%. The internal conversion coefficients and their uncertainties were used to obtain the complete decay intensity balance. The other decay characteristics are calculated using the ENSDF analysis program. Finally the 109Cd decay scheme was given.