Intensity Of Gamma-ray Emission Research Articles

Measurements of the absolute gamma-ray emission intensities from the decay of 166Ho

166Ho (T1/2≈ 26.8 h) is an emerging theragnostic radionuclide of interest in nuclear medicine due to its peculiar decay scheme, featuring high-energy β− emission (≈ 1.8 MeV) coupled with the main gamma-ray emission (≈ 80.6 keV). Using the new 166Ho activity standard and the well-calibrated, high-energy resolution HPGe detector, both available at ENEA-INMRI, a new determination of several 166Ho gamma-ray emission intensities, Iγ, was performed with low uncertainty. The new Iγ values contributed to the Decay Data Evaluation Project.

Absolute emission intensities of the gamma rays from the decay of 224Ra and 212Pb progenies and the half-life of the 212 Pb decay

Absolute gamma-ray emission intensities for 36 characteristic gamma rays from the decay of 224Ra, 212Pb, and their progeny were determined by measuring sources calibrated for activity by means of primary methods based on well-defined high-purity germanium (HPGe) detectors at both NIST and NPL. Results from the two laboratories agree with recent data evaluations, except for gamma rays with low emission intensities. The decay schemes have been re-balanced based on the new results. In addition, the half-life for 212Pb was measured using several HPGe detectors, ionization chambers, and a well-type NaI(Tl) detector.

Influence of Extragalactic Magnetic Fields on Extragalactic Cascade Gamma-Ray Emission

We discuss the influence of extragalactic magnetic fields on the intensity of gamma-ray emission produced in electromagnetic cascades from ultra-high energy cosmic rays propagating in extragalactic space. Both cosmic rays and cascade particles propagate mostly out of galaxies, galactic clusters, and large-scale structures, as their relative volume is small. Therefore, their magnetic fields weakly affect emission produced in cascades. Yet, estimates of this influence can be useful in searching for dark matter particles when components of extragalactic gamma-ray background should be known, including cascade gamma-ray emission. To study magnetic field influence on cascade emission, we calculated cosmic particle propagation in fields of ~10−6 and 10−12 G (the former is typical inside galaxies and clusters and the latter is common in voids and outside galaxies and clusters). The calculated spectra of cascade gamma-ray emissions are similar in the range of ~107–109 eV, so analyzing cascade emission in this range it is not necessary to specify models of an extragalactic magnetic field.

Measurement of the absolute gamma-ray emission intensities from the decay of 103Pd

Palladium-103 decays through electron capture to excited levels of 103Rh, and especially to the 39.748-keV metastable state. A high activity palladium chloride solution was standardized by liquid scintillation, using the Triple-to-Double Coincidence Ratio method. The absolute photon emission intensities were determined by gamma-ray spectrometry using point sources prepared with the standard solution. Different detectors and measuring conditions were used to cross-reference the results. The most intense photon emission intensities are derived with about 1% relative combined standard uncertainty.

Measurement of the absolute gamma-ray emission intensities from the decay of 147Nd

The 2011 Decay Data Evaluation Project (DDEP) evaluation for 147Nd includes recommended absolute emission intensities for the two main gamma-rays at 91.105 (2) keV and 531.016 (22) keV of 0.284 (18) and 0.127 (9) respectively, i.e. with uncertainties of 6.3% and 7.1%. These large uncertainties stem from inconsistencies in the published data and are unfit for modern purposes, since the production of 147Nd is used as an important neutron flux dosimeter.The LNE-LNHB has undertaken new absolute gamma-ray emission intensity measurements. The results of these measurements will be presented, along with a full uncertainty budget, and their effect on the recommended data uncertainties will be discussed.

Primary standardization and determination of gamma ray emission intensities of Ho-166

The procedure followed by the Nuclear Metrology Laboratory (LMN) at the IPEN-CNEN/SP, in São Paulo, for the primary standardization of 166Ho is described. The activity of 166Ho was determined by the efficiency extrapolation technique applied to a 4πβ(PC)-γ coincidence system using a gas flow proportional counter in 4π geometry coupled to a 76 × 76 mm NaI(Tl) crystal. The results for the γ-rays intensities at 80.57 and 1379.45 keV were 0.0651(11) and 0.00904(11), respectively.

Determination of X- and gamma-ray emission intensities in the decay of 131I

The activity per unit mass of an iodine-131 solution was absolutely standardized by both the 4πβ–γ coincidence method and the 4πγ counting technique. The calibrated solution was used to prepare point sources after a preliminary deposit of AgNO3 to prevent the loss of volatile iodine. Relative and absolute photon emission intensities of 15 sgamma-rays and those of the two K X-rays of xenon were determined by gamma-ray spectrometry, with relative uncertainties of 0.8% for the three main emissions.

Using gamma-ray emission to measure areal density of inertial confinement fusion capsules

Fusion neutrons streaming from a burning inertial confinement fusion capsule generate gamma rays via inelastic nuclear scattering in the ablator of the capsule. The intensity of gamma-ray emission is proportional to the product of the ablator areal density (ρR) and the yield of fusion neutrons, so by detecting the gamma rays we can infer the ablator areal density, provided we also have a measurement of the capsule's total neutron yield. In plastic-shell capsules, for example, (12)C nuclei emit gamma rays at 4.44 MeV after excitation by 14.1 MeV neutrons from D+T fusion. These gamma rays can be measured by a new gamma-ray detector under development. Analysis of predicted signals is in progress, with results to date indicating that the method promises to be useful for diagnosing imploded capsules.

Primary radioactivity standardization and gamma intensities determination of 124Sb

A solution containing 124Sb was primarily standardized by the 4πβ−γ coincidence and anticoincidence extrapolation methods in the frame of the EUROMET 907 international comparison organized by Laboratoire National Henri Bequerel (LNHB)/France, in 2007. The main purposes of this exercise are the improvement in the uncertainties on the gamma-ray emission intensities and they clarify the discrepancies verified among the intensity values for many weak gamma rays reported in the literature. In this work the results of the activity obtained were used to determine the absolute and relative gamma-ray intensities using a planar and coaxial HPGe detectors calibrated by 152Eu and 116mHo multi-gamma standard sources covering the energy range from 20 to 1408 keV. Additionally the half-life of 124Sb was determined following the decay of a solution of 124Sb contained in a glass ampoule over a period of three half-lives using two 4πγ ionization chambers.

Extragalactic electromagnetic cascades as a possible instrument for the study of background radio emission

We analyzed the diffuse gamma-ray emission generated in the interactions between cosmic rays of ultrahigh energies and the background radiation in extragalactic space. The intensity of gamma-ray emission was calculated within a simplified model for energies E ≈ 1014 eV in different assumptions concerning the cosmic ray sources with the use of different estimates of nonthermal background radiation. It was shown that the gamma-ray radiation intensity in this energy range depends on the background radio emission and that under different assumptions concerning the radio background it can differ tens of times. It was concluded that gamma-ray emission can serve as a test for the models of background radio-frequency radiation.

Activity measurements and determination of gamma-ray emission intensities in the decay of 65Zn

An International EUROMET exercise, Action 721, was organized with the objective of obtaining more reliable decay data on the disintegration of 65Zn. Nine laboratories participated, sending their results relating to activity measurements and 1115-keV gamma-ray emission intensity. Participants mainly used the 4 πβ- γ coincidence method for the activity measurement, the resulting values and uncertainty budgets are described. New gamma-ray emission intensities were also measured in this exercise and, taking into account previously published values, the intensity of the 1115-keV gamma-ray emission has been determined to be 50.22(11)%.

Gamma ray emission intensities of226Ra in equilibrium with its daughter products

A226 Ra source of known disintegration rate has been measured to determine the absolute γ-ray emission intensities of members of its decay chain in radioactive equilibrium. The results are compared with other values from the literature.