Hiroshi Miyahara

Precise measurements of the gamma-ray emission probabilities of 186Re and 188Re.

Gamma-ray emission probabilities of 186Re and 188Re are important in nuclear medicine, and have been precisely measured by 4pibeta-gamma coincidence using a live-timed two-dimensional data-acquisition system. The gamma-ray emission probabilities of the 137.2 keV for 186Re and 155.1 keV for 188Re were 0.09487+/-0.00029 and 0.15425+/-0.00072, respectively.

Standardisation of 169Yb and precise measurement of gamma-ray emission probabilities

Abstract The gamma-ray emission probabilities of 169 Yb were determined directly from the disintegration rate and the gamma-ray intensities. The disintegration rates of 169 Yb sources were measured by using a 4πβ(ppc)–γ(HPGe) coincidence system with resolving times of both 2.06 and 5.66xa0μs and the γ-ray intensities were measured with HPGe detectors. The measured γ-ray emission probabilities agreed relatively well with those reported by Funck et al. (Int. J. Appl. Radiat. Isotopes 34 (1983) 1215) but their results were slightly larger. The uncertainties were improved.

Determination of the emission probabilities of the principal γ-rays for 134Cs to a high precision

While multi-gamma-ray emitting nuclides such as 75Se, 134Cs and 152Eu have reasonably well-defined decay scheme, some inconsistencies still remain. Detailed evaluations and weighted-mean analyses result in the recommendation of gamma-ray emission probabilities with small uncertainties, although significant deviations exist in the measured values. Therefore, the gamma-ray emission probabilities of 134Cs have been measured to a high precision after an extremely accurate calibration of detection efficiency. The resulting data agree extremely well with the evaluated values in IAEA-TECDOC-619 (IAEA, X-ray and gamma-ray standards for detector calibration, IAEA-TECDOC-619, IAEA, Vienna, 1991).

Determination of precise gamma-ray emission probabilities for 88Rb.

Precise gamma-ray emission probabilities of 88Rb have been measured by 4pi beta-gamma coincidence using a live-timed two-dimensional data-acquisition system. The absolute emission probabilities of the 898.1, 1836.1 and 2677.9 keV gamma rays were determined from the absolute gamma-ray intensities and the disintegration rates to be 14.68+/-0.13%, 22.73+/-0.15% and 2.123+/-0.021%, respectively. The relative intensities were measured for the weak gamma rays by a gamma-ray spectrometer, and the 88Rb decay scheme was determined from these results.

γ-ray emission probabilities of 193Os

Abstract Precise measurements of disintegration rates by using a 4πβ-γ coincidence apparatus have resulted in improved certainties of the principal γ-ray emission probabilities of 193Os. Most of the uncertainties are less than 1%, whereas the uncertainties of emission probabilities evaluated in the Nuclear Data Sheets (83 (1998) 921) are more than 6%. The precision is improved for the β-ray branching ratio for direct transition to the ground state and the value is larger than the evaluated value by about 6%.

High accuracy measurement of the relative efficiency curve and determination of gamma-ray relative intensity for 38Cl

Relative efficiency curves were accurately determined for Ge gamma-ray detectors from measurements for radionuclides which emit two gamma-rays with essentially the same emission probabilities. The relative intensity of the 1643 and 2167 keV gamma-rays from 38Cl was determined to be 0.7496 (11) by using these highly accurate efficiency curves.

Precise Measurement of Gamma-Ray Emission Probabilities for 187W by Using a Two-Dimensional 4πβ-γ Coincidence System

Gamma-ray emission probabilities for 187W have been determined with uncertainties less than 1% from measurement of absolute γ-ray intensities and disintegration rate. The measured emission probabilities are larger than those previously reported by about 20% and hence the β-ray branching ratio to the ground state has to be smaller than about 40%. The decay scheme of 187W calculated by using the present results is given as a final result.

Development of Two-dimensional Data-acquisition Apparatus Using 8 mm Data Cartridge for 4πβ-γ Coincidence Measurement

A two-dimensional data-acquisition apparatus using 8 mm data cartridge (DAT) has been developed for 4πβ-† coincidence measurement. The DAT system was replaced for a magnetic tape (MT) system that was being used in large computer system and that was used in our old πβ-† coincidence apparatus. Furthermore, beta, gamma and coincidence live-times can be measured in this system. The improvement brought a small size of the system, the storage of large data and simple determination of live-times.

Production of 147Eu for Gamma-Ray Emission Probability Measurement

Gamma-ray emission probability is one of the most important decay parameters of radionuclide and many researchers are paying efforts to improve the certainty of it. The certainties ofγ -ray emission probabilities for neutron-rich nuclides are being improved little by little, but the improvements of those for proton-rich nuclides are still insufficient. Europium147 that decays by electron capture or β+-particle emission is a proton-rich nuclide and the γ -ray emission probabilities evaluated by Mateosian and Peker 1) have large uncertainties. They referred to only one report 2) concerning withγ -ray emission probabilities. Our final purpose is to determine the preciseγ -ray emission probabilities of 147Eu from disintegration rates andγ -ray intensities by using a 4 πβ-γ coincidence apparatus. 3) Impurity nuclides affect largely to the determination of disintegration rate; therefore, a highly pure 147Eu source is required. This short note will describe the most proper energy for147Eu production through147Sm(p, n) reaction.

Precise emission probabilities of gamma-rays of 159Gd

Measurement of emission probabilities for principal gamma-rays of 159Gd with 4pibeta(ppc)-gamma(HPGe) coincidence apparatus has given precise values as indicated by uncertainties of about 1%. Improved certainties are seen when comparing the present results with emission probabilities evaluated in Nuclear Data Sheets (Helmer, 1994, p. 72) for which the uncertainties are about 24%. The improvement resulted in precise decay scheme parameters of the nuclide.