２００３年核データ研究会

２００３年１１月２７，２８日に行われた核データ研究会のポスターセッションでの発表について紹介します。


Identification of 156mPm
through the b-decay of 156Nd
Abstract

　The b-decay of 156Nd has been studied for the　purpose of searching isomers of 156Pm. A source preparation was made by a thermal neutron irradiation of 235U followed by an on-line isotope separator installed at the Kyoto University Reactor (KUR-ISOL). A Si(Li) detector, plastic scintillators and two HPGe detectors (GMX, LOAX) were used to measure conversion electrons, b-rays and g-rays, respectively.
　The isomer of 156Pm was identified. The 150.5 keV isomeric transition was assigned to M3 multipolarity from the result of a conversion electron measurement. The isomeric state was likely 1- state.






Development of Total Absorption
Ge Detector for Qb Measurement
Abstract

　Developing a total absorption HPGe detector is available for Qb measurement without knowledge of decay scheme. The detector is based on a large well-type HPGe detector and Anti-Compton BGO scintillator.
　Four b-sources (142Pr, 90Y, 42K, 38Cl) are measured, and discuss a way to analyze. First, Electron response functions are generated by Monte-Carlo transport code (EGS4) at an energy range 1-8 MeV. Second, EGS4 simulation reveals a way to strip distortions from incomplete g-absorptions. Third, if we use folding method against total absorption spectrum, single component b-spectra not considering decay scheme gives nearly true Qb within 10 keV.
　From analysis of these spectra, we obtain a hope that this HPGe detector is effective for Qb measurement.






Measurement methods of the thermal neutron capture
cross sections by detecting prompt and b-decay g-rays.
Abstract

　We verified new method of measurement cross sections for the thermal neutron capture detecting prompt g-rays (the prompt-g method). To verify the method, we compared with reliable measurement method, the activation method. Then, the two measured cross section values were measured by using both methods and compared each other.
　We measured the cross sections for nine reactions. The ratios measured cross section values by using activation method and prompt-g method were analyzed. The ratios lower systematically from 1.0 (sprompt=sdecay). It is considered the reason is inaccuracy of the emission probabilities of prompt g-rays.
　The prompt-g method cannot determine cross sections within 10%, because precision of emission probabilities is not enough. It is necessary to measure systematically more precise emission probabilities of prompt g-rays in (n, g) reactions when we determine the (n, g) cross sections.





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