International Conference on NUCLEAR DATA for Science and Technology

２００４年９月２６日から１０月１日の期間に行われた核データ国際会議のポスターセッションでの発表について紹介します。


Measurement of activation cross sections producing
short-lived nuclei with pulsed neutron beam.
Abstract

　Activation cross sections for the (n, n') reaction were measured by means of the activation method at the neutron energy of 3.1, and 2.54 MeV by using pulsed neutron beam. Target nuclei were 79Br, 90Zr, 197Au, and 207Pb whose half-lives were between 0.8 and 8 s. 90Zr (n, n') 90mZr reaction was obtained for the first time. The d-D neutrons were generated by bombarding a deuterated titanium target with a 350 keV d+-beam at the 80-degree beam line of the Fusion Neutronics Source at the Japan Atomic Energy Research Institute. In order to obtain reliable activation cross sections, careful attention was paid to correct the efficiency for a volume source, and the self-absorption of gamma-rays in irradiated sample. The systematics of (n, n') reaction at the neutron energy of 3.1 MeV, which could be predicted within an accuracy of 50%, was proposed on the basis of our data.

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Reliability of prompt g-ray intensities for the
measurement of neutron capture cross sections.
Abstract

　We examined reliability of prompt g-ray intensities by measuring ratios of thermal neutron capture cross sections on 23Na, 27Al, 51V, 55Mn, 64Ni, 65Cu, 141Pr, 186W and 197Au at the Kyoto University Research Reactor Institute. The cross sections were obtained by two methods: one is detecting prompt g-rays (we call the prompt-g method) and the other is detecting g-rays following b-decay (the activation method). Intensities of prompt g-rays and decay g-rays have been reported to be with an uncertainty of about 5% and 1%, respectively. It is found that values of 65Cu and 186W have large discrepancies in results of the two methods, by about 30%. The disagreement would be caused by inaccuracy of the absolute intensities of prompt g-rays. The inaccuracy is estimated due to incompleteness of level schemes and detector efficiency of prompt g-rays. We need to examine absolute intensities of prompt g-rays when we use the prompt-g method.





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