Monday, 5 September 2005

This presentation is part of: Poster Session I

Measurements of cross sections for the 7Be and 10Be production by 400-MeV alpha particles

Hiroshi Matsumura1, Toshiya Sanami1, Kazuyoshi Masumoto1, Takahiro Aze2, Kotaro Bessho1, Hisao Nagai3, Hiroyuki Matsuzaki4, Masashi Takada5, and Takeshi Murakami6. (1) Radiation Science Center, High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba, Japan, (2) Department of Earth and Planetary Sciences, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, Japan, (3) Department of Chemistry, College of Humanities and Sciences, Nihon University, 3-25-40 Sakura-Josui, Setagaya-ku, Tokyo, Japan, (4) Department of Nuclear Engineering and Management, The University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, Tokyo, Japan, (5) Research Center for Radiation Safety, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba, Japan, (6) Department of Accelerator Physics and Engineering, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba, Japan

In high and intermediate energy nuclear-reactions, it has become apparent that nuclear fragmentation, the formation of light fragments such as 7Be and 24Na from medium- to heavy-mass targets, is always observed [1]. As the reaction mechanism of the fragmentation is still not clear [1, 2], present calculation codes cannot satisfactorily reproduce the experimental data. In order to evaluate the reaction mechanisms and the calculation codes of fragmentation, we need various experimental results, such as cross sections for the fragment production and energy spectra and angular distributions of the fragments. The cross sections for the fragment production, which are the most basic experimental data, are still lacking at the intermediate energy region. Therefore, we have been measuring the yields of the fragmentation products systematically in various nuclear reactions at intermediate energies using radiochemical techniques. In previous work [3-5], we measured the yields of several light products (7Be, 10Be, 22Na, 24Na, and 28Mg) of bremsstrahlung-induced reactions from 23 targets at the maximum end-point energies (E0) of 200 to 1200 MeV. Furthermore, we measured the 7Be yields from natC, 27Al, natCu, natAg, and 197Au targets and the 10Be yields from natCu, natAg, and 197Au targets in alpha- (400 MeV) and neutron- (E0 = 500 MeV) induced reactions [6]. We found that the neutron-to-proton ratios of the targets strongly affect the formation of nuclei by fragmentation, as revealed by the yields of the isotopic pairs. Furthermore, we suggested that the incident particle also affects the neutron-to-proton ratios of the beryllium fragments. In this study, we obtained new cross sections for the 7Be and 10Be production from other targets by 400-MeV alpha particles. We are going to report the results and have more detail discussion of the fragmentation peculiarity. These measurements are also expected to provide database for various practical uses of cosmochemistry, environmental science, etc.

[1] W. G. Lynch, Annu. Rev. Nucl. Part. Sci. 37, 493 (1987). [2] J. Hüfner, Phys. Rep. 125, 129 (1985). [3] S. Shibata et al., Radiochim. Acta 80, 181 (1998). [4] H. Matsumura et al., Radiochim. Acta, 88, 313 (2000). [5] H. Matsumura et al., Nucl. Instr. Meth. B, 223-224, 807 (2004). [6] H. Matsumura et al., Radiochim. Acta, to be published.


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