Velocity distribution of ion beams from the RIKEN Ion-Guide Isotope Separator On-Line

理研イオンガイド型オンライン同位体分離器からのイオンビームの速度分布

Koizumi Mitsuo

The nuclei close to the N = 104 show an interesting feature. Extremely large shape staggering in the isotope and isomer shifts was observed for Hg and Tl isotopes, and shape coexistence at low excitation energy was observed for Hg, Au, and Pt isotopes. It should also be noted that many high-spin isomers exist in the nuclei of this region, such as Hf, W and Os. For many elements in this region, however, laser spectroscopy has not been reported, because these elements are refractory ones. At RIKEN, we have constructed an ISOL system GARIS/IGISOL which is powerful to extract radioactive isotopes of refractory elements. Taking full advantages of this feature, we aim at performing collinear laser spectroscopy to study exotic nuclei of these elements. To make on-line collinear laser spectroscopy, the radioactive beams from the GARIS/IGISOL is required to have adequate quality (velocity spread) and quantity. Therefore, direct measurement of the velocity spread of Ar1+ ion beams from the IGISOL was carried out with a technique of laser spectroscopy. The skimmer-potential and the gas-cell pressure dependences of the velocity spread were systematically investigated. A new focusing device SQUEEZER was introduced to reduce the velocity spread, and the effect of this was experimentally examined. From these measurements, it was pointed. out that the ion beam from the GARIS/IGISOL has adequate quality for making collinear laser spectroscopy. An estimation of the yield of radioactive isotopes from the GARIS/IGISOL was also made for a fusion reaction 9Be(166Er, xn)175-xHf . The estimated yield was expected to be more than 104 particles/s. The yield of the radioactive isotope is adequate to make collinear laser spectroscopy with a coincidence method. We have for the first time in the world extracted the radioactive isotope of refractory element 169Hf with the GARIS/IGISOL. We conclude, thus, that the collinear laser spectroscopy of refractory elements with the GARIS/IGISOL is promising.

Astronomy. Space sciences [ 440 ]

eng

Copyright(c) by Author

1) Velocity distribution of ion beams from the RIKEN IGISOL(理研IGISOLからのイオンビームの速度分布) M. Koizumi, Y. Yoshida, K. Morita, M. Takami, T.T. Inamura, M. Azuma, H. Katsuragawa, M. Nakaoka, I. Nakamura, T. Ishizuka, T. murayama, A. Iivonen, K. Valli, K. Shimomura, S. Matsuki, and I. Sugai, to be published in Nucl. Instr. and Meth. (Dec. 1991). references

2) Collinear fast atomic-beam laser spectroscopy at RIKEN GARIS/IGISOL (理研GARIS/IGISOLにおける共線高速原子線レーザー分光) M. Koizurni, M. Azuma, T. Horiguchi, T.T. Inamura, T. Ishizuka, A. Iivonen, H. Katsuragawa, S. Matsuki, K. Morita, T. Murayama, I. Nakamura, M. Nakaoka, K. Shimomura, T. Shinozuka, I. Sugai, Y. Tagishi, M. Takami, K. Valli, M. Wakasugi, and A. Yoshida, presented at the Int. symposium on lasers in nuclear physics (Wako, 1991), and to be published in Hyp. Int. references

[DOI] http://dx.doi.org/10.1016/0168-9002(92)90079-J references

[DOI] http://dx.doi.org/10.1007/BF02398628 references

広島大学