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Journal Articles

First $$alpha$$-$$gamma$$ spectroscopy using Si-Ge detector array installed at focal plane of GARIS

Kaji, Daiya*; Morimoto, Koji*; Wakabayashi, Yasuo*; Takeyama, Mirei*; Asai, Masato

JPS Conference Proceedings (Internet), 6, p.030106_1 - 030106_4, 2015/06

A Si-Ge detector array was newly installed at the focal plane of the gas-filled recoil ion separator GARIS to perform $$alpha$$-$$gamma$$ (X-rays) spectroscopy for superheavy nuclei. The performance of the array was tested using the $$^{207}$$Pb($$^{48}$$Ca,2n)$$^{253}$$No and $$^{208}$$Pb($$^{48}$$Ca,xn)$$^{256-x}$$No [x=1,2,3] reactions. $$gamma$$ rays originating from the $$alpha$$ decay of $$^{253}$$No and $$^{255}$$No were clearly observed in prompt coincidence with the $$alpha$$ particles.

Journal Articles

Performance of new gas-filled recoil ion separator GARIS-II for asymmetric fusion reaction

Kaji, Daiya*; Morimoto, Koji*; Wakabayashi, Yasuo*; Takeyama, Mirei*; Yamaki, Sayaka*; Tanaka, Kengo*; Haba, Hiromitsu*; Huang, M.*; Murakami, Masashi*; Kanaya, Jumpei*; et al.

JPS Conference Proceedings (Internet), 6, p.030107_1 - 030107_4, 2015/06

Performance of the new gas-filled recoil ion separator GARIS-II was investigated using asymmetric $$^{22}$$Ne-induced fusion reactions. The use of He-H$$_{2}$$ mixture gas for the gas-filled magnet significantly reduced background scattered particles detected at the focal-plane Si detector, and increased a transmission of the asymmetric reaction products. A target-identification system was newly installed for efficient measurements of excitation functions without changing beam energy nor target.

Journal Articles

Decay modes of heavy and superheavy nuclei

Koura, Hiroyuki

RIKEN Accelerator Progress Report, Vol.38, P. 9, 2005/05

We calculate proton-emission partial half lives and discuss dominant decay modes in the heavy and superheavy nuclidic region. The proton-emission partial half-lives are calculated from the one-dimensional WKB method with single-proton potentials and a mass formula that our group has developed. The calculated half lives well reproduce experimental ones in order of 100 or 1/100 which is similar predictability to other predictions as the alpha decay and the beta decay. We apply this result to calculation of branching ratios of nuclear decays considered the alpha decay, beta decay and spontaneous fission in the heavy and superheavy nuclide region. In this analysis we point out that proton-emitting nuclei are expected to be in the unknown proton-rich nuclidic region with $$N = 126$$. On the other hand, proton-rich nuclei with $$130 < N <160$$ have much shorter spontaneous-fission half-lives than ones of proton emissions on this calculation, therefore we conclude that ground-state proton emissions would not occur in that region.

Oral presentation

Fine-structure $$alpha$$-decay spectroscopy of superheavy nuclei

Asai, Masato

no journal, , 

To investigate nuclear structure of superheavy nuclei experimentally, spectroscopic methods which can reveal level structure of ground- and excited states are the most effective. In particular, fine-structure $$alpha$$-decay spectroscopy is expected to be a very sensitive method because spectroscopic information can be obtained only through $$alpha$$-particle measurements. However, it is difficult to measure $$alpha$$ particles of superheavy nuclei with high energy resolution. Moreover, the observed $$alpha$$ energy spectra are significantly distorted by coincidence summing effects. I would like to demonstrate how we can overcome these difficulties, and how useful the fine-structure $$alpha$$-decay spectroscopy is to investigate nuclear structure of superheavy nuclei.

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