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Xiao, Y.*; Go, S.*; Grzywacz, R.*; Orlandi, R.; Andreyev, A. N.; 浅井 雅人; Bentley, M. A.*; de Angelis, G.*; Gross, C. J.*; Hausladen, P.*; et al.
Physical Review C, 100(3), p.034315_1 - 034315_8, 2019/09
被引用回数:17 パーセンタイル:82.71(Physics, Nuclear)A search for super-allowed decay of N=Z nuclei
Te and
Xe was carried out using a novel recoil-decay scintillator detector at the tandem accelerator facility at Japan Atomic Energy Agency. Inorganic crystal scintillation material of YAP:Ce (Yttrium Aluminium Perovskite) coupled to position-sensitive photo-multiplier tube (PSPMT) was implemented for the first time in a radioactive decay experiment. Residues from the fusion-evaporation reaction
Ni+
Fe
Xe
were separated by the JAEA Recoil Mass Separator (RMS) and implanted into the YAP:Ce crystal.
decays of neutron-deficient tellurium isotopes were identified and proton-emission of
I was observed. No conclusive evidence was found for the decay chain
Xe
Te
Sn within 3 days experiment. The cross section limit of 130 pb was obtained for production of two events of
Xe, about an order of magnitude below the expectation based on earlier cross section measurements and HIVAP calculations.
Das, S. K.*; 福田 共和*; 溝井 浩*; 石山 博恒*; 宮武 宇也*; 渡辺 裕*; 平山 賀一*; Jeong, S. C.*; 池添 博*; 松田 誠; et al.
Physical Review C, 95(5), p.055805_1 - 055805_4, 2017/05
被引用回数:3 パーセンタイル:25.71(Physics, Nuclear)The Li(
,n)
B reaction is regarded as the key reaction in the inhomogeneous big bang and in type-II supernova nucleosynthesis. Recently, the importance of this reaction to solving the
Li problem, i.e., the inconsistency between the predicted and the observed primordial
Li abundances, has also been noted. The most recent cross-section data published by our collaboration group in 2006 [H. Ishiyama et al., Phys. Lett. B 640, 82 (2006)] cover the 0.7- to 2.6-MeV energy region in the center-of-mass system. Here, we present additional data spanning the 0.45- to 1.80-MeV energy region. Thus, the predominant energy region for the big bang nucleosynthesis, corresponding to T
= 1 (where T
is a temperature unit equivalent to 109 K), is almost completely spanned by the previous [H. Ishiyama et al., Phys. Lett. B 640, 82 (2006)] and present results together.
西尾 勝久; Andreyev, A. N.*; Chapman, R.*; Derkx, X.*; Dllmann, C. E.*; Ghys, L.*; He
berger, F. P.*; 廣瀬 健太郎; 池添 博*; Khuyagbaatar, J.*; et al.
Physics Letters B, 748, p.89 - 94, 2015/09
被引用回数:53 パーセンタイル:94.43(Astronomy & Astrophysics)Mass distributions of fission fragments from the compound nuclei Hg and
Hg formed in fusion reactions
Ar+
Sm and
Ar+
Sm, respectively, were measured at initial excitation energies of
(
Hg)=,33
66 MeV and
(
Hg)=,48
71 MeV. In the fission of
Hg, the mass spectra were well reproduced by assuming only an asymmetric-mass division, with most probable light and heavy fragment masses
/
79
101. The mass asymmetry for
Hg agrees well with that obtained in the low-energy
/EC-delayed fission of
Tl, from our earlier ISOLDE(CERN) experiment. Fission of
Hg is found to proceed in a similar way, delivering the mass asymmetry of
/
83
107, throughout the measured excitation energy range. The persistence as a function of excitation energy of the mass-asymmetric fission for both proton-rich Hg isotopes gives strong evidence for the survival of microscopic effects up to effective excitation energies of compound nuclei as high as 40,MeV. This behavior is different from fission of actinide nuclei and heavier mercury isotope
Hg.
西尾 勝久; 池添 博; Hofmann, S.*; Ackermann, D.*; 有友 嘉浩*; Comas, V. F.*; Dllmann, Ch. E.*; Heinz, S.*; Heredia, J. A.*; He
berger, F. P.*; et al.
AIP Conference Proceedings 1524, p.68 - 72, 2013/04
被引用回数:0 パーセンタイル:0.00(Physics, Nuclear)Fission fragment mass and kinetic energies distributions were measured in the heavy-ion induced reactions using U target nucleus at the energies around the Coulomb barrier. We observed strong variation of the fragment mass distribution with incident energy, which was explained by an energy dependence of the probabilities for fusion and quasifission. A calculation based on a fluctuation-dissipation model was carried out to determine the fusion probability in the reactions of
Si+
U and
S+
U. The fusion probabilities were consistent with those determied from the evaporation residue cross sections for both reactions, showing that in-beam fission measurement and analysis can give a reasonable estimation for the cross sections to produce super-heavy nuclei. We also discss the results for in-beam fission measurement of
Ca+
U.
Khuyagbaatar, J.*; 西尾 勝久; Hofmann, S.*; Ackermann, D.*; Block, M.*; Heinz, S.*; Heberger, F. P.*; 廣瀬 健太郎; 池添 博; Kindler, B.*; et al.
Physical Review C, 86(6), p.064602_1 - 064602_6, 2012/12
被引用回数:25 パーセンタイル:76.29(Physics, Nuclear)The influence of the structure of projectile and target nuclei on the capture cross-sections was investigated for the reactions S+
Pb and
S+
Pb. Capture cross-sections were deduced by measuring the fission fragments using multi-wire proportional counters. An enhancement of the capture cross-sections relative to an one-dimensional barrier penetration model was observed for all reactions at energies below the interaction barriers. The enhancement is larger in the case of reactions with
S than with
S. This observation is explained by a stronger coupling to the vibrational states in the reactions with
S. Comparing the capture cross-sections and the evaporation-residue cross-sections for the reactions
S+
Pb and
S+
Pb, both yielding the same compound nucleus
Cf, it is shown that the latter reaction has a lower fusion probability.
西尾 勝久; 光岡 真一; 西中 一朗; 牧井 宏之; 若林 泰生*; 池添 博; 廣瀬 健太郎*; 大槻 勤*; 有友 嘉浩*; Hofmann, S.*
Physical Review C, 86(3), p.034608_1 - 034608_6, 2012/09
被引用回数:86 パーセンタイル:95.54(Physics, Nuclear)Fission cross sections and fission fragment mass distributions were measured in the reactions of Ca +
U and
Ca +
U at energies around the Coulomb barrier. Fusion probabilities were calculated based on the fluctuation dissipation model. The measured mass distributions for both reactions showed an asymmetric shape at low incident energies, whereas the distribution changed to a flat shape at higher energies. The variation of the mass distribution is explained by a change of the ratio between fusion and qasifission with nuclear orientation. The calculation reproduced the mass distributions and their energy dependence. The trajectories for fusion-fission were used to determine the fusion probability. Fusion probabilities for both reactions are identical as function of the center-of-mass energy, but they differ when plotted as function of the excitation energy. The calculated evaporation residue cross sections for the reaction
Ca +
U using a statistical model showed that sub-barrier fusion reaction can be applied to form the element 112.
西尾 勝久; 池添 博; Hofmann, S.*; Ackermann, D.*; Antalic, S.*; 有友 嘉浩; Comas, V. F.*; Dllmann, Ch. E.*; Gorshkov, A.*; Graeger, R.*; et al.
EPJ Web of Conferences, 17, p.09005_1 - 09005_4, 2011/10
被引用回数:1 パーセンタイル:47.05(Physics, Nuclear)Fission fragment mass distributions after full momentum transfer of the projectile were measured in the reactions using a U target nucleus bombarded by
Si,
P,
S,
Ar,
Ca projectiles. We observed a strong variation of the distribution as function of bombarding energy. The results were interpreted by the effects of nuclear deformation of the target nucleus on the competition between fusion and quasifission. The symmetric fission includes fusion-fission, wheres as the asymmetric fission represents quasifission. The fusion probabilities were determined with the help of fluctuation-dissipation model. The estimated evaporation residue cross sections (
Sg and
Hs) produced in
Si +
U and
S+
U reproduced the experimental data.
西尾 勝久; Hofmann, S.*; Heberger, F. P.*; Ackermann, D.*; Antalic, S.*; 有友 嘉浩; Comas, V. F.*; D
llmann, Ch. E.*; Gorshkov, A.*; Graeger, R.*; et al.
Physical Review C, 82(2), p.024611_1 - 024611_9, 2010/08
被引用回数:82 パーセンタイル:95.87(Physics, Nuclear)Synthesis of isotopes of the element hassium was studied using the reaction S+
U
Hs*. At a kinetic energy of 163.0 MeV in the center of mass system we observed one
-decay chain starting at the isotope
Hs. The cross-section was 1.8
pb. At 152.0 MeV one decay of the new isotope
Hs was observed. It decays with a half-life of 0.38
s by 9479
16 keV
-particle emission. Spontaneous fission of the daughter nucleus
Sg was confirmed. The measured cross-section was 0.54
pb. In-beam measurements of fission fragment mass distributions were performed to obtain information on the fusion probability at various orientation of the deformed target nucleus. The distributions changed from symmetry to asymmetry when the beam energy was changed from above-barrier to sub-barrier values, indicating orientation effects on fusion and/or quasifission. It was found that the distribution of symmetric mass fragments originates not only from fusion-fission, but has a strong component from quasifission. This result significantly influences the interpretation of data obtained from measurements of symmetric mass distributions with respect to extracting evaporation residue cross-sections.
光岡 真一; 池添 博; 西尾 勝久; 渡辺 裕*; Jeong, S. C.*; 石山 博恒*; 平山 賀一*; 今井 伸明*; 宮武 宇也
International Journal of Modern Physics E, 19(5&6), p.989 - 996, 2010/07
被引用回数:0 パーセンタイル:0.00(Physics, Nuclear)原子力科学研究所タンデムブースター加速器からの重イオンビームTi,
Cr,
Fe,
Ni,
Znを薄膜標的
Pbに照射し、172
, 168
, 162
に後方散乱される準弾性散乱断面積を測定した。入射エネルギーを1.5MeVごとに変えながら測定した励起関数を1階微分することにより、超重元素104-112番元素を合成する冷たい融合反応における融合障壁分布を実験的に導出した。これにより測定された融合障壁は、従来用いられてきた理論値より5-10MeV程度低いことがわかった。また障壁分布の形状は、接近時の励起効果を考慮したチャンネル結合計算結果と良い一致を示すことがわかった。最近、さらに重い反応系
Ge,
Kr+
Pbについても実験を行い、同様の結果が得られた。
西尾 勝久; 池添 博; 光岡 真一; 西中 一朗; 牧井 宏之; 渡辺 裕*; 永目 諭一郎; 大槻 勤*; 廣瀬 健太郎*; Hofmann, S.*
AIP Conference Proceedings 1224, p.301 - 310, 2010/04
被引用回数:5 パーセンタイル:84.30(Physics, Nuclear)Results on the measurements of (1) evaporation residue (ER) cross-sections for Si,
S +
U and of (2) fission fragment mass distributions for
Si,
S,
Ar +
U will be discussed. Measurement of ER cross-section was carried out at GSI by using the velocity filter SHIP. Measurement of fission fragment mass distributions was made by using the JAEA tandem accelerator. In the reaction
Si +
U, the ER cross-section for
Sg(5n) suggested no fusion hindance at above-barrier energy, whereas the one for
Sg(4n) suggested competition between fusion and quasi-fission at sub-barrier energy. This conclusion is consistent with the measured fragment mass distributions, where the asymmetric fission component associated with quasi-fission appears only at sub-barrier energies. In the reaction of
S +
U, the ER cross-sections for
Hs(5n) and
Hs(4n, new isotope) suggested fusion hindrance both for above- and sub-barrier energies. With the results of fission fragment mass distributions, it is found that quasi-fission has symmetric fission components when projectile mass is relatively large. We will also discuss the variation of the fragment mass distributions for
Si,
S,
Ar +
U.
西尾 勝久; 池添 博; 光岡 真一; 西中 一朗; 永目 諭一郎; 大槻 勤*; 廣瀬 健太郎*; Hofmann, S.*
EPJ Web of Conferences, 2, p.10001_1 - 10001_3, 2010/03
被引用回数:0 パーセンタイル:0.00(Physics, Nuclear)We have measured the (1) evaporation residue (ER) cross-sections for Si,
S +
U and (2) fission fragment mass distributions for
Si,
S,
Ar. Measurement of ER cross-section was carried out at GSI by using the velocity filter SHIP. Measurement of fission fragment mass distribution was made by using the JAEA tandem accelerator. In the reaction
Si +
U, the ER cross-section for
Sg(5n) suggested no fusion hindrance at above-barrier energy, whereas the one for
Sg(4n) suggested competition between fusion and fission at sub-barrier energy. This conclusion is consistent with the measured fragment mass distributions, where the asymmetric fission component associated with quasi-fission appears only at sub-barrier energies. In the reaction of
S +
U, the ER cross-sections for
Hs(5n) and
Hs(4n, new isotope) suggested fusion hindrance both for above- and sub-barrier energies. With the results of fission fragment mass distributions, it is found that quasi-fission has symmetric fission components when projectile mass is relatively large. We will also discuss the variation of the fragment mass distributions for
Si,
S,
Ar +
U.
池添 博; 光岡 真一; 西尾 勝久; 渡辺 裕*; Jeong, S. C.*; 大槻 勤*; 廣瀬 健太郎*
Nuclear Physics A, 834(1-4), p.172c - 175c, 2010/03
被引用回数:1 パーセンタイル:13.57(Physics, Nuclear)重い原子核間のクーロン障壁は衝突時に核の励起効果や核子の移行過程が結合して、幅を持って分布する。クーロン障壁分布をPb標的に
Ti,
Cr,
Fe,
Ni,
Zn,
Ge,
Krを衝突させる反応系で実験的に導出した。その結果、障壁の中心値は簡単なクーロンパラメータでよくスケールされること、分布の幅は
Pbの8重極振動モードの結合と核子移行反応の結合で説明できること、さらに、導出した障壁は原子核同士の融合障壁とは異なること、がわかった。また、変形核に球形核が衝突する場合、変形核の長軸側での衝突は原子核同士の融合に向かわず、質量の非対象な準核分裂過程に向かうことを、ウラン標的に
Si,
S,
Arを衝突させる反応実験で明らかにした。
西尾 勝久; 池添 博; 西中 一朗; 光岡 真一; 廣瀬 健太郎*; 大槻 勤*; 渡辺 裕*; 有友 嘉浩*; Hofmann, S.*
Physical Review C, 82(4), p.044604_1 - 044604_5, 2010/00
被引用回数:50 パーセンタイル:91.06(Physics, Nuclear)Fragment mass distributions for fission after full momentum transfer were measured for the reaction Si,+,
U at bombarding energies around the Coulomb barrier. At energies above the Bass barrier, the mass distributions were Gaussian with mass symmetry. An asymmetric fission channel with mass
,
,90
178 emerged at the sub-barrier energies, where competition between fusion and quasifission was suggested from the measured evaporation residue (ER) cross-section produced in fusion
Si,+,
U. We thus conclude the asymmetric channel is attributed to quasifission. The observed mass asymmetry is significantly smaller than those observed in actinide targets bombarded with heavier projectile, which suggests that the system
Si,+,
U approaches the shape of compound nucleus before disintegrating as quasifission.
西尾 勝久; 池添 博; 光岡 真一; 西中 一朗; 牧井 宏之; 渡辺 裕*; 永目 諭一郎; 大槻 勤*; 廣瀬 健太郎*; Hofmann, S.*
AIP Conference Proceedings 1175, p.111 - 118, 2009/10
The influence of nuclear deformation of U target nucleus on fusion and fission process was investigated. The study was motivated by larger cross-sections to produce super-heavy nuclei in reactions using actinide target nuclei, compared to those using lead or bismuth target nuclei. We have measured fission fragment mass distributions in the reaction of
Si,
P,
S,
Ar +
U at JAEA tandem facility. We observed strong variation of the distributions on bombarding energy of projectiles, which indicates that competition between fusion and fission is sensitive to the colliding angle of the projectile to the symmetric axis of
U. We also measured the evaporation residue cross-sections for
Si+
U and
S+
U as a direct evidence for fusion. The experiment was carried out at GSI. The results showed that fusion is much hindered in the subbarrier energy, where projectile collides only on the pollar side of the
U nucleus, whereas the equatorial collision has smaller fusion hindrance. These results indicate that the initial touching configuration influence the subsequent reaction process.
西尾 勝久; 池添 博; 光岡 真一; 西中 一朗; 牧井 宏之; 渡辺 裕*; 永目 諭一郎; 大槻 勤*; 廣瀬 健太郎*; Hofmann, S.*
AIP Conference Proceedings 1175, p.111 - 118, 2009/10
Fission fragment properties for the reactions involving actinide target nuclei have been investigated at the JAEA tandem facility. The results showed firstly the appearance of new fission channels. The experimental data are useful for the theoretical study to produce super heavy elements. Also the new fission channels suggested the possible production of the neutron rich nuclei by taking advantage of the new fission channels.
池添 博
JAEA-Review 2009-026, 55 Pages, 2009/09
平成20年度に実施された8件の黎明研究の成果をまとめた報告書である。原子力に関する基礎・基盤研究の発展の一助とするため、本報告書により得られた成果を公表する。
西尾 勝久; 池添 博; 光岡 真一; 西中 一朗; 渡辺 裕*; 永目 諭一郎; 大槻 勤*; 廣瀬 健太郎*; Hofmann, S.*
AIP Conference Proceedings 1120 (Internet), p.275 - 279, 2009/05
Effects of nuclear deformation of U on fusion and fission was investigated in the reactions of
Si+
U and
S +
U. From the measurement of evaporation residue cross-sections for
Si+
U, carried out at GSI, it is concluded that in the sub-barrier region competition between fusion and quasi-fission was suggested whereas at the above barrier region fusion is the main process after the system is captured inside the Coulomb barrier. The fission fragment mass distributions were measured in
Si+
U and
S+
U at the JAEA tandem facility. Symmetric fission was observed at the above-barrier region, showing the fusion-fission character. In decreasing the energy to the sub-barrier, the asymmetric fission starts to dominate, showing the signature of quasi-fission. The results suggest that the equatorial collision results in fusion whereas the polar collision results in quasi-fission.
橋本 尚志; 石山 博恒*; 渡辺 裕*; 平山 賀一*; 今井 伸明*; 宮武 宇也; Jeong, S.-C.*; 田中 雅彦*; 吉川 宣治*; 野村 亨*; et al.
Physics Letters B, 674(4-5), p.276 - 280, 2009/04
被引用回数:7 パーセンタイル:46.60(Astronomy & Astrophysics)Li(d,t)
Li反応の反応断面積を重心系で1.2から0.3MeVのエネルギーで7点直接測定した。これらのエネルギーは1
3
10
Kのガモフピーク領域をカバーする。重心系で0.8MeVのエネルギーで断面積の増大が観測され、これは複合核である
Beの22.4MeVの励起状態の寄与によると考えられる。また、この寄与によって天体核反応率は1
10
Kで従来用いられていた値よりも1桁大きいことが明らかとなった。
西尾 勝久; 池添 博; 光岡 真一; 西中 一朗; 渡辺 裕*; 永目 諭一郎; 大槻 勤*; 廣瀬 健太郎*; Hofmann, S.*
AIP Conference Proceedings 1098, p.289 - 294, 2009/03
Fragment mass distributions for fission after full momentum transfer were measured for the reaction S,+,
U at bombarding energies around the Coulomb barrier. The experiment was carried out by using the sulfur beams supplied by the JAEA tandem accelerator. The experimental data revealed a transition from symmetry to asymmetry mass distributions when the beam energies were decreased from above-barrier to sub-barrier values. The main components of the asymmetric mass distribution are at
=200 and
74. The asymmetric fission is attributed to quasifission of the reacting system at polar collisions, whereas the symmetric fission originates from the compound nucleus produced in equatorial collisions. The results suggest a strong influence of orientation effects of the deformed target nuclei on fusion.
池添 博
JAEA-Review 2008-066, 55 Pages, 2009/02
平成19年度に実施された9件の黎明研究の成果をまとめた報告書である。原子力に関する基礎・基盤研究の発展の一助とするため、本報告書により得られた成果を公表する。