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論文

Competition between allowed and first-forbidden $$beta$$ decays of $$^{208}$$At and expansion of the $$^{208}$$Po level scheme

Brunet, M.*; Podoly$'a$k, Zs.*; Berry, T. A.*; Brown, B. A.*; Carroll, R. J.*; Lica, R.*; Sotty, Ch.*; Andreyev, A. N.; Borge, M. J. G.*; Cubiss, J. G.*; et al.

Physical Review C, 103(5), p.054327_1 - 054327_13, 2021/05

https://doi.org/10.1103/PhysRevC.103.054327
 被引用回数：4 パーセンタイル：57.13(Physics, Nuclear)

The structure of $$^{208}$$Po populated through the EC/$$beta^{+}$$ decay of $$^{208}$$At is investigated using $$gamma$$-ray spectroscopy at the ISOLDE Decay Station. The presented level scheme contains 27 new excited states and 43 new transitions, as well as a further 50 previously observed $$gamma$$ rays which have been (re)assigned a position. Through the analysis using the shell model calculations approximately half of the $$beta$$-decay strength of $$^{208}$$At is found to proceed via allowed decay and half via first-forbidden decay. The first-forbidden transitions predominantly populate core excited states at high excitation energies, which is qualitatively understood using shell model considerations.

論文

Population of a low-spin positive-parity band from high-spin intruder states in $$^{177}$$Au; The Two-state mixing effect

Venhart, M.*; Balogh, M.*; Herz$'a$$v{n}$, A.*; Wood, J. L.*; Ali, F. A.*; Joss, D. T.*; Andreyev, A. N.; Auranen, K.*; Carroll, R. J.*; Drummond, M. C.*; et al.

Physics Letters B, 806, p.135488_1 - 135488_6, 2020/07

https://doi.org/10.1016/j.physletb.2020.135488
 被引用回数：6 パーセンタイル：59.56(Astronomy & Astrophysics)

The extremely neutron-deficient isotopes $$^{177,179}$$Au were studied by means of in-beam $$gamma$$-ray spectroscopy. Specific tagging techniques, $$alpha$$-decay tagging in $$^{177}$$Au and isomer tagging in $$^{179}$$Au, were used for these studies. Feeding of positive-parity, nearly spherical states, which are associated with 2$$d_{3/2}$$ and 3$$s_{1/2}$$ proton-hole configurations, from the 1$$i_{13/2}$$ proton-intruder configuration was observed in $$^{177}$$Au. Such a decay path has no precedent in odd-Au isotopes and it is explained by the effect of mixing of wave functions of the initial state.

論文

Investigation of the $$Delta$$$$n$$ = 0 selection rule in Gamow-Teller transitions; The $$beta$$-decay of $$^{207}$$Hg

Berry, T. A.*; Podoly$'a$k, Zs.*; Carroll, R. J.*; Lic$u{a}$, R.*; Grawe, H.*; Timofeyuk, N. K.*; Alexander, T.*; Andreyev, A. N.; Ansari, S.*; Borge, M. J. G.*; et al.

Physics Letters B, 793, p.271 - 275, 2019/06

https://doi.org/10.1016/j.physletb.2019.04.039
 被引用回数：5 パーセンタイル：47.88(Astronomy & Astrophysics)

Gamow-Teller $$beta$$ decay is forbidden if the number of nodes in the radial wave functions of the initial and final states is different. This $$Delta$$$$n$$ = 0 requirement plays a major role in the $$beta$$ decay of heavy neutron-rich nuclei, affecting the nucleosynthesis through the increased half-lives of nuclei on the astrophysical $$r$$-process pathway below both $$Z$$ = 50 (for $$N >$$ 82) and $$Z$$ = 82 (for $$N >$$ 126). The level of forbiddenness of the $$Delta$$$$n$$ = 1 $$nu$$1$$g_{9/2} rightarrow pi$$0$$g_{7/2}$$ transition has been investigated from the $$beta^{-}$$ decay of the ground state of $$^{207}$$Hg into the single-proton-hole nucleus $$^{207}$$Tl in an experiment at the ISOLDE Decay Station. From statistical observational limits on possible $$gamma$$-ray transitions depopulating the $$pi$$0$$g^{-1}_{7/2}$$ state in $$^{207}$$Tl, an upper limit of 3.9$$times$$10$$^{-3}$$ % was obtained for the probability of this decay, corresponding to log$$ft >$$ 8.8 within a 95% confidence limit. This is the most stringent test of the $$Delta$$$$n$$ = 0 selection rule to date.

論文

EXILL; A High-efficiency, high-resolution setup for $$gamma$$-spectroscopy at an intense cold neutron beam facility

Jentschel, M.*; Blanc, A.*; de France, G.*; K$"o$ster, U.*; Leoni, S.*; Mutti, P.*; Simpson, G.*; Soldner, T.*; Ur, C.*; Urban, W.*; et al.

Journal of Instrumentation (Internet), 12(11), p.P11003_1 - P11003_33, 2017/11

https://doi.org/10.1088/1748-0221/12/11/P11003
 被引用回数：38 パーセンタイル：84.92(Instruments & Instrumentation)

A highly efficient array of high-purity germanium (HPGe) detectors was developed and operated at the cold neutron beam facility PF1B of the Institut Laue-Langevin (ILL) to carry out nuclear structure studies, via measurements of $$gamma$$-rays following neutron-induced capture and fission reactions. The setup consisted of a collimation system producing a pencil beam with a thermal capture equivalent flux of about 10$$^8$$ns$$^{-1}$$cm$$^{-2}$$ at the target position and negligible neutron halo. The target was surrounded by an array of eight to ten anti-Compton shielded EXOGAM Clover detectors, four to six anti-Compton shielded large coaxial GASP detectors and two standard Clover detectors. For a part of the campaign the array was combined with 16 LaBr$$_{3}$$:(Ce) detectors from the FATIMA collaboration.

論文

Shell evolution beyond $$Z$$=28 and $$N$$=50; Spectroscopy of $$^{81,82,83,84}$$Zn

Shand, C. M.*; Podoly$'a$k, Zs.*; G$'o$rska, M.*; Doornenbal, P.*; Obertelli, A.*; Nowacki, F.*; Otsuka, T.*; Sieja, K.*; Tostevin, J. A.*; Tsunoda, T.*; et al.

Physics Letters B, 773, p.492 - 497, 2017/10

https://doi.org/10.1016/j.physletb.2017.09.001
 被引用回数：25 パーセンタイル：87.36(Astronomy & Astrophysics)

Low-lying states in neutron-rich $$^{81,82.83.84}$$Zn nuclei were measured for the first time via in-beam $$gamma$$-ray spectroscopy at RIKEN. These include the 4$$_1^+$$ to 2$$_1^+$$ in $$^{82}$$Zn and the 2$$_1^+$$ to 0$$_1^+$$ and 4$$_1^+$$ to 2$$_1^+$$ in $$^{84}$$Zn. The reduced E($$2^+$$) energies and increased E(4$$^+$$)/E(2$$^+$$) ratios at $$N$$=52,54 compared to $$^{80}$$Zn attest that the magicity is confined just on the neutron number $$N$$=50 only. The levels observed in $$^{84}$$Zn suggest the onset of deformation towards heavier Zn isotopes. The data were compared to state-of-the-art shell model calculations.

論文

Shape evolution in neutron-rich krypton isotopes beyond N=60; First spectroscopy of $$^{98,100}$$Kr

Flavigny, F.*; Doornenbal, P.*; Obertelli, A.*; Delaroche, J.-P.*; Girod, M.*; Libert, J.*; Rodriguez, T. R.*; Authelet, G.*; 馬場 秀忠*; Calvet, D.*; et al.

Physical Review Letters, 118(24), p.242501_1 - 242501_6, 2017/06

https://doi.org/10.1103/PhysRevLett.118.242501
 被引用回数：38 パーセンタイル：86.73(Physics, Multidisciplinary)

The first $$gamma$$-ray spectroscopy of very neutron rich $$^{98,100}$$Kr isotopes was carried out at the RIBF at RIKEN Nishina center. Excited states in these isotopes were populated via (p,2p) reactions using radioactive $$^{99,101}$$Rb beams accelerated to 220 MeV/nucleon. The new data show a significant increase in deformation beyond N=60, as well as competing configurations (shape-coexistence) at low energy. The data were compared with beyond-mean-field calculations which predict level energies in good agreement with observation, and suggest oblate-prolate shape coexistence.

論文

Low-lying structure and shape evolution in neutron-rich Se isotopes

Chen, S.*; Doornenbal, P.*; Obertelli, A.*; Rodriguez, T. R.*; Authelet, G.*; 馬場 秀忠*; Calvet, D.*; Ch$^a$teau, F.*; Corsi, A.*; Delbart, A.*; et al.

Physical Review C, 95(4), p.041302_1 - 041302_6, 2017/04

https://doi.org/10.1103/PhysRevC.95.041302
 被引用回数：26 パーセンタイル：88.02(Physics, Nuclear)

Neutron-rich isotopes of selenium, $$^{88,90,92,94}$$Se, where studied via in beam $$gamma$$-ray spectroscopy after nucleon removal reactions at RIBF in RIKEN. The low-energy excitations of these nuclei were investigated using $$gamma$$-$$gamma$$ coincidences, and the first and second excited 2$$^+$$ states were found at remarkably low energies. The analysis and comparison with self-consistent beyond-mean field calculations suggest that both shape coexistence and triaxiality are needed to describe these isotopes.

論文

Are there signatures of harmonic oscillator shells far from stability?; First spectroscopy of $$^{110}$$Zr

Paul, N.*; Corsi, A.*; Obertelli, A.*; Doornenbal, P.*; Authelet, G.*; 馬場 秀忠*; Bally, B.*; Bender, M.*; Calvet, D.*; Ch$^a$teau, F.*; et al.

Physical Review Letters, 118(3), p.032501_1 - 032501_7, 2017/01

https://doi.org/10.1103/PhysRevLett.118.032501
 被引用回数：43 パーセンタイル：88.64(Physics, Multidisciplinary)

The first measurement of $$gamma$$ rays emitted by the very neutron rich nuclei $$^{112}$$Mo (Z=42) and $$^{110}$$Zr (Z=40) was carried out at the RIBF facility at RIKEN. These data shine light on the postulated N=70 harmonic oscillator shell. If the spin-orbit splitting which gives rise to the N=82 shell gap is reduced in very neutron-rich nuclei, the harmonic oscillator gap at N=70 should open instead. However, both the measured energy of the first excited state $$^{112}$$Mo and $$^{110}$$Zr, respectively 235(7) keV and 185(11) keV, and their E(4$$^+$$)/E(2$$^+$$) ratio, indicate that these nuclei are good rotors, and exclude the shell stabilization scenario at Z=40 and N=70. These results were compared to state-of-the-art density functional theoretical calculations using Gogny and Skyrme effective interactions.

論文

$$B(E2;2^+_1rightarrow 0^+_1)$$ value in $$^{90}$$Kr

R$'e$gis, J.-M.*; Jolie, J.*; Saed-Samii, N.*; Warr, N.*; Pfeiffer, M.*; Blanc, A.*; Jentschel, M.*; K$"o$ster, U.*; Mutti, P.*; Soldner, T.*; et al.

Physical Review C, 90(6), p.067301_1 - 067301_4, 2014/12

https://doi.org/10.1103/PhysRevC.90.067301
 被引用回数：23 パーセンタイル：80.23(Physics, Nuclear)

A smooth onset of collectivity in $$^{88,92,94,96}$$Kr has been determined from reported $$B(E2;2^+_1rightarrow 0^+_1)$$ and E(2$$^+_1$$) values. This is in contrast to the sudden onset in even-even Zr, Mo, and Sr isotopes. Our objective was to complete the systematics by determining the $$B(E2;2^+_1rightarrow 0^+_1)$$ value in $$^{90}$$Kr, which was produced by cold-neutron-induced fission of $$^{235}$$U. The lifetime of the 2$$^+_1$$ state in $$^{90}$$Kr was measured via the electronic $$gamma - gamma$$ timing technique using the EXILL and FATIMA spectrometers. Based on the measured mean lifetime of $$tau$$ = 15(10) ps, the $$B(E2;2^+_1rightarrow 0^+_1)$$ value of 13$$^{+26}_{-5}$$ W.u. in $$^{90}$$Kr is determined for the first time and the smooth onset of deformation in the even-even Kr isotopes beyond neutron number N=50 is confirmed.

論文

Instrumentation for diagnostics and control of laser-accelerated proton (ion) beams

Bolton, P.; Borghesi, M.*; Brenner, C.*; Carroll, D. C.*; De Martinis, C.*; Fiorini, F.*; Flacco, A.*; Floquet, V.*; Fuchs, J.*; Gallegos, P.*; et al.

Physica Medica; European Journal of Medical Physics, 30(3), p.255 - 270, 2014/05

https://doi.org/10.1016/j.ejmp.2013.09.002
 被引用回数：77 パーセンタイル：88.84(Radiology, Nuclear Medicine & Medical Imaging)

Suitable instrumentation for laser-accelerated proton (ion) beams is critical to the development of integrated, laser-driven ion accelerator systems. Instrumentation aimed at beam diagnostics and control must be applied to the driving laser pulse, the laser-plasma that it forms at the target and the emergent proton (ion) bunch in a correlated way to develop these novel accelerators. This report is a brief overview of established diagnostic techniques and new developments based on material presented at the first workshop on "Instrumentation for Diagnostics and Control of Laser-accelerated Proton (ion) Beams" in Abingdon, UK. It includes radiochromic film (RCF), image plate (IP), the micro-channel plate (MCP), the Thomson spectrometer, prompt inline scintillation, time and space-resolved interferometry (TASRI) and nuclear activation schemes. Repetition-rated instrumentation requirements for target metrology are also addressed.

口頭

Recommendations for measurement systems for nuclear material accountancy of Fukushima Daiichi fuel debris; $$gamma$$ technologies

富川 裕文; Heinberg, C.; 名内 泰志*; Vo, D.*; Carroll, C.*; 堀 啓一郎

no journal, , 

福島第一原子力発電所の燃料デブリ中の核物質量を測定する技術については原子力機構と米国エネルギー省が協力して検討を進めてきた。日米のメンバーで構成する$$gamma$$線測定技術のついて検討するワーキンググループ設置され、このグループにおいて測定器のコストや大きさ、測定時間、開発期間などの燃料デブリへの適用性を検討した。この結果に基づく測定システムの提案を行う。

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