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論文

Automatic retuning of superconducting linacs using LightWin

Pla$c{c}$ais, A.*; Bouly, F.*; Froidefond, E.*; Lagniel, J.-M.*; Normand, G.*; Orduz, A. K.*; Yee-Rendon, B.; De Keukeleere, L.*; Van De Walle, J.*

Proceedings of 32nd Linear Accelerator Conference (LINAC 2024) (Internet), p.563 - 568, 2024/10

https://doi.org/10.18429/JACoW-LINAC2024-THXA001

高出力粒子加速器にとって信頼性は重要である。特に加速器駆動システム(ADS)では、ビームの停止が原子炉の稼働率に大きく影響し、停止の多くは、加速空洞やその関連システムの損失に起因する。空洞に起因するビーム停止は、リニアックの他の空洞を再調整することで補償できる。しかし、理想的な補償設定を見つけることは、ビームダイナミクスと多目的最適化を伴う難しい課題であり、対象のリニアックによって大きく異なる問題が生じる。SPIRAL2リニアックでは、多くの空洞が補償のために動員され、探索空間は非常に多くの次元を持ち、ビーム進行方向の許容マージンがかなり低い。MYRRHAやJAEAで検討を進めているADS用リニアックには、最適化を容易にする特定の耐故障設計を適用しているものの、空洞は数秒で再調整する必要がある。そこで我々は、任意のリニアックのすべての空洞障害に対する補償設定を自動的かつ体系的に見つけるツールであるLightWinを開発した。本研究では、LightWinの最新の開発状況と、SPIRAL2とADSリニアック用に開発した補償戦略について、ビームダイナミクスと数学的な観点から紹介する。

論文

Electromagnetic properties of low-lying states in neutron-deficient Hg isotopes; Coulomb excitation of $$^{182}$$Hg, $$^{184}$$Hg, $$^{186}$$Hg and $$^{188}$$Hg

Wrzosek-Lipska, K.*; Rezynkina, K.*; Bree, N.*; Zieli$'n$ska, M.*; Gaffney, L. P.*; Petts, A.*; Andreyev, A. N.; Bastin, B.*; Bender, M.*; Blazhev, A.*; et al.

European Physical Journal A, 55(8), p.130_1 - 130_23, 2019/08

https://doi.org/10.1140/epja/i2019-12815-2
 被引用回数：16 パーセンタイル：79.76(Physics, Nuclear)

The neutron-deficient mercury isotopes serve as a classical example of shape coexistence, whereby at low energy near-degenerate nuclear states characterized by different shapes appear. The electromagnetic structure of even-mass $$^{182-188}$$Hg isotopes was studied using safe-energy Coulomb excitation of neutron-deficient mercury beams delivered by the REX-ISOLDE facility at CERN. The population of 0$$^{+}_{1,2}$$, 2$$^{+}_{1,2}$$, and 4$$^{+}_{1}$$ states was observed in all nuclei under study. Reduced $$E2$$ matrix elements coupling populated yrast and non-yrast states were extracted, including their relative signs. These are a sensitive probe of shape coexistence and may be used to validate nuclear models. The experimental results are discussed in terms of mixing of two different configurations and are compared with three different model calculations: the Beyond Mean Field model, the Interacting Boson Model with configuration mixing and the General Bohr Hamiltonian. Partial agreement with experiment was observed, hinting to missing ingredients in the theoretical descriptions.

論文

Detailed $$alpha$$-decay study of $$^{180}$$Tl

Andel, B.*; Andreyev, A. N.; Antalic, S.*; Barzakh, A.*; Bree, N.*; Cocolios, T. E.*; Comas, V. F.*; Diriken, J.*; Elseviers, J.*; Fedorov, D. V.*; et al.

Physical Review C, 96(5), p.054327_1 - 054327_11, 2017/12

https://doi.org/10.1103/PhysRevC.96.054327
 被引用回数：3 パーセンタイル：25.05(Physics, Nuclear)

A detailed $$alpha$$-decay spectroscopy study of $$^{180}$$Tl has been performed at ISOLDE (CERN). Z-selective ionization by the Resonance Ionization Laser Ion Source (RILIS) coupled to mass separation provided a high-purity beam of $$^{180}$$Tl. Fine-structure $$alpha$$ decays to excited levels in the daughter $$^{176}$$Au were identified and an $$alpha$$-decay scheme of $$^{180}$$Tl was constructed based on an analysis of $$alpha$$-$$gamma$$ and $$alpha$$-$$gamma$$ -$$gamma$$ coincidences. Multipolarities of several $$gamma$$-ray transitions deexciting levels in $$^{176}$$Au were determined. Based on the analysis of reduced $$alpha$$-decay widths, it was found that all $$alpha$$ decays are hindered, which signifies a change of configuration between the parent and all daughter states.

論文

Collectivity in the light radon nuclei measured directly via Coulomb excitation

Gaffney, L. P.*; Robinson, A. P.*; Jenkins, D. G.*; Andreyev, A. N.; Bender, M.*; Blazhev, A.*; Bree, N.*; Bruyneel, B.*; Butler, P.*; Cocolios, T. E.*; et al.

Physical Review C, 91(6), p.064313_1 - 064313_11, 2015/06

https://doi.org/10.1103/PhysRevC.91.064313
 被引用回数：11 パーセンタイル：58.34(Physics, Nuclear)

Radioactive ion beams of $$^{202,204}$$Rn were studied by means of low-energy Coulomb excitation at REX-ISOLDE, CERN. The electric-quadrupole (E2) matrix elements connecting the first excited 2$$^+$$ to the ground state of these nuclei was extracted, which permits to determine the collectivity of these isotopes, which in both cases is deduced to be weak, as expected from the low-lying level-energy scheme. Comparisons were also made with beyond-mean-field model calculations and the magnitude of the transitional quadrupole moments are well reproduced.

論文

Experimental study of the $$^{66}$$Ni($$d$$,$$p$$)$$^{67}$$Ni one-neutron transfer reaction

Diriken, J.*; Patronis, N.*; Andreyev, A. N.; Antalic, S.*; Bildstein, V.*; Blazhev, A.*; Darby, I. G.*; De Witte, H.*; Eberth, J.*; Elseviers, J.*; et al.

Physical Review C, 91(5), p.054321_1 - 054321_15, 2015/05

https://doi.org/10.1103/PhysRevC.91.054321
 被引用回数：10 パーセンタイル：55.51(Physics, Nuclear)

Excited states up to an excitation energy of 5.8 MeV were populated in the neutron-rich isotope $$^{67}$$Ni via the $$^{66}$$Ni(d,p) transfer reaction at REX-Isolde, CERN. In particular, single-neutron states above the N=40 sub-shell gap were populated, and the relative spectroscopic factors were extracted using distorted-wave Born approximation analysis. The positive parity g$$_{9/2}$$, d$$_{5/2}$$ and s$$_{1/2}$$ neutron orbits above the shell closure are assumed to induce strong quadrupole collectivity in neutron-rich Fe and Cr isotopes. The extracted relative spectroscopic factors show that the strength of the d$$_{5/2}$$ orbit is mostly split over two states, hinting to substantial mixing of the neutron d$$_{5/2}$$ configuration with collective modes of the core. The size of the N=50 shell gap was also estimated, and found to be 2.6 MeV near $$^{68}$$Ni, as also determined in lighter Ni isotopes.

論文

Study of the deformation-driving $$nu$$d$$_{5/2}$$ orbital in $$_{28}^{67}$$Ni$$_{39}$$ using one-neutron transfer reactions

Diriken, J.*; Patronis, N.*; Andreyev, A. N.*; Antalic, S.*; Bildstein, V.*; Blazhev, A.*; Darby, I. G.*; De Witte, H.*; Eberth, J.*; Elseviers, J.*; et al.

Physics Letters B, 736, p.533 - 538, 2014/09

https://doi.org/10.1016/j.physletb.2014.08.004
 被引用回数：19 パーセンタイル：74.32(Astronomy & Astrophysics)

The neutron orbits $$g_{9/2}$$, d$$_{5/2}$$ and s$$_{1/2}$$ are assumed to be responsible for the swift onset of collectivity observed in the region below $$^{68}$$Ni. In order to gather information on the single-particle energies and spectroscopic factors of these orbitals, single-particle states in the nucleus $$^{67}$$Ni were populated using the reaction $$^{66}$$Ni(d,p), in inverse kinematics, at REX-ISOLDE, CERN. The new isotope was studied using combined particle-$$gamma$$ spectroscopy. Comparison with DWBA calculations, permitted the identification of positive parity states with a substantial amount of $$nu$$d$$_{9/2}$$ (1007 keV) and $$nu$$d$$_{5/2}$$ (2207 and 3277 keV) single-particle strength. Comparisons with extended Shell-Model calculations was also performed to confirm the single-particle nature of these states, and to deduce general properties around $$^{68}$$Ni.

論文

$$beta$$-delayed fission of $$^{180}$$Tl

Elseviers, J.*; Andreyev, A. N.*; Huyse, M.*; Van Duppen, P.*; Antalic, S.*; Barzakh, A.*; Bree, N.*; Cocolios, T. E.*; Comas, V. F.*; Diriken, J.*; et al.

Physical Review C, 88(4), p.044321_1 - 044321_13, 2013/10

https://doi.org/10.1103/PhysRevC.88.044321
 被引用回数：40 パーセンタイル：88.52(Physics, Nuclear)

The detailed analysis of the $$beta$$-delayed fission data of $$^{180}$$Tl is presented. The experiment was performed by producing a pure beam of $$^{180}$$Tl by means of highly selective resonance laser ionization followed by mass separation with the ISOLDE isotope separator. A surprising asymmetric mass distribution of fission fragments from $$^{180}$$Hg, the daughter of $$^{180}$$Tl $$beta$$ decays, was obtained. Here, the energy calibration of the silicon detectors, which is crucial for a proper determination of the fission fragments' energy and mass split, is presented and the total kinetic energy and its dependence on the mass split ratio is discussed. A more precise $$beta$$-delayed fission probability of 3.2(2)$$times$$10$$^{-3}$$$$%$$ was deduced.

論文

New type of asymmetric fission in proton-rich nuclei

Andreyev, A. N.*; Elseviers, J.*; Huyse, M.*; Van Duppen, P.*; Antalic, S.*; Barzakh, A.*; Bree, N.*; Cocolios, T. E.*; Comas, V. F.*; Diriken, J.*; et al.

Physical Review Letters, 105(25), p.252502_1 - 252502_5, 2010/12

https://doi.org/10.1103/PhysRevLett.105.252502
 被引用回数：204 パーセンタイル：97.25(Physics, Multidisciplinary)

A very exotic process of $$beta$$-delayed fission of $$^{180}$$Tl is studied in detail by using resonant laser ionization with subsequent mass separation at ISOLDE (CERN). In contrast to common expectations, the fission-fragment mass distribution of the post-$$beta$$-decay daughter nucleus $$^{180}$$Hg ($$N$$/$$Z$$ = 1.25) is asymmetric. This asymmetry is more surprising since a mass-symmetric split of this extremely neutron-deficient nucleus would lead to two $$^{90}$$Zr fragments, with magic $$N$$ = 50 and semi-magic $$Z$$ = 40. This is a new type of asymmetric fission, not caused by large shell effects related to fragment magic proton and neutron numbers, as observed in the actinide region. The newly-measured branching ratio for $$beta$$-delayed fission of $$^{180}$$Tl is 3.6(7)$$times$$10$$^{-3}$$ %.

口頭

陽子過剰原子核の核分裂

西尾 勝久; Andreyev, A. N.*; Elseviers, J.*; Huyse, M.*; Van Duppen, P.*; Antalic, S.*; Barzakh, A.*; Bree, N.*; Cocolios, T. E.*; Comas, V. F.*; et al.

no journal, , 

陽子過剰な原子核$$^{180}$$Hgの低励起エネルギー核分裂を測定した。CERN-ISOLDEにおいて$$^{180}$$Tlをアイソトープ分離し、このベータ崩壊によって娘核$$^{180}$$Hgを励起さることで、この核分裂を観測した(ベータ崩壊遅延核分裂)。核分裂特性を調べたところ、中性子数50の閉殻を有する$$^{90}$$Zr原子核は生成されず、質量数80と100に収率の最大を有する非対称な核分裂を示した。また、原子力機構タンデム加速器において、陽子過剰原子核のインビーム核分裂実験を行った。この結果、ウランなど従来の核分裂と異なり、励起エネルギーが増加しても質量非対称度が変化しないことがわかった。

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