20 research outputs found
Performance of the AGATA γ-ray spectrometer in the PreSPEC set-up at GSI
No full textInternational audienceIn contemporary nuclear physics, the European Advanced GAmma Tracking Array (AGATA) represents a crucial detection system for cutting-edge nuclear structure studies. AGATA consists of highly segmented high-purity germanium crystals and uses the pulse-shape analysis technique to determine both the position and the energy of the γ-ray interaction points in the crystals. It is the tracking algorithms that deploy this information and enable insight into the sequence of interactions, providing information on the full or partial absorption of the γ ray. A series of dedicated performance measurements for an AGATA set-up comprising 21 crystals is described. This set-up was used within the recent PreSPEC–AGATA experimental campaign at the GSI Helmholtzzentrum für Schwerionenforschung. Using the radioactive sources 56Co, 60Co and 152Eu, absolute and normalized efficiencies and the peak-to-total of the array were measured. These quantities are discussed using different data analysis procedures. The quality of the pulse-shape analysis and the tracking algorithm are evaluated. The agreement between the experimental data and the Geant4 simulations is also investigated
On the Road to FAIR: 1st Operation of AGATA in PreSPEC at GSI
No full textInternational audienceThe Facility for Antiproton and Ion Research (FAIR), under construction at Darmstadt will provide intense relativistic beams of exotic nuclei at its Superconducting-FRagment Separator. High-resolution in-beam γ-ray spectroscopy will be performed in the HISPEC experiment, using the European Advanced GAmma-ray Tracking Array (AGATA). The PreSPEC-AGATA campaign is the predecessor of HISPEC and runs from 2012 to 2014 at GSI Helmholtzzentrum für Schwerionenforschung GmbH. Up to19 AGATA modules were used at GSI's F Ragment Separator in 2012. We report on the status of the experiment including preliminary results from performance commissioning
Data-flow coupling and data-acquisition triggers for the PreSPEC-AGATA campaign at GSI
No full textThe PreSPEC setup for high-resolution 'gamma-ray spectroscopy using radioactive ion beams was employed for experimental campaigns in 2012 and 2014. The setup consisted of the state of the art Advanced GAmma Tracking Array (AGATA) and the High Energy gamma cleteCTOR (HECTOR+) positioned around a secondary target at the final focal plane of the GSI FRagment Separator (FRS) to perform in-beam gamma-ray spectroscopy of exotic nuclei. The Lund York Cologne CAlorimeter (LYCCA) was used to identify the reaction products. In this paper we report on the trigger scheme used during the campaigns. The dataflow coupling between the Multi-Branch System (MBS) based Data AcQuisition (DAQ) used for FRS-LYCCA and the "Nouvelle Acquisition temps Reel Version 1.2 Avec Linux" (NARVAL) based acquisition system used for AGATA are also described. (C) 2015 Elsevier B.V. All rights reserved
Shape evolution in Ru-116,Ru-118: Triaxiality and transition between the O(6) and U(5) dynamical symmetries
No full textRu-116 and Ru-118 have been studied via beta-delayed gamma-ray spectroscopy of nuclei produced in fragmentation reactions at the Radioactive Ion-Beam Factory (RIBF) facility. Level schemes with positive-parity states up to spin J = 6 have been constructed. The results have been discussed in terms of the interacting boson model, the algebraic collective model, and total Routhian surfaces. We conclude that the very neutron-rich nuclei still show many features associated with triaxial gamma-soft nuclei, represented by the O(6) symmetry, but are approaching a spherical structure, the U(5) symmetry, with increasing neutron number towards the N = 82 shell closure. In Ru-118, hints of a shape transition in the ground state have been observed.This work was carried out at the RIBF operated by the RIKEN Nishina Center, RIKEN and CNS, University of Tokyo. We acknowledge the EUROBALL Owners Committee for the loan of germanium detectors and the PreSpec Collaboration for the readout electronics of the cluster detectors. Part of the WAS3ABi was supported by the Rare Isotope Science Project which is funded by the Ministry of Science, ICT & Future Planning (MSIP) and the National Research Foundation (NRF) of Korea. P.A.S. was financed by the Japan Society for the Promotion of Science (JSPS) Kakenhi Grant No. 23.01752. F.G.K. was supported by the US Department of Energy, Office of Nuclear Physics, under Contract No. DE-AC02-06CH11357. Zs.V. was supported by OTKA Contract No. K100835. We acknowledge financial support from the Spanish Ministerio de Ciencia e Innovacion under Contracts No. FPA2009-13377-C02 and No. FPA2011-29854-C04. H.S.J. was supported by the Priority Centers Research Program in Korea (2009-0093817). K.Y.C. was supported by National Research Foundation of Korea Grant No. NRF-2012R1A1A1041763. F.N. was supported by U.S. DOE Grant No. DE-FG02-91ER-40609
Isomer-delayed γ -ray spectroscopy of A=159-164 midshell nuclei and the variation of K -forbidden E1 transition hindrance factors
No full textZ. Patel et al. -- 10 pags., 18 figs., 11 tabs.Excited states have been studied in Sm159, Sm161, Sm162 (Z=62), Eu163 (Z=63), and Gd164 (Z=64), populated by isomeric decay following U238 projectile fission at RIBF, RIKEN. The isomer half-lives range from 50 ns to 2.6μs. In comparison with other published data, revised interpretations are proposed for Sm159 and Eu163. The first data for excited states in Sm161 are presented, where a 2.6-μs isomer is assigned a three-quasiparticle, Kπ=17/2- structure. The interpretation is supported by multi-quasiparticle Nilsson-BCS calculations, including the blocking of pairing correlations. A consistent set of reduced E1 hindrance factors is obtained. Limited evidence is also reported for isomeric decay in Sm163, Eu164, and Eu165.This work was carried out at the RIBF operated by RIKEN
Nishina Center, RIKEN, and CNS, University of Tokyo.
All UK authors are supported by STFC. P.H.R. is partially
supported by the UK National Measurement Office (NMO).
P.-A.S. was financed by JSPS Grant No. 2301752 and the
RIKEN Foreign Postdoctoral Researcher Program. J.T. was
financed by Spanish Ministerio de Ciencia e Innovación under
ContractsNo. FPA2009-13377-C02 and No. FPA2011-29854-
C04. Zs.V. and I.K. were supported by OTKA Contract
No. K100835. We acknowledge the EUROBALL Owners
Committee for the loan of germanium detectors and the
PreSpec Collaboration for the readout electronics of the cluster
detectors. This work was also supported by JSPS KAKENHI
Grant No. 25247045Peer Reviewe
μ s isomers of Nd 158,160
No full text5 pags., 5 figs., 1 tab.The neutron-rich nuclei Nd158,160 have been studied via delayed γ-ray spectroscopy of μs isomeric states at the RIBF facility, RIKEN. These nuclei were produced following the projectile fission of a 345 AMeVU238 beam and delayed γ rays were detected by the EURICA cluster Ge array. The isomeric states have measured half-lives of 339(20) ns and 1.63(21) μs for Nd158 and Nd160, respectively. From the observed γ decays and the systematics of levels in the neighboring Nd isotopes first level schemes were constructed for these nuclei. The isomeric states of Nd158,160 have been assigned spins of (6-) and (4-), with proposed ν5/2[523] - ν7/2[633] and ν1/2[521] - ν7/2[633] configurations, respectively. ©2016 American Physical SocietyWe acknowledge financial support from KAKENHI
(25247045). This work was carried out at the RIBF operated
by RIKEN Nishina Center, RIKEN and CNS, University of
Tokyo.We acknowledge the EUROBALL Owners Committee
for the loan of germanium detectors and the PreSpec Collaboration
for the readout electronics of the cluster detectors.
Part of the WAS3ABi was supported by the Rare Isotope
Science Project which is funded by the Ministry of Science,
ICT and Future Planning (MSIP) and National Research
Foundation (NRF) of Korea. This work was supported by the
Spanish Ministerio de Ciencia e Innovación under Contracts
No. FPA2009-13377-C02 and FPA2011-29854-C04 and the
Hungarian Research Fund (OTKA), Contract No. K100835.Peer Reviewe
K selection in the decay of the (ν 52 [532]- 32 [411])4- isomeric state in Zr 102
No full textF. Browne et al. -- 7 pags. 8 figs., 2 tabs.The (ν52[532]- 32[411]) 4- state in Zr102, populated in the β decay of Y102, has been measured to be isomeric with a mean lifetime of 9.5(7) ns. It decays via four transitions, two of which are ΔK=2 (to the 3+ and 4+ members of the 2γ+ band) and one is ΔK=4 (to the 4+ member of the ground state 0+ band). The fourth (low-energy) transition is inferred to decay to an as-yet unassigned state. Hindrances of 106 were derived for the ΔK=2 transitions compared to Weisskopf estimates and the ΔK=4 transition hindered by a factor of 109. These values are consistent with the decay pattern of the analogous isomeric state in the neighboring N=62 nucleus Sr100 and with the broader systematics of such transitions. A comparison of the hindrances for the ΔK=4 transitions suggests that Zr102 is hardened against the γ degree of freedom compared to Sr100.This work was supported by JSPS KAKENHI Grants No.
26800117 and No. 25247045. UK authors were supported by
STFC Grants No. ST/J000132/1, No. ST/J000051/1, and No.
ST/K502431/1. P.H.R. acknowledges support from the UK
National Measurement Office. P.-A.S. was financed by JSPS
Grant No. 23 01752 and the RIKEN Foreign Postdoctoral
Researcher Program. V.W. was supported by DOE Grant No.
DE-FG02-91ER-40609 and the German BMBF Grant No.
05P12RDFN8. J.T. was financed by Spanish Ministerio de
Ciencia e Innovación under Contracts No. FPA2009-13377-
C02 and No. FPA2011-29854-C04. F. B. is grateful for helpful
discussions with Professor P. M.Walker.We acknowledge the
EUROBALL Owners Committee for the loan of germanium
detectors and the PreSpec Collaboration for the readout
electronics of the cluster detectors.Peer Reviewe
β decay of semi-magic 130Cd: Revision and extension of the level scheme of 130 In
No full textA. Jungclaus et al.; 8 págs.; 5 figs.; 3 tabs.The β decay of the semi-magic nucleus Cd130 has been studied at the RIBF facility at the RIKEN Nishina Center. The high statistics of the present experiment allowed for a revision of the established level scheme of In130 and the observation of additional β feeding to high-lying core-excited states in In130. The experimental results are compared to shell-model calculations employing a model space consisting of the full major N=50-82 neutron and Z=28-50 proton shells and the NA-14 interaction, and good agreement is found. ©2016 American Physical SocietyWe thank the staff of the RIKEN Nishina Center accelerator
complex for providing stable beams with high intensities
to the experiment. We acknowledge the EUROBALL
Owners Committee for the loan of germanium detectors
and the PreSpec Collaboration for the readout electronics
of the cluster detectors. This work was supported by the
Spanish Ministerio de Ciencia e Innovación under contract
FPA2011-29854-C04 and the Spanish Ministerio de Economía
y Competitividad under Contract No. FPA2014-57196-C5-
4-P, the Generalitat Valenciana (Spain) under Grant No.
PROMETEO/2010/101, the National Research Foundation of
Korea (NRF) grant funded by the Korea government (MEST)
(NRF-2014S1A2A2028636, 2016K1A3A7A09005579), the
Priority Centers Research Program in Korea (2009-0093817),
OTKA Contract No. K-100835, JSPS KAKENHI (Grant No.
25247045), the European Commission through the Marie
Curie Actions call FP7-PEOPLE-2011-IEF under Contract
No. 300096, the US Department of Energy, Office of Nuclear
Physics, under Contract No.DE-AC02-06CH11357, the STFC
(UK), the “RIKEN foreign research program,” the German
BMBF (No. 05P12RDCIA, No. 05P12RDNUP, and No.
05P12PKFNE), HIC for FAIR, the DFG cluster of excellence
“Origin and Structure of the Universe,” and DFG (Contract
No. KR2326/2-1).Peer Reviewe
1p3=2 Proton-Hole State in 132Sn and the Shell Structure Along N ¼ 82
No full textA low-lying state in 131In82, the one-proton hole nucleus with respect to double magic 132Sn, was
observed by its γ decay to the Iπ ¼ 1=2− β-emitting isomer. We identify the new state at an excitation
energy of Ex ¼ 1353 keV, which was populated both in the β decay of 131Cd83 and after β-delayed neutron
emission from 132Cd84, as the previously unknown πp3=2 single-hole state with respect to the 132Sn core.
Exploiting this crucial new experimental information, shell-model calculations were performed to study the
structure of experimentally inaccessible N ¼ 82 isotones below 132Sn. The results evidence a surprising
absence of proton subshell closures along the chain of N ¼ 82 isotones. The consequences of this finding
for the evolution of the N ¼ 82 shell gap along the r-process path are discussed.sponsorship: We thank the staff of the RIKEN Nishina Center
accelerator complex for providing stable beams with high
intensities to the experiment. We acknowledge the
EUROBALL Owners Committee for the loan of germanium
detectors and the PreSpec Collaboration for the
readout electronics of the cluster detectors. This work
was supported by the Spanish Ministerio de Ciencia e
Innovación under Contracts No. FPA2009-13377-C02 and
No. FPA2011-29854-C04, the Generalitat Valenciana
(Spain) under grant PROMETEO/2010/101, the Japanese
government under contract KAKENHI (25247045), the
National Research Foundation of Korea (NRF) grant
funded by the Korea government (MEST) (No. NRF-
2012R1A1A1041763), the Priority Centers Research
Program in Korea (2009-0093817), OTKA contract number
K-100835, the European Commission through the
Marie Curie Actions call FP7-PEOPLE-2011-IEF under
Contract No. 300096, the U.S. Department of Energy,
Office of Nuclear Physics, under Contract No. DE-AC02-
06CH11357 and the German BMBF (No. 05P12RDCIA
and 05P12RDNUP) and HIC for FAIR.status: Publishe
First observation of γ rays emitted from excited states south-east of Sn132: The πg−19/2⊗νf7/2 multiplet of In83132
No full textA. Jungclaus et al. ; 6 págs.; 4 figs. ; Rapid CommunicationsFor the first time, the γ decay of excited states has been observed in a nucleus situated in the quadrant south-east of doubly magic Sn132, a region in which experimental information so far is limited to ground-state properties. Six γ rays with energies of 50, 86, 103, 227, 357, and 602 keV were observed following the β-delayed neutron emission from Cd85133, populated in the projectile fission of a U238 beam at the Radioactive Isotope Beam Factory at RIKEN within the EURICA project. The new experimental information is compared to the results of a modern realistic shell-model calculation, the first one in this region very far from stability, focusing in particular on the π0g9/2-1 - ν1f7/2 particle-hole multiplet in In83132. In addition, theoretical estimates based on a scaling of the two-body matrix elements for the πh11/2-1 - νg9/2 analog multiplet in Tl127208, one major proton and one major neutron shell above, are presented. ©2016 American Physical SocietyWe thank the staff of the RIKEN Nishina Center accelerator
complex for providing stable beams with high intensities to
the experiment. We acknowledge the EUROBALL Owners
Committee for the loan of germanium detectors and the
PreSpec Collaboration for the readout electronics of the
cluster detectors. This work was supported by the Spanish
Ministerio de Ciencia e Innovación under Contract No.
FPA2011-29854-C04 and the Spanish Ministerio de Economía
y Competitividad under Contract No. FPA2014-57196-C5-
4-P, the Generalitat Valenciana (Spain) under Grant No.
PROMETEO/2010/101, the National Research Foundation of
Korea (NRF) grant funded by the Korea government (MEST)
(No. NRF-2012R1A1A1041763), the Priority Centers Research
Program in Korea (2009-0093817), OTKA Contract
No. K-100835, JSPS KAKENHI (Grant No. 25247045), the
European Commission through the Marie Curie Actions call
PEOPLE-2011FP7-IEF under Contract No. 300096 and the
German BMBF (No. 05P12RDCIA and No. 05P12RDNUP),
and Helmholtz International Center for FAIR.Peer Reviewe
