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Petrache, C. M., Frauendorf, S., Lv, B. F., Astier, A., Dupont, E., Guo, S., . . . Andreoiu, C. (2019). Collective rotation of an oblate nucleus at very high spin. Physical Review C: Covering Nuclear Physics, 99(4), Article ID 041301.
Open this publication in new window or tab >>Collective rotation of an oblate nucleus at very high spin
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2019 (English)In: Physical Review C: Covering Nuclear Physics, ISSN 2469-9985, E-ISSN 2469-9993, Vol. 99, no 4, article id 041301Article in journal (Refereed) Published
Abstract [en]

A sequence of nine almost equidistant quadrupole transitions is observed in Nd-137. The sequence represents an extremely regular rotational band that extends to a spin of about 75/2 and an excitation energy of approximate to 4.5 MeV above yrast. Cranked mean-field calculations of the Nilsson-Strutinsky type suggest an oblate shape for the band. They reproduce the observed I(I +1) dependence of the rotational energy whereas predicting a pronounced decrease in the deformation, which is the hallmark of antimagnetic rotation.

Place, publisher, year, edition, pages
American Physical Society, 2019
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-249862 (URN)10.1103/PhysRevC.99.041301 (DOI)000462906600001 ()2-s2.0-85064077764 (Scopus ID)
Note

QC 20190426

Available from: 2019-04-26 Created: 2019-04-26 Last updated: 2019-04-26Bibliographically approved
Trombetta, D. M., Klintefjord, M., Axell, K. & Cederwall, B. (2019). Fast neutron- and γ-ray coincidence detection for nuclear security and safeguards applications. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 927, 119-124
Open this publication in new window or tab >>Fast neutron- and γ-ray coincidence detection for nuclear security and safeguards applications
2019 (English)In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 927, p. 119-124Article in journal (Refereed) Published
Abstract [en]

The use of passive and active interrogation techniques to evaluate materials concerning their content of special nuclear materials (SNM) is fundamental in fields such as nuclear safeguards and security. Detection of fast neutrons and γ rays, which are a characteristic signature of SNM, has several potential advantages compared with the commonly used systems based on thermal and epithermal neutron counters, the most important being the much shorter required coincidence times and the correspondingly reduced rate of background events due to accidental coincidences. Organic scintillators are well suited for this purpose due to their fast timing properties and composition being based on carbon and hydrogen with large elastic scattering cross-sections for fast neutrons. Organic scintillators also have suitable detection efficiency for γ rays and exhibit pulse shape properties which are favorable for distinguishing between neutrons and γ rays. This paper presents experimental results and Monte Carlo simulations for a neutron–neutron and γ-neutron coincidence detection setup for identification and characterization of SNM based on such detectors. The measurements were carried out on different samples of PuO 2 material with varying content of 240 Pu at the Joint Research Center (JRC) of the European Commission, Ispra, Italy. The results demonstrate significant advantages of fast neutron-γ coincidence detection over fast neutron–neutron coincidence counting for certain applications, e.g. for nuclear security systems, even in the presence of moderate amounts of shielding.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Fast neutron and gamma detection, Monte Carlo simulations, Non-destructive analysis (NDA), Nuclear safeguards, Nuclear security, Organic liquid scintillator detector
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-246418 (URN)10.1016/j.nima.2019.01.081 (DOI)000462142700014 ()2-s2.0-85061781911 (Scopus ID)
Note

QC 20190319

Available from: 2019-03-19 Created: 2019-03-19 Last updated: 2019-04-24Bibliographically approved
Qiang, Y. H., Cederwall, B. & Xu, F. R. (2019). Identification of high-K rotation in Ba-130: Testing the consistency of electromagnetic observables. Physical Review C: Covering Nuclear Physics, 99(1), Article ID 014307.
Open this publication in new window or tab >>Identification of high-K rotation in Ba-130: Testing the consistency of electromagnetic observables
2019 (English)In: Physical Review C: Covering Nuclear Physics, ISSN 2469-9985, E-ISSN 2469-9993, Vol. 99, no 1, article id 014307Article in journal (Refereed) Published
Abstract [en]

The band built on the K-pi = 8(-), T-1/2 = 9.4 ms isomer of( 130)Ba has been identified, filling the gap in the systematics of the dipole bands built on the 8(- )isomers in the N = 74 isotones from( 128)Xe to Gd-138. The use of the GALILEO array in conjunction with its ancillaries EUCLIDES and Neutron Wall, helped to firmly place the newly identified transitions on top of the long-lived isomer. The extracted g(K)and g(R) gyromagnetic factors are in agreement with the 7/2(+)[404] circle times 9/2(-)[514] two-neutron Nilsson configuration. Particle-rotor model calculations give an understanding of the limited degree of K mixing. The experimental information on the K-pi = 8(-) isomer of Ba-130 is now the most complete among the K isomers of the N = 74 isotones.

Place, publisher, year, edition, pages
AMER PHYSICAL SOC, 2019
National Category
Subatomic Physics
Identifiers
urn:nbn:se:kth:diva-242243 (URN)10.1103/PhysRevC.99.014307 (DOI)000455164000003 ()2-s2.0-85059834023 (Scopus ID)
Note

QC 20190129

Available from: 2019-01-29 Created: 2019-01-29 Last updated: 2019-08-06Bibliographically approved
Barucca, G., Davi, F., Lancioni, G., Mengucci, P., Montalto, L., Natali, P. P., . . . Zmeskal, J. (2019). Precision resonance energy scans with the PANDA experiment at FAIR: Sensitivity study for width and line shape measurements of the X(3872). European Physical Journal A, 55(3), Article ID 42.
Open this publication in new window or tab >>Precision resonance energy scans with the PANDA experiment at FAIR: Sensitivity study for width and line shape measurements of the X(3872)
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2019 (English)In: European Physical Journal A, ISSN 1434-6001, E-ISSN 1434-601X, Vol. 55, no 3, article id 42Article in journal (Refereed) Published
Abstract [en]

.This paper summarises a comprehensive Monte Carlo simulation study for precision resonance energy scan measurements. Apart from the proof of principle for natural width and line shape measurements of very narrow resonances with PANDA, the achievable sensitivities are quantified for the concrete example of the charmonium-like X(3872) state discussed to be exotic, and for a larger parameter space of various assumed signal cross-sections, input widths and luminosity combinations. PANDA is the only experiment that will be able to perform precision resonance energy scans of such narrow states with quantum numbers of spin and parities that differ from JPC=1--.

Place, publisher, year, edition, pages
Springer, 2019
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-249877 (URN)10.1140/epja/i2019-12718-2 (DOI)000462672600001 ()2-s2.0-85063462704 (Scopus ID)
Note

QC 20190503

Available from: 2019-05-03 Created: 2019-05-03 Last updated: 2019-05-03Bibliographically approved
B Singh, ., Bäck, T., Cederwall, B., Zmeskal, J. & et al., . (2019). Technical design report for the (P)over-barANDA Barrel DIRC detector. JOURNAL OF PHYSICS G-NUCLEAR AND PARTICLE PHYSICS (4)
Open this publication in new window or tab >>Technical design report for the (P)over-barANDA Barrel DIRC detector
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2019 (English)In: JOURNAL OF PHYSICS G-NUCLEAR AND PARTICLE PHYSICS, no 4Article in journal (Refereed) Published
Abstract [en]

The (P) over bar ANDA (anti-Proton ANnihiliation at DArmstadt) experiment will be one of the four flagship experiments at the new international accelerator complex FAIR (Facility for Antiproton and Ion Research) in Darmstadt, Germany. (P) over bar ANDA will address fundamental questions of hadron physics and quantum chromodynamics using high-intensity cooled antiproton beams with momenta between 1.5 and 15 GeV/c and a design luminosity of up to 2 x 10(32) cm(-2) S-1. Excellent particle identification (PID) is crucial to the success of the (P) over bar ANDA physics program. Hadronic PID in the barrel region of the target spectrometer will be performed by a fast and compact Cherenkov counter using the detection of internally reflected Cherenkov light (DIRC) technology. It is designed to cover the polar angle range from 22 degrees to 140 degrees and will provide at least 3 standard deviations (s.d.) pi/K separation up to 3.5 GeV/c, matching the expected upper limit of the final state kaon momentum distribution from simulation. This documents describes the technical design and the expected performance of the (P) over bar ANDA Barrel DIRC detector. The design is based on the successful BaBar DIRC with several key improvements. The performance and system cost were optimized in detailed detector simulations and validated with full system prototypes using particle beams at GSI and CERN. The final design meets or exceeds the PID goal of clean pi/K separation with at least 3 s.d. over the entire phase space of charged kaons in the Barrel DIRC.

Place, publisher, year, edition, pages
Institute of Physics (IOP), 2019
Keywords
particle identification; ring imaging Cherenkov detector; DIRC counter; PANDA experiment; hadron physics
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-247986 (URN)10.1088/1361-6471/aade3d (DOI)000460153900001 ()
Note

QC 20190401

Available from: 2019-04-01 Created: 2019-04-01 Last updated: 2019-04-01Bibliographically approved
Petrache, C. M., Lv, B. F., Astier, A., Dupont, E., Wang, Y. K., Zhang, S. Q., . . . Andreoiu, C. (2018). Evidence of chiral bands in even-even nuclei. Physical Review C: Covering Nuclear Physics, 97(4), Article ID 041304.
Open this publication in new window or tab >>Evidence of chiral bands in even-even nuclei
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2018 (English)In: Physical Review C: Covering Nuclear Physics, ISSN 2469-9985, E-ISSN 2469-9993, Vol. 97, no 4, article id 041304Article in journal (Refereed) Published
Abstract [en]

Evidence for chiral doublet bands has been observed for the first time in the even-even nucleus Nd136. One chiral band was firmly established. Four other candidates for chiral bands were also identified, which can contribute to the realization of the multiple pairs of chiral doublet bands (MχD) phenomenon. The observed bands are investigated by the constrained and tilted axis cranking covariant density functional theory (TAC-CDFT). Possible configurations have been explored. The experimental energy spectra, angular momenta, and B(M1)/B(E2) values for the assigned configurations are globally reproduced by TAC-CDFT. Calculated results support the chiral interpretation of the observed bands, which correspond to shapes with maximum triaxiality induced by different multiquasiparticle configurations in Nd136.

Place, publisher, year, edition, pages
American Physical Society, 2018
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-229638 (URN)10.1103/PhysRevC.97.041304 (DOI)000431992700001 ()2-s2.0-85046626065 (Scopus ID)
Funder
Swedish Research Council, 621-2014-5558EU, FP7, Seventh Framework Programme, 262010 (ENSAR)
Note

QC 20180605

Available from: 2018-06-05 Created: 2018-06-05 Last updated: 2018-06-05Bibliographically approved
Lv, B. F., Petrache, C. M., Astier, A., Dupont, E., Lopez-Martens, A., Greenlees, P. T., . . . Andreoiu, C. (2018). Evolution from γ -soft to stable triaxiality in Nd 136 as a prerequisite of chirality. Physical Review C: Covering Nuclear Physics, 98(4), Article ID 044304.
Open this publication in new window or tab >>Evolution from γ -soft to stable triaxiality in Nd 136 as a prerequisite of chirality
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2018 (English)In: Physical Review C: Covering Nuclear Physics, ISSN 2469-9985, E-ISSN 2469-9993, Vol. 98, no 4, article id 044304Article in journal (Refereed) Published
Abstract [en]

The level structure of Nd136 has been investigated using the Mo100(Ar40,4n) reaction and the JUROGAM II+RITU+GREAT setup. The level scheme has been extended significantly. Many new bands have been identified both at low and high spin, among which are five nearly degenerate bands interpreted as chiral partners. Excitation energies, spins, and parities of the previously known bands are revised and firmly established, and some previously known bands have been revised. Configurations are assigned to the observed bands based on cranked Nilsson-Strutinsky calculations. The band structure of Nd136 is now clarified and the various types of single-particle and collective excitations are well understood.

Place, publisher, year, edition, pages
American Physical Society, 2018
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-247148 (URN)10.1103/PhysRevC.98.044304 (DOI)000446556100001 ()2-s2.0-85054507682 (Scopus ID)
Funder
Swedish Research Council, 621-2014-5558
Note

QC 20190507

Available from: 2019-05-07 Created: 2019-05-07 Last updated: 2019-05-07Bibliographically approved
Ertoprak, A., Cederwall, B., Qi, C., Doncel, M., Jakobsson, U., Nyako, B. M., . . . Xiao, Z. G. (2018). M1 and E2 transition rates from core-excited states in semi-magic Ru-94. European Physical Journal A, 54(9), Article ID 145.
Open this publication in new window or tab >>M1 and E2 transition rates from core-excited states in semi-magic Ru-94
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2018 (English)In: European Physical Journal A, ISSN 1434-6001, E-ISSN 1434-601X, Vol. 54, no 9, article id 145Article in journal (Refereed) Published
Abstract [en]

Lifetimes of high-spin states have been measured in the semi-magic (N = 50) nucleus Ru-94. Excited states in Ru-94 were populated in the Ni-58(Ca-40, 4p)Ru-94* fusion-evaporation reaction at the Grand Accelerateur National d'Ions Lourds (GANIL) accelerator complex. DSAM lifetime analysis was performed on the Doppler broadened line shapes in energy spectra obtained from gamma-rays emitted while the residual nuclei were slowing down in a thick 6 mg/cm(2) metallic Ni-58 target. In total eight excited-state lifetimes in the angular momentum range I = (13-20)h have been measured, five of which were determined for the first time. The corresponding B(M1) and B(E2) reduced transition strengths are discussed within the framework of large-scale shell model calculations to study the contribution of different particle-hole configurations, in particular for analyzing contributions from core-excited configurations.

Place, publisher, year, edition, pages
Springer, 2018
National Category
Subatomic Physics
Identifiers
urn:nbn:se:kth:diva-234570 (URN)10.1140/epja/i2018-12581-7 (DOI)000443091000003 ()2-s2.0-85052645166 (Scopus ID)
Funder
Swedish Research Council, 621-2014-5558Swedish Research Council, 621-2012-3805Swedish Research Council, 621-2013-4323Göran Gustafsson Foundation for Research in Natural Sciences and Medicine
Note

QC 20180917

Available from: 2018-09-19 Created: 2018-09-19 Last updated: 2018-09-19Bibliographically approved
Delafosse, C., Verney, D., Cederwall, B. & Dobon, J. J. (2018). Pseudospin Symmetry and Microscopic Origin of Shape Coexistence in the Ni-78 Region: A Hint from Lifetime Measurements. Physical Review Letters, 121(19), Article ID 192502.
Open this publication in new window or tab >>Pseudospin Symmetry and Microscopic Origin of Shape Coexistence in the Ni-78 Region: A Hint from Lifetime Measurements
2018 (English)In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 121, no 19, article id 192502Article in journal (Refereed) Published
Abstract [en]

Lifetime measurements of excited states of the light N = 52 isotones Kr-88, Se-86, and Ge-84 have been performed, using the recoil distance Doppler shift method and VAMOS and AGATA spectrometers for particle identification and gamma spectroscopy, respectively. The reduced electric quadrupole transition probabilities B(E2; 2(+)-> 0(+)) and B(E2; 4(+)-> 2(+)) were obtained for the first time for the hard-to-reach 84Ge. While the B(E2; 2(+)-> 0(+) ) values of Kr-88, Se-86 saturate the maximum quadrupole collectivity offered by the natural valence (3s, 2d, 1g(7/2), 1h(11/2)) space of an inert Ni-78 core, the value obtained for Ge-84 largely exceeds it, suggesting that shape coexistence phenomena, previously reported at N less than or similar to 49, extend beyond N = 50. The onset of collectivity at Z = 32 is understood as due to a pseudo-SU(3) organization of the proton single-particle sequence reflecting a clear manifestation of pseudospin symmetry. It is realized that the latter provides actually reliable guidance for understanding the observed proton and neutron single particle structure in the whole medium-mass region, from Ni to Sn, pointing towards the important role of the isovector-vector rho field in shell-structure evolution.

Place, publisher, year, edition, pages
AMER PHYSICAL SOC, 2018
National Category
Subatomic Physics
Identifiers
urn:nbn:se:kth:diva-239782 (URN)10.1103/PhysRevLett.121.192502 (DOI)000449791600008 ()30468583 (PubMedID)2-s2.0-85056396057 (Scopus ID)
Note

QC 20190108

Available from: 2019-01-08 Created: 2019-01-08 Last updated: 2019-01-08Bibliographically approved
Litzinger, J., Blazhev, A., Dewald, A., Didierjean, F., Duchene, G., Fransen, C., . . . Vogt, A. (2018). Transition probabilities in neutron-rich Se-80,Se-82 and the role of the nu g(9/2) orbital. Physical Review C: Covering Nuclear Physics, 97(4), Article ID 044323.
Open this publication in new window or tab >>Transition probabilities in neutron-rich Se-80,Se-82 and the role of the nu g(9/2) orbital
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2018 (English)In: Physical Review C: Covering Nuclear Physics, ISSN 2469-9985, E-ISSN 2469-9993, Vol. 97, no 4, article id 044323Article in journal (Refereed) Published
Abstract [en]

Transition probabilities of intermediate-spin yrast and non-yrast excitations in Se-80,Se-82 were investigated in a recoil distance Doppler-shift (RDDS) experiment performed at the Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Legnaro. The Cologne Plunger device for deep inelastic scattering was used for the RDDS technique and was combined with the AGATA Demonstrator array for the gamma-ray detection and coupled to the PRISMA magnetic spectrometer for an event-by-event particle identification. In Se-80, the level lifetimes of the yrast (6(1)(+)) and (8(1)(+)) states and of a non-yrast band feeding the yrast 4(1)(+) state are determined. A spin and parity assignment of the head of this sideband is discussed based on the experimental results and supported by large-scale shell-model calculations. In Se-82, the level lifetimes of the yrast 6(1)(+) state and the yrare 4(2)(+) state and lifetime limits of the yrast (10(1)(+)) state and of the 5(1)(-) state are determined. Although the experimental results contain large uncertainties, they are interpreted with care in terms of large-scale shell-model calculations using the effective interactions JUN45 and jj44b. The excited states' wave functions are investigated and discussed with respect to the role of the neutron g(9/2) orbital.

Place, publisher, year, edition, pages
American Physical Society, 2018
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-230544 (URN)10.1103/PhysRevC.97.044323 (DOI)000431992700002 ()2-s2.0-85046622604 (Scopus ID)
Note

QC 20180723

Available from: 2018-07-23 Created: 2018-07-23 Last updated: 2018-07-23Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0003-1771-2656

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