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1. Overview of physics results from MAST upgrade towards core-pedestal-exhaust integration

Author

J.R. Harrison, A. Aboutaleb, S. Ahmed, M. Aljunid, S.Y. Allan, H. Anand, Y. Andrew, L.C. Appel, A. Ash, J. Ashton, O. Bachmann, M. Barnes, B. Barrett, D. Baver, D. Beckett, J. Bennett, J. Berkery, M. Bernert, W. Boeglin, C. Bowman, J. Bradley, D. Brida, P.K. Browning, D. Brunetti, P. Bryant, J. Bryant, J. Buchanan, N. Bulmer, A. Carruthers, M. Cecconello, Z.P. Chen, J. Clark, C. Cowley, M. Coy, N. Crocker, G. Cunningham, I. Cziegler, T. Da Assuncao, Y. Damizia, P. Davies, I.E. Day, G.L. Derks, S. Dixon, R. Doyle, M. Dreval, M. Dunne, B.P. Duval, T. Eagles, J. Edmond, H. El-Haroun, S.D. Elmore, Y. Enters, M. Faitsch, F. Federici, N. Fedorczak, F. Felici, A.R. Field, M. Fitzgerald, I. Fitzgerald, R. Fitzpatrick, L. Frassinetti, W. Fuller, D. Gahle, J. Galdon-Quiroga, L. Garzotti, S. Gee, T. Gheorghiu, S. Gibson, K.J. Gibson, C. Giroud, D. Greenhouse, V.H. Hall-Chen, C.J. Ham, R. Harrison, S.S. Henderson, C. Hickling, B. Hnat, L. Howlett, J. Hughes, R. Hussain, K. Imada, P. Jacquet, P. Jepson, B. Kandan, I. Katramados, Y.O. Kazakov, D. King, R. King, A. Kirk, M. Knolker, M. Kochan, L. Kogan, B. Kool, M. Kotschenreuther, M. Lees, A.W. Leonard, G. Liddiard, B. Lipschultz, Y.Q. Liu, B.A. Lomanowski, N. Lonigro, J. Lore, J. Lovell, S. Mahajan, F. Maiden, C. Man-Friel, F. Mansfield, S. Marsden, R. Martin, S. Mazzi, R. McAdams, G. McArdle, K.G. McClements, J. McClenaghan, D. McConville, K. McKay, C. McKnight, P. McKnight, A. McLean, B.F. McMillan, A. McShee, J. Measures, N. Mehay, C.A. Michael, F. Militello, D. Morbey, S. Mordijck, D. Moulton, O. Myatra, A.O. Nelson, M. Nicassio, M.G. O’Mullane, H.J.C. Oliver, P. Ollus, T. Osborne, N. Osborne, E. Parr, B. Parry, B.S. Patel, D. Payne, C. Paz-Soldan, A. Phelps, L. Piron, C. Piron, G. Prechel, M. Price, B. Pritchard, R. Proudfoot, H. Reimerdes, T. Rhodes, P. Richardson, J. Riquezes, J.F. Rivero-Rodriguez, C.M. Roach, M. Robson, K. Ronald, E. Rose, P. Ryan, D. Ryan, S. Saarelma, S. Sabbagh, R. Sarwar, P. Saunders, O. Sauter, R. Scannell, T. Schuett, R. Seath, R. Sharma, P. Shi, B. Sieglin, M. Simmonds, J. Smith, A. Smith, V. A. Soukhanovskii, D. Speirs, G. Staebler, R. Stephen, P. Stevenson, J. Stobbs, M. Stott, C. Stroud, C. Tame, C. Theiler, N. Thomas-Davies, A.J. Thornton, M. Tobin, M. Vallar, R.G.L. Vann, L. Velarde, K. Verhaegh, E. Viezzer, C. Vincent, G. Voss, M. Warr, W. Wehner, S. Wiesen, T.A. Wijkamp, D. Wilkins, T. Williams, T. Wilson, H.R. Wilson, H. Wong, M. Wood, and V. Zamkovska

Subjects
MAST upgrade, exhaust, integrated scenarios, alternative divertors, pedestal, fast ions, Nuclear and particle physics. Atomic energy. Radioactivity, QC770-798
Abstract

Recent results from MAST Upgrade are presented, emphasising understanding the capabilities of this new device and deepening understanding of key physics issues for the operation of ITER and the design of future fusion power plants. The impact of MHD instabilities on fast ion confinement have been studied, including the first observation of fast ion losses correlated with Compressional and Global Alfvén Eigenmodes. High-performance plasma scenarios have been developed by tailoring the early plasma current ramp phase to avoid internal reconnection events, resulting in a more monotonic q profile with low central shear. The impact of m / n = 3/2, 2/1 and 1/1 modes on thermal plasma confinement and rotation profiles has been quantified, and scenarios optimised to avoid them have transiently reached values of normalised beta approaching 4.2. In pedestal and ELM physics, a maximum pedestal top temperature of ∼350 eV has been achieved, exceeding the value achieved on MAST at similar heating power. Mitigation of type-I ELMs with n = 1 RMPs has been observed. Studies of plasma exhaust have concentrated on comparing conventional and Super-X divertor configurations, while X-point target, X-divertor and snowflake configurations have been developed and studied in parallel. In L-mode discharges, the separatrix density required to detach the outer divertors is approximately a factor 2 lower in the Super-X than the conventional configuration, in agreement with simulations. Detailed analysis of spectroscopy data from studies of the Super-X configuration reveal the importance of including plasma-molecule interactions and D _2 Fulcher band emission to properly quantify the rates of ionisation, plasma-molecule interactions and volumetric recombination processes governing divertor detachment. In H-mode with conventional and Super-X configurations, the outer divertors are attached in the former and detached in the latter with no impact on core or pedestal confinement.

Published
2024
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2. First application of Markov chain Monte Carlo-based Bayesian data analysis to the Doppler-shift attenuation method

Author

L.J. Sun, C. Fry, B. Davids, N. Esker, C. Wrede, M. Alcorta, S. Bhattacharjee, M. Bowry, B.A. Brown, T. Budner, R. Caballero-Folch, L. Evitts, M. Friedman, A.B. Garnsworthy, B.E. Glassman, G. Hackman, J. Henderson, O.S. Kirsebom, J. Lighthall, P. Machule, J. Measures, M. Moukaddam, J. Park, C. Pearson, D. Pérez-Loureiro, C. Ruiz, P. Ruotsalainen, J. Smallcombe, J.K. Smith, D. Southall, J. Surbrook, L.E. Weghorn, and M. Williams

Subjects
Lifetimes of 31S states, 30P(p,γ)31S reaction, Nova nucleosynthesis, Bayesian analysis, Markov chain Monte Carlo, Physics, QC1-999
Abstract

Motivated primarily by the large uncertainties in the thermonuclear rate of the 30P(p,γ)31S reaction that limit our understanding of classical novae, we carried out lifetime measurements of 31S excited states using the Doppler Shift Lifetimes (DSL2) facility at the TRIUMF Isotope Separator and Accelerator (ISAC-II) facility. The 31S excited states were populated by the 3He(32S,α)31S reaction. The deexcitation γ rays were detected by a clover-type high-purity germanium detector in coincidence with the α particles detected by a silicon detector telescope. We have applied modern Markov chain Monte Carlo-based Bayesian statistical techniques to perform lineshape analyses of Doppler-shift attenuation method γ-ray data for the first time. We have determined the lifetimes of the two lowest-lying 31S excited states. First experimental upper limits on the lifetimes of four higher-lying states have been obtained. The experimental results were compared to shell-model calculations using five universal sd-shell Hamiltonians. Evidence for γ rays originating from the astrophysically important Jπ=3/2+, 260-keV 30P(p,γ)31S resonance with an excitation energy of Ex=6390.2(7) keV in 31S has also been observed, although strong constraints on the lifetime will require better statistics.

Published
2023
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3. Proton inelastic scattering reveals deformation in 8He

Author

M. Holl, R. Kanungo, Z.H. Sun, G. Hagen, J.A. Lay, A.M. Moro, P. Navrátil, T. Papenbrock, M. Alcorta, D. Connolly, B. Davids, A. Diaz Varela, M. Gennari, G. Hackman, J. Henderson, S. Ishimoto, A.I. Kilic, R. Krücken, A. Lennarz, J. Liang, J. Measures, W. Mittig, O. Paetkau, A. Psaltis, S. Quaglioni, J.S. Randhawa, J. Smallcombe, I.J. Thompson, M. Vorabbi, and M. Williams

Subjects
Physics, QC1-999
Abstract

A measurement of proton inelastic scattering of 8He at 8.25A MeV at TRIUMF shows a resonance at 3.54(6) MeV with a width of 0.89(11) MeV. The energy of the state is in good agreement with coupled cluster and no-core shell model with continuum calculations, with the latter successfully describing the measured resonance width as well. Its differential cross section analyzed with phenomenological collective excitation form factor and microscopic coupled reaction channels framework consistently reveals a large deformation parameter β2 = 0.40(3), consistent with no-core shell model predictions of a large neutron deformation. This deformed double-closed shell at the neutron drip-line opens a new paradigm.

Published
2021
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4. Testing microscopically derived descriptions of nuclear collectivity: Coulomb excitation of 22Mg

Author

J. Henderson, G. Hackman, P. Ruotsalainen, S.R. Stroberg, K.D. Launey, J.D. Holt, F.A. Ali, N. Bernier, M.A. Bentley, M. Bowry, R. Caballero-Folch, L.J. Evitts, R. Frederick, A.B. Garnsworthy, P.E. Garrett, B. Jigmeddorj, A.I. Kilic, J. Lassen, J. Measures, D. Muecher, B. Olaizola, E. O'Sullivan, O. Paetkau, J. Park, J. Smallcombe, C.E. Svensson, R. Wadsworth, and C.Y. Wu

Subjects
Physics, QC1-999
Abstract

Many-body nuclear theory utilizing microscopic or chiral potentials has developed to the point that collectivity might be studied within a microscopic or ab initio framework without the use of effective charges; for example with the proper evolution of the E2 operator, or alternatively, through the use of an appropriate and manageable subset of particle–hole excitations. We present a precise determination of E2 strength in 22Mg and its mirror 22Ne by Coulomb excitation, allowing for rigorous comparisons with theory. No-core symplectic shell-model calculations were performed and agree with the new B(E2) values while in-medium similarity-renormalization-group calculations consistently underpredict the absolute strength, with the missing strength found to have both isoscalar and isovector components. The discrepancy between two microscopic models demonstrates the sensitivity of E2 strength to the choice of many-body approximation employed. Keywords: 22Mg, 22Ne, Ab initio, Collectivity, Coulomb excitation

Published
2018
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5. Coulomb excitation of the |Tz|=12, A=23 mirror pair

Author

J. Henderson, G. Hackman, P. Ruotsalainen, J. D. Holt, S. R. Stroberg, C. Andreoiu, G. C. Ball, N. Bernier, M. Bowry, R. Caballero-Folch, S. Cruz, A. Diaz Varela, L. J. Evitts, R. Frederick, A. B. Garnsworthy, M. Holl, J. Lassen, J. Measures, B. Olaizola, E. O'Sullivan, O. Paetkau, J. Park, J. Smallcombe, C. E. Svensson, K. Whitmore, and C. Y. Wu

Published
2022

6. Ba145 and La145,146 structure from lifetime measurements

Author

G. Hackman, R. Umashankar, A. Estrade, B. Olaizola, A. Diaz-Varela, C. E. Svensson, A. D. MacLean, D. Southall, P. E. Garrett, J. Measures, R. Dunlop, A. B. Garnsworthy, R. Cabellero-Folch, B. Shaw, K. Whitmore, Iris Dillmann, M. Bowry, G. C. Ball, C. J. Pearson, T. Zidar, C. Burbadge, V. Bildstein, A. Babu, and J. Turko

Subjects
Physics, 010308 nuclear & particles physics, 0103 physical sciences, Structure (category theory), Order (ring theory), Atomic physics, Nuclear Experiment, 010306 general physics, Spin (physics), Parity (mathematics), 01 natural sciences
Abstract

The occurrence of octupole shapes in even-mass neutron-rich Ba isotopes has been well established. However, the situation with the odd-mass Ba and odd or odd-odd La nuclei around them is not so clear. In order to shed light on these less-studied isotopes, a fast-timing experiment was performed using the GRIFFIN spectrometer at TRIUMF-ISAC. A wealth of excited-state lifetimes in the 100 ps to few ns range have been measured in $^{144,145,146}\mathrm{Ba}$ and $^{145,146}\mathrm{La}$ populated in the ${\ensuremath{\beta}}^{\ensuremath{-}}$ and ${\ensuremath{\beta}}^{\ensuremath{-}}\text{\ensuremath{-}}n$ decay of $^{145,146}\mathrm{Cs}$. The results do not allow one to draw firm conclusions about the possible octupole deformation of these nuclei but suggest different spin and parity assignments than previous works. This work highlights the need for more detailed study of the odd and odd-odd isotopes in this region to properly understand their structure.

Published
2021

7. Decay spectroscopy of Sc50 and Sc50m to Ti50

Author

C. E. Svensson, G. Hackman, S. Cruz, H. P. Patel, M. Bowry, A. B. Garnsworthy, B. Olaizola, Jason D. Holt, J. Measures, S. Georges, C. E. Jones, G. C. Ball, and C. J. Pearson

Subjects
Physics, 010308 nuclear & particles physics, Excited state, 0103 physical sciences, Nuclear structure, Ab initio, Gamma spectroscopy, Atomic physics, 010306 general physics, Ground state, Spectroscopy, 01 natural sciences
Abstract

The $\ensuremath{\beta}$ decay of the isomeric and ground state of $^{50}\mathrm{Sc}$ to the semimagic nucleus $_{22}^{50}\mathrm{Ti}_{28}$ has been studied using a $^{50}\mathrm{Ca}$ beam delivered to the GRIFFIN $\ensuremath{\gamma}$-ray spectrometer at the TRIUMF-ISAC facility. $\ensuremath{\beta}$-decay branching ratios are reported to 16 excited states with a total of 38 $\ensuremath{\gamma}$-ray transitions linking them. These new data significantly expand the information available over previous studies. Relative intensities are measured to less than 0.001 $%$ that of the strongest transition with the majority of $\ensuremath{\gamma}$-ray transitions observed here in $\ensuremath{\beta}$ decay for the first time. The data are compared with shell-model calculations utilizing both phenomenologically derived interactions employed in the $pf$ shell as well as a state-of-the-art ab initio-based interaction built in the valence-space in-medium similarity renormalization-group framework.

Published
2021

8. The GRIFFIN facility for Decay-Spectroscopy studies at TRIUMF-ISAC

Author

Y. Linn, Mustafa Rajabali, D. Morris, Corina Andreoiu, C. Bartlett, S. W. Yates, E. T. Rand, K. Whitmore, R. Braid, D. S. Cross, D. Miller, J.E. Ash, T. Bruhn, M. Bowry, Erin E. Peters, James Smallcombe, A. B. Garnsworthy, S. Georges, F. A. Ali, D. Kisliuk, D. Brennan, G. Hackman, Elizabeth Padilla-Rodal, A.I. Kilic, R. Dunlop, E. MacConnachie, E. F. Zganjar, N. Bernier, S. Cruz, A.R. Mathews, E. McGee, J. Measures, M. Kuwabara, M. Ticu, E. Peters, V. Bildstein, C. Burbadge, R. Gudapati, P. C. Bender, R. Caballero-Folch, L.N. Morrison, B. Davids, Baharak Hadinia, R. Kokke, Panu Ruotsalainen, U. Rizwan, H. P. Patel, E. Timakova, B. Jigmeddorj, S. S. Bhattacharjee, S. Ciccone, K. G. Leach, Jack Henderson, M. R. Dunlop, F. H. Garcia, R Umashankar, W. J. Mills, W. Moore, Joochun Park, J. K. Smith, D. Southall, A. T. Laffoley, A. Cheeseman, Z. Beadle, P. E. Garrett, Z. M. Wang, M. Moukaddam, L. J. Evitts, C.R. Natzke, C. Lim, B. Olaizola, T. Ballast, K. Ortner, F. Sarazin, P. Boubel, H. Bidaman, R. Churchman, J. R. Leslie, S. A. Gillespie, C. E. Svensson, K. Kuhn, S. Wong, T. Zidar, B. Shaw, W.H. Ashfield, R. Krücken, Iris Dillmann, J. Turko, O. Paetkau, S. V. Ilyushkin, R. Lafleur, S. Hallam, G. C. Ball, D. Bishop, C. Unsworth, K. Raymond, A. Diaz Varela, J. L. Pore, Y. Saito, C. J. Pearson, A. J. Radich, K. Starosta, A. D. MacLean, and Aaron Chester

Subjects
Radioactive ion beams, Nuclear and High Energy Physics, Physics - Instrumentation and Detectors, Physics::Instrumentation and Detectors, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, chemistry.chemical_element, Germanium, 01 natural sciences, 7. Clean energy, Nuclear physics, 0103 physical sciences, Nuclear Experiment (nucl-ex), Nuclear Experiment, 010306 general physics, Spectroscopy, Instrumentation, Digital data acquisition system, Physics, Spectrometer, 010308 nuclear & particles physics, Detector, Instrumentation and Detectors (physics.ins-det), Semiconductor detector, chemistry, Physics::Accelerator Physics
Abstract

Gamma-Ray Infrastructure For Fundamental Investigations of Nuclei, GRIFFIN, is a new high-efficiency γ -ray spectrometer designed for use in decay spectroscopy experiments with low-energy radioactive ion beams provided by TRIUMF’s Isotope Separator and Accelerator (ISAC-I) facility. GRIFFIN is composed of sixteen Compton-suppressed large-volume clover-type high-purity germanium (HPGe) γ -ray detectors combined with a suite of ancillary detection systems and coupled to a custom digital data acquisition system. The infrastructure and detectors of the spectrometer as well as the performance characteristics and the analysis techniques applied to the experimental data are described.

Published
2019

9. Spectroscopic studies of neutron-rich In129 and its β -decay daughter, Sn129 , using the GRIFFIN spectrometer

Author

C. E. Svensson, J. Measures, Corina Andreoiu, N. Bernier, M. Ticu, Jack Henderson, H. Bidaman, J. L. Pore, M. Bowry, A. B. Garnsworthy, P. E. Garrett, J. K. Smith, K. Ortner, M. R. Dunlop, J. Turko, D. S. Cross, G. C. Ball, D. Southall, T. Zidar, V. Bildstein, K. Whitmore, C. M. Petrache, R. Dunlop, B. Olaizola, K. Raymond, Joochun Park, and F. H. Garcia

Subjects
Physics, Nuclear physics, Spectrometer, 010308 nuclear & particles physics, Branching fraction, Excited state, 0103 physical sciences, Neutron, 010306 general physics, Spin (physics), Ground state, 01 natural sciences, Beta decay
Abstract

The $\beta$-decay of neutron-rich $^{129}$In into $^{129}$Sn was studied using the GRIFFIN spectrometer at the ISAC facility at TRIUMF. The study observed the half-lives of the ground state and each of the $\beta$-decaying isomers. The level scheme of $^{129}$Sn has been expanded with thirty-one new $\gamma$-ray transitions and nine new excited levels, leading to a re-evaluation of the $\beta$-branching ratios and level spin assignments. The observation of the $\beta$-decay of the (29/2$^{+}$) 1911-keV isomeric state in $^{129}$In is reported for the first time, with a branching ratio of 2.0(5)$\%$.

Published
2021

10. High-spin structure of thesdshell nucleiNa25andNe22

Author

James Smallcombe, P. C. Srivastava, R. Krücken, M. Williams, Jack Henderson, T. Domingo, Priyanka Choudhary, O. Paetkau, A. B. Garnsworthy, R. Henderson, J. Williams, C. E. Svensson, J. Measures, R. S. Lubna, G. C. Ball, Aaron Chester, K. Starosta, Joochun Park, G. Hackman, and K. Whitmore

Subjects
Physics, 010308 nuclear & particles physics, Shell (structure), Spin structure, 01 natural sciences, 0103 physical sciences, Level structure, Neutron, Atomic physics, 010306 general physics, Spectroscopy, Spin (physics), Energy (signal processing), Excitation
Abstract

The level structure of $^{25}\mathrm{Na}$ and $^{22}\mathrm{Ne}$ in the high excitation energy/high spin regime was studied using $\ensuremath{\gamma}$-ray spectroscopy and Doppler shift lifetime measurements following $^{12}\mathrm{C}(^{18}\mathrm{O},\ensuremath{\alpha}p)^{25}\mathrm{Na}$ and $^{12}\mathrm{C}(^{18}\mathrm{O},2\ensuremath{\alpha})^{22}\mathrm{Ne}$ reactions. Multiple new levels and transitions were identified in both nuclides based on $\ensuremath{\gamma}\text{\ensuremath{-}}\ensuremath{\gamma}$ coincidence data. In $^{25}\mathrm{Na}$, evidence was found for higher-spin negative-parity states up to ${I}^{\ensuremath{\pi}}=13/{2}^{\ensuremath{-}}$ resulting from neutron excitation into the $pf$ shell, in good agreement with shell model calculations using the SDPF-MU and FSU interactions. Candidates for the yrast ${7}^{+}$ and ${8}^{+}$ levels in $^{22}\mathrm{Ne}$, consistent with calculations using the USDB interaction, were also identified.

Published
2020

11. β decay of In132 and spectroscopy of Sn132 and Sb131 with the GRIFFIN spectrometer

Author

J. L. Pore, A. B. Garnsworthy, D. S. Cross, F. H. Garcia, M. R. Dunlop, G. C. Ball, Jason D. Holt, P. E. Garrett, T. Miyagi, D. Southall, H. Bidaman, R. Dunlop, M. Bowry, K. Ortner, B. Olaizola, C. M. Petrache, V. Bildstein, Joochun Park, N. Bernier, J. K. Smith, J. Measures, Corina Andreoiu, T. Zidar, J. Turko, K. Whitmore, M. Ticu, Jack Henderson, and C. E. Svensson

Subjects
Physics, Spectrometer, 010308 nuclear & particles physics, Neutron emission, 01 natural sciences, 7. Clean energy, Ab initio quantum chemistry methods, Excited state, 0103 physical sciences, Neutron, Atomic physics, 010306 general physics, Spin (physics), Spectroscopy
Abstract

Spectroscopy of doubly magic $^{132}_{50}$Sn$_{82}$ has been performed with the GRIFFIN spectrometer at TRIUMF-ISAC following the $\beta$ decay of $^{132}_{49}$In$_{83}$. The analysis has allowed for the placement of a total of 70 transitions and 29 excited states in $^{132}$Sn. Detailed spectroscopy has also been performed on $^{131}$Sb, resulting from the $\beta$ decay of $^{131}$Sn, produced from the $\beta$-delayed neutron decay of $^{132}$In. Measurement of $\gamma$-rays in both $^{131}$Sn and $^{131}$Sb has led to the determination of the $\beta$-delayed neutron emission probability, $P_{n}$, from $^{132}$In. This is the first time the $P_{n}$ has been measured for this nucleus using $\gamma$ spectroscopy, and the new value of 12.3(4)% is consistent with the most recent $\beta-n$ counting experiment. Additionally, $\gamma$-$\gamma$ angular correlations have been performed in $^{132}$Sn, supporting the spin assignments of several excited states. Novel ab initio calculations are presented which describe several of the excited states, and these are compared to the experimental spectrum.

Published
2020

12. Collective 2p-2h intruder states in Sn118 studied via β decay of In118 using the GRIFFIN spectrometer at TRIUMF

Author

B. Olaizola, Joochun Park, C. M. Petrache, J. L. Pore, A. B. Garnsworthy, M. Bowry, D. Southall, T. Zidar, K. Whitmore, P. E. Garrett, M. R. Dunlop, R. Dunlop, K. Ortner, F. H. Garcia, G. C. Ball, V. Bildstein, D. S. Cross, M. Spieker, H. Bidaman, J. Measures, N. Bernier, J. K. Smith, K. Raymond, Corina Andreoiu, M. Ticu, J. Turko, Jack Henderson, and C. E. Svensson

Subjects
Nuclear physics, Physics, Spectrometer, 010308 nuclear & particles physics, Griffin, 0103 physical sciences, 010306 general physics, 01 natural sciences
Published
2020

13. Structure of Mg28 and influence of the neutron pf shell

Author

R. Krücken, G. H. Sargsyan, J. Williams, A. B. Garnsworthy, Joochun Park, P. C. Srivastava, Anil Kumar, G. C. Ball, J. Measures, Aaron Chester, R. Henderson, M. Williams, K. Starosta, Kristina D. Launey, T. Domingo, C. E. Svensson, O. Paetkau, Jack Henderson, G. Hackman, K. Whitmore, and James Smallcombe

Subjects
Physics, education.field_of_study, 010308 nuclear & particles physics, Island of inversion, Population, Ab initio, Gamma ray, 01 natural sciences, Atomic orbital, 0103 physical sciences, Neutron, Atomic physics, 010306 general physics, education, Spectroscopy, Excitation
Abstract

Gamma-ray spectroscopy and lifetime measurements using the Doppler shift attenuation method (DSAM) were performed on the nucleus $^{28}\mathrm{Mg}$ near the $N=20$ ``island of inversion,'' which was populated using a $^{12}\mathrm{C}(^{18}\mathrm{O},2\mathrm{p})^{28}\mathrm{Mg}$ fusion-evaporation reaction to investigate the impact of shell evolution on its high-lying structure. Three new levels were identified at 7203(3), 7747(2), and 7929.3(12) keV along with several new gamma rays. A newly extracted $B(E2;{4}_{1}^{+}\ensuremath{\rightarrow}{2}_{1}^{+})$ of 42(7) ${e}^{2}{\mathrm{fm}}^{4}$ indicates reduced collectivity in the yrast band at high spin, consistent with ab initio symmetry adapted no-core shell model (SA-NCSM) calculations. At high excitation energy, evidence for the population of intruder orbitals was obtained through identification of negative parity levels $[{I}^{\ensuremath{\pi}}={(0,4)}^{\ensuremath{-}}$, ${(4,5)}^{\ensuremath{-}}]$. Calculations using the SDPF-MU interaction indicate that these levels arise from single neutron excitation to the $pf$ shell and provides evidence for the lowering of these intruder orbitals approaching the island of inversion.

Published
2019

14. Isospin symmetry in B(E2) values: Coulomb excitation study of Mg21

Author

M. Holl, S. R. Stroberg, N. Bernier, Paul Greenlees, Tuomas Grahn, Corina Andreoiu, Ching-Yen Wu, Janne Pakarinen, L. J. Evitts, M. Q. Buckner, G. C. Ball, Joochun Park, A. Kurkjian, G. Hackman, J. K. Smith, Aaron Chester, D. Kisliuk, E. McGee, A. B. Garnsworthy, Panu Ruotsalainen, S. Cruz, R. Frederick, G. H. Sargsyan, K. Starosta, R. Caballero-Folch, Archana Saxena, D. Mücher, K. G. Leach, J. Measures, P. C. Srivastava, D. Southall, M. Williams, K. Whitmore, M. Bowry, James Smallcombe, Rauno Julin, F. Sarazin, Kristina D. Launey, C. E. Svensson, and Jack Henderson

Subjects
Physics, 010308 nuclear & particles physics, Nuclear structure, Ab initio, Coulomb excitation, 01 natural sciences, Symmetry (physics), Excited state, Isospin, 0103 physical sciences, Mirror nuclei, Atomic physics, 010306 general physics, Ground state
Abstract

The Tz=−32 nucleus 21Mg has been studied by Coulomb excitation on 196Pt and 110Pd targets. A 205.6(1)-keV γ-ray transition resulting from the Coulomb excitation of the 52+ ground state to the first excited 12+ state in 21Mg was observed for the first time. Coulomb excitation cross-section measurements with both targets and a measurement of the half-life of the 12+ state yield an adopted value of B(E2;52+→12+)=13.3(4) W.u. A new excited state at 1672(1) keV with tentative 92+ assignment was also identified in 21Mg. This work demonstrates a large difference in the B(E2;52+→12+) value between T=32, A=21 mirror nuclei. The difference is investigated in the shell-model framework employing both isospin conserving and breaking USD interactions and using modern ab initio nuclear structure calculations, which have recently become applicable in the sd shell. (Less)

Published
2019

15. β decay and β -delayed neutron decay of the N=82 nucleus In8249131

Author

G. C. Ball, J. L. Pore, M. Ticu, D. S. Cross, K. Whitmore, Jack Henderson, J. Measures, J. Turko, M. R. Dunlop, N. Bernier, B. Olaizola, M. Bowry, G. Hackman, D. Southall, T. Zidar, C. E. Svensson, J. K. Smith, H. Bidaman, V. Bildstein, P. E. Garrett, D. Mücher, Iris Dillmann, K. Ortner, Corina Andreoiu, C. M. Petrache, R. Dunlop, F. H. Garcia, Joochun Park, and A. B. Garnsworthy

Subjects
Physics, Decay scheme, 010308 nuclear & particles physics, Neutron emission, 01 natural sciences, medicine.anatomical_structure, Excited state, 0103 physical sciences, Nuclear astrophysics, medicine, Atomic physics, 010306 general physics, Nucleus, Delayed neutron
Abstract

The half-lives of three β-decaying states of 13149In82 have been measured with the GRIFFIN γ-ray spectrometer at the TRIUMF-ISAC facility to be T1/2(1/2−)=328(15)ms, T1/2(9/2+)=265(8)ms, and T1/2(21/2+)=323(55)ms, respectively. The first observation of γ rays following the βn decay of 131In into 130Sn is reported. The β-delayed neutron emission probability is determined to be P1n=12(7)% for the 21/2+ state and 2.3(3)% from the combined 1/2− and 9/2+ states of 13149In82 observed in this experiment. A significant expansion of the decay scheme of 131In, including 17 new excited states and 35 new γ-ray transitions in 13150Sn81 is also reported. This leads to large changes in the deduced β-branching ratios to some of the low-lying states of 131Sn compared to previous work with implications for the strength of the first-forbidden β transitions in the vicinity of doubly magic 13250Sn82. (Less)

Published
2019

16. Observation of excited states in Mg20 sheds light on nuclear forces and shell evolution

Author

J.C. Lighthall, M. Holl, M. Moukaddam, Devin Burke, Corina Andreoiu, R. Kanungo, E. McGee, M. Keefe, P. Jassal, G. Hackman, S. Cruz, S. R. Stroberg, Gustav R. Jansen, Julia Even, Elizabeth Padilla-Rodal, A. C. Shotter, R. Krücken, G. Christian, A. Chen, Ian J. Thompson, Orry Workman, C. Burbadge, Gaute Hagen, J. Measures, J. S. Randhawa, M. Williams, Jack Henderson, C. Barnes, D. Kisliuk, M. Alcorta, Barry Davids, S. Kaur, J. Turko, Aaron Chester, Petr Navrátil, Jason D. Holt, S. Ishimoto, and J. F. Liang

Subjects
Physics, Proton, 010308 nuclear & particles physics, Nuclear Theory, Nuclear structure, 01 natural sciences, Borromean nucleus, Excited state, 0103 physical sciences, Bound state, Nuclear force, Neutron, Atomic physics, Born approximation, Nuclear Experiment, 010306 general physics
Abstract

The exotic Borromean nucleus $^{20}$Mg with $N$ = 8, located at the proton drip-line provides a unique testing ground for nuclear forces and the evolution of shell structure in the neutron-deficient region. We report on the first observation of proton unbound resonances together with bound states in $^{20}$Mg from the $^{20}$Mg($d$,$d'$) reaction performed at TRIUMF. Phenomenological shell-model calculations offer a reasonable description. However, our experimental results present a challenge for current first-principles nuclear structure approaches and point to the need for improved chiral forces and {\it ab initio} calculations. Furthermore, the differential cross section of the first excited state is compared with distorted-wave Born approximation calculations to deduce a neutron quadrupole deformation parameter of $\beta_n$=0.46$\pm$0.21. This provides the first indication of a possible weakening of the $N$ = 8 shell closure at the proton drip-line.

Published
2019

17. Testing microscopically derived descriptions of nuclear collectivity: Coulomb excitation of Mg-22

Author

A. B. Garnsworthy, Jens Lassen, Jack Henderson, P. E. Garrett, Ching-Yen Wu, Dennis Muecher, C. E. Svensson, N. Bernier, B. Olaizola, G. Hackman, F. A. Ali, R. Caballero-Folch, B. Jigmeddorj, Joochun Park, Panu Ruotsalainen, Kristina D. Launey, S. R. Stroberg, J. Measures, R. Wadsworth, O. Paetkau, M. Bowry, E. O'Sullivan, Jason D. Holt, M. A. Bentley, James Smallcombe, L. J. Evitts, A.I. Kilic, and R. Frederick

Subjects
Nuclear and High Energy Physics, Isoscalar, Collectivity, Coulomb excitation, Ab initio, FOS: Physical sciences, 22Ne, Astronomy & Astrophysics, 01 natural sciences, Physics, Particles & Fields, Mg-22, Quantum mechanics, 0103 physical sciences, Sensitivity (control systems), collectivity, Nuclear Experiment (nucl-ex), 010306 general physics, Nuclear theory, Nuclear Experiment, Physics, Science & Technology, Isovector, ta114, 010308 nuclear & particles physics, Operator (physics), 22Mg, Ne-22, lcsh:QC1-999, Physics, Nuclear, STATES, Physical Sciences, lcsh:Physics, Symplectic geometry
Abstract

Many-body nuclear theory utilizing microscopic or chiral potentials has developed to the point that collectivity might be dealt with in an {\it ab initio} framework without the use of effective charges; for example with the proper evolution of operators, or alternatively, through the use of an appropriate and manageable subset of particle-hole excitations. We present a precise determination of $E2$ strength in $^{22}$Mg and its mirror $^{22}$Ne by Coulomb excitation, allowing for rigorous comparisons with theory. No-core symplectic shell-model calculations were performed and agree with the new $B(E2)$ values while in-medium similarity-renormalization-group calculations consistently underpredict the absolute strength, with the missing strength found to have both isoscalar and isovector components., 7 pages, 5 figures. To be submitted to Physics Letters B

Published
2018

18. High-precision half-life measurement for the superallowed Fermi β+ emitter Mg22

Author

A. Diaz Varela, C. Burbadge, J. K. Smith, P. E. Garrett, K. G. Leach, Corina Andreoiu, A. D. MacLean, G. C. Ball, R. Caballero-Folch, N. Bernier, C.R. Natzke, B. Olaizola, M. R. Dunlop, V. Bildstein, M. Bowry, B. Jigmeddorj, R. Dunlop, J. Turko, Y. Saito, H. Bidaman, T. Zidar, G. Hackman, J. Measures, A. B. Garnsworthy, J. R. Leslie, and C. E. Svensson

Subjects
Physics, 010308 nuclear & particles physics, 0103 physical sciences, Half-life, Beta (velocity), Atomic physics, 010306 general physics, 01 natural sciences, Common emitter, Fermi Gamma-ray Space Telescope
Abstract

A high-precision half-life measurement for the superallowed Fermi ${\ensuremath{\beta}}^{+}$ emitter $^{22}\mathrm{Mg}$ was performed at the TRIUMF-ISAC facility using a $4\ensuremath{\pi}$ proportional gas counter. The result of ${T}_{1/2}=3.87400\ifmmode\pm\else\textpm\fi{}0.00079$ s is a factor of 3 more precise than the previously adopted world average and resolves a discrepancy between the two previously published $^{22}\mathrm{Mg}$ half-life measurements.

Published
2017

19. Spectroscopy ofSc50andab initiocalculations ofB(M3)strengths

Author

S. Georges, H. P. Patel, B. Olaizola, S. R. Stroberg, C. J. Pearson, Jason D. Holt, S. Cruz, C. E. Svensson, G. Hackman, A. D. MacLean, J. Measures, M. Bowry, and A. B. Garnsworthy

Subjects
Physics, Isovector, Spins, 010308 nuclear & particles physics, Isoscalar, Renormalization group, 01 natural sciences, Ab initio quantum chemistry methods, Excited state, 0103 physical sciences, Atomic physics, 010306 general physics, Spectroscopy, Order of magnitude
Abstract

The GRIFFIN spectrometer at TRIUMF-ISAC has been used to study excited states and transitions in $^{50}\mathrm{Sc}$ following the $\ensuremath{\beta}$ decay of $^{50}\mathrm{Ca}$. Branching ratios were determined from the measured $\ensuremath{\gamma}$-ray intensities, and angular correlations of $\ensuremath{\gamma}$ rays have been used to firmly assign the spins of excited states. The presence of an isomeric state that decays by an $M3$ transition with a $B(M3)$ strength of 13.6(7) W.u. has been confirmed. We compare the first ab initio calculations of $B(M3$) strengths in light- and medium-mass nuclei from the valence-space in-medium similarity renormalization group approach, using consistently derived effective Hamiltonians and effective $M3$ operator. The experimental data are well reproduced for isoscalar $M3$ transitions when using bare $g$ factors, but the strength of isovector $M3$ transitions are found to be underestimated by an order of magnitude.

Published
2017

20. List of Contributors

Author

B. Abbas, A. Abreu, R. Adams, M. Adolfsson-Erici, A. Afonso, C. Afonso-Olivares, E. Agirbas, J.M. Aguiló, L. Airoldi, H. Aksoy, M. Albentosa, L. Alcaro, S. Aliani, I. Al-Maslamani, C. Alomar, D. Altin, E. Álvarez, L.A. Amaral-Zettler, E. Amato, A. Anderson, A.L. Andrady, G. Andrius, D. Angel, F. Ariese, H.P. Arp, M. Asensio, K. Assidqi, C.G. Avio, U. Aytan, T. Bahri, M. Baini, A. Bakir, H. Ball, C. Baranyi, L.G.A. Barboza, U. Barg, L. Bargelloni, H. Barras, C. Barrera, P. Barria, A. Barrows, A. Barth, A. Batel, J. Baztan, P. Baztan, R. Beiras, M. Benedetti, A.A. Berber, N. Berber, M. Bergmann, M. Berlino, S. Berrow, F. Bessa, E. Besseling, B. Beyer, M. Binaglia, T. Bizjak, K.A. Bjorndal, R. Blust, M. Boertien, A.B. Bolten, A.M. Booth, B. Bounoua, P. Bourseau, N. Brahimi, M. Bramini, N. Brennholt, E. Breuninger, J. Bried, A. Broderick, E. Broglio, M.A. Browne, S. Bruzaud, J. Buceta, S. Buchinger, S. Budimir, H. Budzin-ski, E. Butter, J. Cachot, M. Caetano, A. Callaghan, A. Camedda, S. Capella, L. Cardelli, S. Carpentieri, A. Carrasco, R. Carriço, A. Caruso, A.-L. Cassone, A. Castillo, R.O. Castro, A.I. Catarino, P.W. Cazenave, İ. Çelik, P. Cerralbo, G. César, O. Chouinard, I. Chubarenko, I.P. Chubarenko, A.M. Cicero, G. Clarindo, B. Clarke, C. Clérandeau, M. Clüsener-Godt, M. Codina-García, M. Cole, F. Collard, A. Collignon, T. Collins, M. Compa, P. Conan, M. Constant, M. Cordier, W. Courtene-Jones, X. Cousin, P. Covelo, A. Cózar, E. Crichton, O. Crispi, M. Cronin, P.L. Croot, M.J. Cruz, G. d’Errico, C. Dâmaso, K. Das, L.F. de Alencastro, F.V. de Araujo, J.F. de Boer, G.A. de Lucia, P. Debeljak, A. Dehaut, S. Deudero, L. Devrieses, S. Di Vito, A. Díaz, J. Donohue, P. Doumenq, T.K. Doyle, R. Dris, J.-N. Druon, C.M. Duarte, G. Duflos, M. Dumontier, E. Duncan, C. Dussud, A. Eckerlebe, M. Egelkraut-Holtus, D.P. Eidsvoll, C. Ek, S. Elena, A. Elineau, H. Enevoldsen, G. Eppe, M. Eriksen, R. Ernsteins, M. Espino, N. Estévez-Calvar, C. Ewins, P. Fabre, M. Faimali, D. Fattorini, F. Faure, S. Ferrando, J.C. Ferreira, M. Ferreira-da-Costa, E. Fileman, M. Fischer, A.B. Fortunato, M.C. Fossi, V. Foulon, A. Frank, M. Frenzel, L. Frère, J.P.G.L. Frias, H. Frick, P.W. Froneman, V.M. Gabet, G.W. Gabrielsen, J. Gago, T. Gajst, F. Galgani, M. Gallinari, T.S. Galloway, E.G. Gamarro, C. Gambardella, F. Garaventa, S. Garcia, J. Garrabou, P. Garrido, S.F. Gary, J. Gasperi, W. Gaze, T. Geertz, M.D. Gelado-Caballero, M. George, J. Gercken, G. Gerdts, J.-F. Ghiglione, E. Gies, B. Gilbert, L. Giménez, D. Glassom, M. Glockzin, B. Godley, K. Goede, A. Goksøyr, M. Gómez, A. Gómez-Parra, D. González-Marco, J. González-Solís, S. Gorbi, E. Gorokhova, G. Gorsky, M. Gosch, J. Grose, G.M. Guebitz, R. Guedes-Alonso, B. Guijarro, L. Guilhermino, T. Gundry, L. Gutow, M. Haave, M. Haeckel, K. Haernvall, S. Hajbane, M. Hamann, J. Hämer, T. Hamm, B.H. Hansen, B.D. Hardesty, B. Harth, S. Hartikainen, M. Hassellöv, S. Hatzky, M.G. Healy, H. Hégaret, T.B. Henry, L. Hermabessiere, J.J. Hernández-Brito, A. Hernandez-Gonzalez, G. Hernandez-Milian, G. Hernd, A. Herrera, C. Herring, D. Herzke, S. Heussner, V. Hidalgo-Ruz, C. Himber, M. Holland, N.-H. Hong, A.A. Horton, P. Horvat, T. Huck, M. Huhn, A. Huvet, M. Iglesias, C. Igor, I.A. Isachenko, J-A. Ivar do Sul, A. Jahnke, B. Janis, K. Janis, U. Janis, A. Jemec, J.C. Jiménez, H. Johnsen, B. Jorgensen, J.H. Jørgensen, H. Jörundsdóttir, Y.-J. Jung, M. Kedzierski, S. Keiter, P. Kershaw, P. Kerhervé, K. Kesy, F. Khan, L.I. Khatmullina, J. Kirby, K. Kiriakoulakis, R. Klein, T. Klunderud, C.M.H. Knudsen, T.B. Knudsen, C. Kochleus, A.A. Koelmans, T. Kögel, A. Koistinen, K. Kopke, Š. Korez, N. Kowalski, B. Kreikemeyer, F. Kroon, T. Krumpen, A. Krzan, A. Kržan, M. Labrenz, C. Lacroix, L. Ladirat, C. Laforsch, F. Lagarde, E. Lahive, C. Lambert, C. Lapucci, G. Lattin, K.L. Law, F. Le Roux, K. Le Souef, V. Le Tilly, L. Lebreton, E. Leemans, M. Lehtiniemi, M. Lenz, J. Leskinen, H. Leslie, H.A. Leslie, C. Levasseur, C. Lewis, P. Licandro, K. Lind, P. Lindeque, P.K. Lindeque, I. Lips, A. Liria, A. Liria-Loza, O. Llinás, S.A. Loiselle, M. Long, C. Lorenz, S.M. Lorenzo, K. Loubar, G. Luna-Jorquera, A.L. Lusher, V. Macchia, S. MacGabban, K. Mackay, M. MacLeod, T. Maes, E. Magaletti, A. Maggiore, K. Magnusson, A.M. Mahon, P. Makorič, O. Mallow, J. Marques, L. Marsili, E. Martí, M. Martignac, J. Martin, I. Martínez, J. Martínez, M. Martinez-Gil, H.R. Martins, M. Matiddi, N. Maximenko, R. Mazlum, R. Mcadam, L. Mcknight, A.W. McNeal, J. Measures, M.S. Mederos, J. Mendoza, M.S. Meyer, A. Miguelez, M. Milan, T. Militão, R.Z. Miller, M. Mino-Vercellio-Verollet, G. Mir, D. Miranda-Urbina, F. Misurale, S. Montesdeoca-Esponda, J. Mora, S. Morgana, B. Moriceau, B. Morin, A. Morley, L. Morrison, F. Murphy, T. Naidoo, P. Näkki, I.E. Napper, B.E. Narayanaswamy, R. Nash, A. Negri, H.A. Nel, M.S. Nerheim, I.L. Nerland, J. Neto, V. Neves, H. Nies, M. Noel, N.H.M. Nor, F. Noren, B. O’ Connell, I. O’ Connor, J.P. Obbard, S. Oberbeckmann, R. Obispo, R. Officer, M. Ogonowski, A. Orbea, M. Ortlieb, A.M. Osborn, P. Ostiategui-Francia, T. Packard, S. Pahl, A. Palatinus, A. Palmqvist, P. Pannetier, C. Panti, E. Parmentier, P. Pasanen, T. Patarnello, C. Pattiaratchi, M. Pauletto, M. Paulus, K. Pavlekovsky, H.B. Pedersen, M.-L. Pedrotti, I. Peeken, D. Peeters, E. Peeters, D. Pellegrini, J.A. Perales, E. Perez, V. Perz, S. Petit, M. Pflieger, C.K. Pham, V. Piazza, M. Pinto, O. Planells, M. Plaza, O. Pompini, A. Potthoff, L. Prades, S. Primpke, M. Proietti, G. Proskurowski, C. Puig, M. Pujo-Pay, K. Pullerits, A.M. Queirós, B. Quinn, E. Raimonds, J. Ramis-Pujol, R. Rascher-Friesenhausen, E. Reardon, F. Regoli, A.M. Reichardt, G. Reifferscheid, K. Reilly, J. Reisser, I. Riba, D. Ribitsch, E. Rinnert, N. Rios, S.E. Rist, M.M. Rivadeneira, G. Rivière, J. Robbens, C.J.R. Robertson, V. Rocher, C.M. Rochman, M. Rodrigues, Y. Rodriguez, A. Rodríguez, G. Rodríguez, J.R.B. Rodríguez, S. Rodríguez, Y. Rodríguez, E. Rogan, E. Rojo-Nieto, T. Romeo, P.S. Ross, A. Roveta, S.J. Rowland, N.A. Ruckstuhl, A-C. Ruiz-Fernández, L.F. Ruiz-Orejón, J. Runge, M. Russell, C. Saavedra, R. Saborowski, B.E. Sahin, S. Sailley, K. Sakaguchi-Söder, I. Salaverria, A. Sánchez-Arcilla, J. Sánchez-Nieva, W. Sanderson, J.J. Santana-Rodríguez, S. Santana-Viera, M.B. Santos, M.R. Santos, M.R. Sanz, R. Sardá, H. Savelli, R. Schoeneich-Argent, B.M. Scholz-Böttcher, F. Sciacca, R.P. Scofield, O. Setälä, M. Selenius, R. Sempere, Y. Senturk, Y. Shashoua, P. Sherman, C. Sick, D. Siegel, J.P. Sierra, F. Silva, C. Silvestri, G. Sintija, O. Sire, B. Slat, A. Smit, P. Sobral, J. Sorvari, Z. Sosa-Ferrera, M.G. Sotillo, P. Soudant, L. Speidel, D.J. Spurgeon, M.K. Steer, C.C. Steindal, R. Stifanese, A. Štindlová, L. Stuurman, G. Suaria, C.G. Suazo, A. Sureda, C. Surette, C. Svendsen, K. Syberg, Z. Tairova, J. Talvitie, B. Tassin, M. Tazerout, M.B. Tekman, A. ter Halle, M. Thiel, K.V. Thomas, R.C. Thompson, T. Tinkara, V. Tirelli, P. Tomassetti, E. Toorman, J. Toppe, A. Tornambè, R. Torres, M.E. Torres-Padrón, A.J. Underwood, M. Urbina, A. Usategui-Martín, R. Usta, L. Valdés, A. Valente, T. Valentina, K. van Arkel, C. Van Colen, N. Van Der Hal, J.A. van Franeker, L. Van Herwerden, M. Van Loosdrecht, A. van Oyen, F. Vandeperre, J-P. Vanderlinden, D. Vani, L. Vasconcelos, D. Vega-Moreno, A. Ventero, A.D. Vethaak, A. Vianello, M. Vicioso, L.R. Vieira, M.K. Viršek, M. Vos, M. Wahl, N. Wallace, A. Walton, J.J. Waniek, A. Watts, L. Webster, C. Wesch, E. Whitfield, A. Wichels, A.M. Wieczorek, C. Wilcox, R.J. Williams, P. Wong-Wah-Chung, S. Wright, K.J. Wyles, R. Young, M. Yurtsever, U. Yurtsever, L. Zada, N.P. Zamani, and G. Zampetti

Published
2017

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