Miniball experiment

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Isotope Separator On Line Device
(ISOLDE)
List of ISOLDE experimental setups
COLLAPS, CRIS, EC-SLI, IDS, ISS, ISOLTRAP, LUCRECIA, Miniball, MIRACLS, SEC, VITO, WISArD
Other facilities
MEDICISMedical Isotopes Collected from ISOLDE
508Solid State Physics Laboratory
Miniball experimental setup at the ISOLDE facility (CERN)

The Miniball experiment is a gamma-ray spectroscopy setup regularly located in the ISOLDE facility at CERN, along with other locations including GSI, Cologne, PSI and RIKEN (HiCARI).[1][2][3][4] Miniball is a high-resolution germanium detector array, specifically designed to work with low-intensity radioactive ion beams (RIB) post-accelerated by HIE-ISOLDE (High Intensity and Energy-ISOLDE), to analyse the decays of short-lived nuclei with the capability of Doppler correction. The array has been used for successful Coulomb-excitation and transfer-reaction experiments with exotic RIBs. Results from Miniball experiments have been used to determine and probe nuclear structure.[5]

Miniball has been operational at the REX-ISOLDE (Radioactive ion beam EXperiment-ISOLDE) post accelerator at CERN since 2001.[6] In 2015, it became part of the HIE-ISOLDE project, connected via the XT01 beamline.[7] It was the first fully operational spectrometer to determine gamma-ray position using germanium detectors and pulse shape analysis.[8]

Background[edit]

The two techniques used for experiments using the Miniball setup at ISOLDE are Coulomb excitation and transfer-reactions.

Coulomb excitation is a technique used to probe the electromagnetic (EM) aspect of nuclear structure. A nucleus is excited by an inelastic collision with another nucleus at a "safe" scattering angle, to ensure its via purely EM interaction. The nucleus then decays to a lower state, emitting a gamma-ray which can be detected using gamma detectors.[9] This method is useful for investigating collectivity in nuclei (motion of individual nucleons are correlated), as collective excitations are often connected by electric quadrupole transitions.[10]

Transfer reaction of projectile and target nucleus

During transfer reactions, one (or a cluster) of nucleons are exchanged between the target nucleus and the projectile, resulting in a different final state nucleus.[11] Measurements of the emission angle and energy for use in two-body kinematic calculations can give the excitation energy of the populated states in the final state nucleus. Additionally, the measured angular distributions are compared to theory to deduce the transferred orbital angular momentum in the reaction. For single-nucleon transfer, this indicates the orbital that the nucleon has been transferred into. Studying transfer reactions is useful in nuclear astrophysics as it replicates stellar evolution and can test theoretical models.[12]

Experimental setup[edit]

Overhead view of the Miniball set up

The Miniball detector array consists of 24 high-purity germanium crystals which have a tapered front end.[8] They have a six-fold segmentation, differing them from other detectors at the time (e.g. EUROBALL), which are coupled to preamplifiers.[13] The crystals are sealed in a aluminium can, allowing access of the cold electronics without the use of a cleanroom, as the can did not need to be broken in to.[6][5]

Each capsule is used to pack together clusters of three six-fold detectors. Housing each cluster are cryostats using liquid nitrogen, which give clusters a common vacuum chamber, cryostat and dewar. Configurations of the clusters can be arranged to provide solid angle coverage in a compact configuration, but this requires flexibility in the setup.[14] At ISOLDE, Miniball achieves this by mounting cryostats on half-circular, rotatable arms with the ability for continuous motion along the arms.[5] At other locations, differing amounts of clusters are arranged in different configurations, in order to achieve different results.[15]

CD detector used at Miniball at CERN

The T-REX (Transfer at REX) setup is designed for measuring transfer reactions at the Miniball detector. The setup consists of a silicon barrel with forward and backward CD detectors, covering a solid angle of 66% of 4π. The T-REX measures the angular distribution of the light reaction products.[11]

Miniball uses digital pulse processing by using real-time digital filter algorithms to produce results for energy and time. The data acquisition and analysis system consists of a front-end system for data readout and transport, and a back-end system for control and data analysis.[1]

Results[edit]

In 2013, results from the Miniball experiment at ISOLDE was named in the Institute of Physics (IoP) "top 10 breakthroughs in physics".[16] The research found evidence of pear-shaped heavy nuclei, in particular in radon-220 and radium-224.[17] The breakthrough was also featured as the cover of Nature 2013.[18]

The main experimental technique used with Miniball is low energy Coulomb excitation. Results from using this technique have resulted in numerical values for the electric-dipole, quadrupole and octupole moments of the transitions.[19] The technique of transfer-reactions is also used in Miniball experiments.[11] The "island of inversion" nucleus 32Mg was of particular interest for experiments, which could be studied using transfer-reactions (as well as with Coulomb excitation).[20][6]

External links[edit]

References[edit]

  1. ^ a b Reiter, P.; Eberth, J.; Faust, H.; Franchoo, S.; Gerl, J.; Gund, C.; Habs, D.; Huyse, M.; Jungclaus, A.; Lieb, K. P.; Scheit, H.; Schwalm, D.; Thomas, H. G.; van Duppen, P.; Weisshaar, D. (2002-04-22). "The MINIBALL array". Nuclear Physics A. 5th International Conference on Radioactive Nuclear Beams. 701 (1): 209–212. Bibcode:2002NuPhA.701..209R. doi:10.1016/S0375-9474(01)01576-7. ISSN 0375-9474.
  2. ^ "Miniball documentation page". www.ikp.uni-koeln.de. Retrieved 2023-08-11.
  3. ^ "muX | LTP | Paul Scherrer Institut (PSI)". www.psi.ch. Retrieved 2023-08-16.
  4. ^ Wimmer, K; Doornenbal, P; Aoi, N; Baba, H; Browne, F; Campbell, C; Crawford, H; De Witte, H; Fransen, C; Hess, H; Iwazaki, S; Kim, J; Kohda, A; Koiwai, T; et al. (2021). "HiCARI: High-resolution Cluster Array at RIBF" (PDF). RIKEN Accelerator Progress Report. 54.
  5. ^ a b c Warr, N.; Van de Walle, J.; Albers, M.; Ames, F.; Bastin, B.; Bauer, C.; Bildstein, V.; Blazhev, A.; Bönig, S.; Bree, N.; Bruyneel, B.; Butler, P. A.; Cederkäll, J.; Clément, E.; Cocolios, T. E. (March 2013). "The Miniball spectrometer". The European Physical Journal A. 49 (3): 40. Bibcode:2013EPJA...49...40W. doi:10.1140/epja/i2013-13040-9. ISSN 1434-6001.
  6. ^ a b c Reiter, P.; Warr, N. (2020-07-01). "Nuclear structure studies with re-accelerated beams at REX-and HIE-ISOLDE". Progress in Particle and Nuclear Physics. 113: 103767. Bibcode:2020PrPNP.11303767R. doi:10.1016/j.ppnp.2020.103767. ISSN 0146-6410. S2CID 213422435.
  7. ^ Borge, M. J. G.; Riisager, K. (2016-11-17). "HIE-ISOLDE, the project and the physics opportunities". The European Physical Journal A. 52 (11): 334. Bibcode:2016EPJA...52..334B. doi:10.1140/epja/i2016-16334-4. ISSN 1434-601X. S2CID 254112292.
  8. ^ a b Schwalm, D. (March 2005), "First Experiments with Rex-Isolde and Miniball", Key Topics in Nuclear Structure, World Scientific, pp. 21–34, Bibcode:2005ktns.conf...21S, doi:10.1142/9789812702265_0003, ISBN 978-981-256-093-3, retrieved 2023-08-02
  9. ^ Zielinska, Magda (27 Jan 2016). "Theoretical description of low-energy Coulomb excitation" (PDF). indico.cern. Retrieved 2 Aug 2023.
  10. ^ Clément, E.; Zielińska, M.; Péru, S.; Goutte, H.; Hilaire, S.; Görgen, A.; Korten, W.; Doherty, D. T.; Bastin, B.; Bauer, C.; Blazhev, A.; Bree, N.; Bruyneel, B.; Butler, P. A.; Butterworth, J. (2016-11-28). "Low-energy Coulomb excitation of Sr 96 , 98 beams". Physical Review C. 94 (5): 054326. Bibcode:2016PhRvC..94e4326C. doi:10.1103/PhysRevC.94.054326. hdl:10852/66640. ISSN 2469-9985.
  11. ^ a b c T-REX Collaboration; Bildstein, Vinzenz; Gernhäuser, Roman; Kröll, Thorsten; Krücken, Reiner; Wimmer, Kathrin; Van Duppen, Piet; Huyse, Mark; Patronis, Nikolas; Raabe, Riccardo (June 2012). "T-REX: A new setup for transfer experiments at REX-ISOLDE". The European Physical Journal A. 48 (6): 85. Bibcode:2012EPJA...48...85B. doi:10.1140/epja/i2012-12085-6. ISSN 1434-6001. S2CID 119716833.
  12. ^ Ingeberg, V W; Siem, S; Wiedeking, M; Choplin, A; Goriely, S; Siess, J; Abrahams, Arnswald; Bello Garrote, F; Bleuel, D L; Cederkall, J; Christoffersen, T L; Cox, D M; De Witte, H; Gaffney, L P; Gorgen, A (14 Jul 2023). "Nuclear Level Density and γ-ray Strength Function of 67Ni and the impact on the i-process". arXiv:2307.07153 [nucl-ex].
  13. ^ Thirolf, P G; Habs, D; Rudolph, D; Fischbeck, C; Schwalma, D; Ebethb, J; Gutknechtc, D. "The MINIBALL-Project". {{cite journal}}: Cite journal requires |journal= (help)
  14. ^ Butler, P A; Cederkall, J; Reiter, P (2017-04-01). "Nuclear-structure studies of exotic nuclei with MINIBALL". Journal of Physics G: Nuclear and Particle Physics. 44 (4): 044012. Bibcode:2017JPhG...44d4012B. doi:10.1088/1361-6471/aa5c4e. ISSN 0954-3899.
  15. ^ "Nuclear structure > Research > ibs". centers.ibs.re.kr. Retrieved 2023-08-11.
  16. ^ iopp (2013-12-13). "Top 10 physics breakthroughs for 2013 announced". IOP Publishing. Retrieved 2023-08-11.
  17. ^ "Nuclear physics goes pear-shaped". Physics World. 2013-05-08. Retrieved 2023-08-11.
  18. ^ "Nature - Volume 497 Issue 7448, 9 May 2013". Nature. 2013-05-08. Retrieved 2023-08-11.
  19. ^ Van Duppen, P; Riisager, K (2011-02-01). "Physics with REX-ISOLDE: from experiment to facility". Journal of Physics G: Nuclear and Particle Physics. 38 (2): 024005. Bibcode:2011JPhG...38b4005V. doi:10.1088/0954-3899/38/2/024005. ISSN 0954-3899. S2CID 123521877.
  20. ^ Wimmer, K.; Kröll, T.; Krücken, R.; Bildstein, V.; Gernhäuser, R.; Bastin, B.; Bree, N.; Diriken, J.; Van Duppen, P.; Huyse, M.; Patronis, N.; Vermaelen, P.; Voulot, D.; Van de Walle, J.; Wenander, F. (2010-12-13). "Discovery of the Shape Coexisting 0 + State in Mg 32 by a Two Neutron Transfer Reaction". Physical Review Letters. 105 (25): 252501. arXiv:1010.3999. Bibcode:2010PhRvL.105y2501W. doi:10.1103/PhysRevLett.105.252501. ISSN 0031-9007. PMID 21231582. S2CID 43334780.
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