The GRIFFIN Facility for Decay-Spectroscopy Studies at TRIUMF-ISAC
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The GRIFFIN Facility for Decay-Spectroscopy Studies at TRIUMF-ISAC A.B. Garnsworthya,∗, C.E. Svenssonb, M. Bowrya, R. Dunlopb, A.D. MacLeanb, B. Olaizolaa, J.K. Smithc, F.A. Alib,d, C. Andreoiue, J.E. Ashg, W.H. Ashfieldc, G.C. Balla, T. Ballasta, C. Bartletta, Z. Beadlec, P.C. Bendera,1, N. Berniera,h, S.S. Bhattacharjeea, H. Bidamanb, V. Bildsteinb, D. Bishopa, P. Boubelb, R. Braidi, D. Brennana, T. Bruhna, C. Burbadgeb, A. Cheesemana, A. Chestere,2, R. Churchmana, S. Cicconea, R. Caballero-Folcha, D.S. Crosse, S. Cruza,h, B. Davidsa,f, A. Diaz Varelab, I. Dillmanna,j, M.R. Dunlopb, L.J. Evittsa,k,3, F.H. Garciae, P.E. Garrettb, S. Georgesa, S. Gillespiea, R. Gudapatia, G. Hackmana, B. Hadiniab, S. Hallama,4, J. Hendersona,5, S.V. Ilyushkini, B. Jigmeddorjb, A.I. Kilicb,6, D. Kisliukb,7, R. Kokkea, K. Kuhni, R. Kr¨uckena,h, M. Kuwabaraa, A.T. Laffoleyb, R. Lafleura, K.G. Leachi, J.R. Lesliel, Y. Linna, C. Lima, E. MacConnachiea, A.R. Mathewsa, E. McGeeb, J. Measuresa, D. Millera,8, W.J. Millsa, W. Moorei, D. Morrisa, L.N. Morrisona,4, M. Moukaddama,4, C.R. Natzkei, K. Ortnere, E. Padilla-Rodalm, O. Paetkaua, J. Parka,h,9, H.P. Patela, C.J. Pearsona, E. Petersa, E.E. Petersn, J.L. Poree,10, A.J. Radichb, M.M. Rajabalig, E.T. Randb, K. Raymonde, U. Rizwane, P. Ruotsalainena,11, Y. Saitoa,h, F. Sarazini, B. Shawa, J. Smallcombea,12, D. Southalla,13, K. Starostae, M. Ticue, E. Timakovaa, J. Turkob, R. Umashankara, C. Unswortha,12, Z.M. Wange,a, K. Whitmoree, S. Wonga, S.W. Yatesn,o, E.F. Zganjarp, T. Zidarb aTRIUMF, 4004 Wesbrook Mall, Vancouver, BC, V6T 2A3, Canada bDepartment of Physics, University of Guelph, Guelph, ON, Canada, N1G 2W1 cDepartment of Physics, Reed College, Portland, OR 97202, USA dDepartment of Physics, College of Education, University of Sulaimani, P.O. Box 334, Sulaimani, Kurdistan Region, Iraq eDepartment of Chemistry, Simon Fraser University, Burnaby, BC, V5A 1S6, Canada fDepartment of Physics, Simon Fraser University, Burnaby, BC, V5A 1S6, Canada gDepartment of Physics, Tennessee Technological University, Cookeville, TN 38505, USA hDepartment of Physics and Astronomy, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada iDepartment of Physics, Colorado School of Mines, Golden, CO 80401, USA jDepartment of Physics and Astronomy, University of Victoria, Victoria, British Columbia V8P 5C2, Canada kDepartment of Physics, University of Surrey, Guildford, Surrey, GU2 7XH, UK lDepartment of Physics, Queen's University, Kingston, ON, K7L 3N6, Canada mUniversidad Nacional Aut´onomade M´exico, Instituto de Ciencias Nucleares, AP 70-543, M´exico City 04510, DF, M´exico nDepartment of Chemistry, University of Kentucky, Lexington, Kentucky 40506-0055, USA oDepartment of Physics & Astronomy, University of Kentucky, Lexington, Kentucky 40506-0055, USA pDepartment of Physics and Astronomy, Louisiana State University, Baton Rouge, LA 70803, USA 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. arXiv:1809.07183v2 [physics.ins-det] 6 Dec 2018 Keywords: HPGe, Decay spectroscopy, TRIUMF, ISAC Physics, University of Massachusetts Lowell, Lowell, MA ∗Corresponding author: 4004 Wesbrook Mall, Vancouver, 01854, USA BC, V6T 2A3, Canada 2Present Address: TRIUMF, 4004 Wesbrook Mall, Van- Email address: [email protected] (A.B. Garnsworthy) couver, BC, V6T 2A3, Canada 1Present Address: Department of Physics and Applied 3Present Address: Nuclear Futures Institute, Bangor Uni- Preprint submitted to Nuclear Instruments and Methods A December 10, 2018 1. Introduction array of eight LaBr3(Ce) scintillators and a fast β scintillator for fast-timing measurements. Two Large arrays of detectors for γ-ray measurements possible configurations of the GRIFFIN array and coupled with auxiliary particle detection systems the ancillary detectors are shown in Figure 1. In provide a powerful and versatile tool for studying addition, GRIFFIN can couple to the DESCANT exotic nuclei through nuclear spectroscopy at ra- array [21, 22] of neutron detectors for β-delayed dioactive ion beam facilities. Decay spectroscopy neutron emission studies with exotic neutron-rich experiments are performed at a number of radioac- beams. This powerful combination of detectors to tive beam facilities world-wide, such as with the be used with the radioactive-ion beams from ISAC EURICA setup at RIKEN [1], the beta counting and in the future the Advanced Rare-IsotopE Lab- station at NSCL [2], the X-Array and SATURN at oratory (ARIEL) [11], supports a broad program of ANL [3], the ISOLDE decay station [4], the implan- research in the areas of nuclear structure, nuclear tation and decay station at Lanzhou [5], the identi- astrophysics, and fundamental interactions. fication station at SPIRAL [6] and in the past the The data acquisition (DAQ) system for GRIFFIN RISING setup at GSI [7, 8] which is transitioning to takes advantage of custom-designed digital elec- DESPEC at FAIR [9]. Gamma-Ray Infrastructure tronics [23]. Unique features of the DAQ system For Fundamental Investigations of Nuclei, GRIF- enable half-life and branching ratio measurements FIN [10], is a new experimental facility for radioac- with levels of precision better than ±0.05%. The tive decay studies at the TRIUMF-ISAC laboratory system is also capable of effectively collecting sig- [11] located in Vancouver, Canada. nals from HPGe crystals at counting rates up to GRIFFIN is used for decay spectroscopy research 50 kHz while maintaining good energy resolution, with stopped low-energy radioactive ion beams. detection efficiency and spectral quality [23]. High γ-ray detection efficiency provided by an ar- This article provides a full description of the in- ray of sixteen Compton-suppressed high-purity ger- frastructure and detectors of the GRIFFIN spec- manium (HPGe) clover detectors [12] is combined trometer as well as the performance characteristics with a suite of ancillary detection systems. Many and includes a discussion of the analysis techniques of the ancillary detector systems, infrastructure and applied to the experimental data. Section 2 details techniques used with GRIFFIN were originally de- the infrastructure of the facility and Section 3 de- veloped for use with the 8π spectrometer during scribes the detector hardware. Typical data anal- its 11 years of operation at ISAC [13{20]. These ysis techniques are discussed in Section 4 together include an array of plastic scintillators for β parti- with the performance achieved with the spectrom- cle detection (SCEPTAR), a set of five in-vacuum eter. Finally, Section 5 presents a look towards fu- LN2-cooled lithium-drifted silicon detectors for con- ture development plans, and a summary is given in version electron measurements (PACES), and an Section 6. versity, Dean Street, Bangor, Gwynedd, LL57 1UT, UK 4Present Address: Department of Physics, University of 2. Infrastructure Surrey, Guildford, Surrey, GU2 7XH, UK 5Present Address: Lawrence Livermore National Labora- 2.1. Beamline and Tape Box tory, 7000 East Ave, Livermore, CA 94550, USA 6Present Address: Nuclear Physics Institute of ASCR, The GRIFFIN spectrometer is used to study the 250 68 Re˘z.Prague,˘ Czech Republic decay of stopped radioactive ion beams produced by 7 Present Address: Department of Physics, University of the ISOL (isotope separation on-line) method. The Toronto, Toronto, ON M5S 1A7, Canada 8Present Address: Idaho National Laboratory, Idaho beam is delivered at a typical energy of 20 to 40 keV. Falls, Idaho 83415, USA. The low energy beam transport (LEBT) beamlines 9Present Address: Department of Physics, Lund Univer- [24] use exclusively electrostatic bending and focus- sity, 22100 Lund, Sweden ing elements. Pressures of <3×10−7 Torr are typi- 10Present Address: Lawrence Berkeley National Labora- tory, Berkeley, CA 94720, USA cal for the beamlines leading to GRIFFIN. The fi- 11Present Address: University of Jyv¨askyl¨a,Department nal beam focus at GRIFFIN is typically <3 mm in of Physics, P.O. Box 35, FI-40014 Jyv¨askyl¨a,Finland diameter with a transverse, 2σ emittance of 10 µm. 12 Present Address: Oliver Lodge Laboratory, The Univer- Vacuum in the GRIFFIN chamber is provided sity of Liverpool, Liverpool, L69 7ZE, UK 13Present Address: Department of Physics, University of by an Agilent Varian Turbo-V 1000HT turbo- Chicago, Chicago, Illinois 60637, USA molecular pump located 95 cm from the array cen- 2 Figure 1: Two possible configurations of the GRIFFIN spectrometer. The beam is delivered from the left. The Pb wall shielding the tape box can be seen on the right. Upper panel showing PACES in the upstream (left) half of the chamber and the fast β scintillator in the downstream (right) chamber. In the ‘High-efficiency’ mode, the HPGe detectors are at 11 cm and the LaBr3(Ce) detectors at 12.5 cm from the implantation point on the tape. Lower panel with SCEPTAR in the upstream and downstream chambers. In the `Optimized peak-to-total' mode, the HPGe and LaBr3(Ce) detectors are retracted to 14.5 cm and 13.5 cm, respectively, in order that they can be fully Compton and background suppressed with BGO shields. The 20 mm Delrin absorber is also installed in the lower panel. 3 tre on the upstream side, and an Oerlikon Ley- bold TurboVac 361 turbo-molecular pump located 160 cm downstream of the array centre in the tape box.