doi:10.1016/j.nima.2006.06.034 
Copyright © 2006 Elsevier B.V. All rights reserved.
Recoil-beta tagging: A novel technique for studying proton-drip-line nuclei
A.N. Steera, 
, 
, D.G. Jenkinsa, R. Glovera, B.S. Nara Singha, N.S. Pattabiramana, R. Wadswortha, S. Eeckhaudtb, T. Grahnb, P.T. Greenleesb, P. Jonesb, R. Julinb, S. Juutinenb, M. Leinob, M. Nymanb, J. Pakarinenb, 1, P. Rahkilab, J. Sarénb, C. Scholeyb, J. Sorrib, J. Uusitalob, P.A. Butlerc, I.G. Darbyc, R.-D. Herzbergc, D.T. Jossc, R.D. Pagec, J. Thomsonc, R. Lemmond, J. Simpsond and B. Blanke
aDepartment of Physics, University of York, Heslington, York YO10 5DD, UK
bDepartment of Physics, University of Jyväskylä, P.O. Box 35 (YFL), FI-40014, Finland
cOliver Lodge Laboratory, University of Liverpool, Liverpool L69 7ZE, UK
dCCLRC Daresbury Laboratory, Keswick Lane, Warrington WA4 4AD, UK
eCentre d’Etudes Nucléaires de Bordeaux-Gradignan, Le Haut-Vigneau, F-33175 Gradignan Cedex, France
Received 9 May 2006;
revised 31 May 2006;
accepted 1 June 2006.
Available online 10 July 2006.
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Abstract
Tagging with charged particles and γ-rays at the focal plane of recoil separators has proven, over the last two decades, to be a very powerful tool for the identification of excited states in exotic nuclei produced with very low cross-sections. One of the key areas so far unexplored in terms of the tagging methodology has been performing correlations with β-particles at the focal plane of a recoil separator. A new technique entitled Recoil-Beta Tagging (RBT) has been developed, this technique exploits the unusual properties of Fermi super-allowed β emitters, which have both a short half-life (
) and high β+-endpoint energy. Correlating with such β-particles using a double-sided silicon strip detector and planar germanium detector as an effective ΔE–E telescope for high-energy positrons has allowed a proof-of-principle of this technique to be carried out, by cleanly identifying excited states in the proton-drip-line nucleus, 74Rb.
Keywords: Recoil-beta tagging; 74Rb; Double-sided silicon strip detectors; Recoil separators
PACS classification codes: 27.50.+e; 29.30.Kv; 29.40.Wk
Fig. 1. A schematic drawing of GREAT showing the arrangement of the silicon and germanium detectors. The recoils implant in the DSSSDs after passing through the MWPC (not shown).
Fig. 2. A schematic side view drawing of GREAT showing recoiling nuclei implanting in the DSSSD, subsequent β-decay products are then detected in the PGD and Clover detectors.
Fig. 3. (Colour online). Energy loss in the MWPC vs. time of flight (arbitrary units), illustrating the excellent separation of reaction products from scattered beam.
Fig. 5. (Colour online). Highest energy of ionising particle recorded in the PGD vs. energy loss in the DSSSD.
Fig. 6. Spectra showing the reduction of contamination and statistics levels with β-particle energy gate reduction at 
: (a) 1–
, (b) 3–
, and (c) 6–10. The characteristic 2+→0+ 74Rb γ-ray transition is indicated by the dashed line.
Fig. 8. Plot showing the measured β-particle energy distribution detected in the PGD (bars), in comparison to the expected Fermi–Kurie distribution for a β+ emitter (solid line).
Fig. 9. Gamma-ray spectrum with β-particle energy between 3 and 
measured in the PGD, in addition to the 
time gate. Gamma-ray transitions associated with 74Rb are indicated. Previously unknown 74Rb transitions are marked by filled squares. Contaminants are marked by asterisks.
Fig. 10. Spectrum showing the event fold measured in the x strips of the PGD.
Fig. 11. Spectrum showing the 
peak detected in the PGD, the Compton background from the 
peak is also shown. The dashed lines indicate the gating condition placed on the PGD.
Table 1.
Beta decay properties of nuclei produced in the 36Ar+40Ca reaction at 
, including the reaction channel, half-life, and Q(EC) value, where known
Cross-sections were estimated using the fusion evaporation code, ALICE. This code overestimates the cross-section by a factor of 
20, however, the relative yields are in accordance with the observed experimental information.
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