A new differentially pumped plunger device to measure excited-state lifetimes in proton emitting nuclei M.J. Taylor a,n , D.M. Cullen a , A.J. Smith a , A. McFarlane a , V. Twist a , G.A. Alharshan a , M.G. Procter a , T. Braunroth b , A. Dewald b , E. Ellinger b , C. Fransen b , P.A. Butler c , M. Scheck c , D.T. Joss c , B. Saygi c , C.G. McPeake c , T. Grahn d , P.T. Greenlees d , U. Jakobsson d , P. Jones d , R. Julin d , S. Juutinen d , S. Ketelhut d , M. Leino d , P. Nieminen d , J. Pakarinen d , P. Peura d , P. Rahkila d , P. Ruotsalainen d , M. Sandzelius d , J. Sare ´n d , C. Scholey d , J. Sorri d , S. Stolze d , J. Uusitalo d a School of Physics & Astronomy, Schuster Laboratory, The University of Manchester, Manchester M13 9PL, UK b Institut f¨ ur Kernphysik der Universit¨ at zu K¨ oln, Cologne, Germany c Department of Physics, University of Liverpool, Liverpool L69 7ZE, UK d Accelerator Laboratory, Department of Physics, University of Jyv¨ askyl¨ a, Jyv¨ askyl¨ a FIN-40014, Finland article info Article history: Received 28 November 2012 Received in revised form 19 December 2012 Accepted 21 December 2012 Available online 8 January 2013 Keywords: Plunger Excited-state lifetimes 134 Nd Proton-emitting nuclei RDDS DDCM Gas mode Vacuum mode abstract A new plunger device has been designed and built to measure the lifetimes of unbound states in exotic nuclei beyond the proton drip-line. The device has been designed to work in both vacuum and dilute- gas environments made possible through the introduction of a low-voltage stepping motor. DPUNS will be used in conjunction with the gas-filled separator RITU and the vacuum separator MARA at the accelerator laboratory of the University of Jyv ¨ askyl ¨ a, Finland, to measure the lifetimes of excited states with low population cross-sections. This is achieved by eliminating the need for a carbon foil to isolate the helium gas of RITU from the beam line thus reducing the background from beam-foil reactions. The inclusion of a high-sampling rate data acquisition card increases further the sensitivity of the device. The plunger will be used to address many key facets of nuclear structure physics with particular emphasis on the effect of deformation on proton emission rates. & 2013 Elsevier B.V. All rights reserved. 1. Introduction and motivation The study of proton emission is key to the understanding of drip-line nuclei far from the valley of stability. Structure information on these exotic proton-emitting nuclei is usually extracted from a comparison between the measured half-life and that determined theoretically. Decay lifetimes calculated within simple barrier penetration models [1] agree fairly well with those measured in near-spherical nuclei but more sophisticated models are required for deformed nuclei [2,3]. Proton emission rates are highly sensitive to nuclear deformation but in all known cases the deformation has never been experimentally determined. Cur- rently, proton emission calculations rely on theoretically deter- mined deformations [4] making experimentally determined values highly sought after for these theoretical models. To address this logical weakness a new plunger device, DPUNS (Differential Plunger for Unbound Nuclear States), has been developed to measure the lifetimes of low-lying excited states in proton emitting nuclei. Nuclei exhibiting ground-state proton emission have very low production cross-sections making lifetime mea- surements experimentally challenging. In addition to a plunger device, the production of clean excited-state lifetime spectra for proton emitting nuclei requires high efficiency proton and g-ray spectrometers along with a highly selective recoil separator possessing excellent transmission efficiency. In order to measure excited-state lifetimes in these weakly populated nuclei with reasonable certainty a new dedicated plunger device, that was optimised for use with high-efficiency gas-filled recoil separators, has been developed. The accurate determination of excited-state lifetimes above proton emitting states can be used to evaluate the extent of deformation in the system. With the aid of state-of-the-art theoretical models [2,5–9], decay half-lives can be calculated for the measured deformation and compared with those determined experimentally. This study will, therefore, test and improve current models and help to shed light on the effect of deformation Contents lists available at SciVerse ScienceDirect journal homepage: www.elsevier.com/locate/nima Nuclear Instruments and Methods in Physics Research A 0168-9002/$ - see front matter & 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.nima.2012.12.120 n Corresponding author. Tel.: þ44 1612754231. E-mail address: m.j.taylor@manchester.ac.uk (M.J. Taylor). Nuclear Instruments and Methods in Physics Research A 707 (2013) 143–148