A time-of-flight correction procedure for fast-timing data of recoils with varying implantation positions at a spectrometer focal plane

M. J. Mallaburn, B. S. Nara Singh, D. M. Cullen, D. Hodge, M. J. Taylor, M. M. Giles, L. Barber, C. R. Niţă, R. E. Mihai, C. Mihai, R. Mărginean, N. Mărginean, C. R. Nobs, E. R. Gamba, A. M. Bruce, C. Scholey, P. Rahkila, P. T. Greenlees, H. Badran, T. GrahnO. Neuvonen, K. Auranen, F. Bisso, D. M. Cox, A. Herzáň, R. Julin, J. Konki, A. K. Lightfoot, J. Pakarinen, P. Papadakis, J. Partanen, M. Sandzelius, J. Sarén, J. Sorri, S. Stolze, J. Uusitalo, P. H. Regan, Zs Podolyák, S. Lalkovski, J.F. Smith, M. Smolen

Research output: Contribution to journalArticle

Abstract

Fast-timing measurements at the focal plane of a separator can suffer from poor timing resolution. This is due to the variations in time-of-flight (ToF) for photons travelling to a given detector, which arise from the changes in the implantation positions of the recoil nuclei emitting the γ rays of interest. In order to minimise these effects on timing measurements, a procedure is presented that improves fast-timing data by performing ToF corrections on an event-by-event basis. This method was used to correct data collected with an array of eight LaBr3 detectors, which detected γ rays from spatially distributed 138Gd recoil-implants at the focal plane of the Recoil-Ion-Transport-Unit (RITU) spectrometer. The Generalised Centroid Difference (GCD) method was used to extract a lifetime from data in conjunction with a new procedure to calibrate the time walk. The lifetime of the first 2+ state in 138Gd, populated by the decay of the Kπ=8 isomeric state, was measured to be 229(24) ps using the ToF-corrected data, which is consistent within three standard deviations to the literature value. The results together with Monte-Carlo simulations show that the ToF correction procedure reduced the uncertainty in the measured lifetimes by 3 % in the case of the spatially distributed nuclei at the focal plane of RITU. However, ∼12 % has been estimated for a similar experiment when using a larger focal plane i.e. the Super-FRS at the FAIR facility.

Original languageEnglish
Pages (from-to)18-29
Number of pages12
JournalNuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
Volume933
DOIs
Publication statusPublished - 9 Apr 2019

Keywords

  • Gd
  • Distributed source
  • Fast-timing
  • Generalised-centroid-difference method
  • LaBr detectors
  • Nuclear-state lifetimes

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