A detector for filtering gamma-ray spectra from weak fusion-evaporation reactions out of strong background and for Doppler correction: the recoil filter detector, RFD

W. Meczynski, P. Bednarczyk, J. Grebosz, J. Heese, M. Janicki, K.H. Maier, J.C. Merdinger, K.M. Spohr, M. Zieblinski, J. Styczen

Research output: Contribution to journalArticlepeer-review

12 Citations (Scopus)

Abstract

A detector has been designed and built to assist in-beam γ-ray spectroscopy with fusion–evaporation reactions. It measures with high efficiency the evaporation residues that recoil out of a thin target into the angular interval from 1.8° to 9.0° at an adjustable distance of 1000–1350 mm from a target, in coincidence with γ-rays detected in a Ge-detector array. This permits filtering of such γ-rays out of a much stronger background of other reaction products and scattered beam. Evaporation residues are identified by their time-of-flight and the pulse height using a pulsed beam. The velocity vector of the γ-emitting recoil is also measured in the event-by-event mode, facilitating to correct the registered γ-ray energy for the Doppler shift, with the resulting significant improvement of the energy resolution. The heavy-ion detection scheme uses emission of secondary electrons caused by the recoiling ions when hitting a thin foil. These electrons are then electrostatically accelerated and focused onto a small scintillator that measures the summed electron energy, which is proportional to the number of electrons. The detector is able to operate at high frequency of the order of 1 MHz and detect very heavy nuclei with as low kinetic energy as 5 MeV. The paper describes the properties of the detector and gives examples of measurements with the OSIRIS, GAREL+ and EUROBALL IV γ-ray spectrometers. The usefulness of the technique for spectroscopic investigations of nuclei with a continuous beam is also discussed.
Original languageEnglish
Pages (from-to)1310-1326
Number of pages17
JournalNuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
Volume580
Issue number3
DOIs
Publication statusPublished - 11 Oct 2007

Keywords

  • In-beam γ-ray spectroscopy
  • Evaporation residue detection
  • Doppler shift correction

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