Abstract
The region of the nuclear chart around neutron-rich A∼100 nuclei is one where prolate and oblate nuclear shapes are predicted to be in close competition. An indirect measurement of the shape of the nucleus can be obtained from measuring level lifetimes which relate, via transition rates, to β2 deformation. In order to make measurements of level lifetimes in the sub nanosecond range an array of 36 LaBr3(Ce) detectors has been constructed for use at the FAIR facility in Darmstadt, Germany. This presentation will give an overview of the array and examples of its use in commissioning experiments at the RIKEN Nishina Center in Japan and the Argonne National Laboratory in the USA.
Highlights
An array of 36 LaBr3 (Ce) detectors [1, 2] has been designed and procured for use at the FAIR facility in Germany
It uses detectors of diameter 38.1 mm and length 50.8 mm, a size selected as a balance between timing resolution and efficiency
Fission fragments were produced at the Radioactive Isotope Beam Factory, operated by the RIKEN Nishina Center and the Center of Nuclear Study, University of Tokyo using the inflight abrasion fission of a 238 U86+ beam of average intensity 6.24×1010 particles/s accelerated to an energy of 345 MeV/nucleon
Summary
An array of 36 LaBr3 (Ce) detectors [1, 2] has been designed and procured for use at the FAIR facility in Germany It uses detectors of diameter 38.1 mm and length 50.8 mm, a size selected as a balance between timing resolution (favouring smaller detectors) and efficiency (favouring larger detectors). Active Silicon Strip Stopper Array for β and Ion detection (WAS3ABi) [3], which detected ion implantations and their subsequent β-decay electrons. For this experiment, WAS3ABi comprised 5 layers of double-sided silicon-strip detectors placed 0.5 mm apart, each with 60 vertical and 40 horizontal strips of width and depth 1 mm. Deformations of ∼ 0.1 [8], but supports the conclusion that the neutron-rich Zr nuclei retain a prolate shape
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