Abstract
A range of high resolution gamma-ray spectroscopy measurements have been carried out using arrays which include a number of Cerium-doped Lanthanum-Tribromide (LrBr3(Ce)) scintillation detectors used in conjunction with high-resolution hyper-pure germanium detectors. Examples of the spectral and temporal responses of such set-ups, using both standard point radioactive sources 152Eu and 56Co, and in-beam fusionevaporation reaction experiments for precision measurements of nuclear excited states in 34P and 138Ce are presented. The current and future use of such arrays at existing (EURICA at RIKEN) and future (NUSTAR at FAIR) secondary radioactive beam facilities for precision measurements of excited nuclear state lifetimes in the 10 ps to 10 ns regime are also discussed.
Highlights
This conference paper presents examples of the performance of arrays of LaBr3 detectors using in coincindence to determine lifetimes of nuclear excited states in the 10−11 → 10−9s regime and presents future plans for the use of a highly modular array of such detectors for use at the focal plane of radioactive beam fragmentation separator devices such as BigRIPS at RIKEN and the SuperFRS at the proposed FAIR facility
The main engine for such measurements has been the use of discreteline coincident spectroscopy between signals measured in LaBr3 gamma-ray detectors, which are shown to couple excellent timing capabilities with acceptable energy resolution for in-beam spectroscopic studies of nuclear structure
Future programmes include the utilisation of a compact, high-efficiency array of LaBr3 detectors as part of the DESPEC-FATIMA collaboration within the NUSTAR project at FAIR
Summary
One way to extract the electromagnetic reduced matrix elements, B(Mλ), is via the measurement of nuclear excited state lifetimes, where the transition probability, T fi(λL) for a state decaying from a state with initial spin. Principal decay time (ns) 230 0.6 ; 620 16 17 not approaching that of germanium, is significantly improved over previous generation scintillation detector materials for gamma-ray spectroscopy, such as barium fluoride BaF2 or sodium iodide (NaI(Tl) The use of such materials has allowed the measurement of lifetimes of excited nuclear states using the delayed coincidence method with LaBr3 detectors [14, 16,17,18]. A summary of the approximate light outputs and timing characteristics for various scintillation materials available for nuclear spectroscopy is given in the table below This conference paper presents examples of the performance of arrays of LaBr3 detectors using in coincindence to determine lifetimes of nuclear excited states in the 10−11 → 10−9s regime and presents future plans for the use of a highly modular array of such detectors for use at the focal plane of radioactive beam fragmentation separator devices such as BigRIPS at RIKEN and the SuperFRS at the proposed FAIR facility.
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