.
A fast-timing method to determine lifetimes of nuclear states in the sub-nanosecond domain is presented. It is based on in-beam measurements of triple-gamma coincidences in heavy-ion ...fusion-evaporation reactions, performed with an array of HPGe and LaBr
3
:Ce detectors. The high-energy resolution HPGe detectors are used to define de-exciting cascades, while the fast LaBr
3
:Ce detectors are used to determine the decay time spectra of selected levels fed by these cascades. A special method to treat the time information of an array of fast detectors is employed in order to fully use the efficiency of the array. Two measurements are presented to illustrate the method: a re-determination of the known half-life
ns of the
keV,
level in
107
Cd (test experiment), and the determination of a half-life
ps for the
keV,
state of
199
Tl .
The ROSPHERE γ-ray spectroscopy array Bucurescu, D.; Căta-Danil, I.; Ciocan, G. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
11/2016, Letnik:
837
Journal Article
Recenzirano
The ROmanian array for SPectroscopy in HEavy ion REactions (ROSPHERE) has been designed as a multi-detector setup dedicated to γ-ray spectroscopy studies at the Bucharest 9MV Tandem accelerator. ...Consisting of up to 25 detectors (either Compton suppressed HPGe detectors or fast LaBr3(Ce) scintillator detectors) together with a state of the art plunger device, ROSPHERE is a powerful tool for lifetime measurements using the Recoil Distance Doppler Shift (RDDS) and the in-beam Fast Electronic Scintillation Timing (FEST) methods. The array's geometry, detectors, electronics and data acquisition system are described. Selected results from the first experimental campaigns are also presented.
We report on a gamma-ray coincidence analysis using a mixed array of hyperpure germanium and cerium-doped lanthanum tri-bromide (LaBr3:Ce) scintillation detectors to study nuclear electromagnetic ...transition rates in the pico-to-nanosecond time regime in 33,34P and 33S following fusion–evaporation reactions between an 18O beam and an isotopically enriched 18O implanted tantalum target. Energies from decay gamma-rays associated with the reaction residues were measured in event-by-event coincidence mode, with the measured time difference information between the pairs of gamma-rays in each event also recorded using the ultra-fast coincidence timing technique. The experiment used the good full-energy peak resolution of the LaBr3:Ce detectors coupled with their excellent timing responses in order to determine the excited state lifetime associated with the lowest lying, cross-shell, Iπ=4− “intruder” state previously reported in the N=19 isotone 34P. The extracted lifetime is consistent with a mainly single-particle M2 multipolarity associated with a f7/2→d5/2 single particle transition.
► Half-life measurements of nuclear states. ► Using fast-timing properties of (LaBr3:Ce) scintillator detectors. ► (LaBr3:Ce) scintillation detectors have an excellent timing resolution.
Isomerism of low-lying states in 86Y Rusu, C.; Bucurescu, D.; Mărginean, N. ...
The European physical journal. A, Hadrons and nuclei,
4/2010, Letnik:
44, Številka:
1
Journal Article
Recenzirano
Low-energy isomeric states of
86
Y were populated in the reaction
73
Ge +
16
O at 57MeV and were investigated by means of delayed n
and
coincidences. A half-life of 70(7)ns was measured for the 5
-
...state at 208keV, yielding an exceptionally small
B
(
M
1) value of 2.0(7)×10
-5
W.u. and a
B
(
E
2) value of 0.34(
+24
-13
) W.u. For the other three known isomeric states at 218, 243, and 302keV, the half-lives extracted from the present experimental data are in very good agreement with previous measurements. Given the newly observed isomeric character of the 5
-
208keV state, the re-analysis of earlier experimental data on the 302keV isomer led to a new spin-parity assignment, 6
+
, for this state. In addition, this re-evaluation provided two
g
-factors, -0.083(3) and +0.63(2) , for the 208 and 302keV states, respectively. The results are discussed in terms of spherical-shell model calculations performed with a truncated space of configurations built on the
f
5/2
,
p
3/2
,
p
1/2
, and
g
9/2
valence orbitals. Effective spin, orbital, and “tensor”
g
-factors were determined empirically for protons and neutrons in the considered configuration space.
In this work, the odd-mass 99-105Pd nuclei were studied via 90-96Zr(12,13C, xnγ) fusion/evaporation reactions. The beam was provided by the IFIN-HH Tandem accelerator at energies of approximately 50 ...MeV. Emitted gamma rays were detected by the hybrid multidetector system RoSphere. The structure of the low-lying excited states in 99-105Pd and their gamma-decay pattern are discussed in the framework of the rigid triaxial rotor plus particle model, providing a reasonable description of the low-lying level energies, electromagnetic transition rates, and magnetic moments.
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.
{gamma} rays were measured at several angles in both singles and coincidence mode in the {sup 119}Sn({alpha},n{gamma}){sup 122}Te reaction at 15 MeV on a thick target. Lifetimes of excited states in ...{sup 122}Te were determined from a Monte Carlo Doppler shift attenuation method (DSAM) analysis of the Doppler broadened lines shapes of {gamma} rays de-exciting the levels. A comparison of several deduced lifetimes with recent results obtained with the (n,n{sup '}) reaction allowed us to validate the choice of a parameter used to calculate the contribution of the side feeding times. The ingredients of the DSAM line-shape analysis (stopping power, description of instrumental line shapes, and side feeding evaluation) are presented in some detail. It is concluded that with proper treatment of side feeding, a DSAM line-shape analysis of peaks in singles or coincidence spectra obtained following the ({alpha},n{gamma}) reaction is able to provide rather accurate values for the lifetimes of levels with low and medium spins.
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