AGATA is a modern
γ
-ray spectrometer for in-beam nuclear structure studies, based on
γ
-ray tracking. Since more than a decade, it has been operated performing experimental physics campaigns in ...different international laboratories (LNL, GSI, GANIL). This paper reviews the obtained results concerning the performances of
γ
-ray tracking in AGATA and associated algorithms. We discuss
γ
-ray tracking and algorithms developed for AGATA. Then, we present performance results in terms of efficiency and peak-to-total for AGATA. The importance of the high effective angular resolution of
γ
-ray tracking arrays is emphasised, e.g. with respect to Doppler correction. Finally, we briefly touch upon the subject of
γ
-ray imaging and its connection to
γ
-ray tracking.
Dual Position Sensitive MWPC for tracking reaction products at VAMOS Vandebrouck, M.; Lemasson, A.; Rejmund, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
03/2016, Letnik:
812
Journal Article
Recenzirano
Odprti dostop
The characteristics and performance of a Dual Position Sensitive Multi-Wire Proportional Counter (DPS-MWPC) used to measure the scattering angle, the interaction position on the target and the ...velocity of reaction products detected in the VAMOS++ magnetic spectrometer, are reported. The detector consists of a pair of position sensitive low pressure MWPCs and provides both fast timing signals, along with the two-dimensional position coordinates required to define the trajectory of the reaction products. A time-of-flight resolution of 305(11)ps (FWHM) was measured. The measured resolutions (FWHM) were 2.5(3)mrad and 560(70)μm for the scattering angle and the interaction point at the target respectively. The subsequent improvement of the Doppler correction of the energy of the γ-rays, detected in the γ-ray tracking array AGATA in coincidence with isotopically identified ions in VAMOS++, is also discussed.
Lifetimes or lifetime limits of a small number of excited states of the sulfur isotopes with mass numbers A=35, 36, 37, and 38 have been measured using the differential recoil-distance method. The ...isotopes of sulfur were populated in binary grazing reactions initiated by a beam of 36S ions of energy 225 MeV incident on a thin 208Pb target which was mounted in the Cologne plunger apparatus. The combination of the PRISMA magnetic spectrometer and an early implementation of the AGATA γ-ray tracking array was used to detect γ rays in coincidence with projectile-like nuclear species. Lifetime measurements of populated states were measured within the range from about 1 to 100 ps. The number of states for which lifetime measurements or lifetime limits were possible was limited by statistics. For 35S, the lifetime was determined for the first 1/2+ state at 1572 keV; the result is compared with a previous published lifetime value. The lifetime of the 3− state of 36S at 4193 keV was determined and compared with earlier measurements. No previous lifetime information exists for the (6+) state at 6690 keV; a lifetime measurement with large associated error was made in the present work. For 37S, the states for which lifetime limits were established were those at 646 keV with Jπ=3/2− and at 2776 keV with Jπ=11/2−; there are no previously published lifetime values for excited states of 37S. Finally, a lifetime limit was established for the Jπ=(6+) state of 38S at 3675 keV; no lifetime information exists for this state in the literature. Measured lifetime values were compared with the results of state-of-the-art shell-model calculations based on the PSDPF, SDPF-U, and FSU effective interactions. In addition, nuclear magnetic-dipole and electric-quadrupole moments, branching ratios, mixing ratios, and electromagnetic transition rates, where available, have been compared with shell-model values. The current work suffers from poor statistics; nevertheless, lifetime values and limits have been possible, allowing a useful discussion of the ability of state-of-the-art shell-model calculations to reproduce the experimental results.
Abstract
Spectroscopic information on exotic Br and Nb nuclei, with odd and even masses around A=100, respectively, was obtained by analyzing fission fragments data collected with AGATA+VAMOS++ at ...GANIL and the FIPPS spectrometer at ILL. The complementarity of these two state-of-the art setups has been used, for the first time, to investigate the structure of these neutron-rich fission fragments via gamma-ray spectroscopy. Details on the two fission experiments will be given, as well as examples of high-resolution gamma-ray spectra used for the reconstruction of the level schemes. The active fission target, used in the neutron-induced fission experiment at ILL, allowed for high-statistics prompt-delayed coincidences for the analysis of a new isomeric state in
100
Nb. Evidence for a spherical isomeric state in
100
Nb will be shown and discussed within the systematic of neighbouring nuclei.
The AGATA tracking detector array represents a significant improvement over previous Compton suppressed arrays. The construction of AGATA led to numerous technological breakthroughs in order to meet ...the requirements and the challenges of building a mobile detector across Europe. This paper focuses on the design and implementation of the data acquisition system responsible of the readout and control of the germanium detectors of AGATA. Our system is highly versatile, capable of instrumenting AGATA and seamlessly adapting it to various configurations with a wide range of ancillary detectors and/or spectrometers. It consists of three main components: an autonomous and independent infrastructure, a dedicated application core ensuring overall consistency, and a high-performance software package providing a fully integrated data flow management including the setting-up, the supervision and the slow control of the instrument. In this paper, we present a comprehensive analysis of the system’s design and performance, particularly under high-counting rate conditions.
Proton inelastic scattering on 68,70,72Ni Galtarossa, F; Scomparin, L; de Angelis, G ...
Journal of physics. Conference series,
09/2023, Letnik:
2586, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The proton inelastic scattering on 68,70,72Ni isotopes was measured at the NSCL at MSU, employing the S800 spectrometer coupled to the GRETINA γ-ray array. The aim of the experiment was to determine ...the degree of collectivity in these neutron-rich Z = 28 isotopes. The use of a hadronic probe allows to complement previous Coulomb excitation measurements of the reduced transition probability B(E2; 0+ → 2+) and deduce the neutron-to-proton transition matrix elements ratio. The high resolution in γ-ray energy achievable with GRETINA gives large control on feeding transitions, thus reducing possible systematics errors in the determination of transition strengths.
A complete-spectroscopy investigation of low-lying, low-spin states in the one-proton-hole and one-neutron-hole nucleus 206Tl has been performed by using thermal neutron capture and γ-coincidence ...technique with the FIPPS Ge array at ILL Grenoble. The new experimental results, together with data for the one-proton-particle and one-neutron-particle nucleus 210Bi (taken from a previous study done at ILL in the EXILL campaign), allowed for an extensive comparison with predictions of shell-model calculations performed with realistic interactions. No phenomenological adjustments were introduced in the calculations. In 210Bi, state energies, transition multipolarities and decay branchings agree well with theory for the three well separated multiplets of states which dominate the low-lying excitations. On the contrary, in 206Tl significant discrepancies are observed: in the same energy region, six multiplets were identified, with a significant mixing among them being predicted, as a consequence of the smaller energy separation between the active orbitals. The discrepancies in 206Tl are attributed to the larger uncertainties in the determination of the off-diagonal matrix elements of the realistic shell-model interaction with respect to the calculated diagonal matrix elements, the only ones playing a major role in the case of 210Bi. The work points to the need of more advanced approaches in the construction of the realistic interactions.
Abstract
The structure of the
11
/
2
1
+
state in
131
Sb was investigated at the LOHENGRIN spectrometer of Institut Laue-Langevin via neutron-induced fission of
235
U and lifetime measurements, ...yielding
T
1
/
2
=
3
(
2
)
, at the edge of the sensitivity of the experimental method. This first result for the
11
/
2
1
+
state half-life in neutron-rich Sb isotopes provides a quadrupole reduced transition probability to the ground state of
B
(
E
2
)
=
1.4
−
0.6
+
1.5
W.u., very close to the
B
(
E
2
;
2
1
+
→
0
1
+
)
in
130
Sn. Realistic shell-model calculations reproduce well both the experimental level scheme of
131
Sb and the
B
(
E
2
;
11
/
2
1
+
→
7
/
2
1
+
)
value, indicting a dominant
2
+
(
130
Sn
)
⊗
π
g
7
/
2
core-proton coupled configuration for the
11
/
2
1
+
state.
Lifetime measurements in 131Sb at LOHENGRIN Bottoni, S.; Gamba, E. R.; De Gregorio, G. ...
Journal of physics. Conference series,
09/2023, Letnik:
2586, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The neutron-rich 131Sb nucleus was studied at Institut Laue-Langevin, with the LOHENGRIN spectrometer, via neutron-induced fission of 235U and lifetime measurements using LaBr3(Ce) detectors. The ...lifetimes of the 11/21+ and 19/21+ states were measured with the generalized centroid difference and the decay slope methods, yielding T½=3(2) ps and T½=1347(171) ps, respectively. The measured value for the 11/21+ is at the limit of the fast-timing technique. The level scheme of 131Sb and the decay properties of the 11/21+ state were described by realistic shell-model calculations, which reproduce well both the experimental spin and energy sequences of 131Sb and the measured B(E2; 11/21+→7/21+) value, pointing to an almost pure 2+(130Sn) ⊗ πg7/2, core-proton coupled configuration for the 11/21+ state.
.
The performance of the Pulse-Shape Analysis (PSA) in AGATA HPGe detectors was investigated and improved employing a
γ
-ray source measurement based on
e
+
e
-
annihilation radiation after decays of
...22
Na by
β
+
decay. The first interaction positions of the two 511keV
γ
rays were determined and the connecting line of these two positions was compared to the known source position as a measure for the PSA performance. The position resolution and its dependence on the PSA parameters were investigated by varying most relevant input quantities: the charge carrier mobility of the holes, the response of the employed measuring electronics especially the preamplifier rise time. The relative statistical weight of charge signals and transient signals was scrutinized. The optimal distance metric of the grid-search algorithm and its impact on the position resolution were determined.
PDF
