Energies and spectroscopic factors of the first 7/2-, 3/2-, 1/2-, and 5/2- states in the (35)Si21 nucleus were determined by means of the (d, p) transfer reaction in inverse kinematics at GANIL using ...the MUST2 and EXOGAM detectors. By comparing the spectroscopic information on the Si35 and S37 isotones, a reduction of the p3/2-p1/2 spin-orbit splitting by about 25% is proposed, while the f7/2-f5/2 spin-orbit splitting seems to remain constant. These features, derived after having unfolded nuclear correlations using shell model calculations, have been attributed to the properties of the two-body spin-orbit interaction, the amplitude of which is derived for the first time in an atomic nucleus. The present results, remarkably well reproduced by using several realistic nucleon-nucleon forces, provide a unique touchstone for the modeling of the spin-orbit interaction in atomic nuclei.
Pulse-shape discrimination in NE213 liquid scintillator detectors Cavallaro, M.; Tropea, S.; Agodi, C. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
02/2013, Letnik:
700
Journal Article
Recenzirano
The 16-channel fast stretcher BaFPro module, originally developed for processing signals of Barium Fluoride scintillators, has been modified to make a high performing analog pulse-shape analysis of ...signals from the NE213 liquid scintillators of the EDEN neutron detector array. The module produces two Gaussian signals, whose amplitudes are proportional to the height of the fast component of the output light and to the total energy deposited into the scintillator, respectively. An in-beam test has been performed at INFN-LNS (Italy) demonstrating a low detection threshold, a good pulse-shape discrimination even at low energies and a wide dynamic range for the measurement of the neutrons energy.
Random coincidences of events could be one of the main sources of background in the search for neutrino-less double-beta decay of
100
Mo with macro-bolometers, due to their modest time resolution. ...Scintillating bolometers as those based on Li
2
MoO
4
crystals and employed in the CROSS and CUPID experiments can eventually exploit the coincident fast signal detected in a light detector to reduce this background. However, the scintillation provides a modest signal-to-noise ratio, making difficult a pile-up pulse-shape recognition and rejection at timescales shorter than a few ms. Neganov–Trofimov–Luke assisted light detectors (NTL-LDs) offer the possibility to effectively increase the signal-to-noise ratio, preserving a fast time-response, and enhance the capability of pile-up rejection via pulse shape analysis. In this article we present: (a) an experimental work performed with a Li
2
MoO
4
scintillating bolometer, studied in the framework of the CROSS experiment, and utilizing a NTL-LD; (b) a simulation method to reproduce, synthetically, randomly coincident two-neutrino double-beta decay events; (c) a new analysis method based on a pulse-shape discrimination algorithm capable of providing high pile-up rejection efficiencies. We finally show how the NTL-LDs offer a balanced solution between performance and complexity to reach background index
∼
10
-
4
counts/keV/kg/year with 280 g Li
2
MoO
4
(
100
Mo enriched) bolometers at 3034 keV, the Q
β
β
of the double-beta decay, and target the goal of a next generation experiment like CUPID.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Abstract
CUPID is a next-generation bolometric experiment aiming at
searching for neutrinoless double-beta decay with ∼250 kg of
isotopic mass of
100
Mo. It will operate at ∼10 mK in a
cryostat ...currently hosting a similar-scale bolometric array for the
CUORE experiment at the Gran Sasso National Laboratory
(Italy). CUPID will be based on large-volume scintillating
bolometers consisting of
100
Mo-enriched Li
2
MoO
4
crystals,
facing thin Ge-wafer-based bolometric light detectors. In the CUPID
design, the detector structure is novel and needs to be
validated. In particular, the CUORE cryostat presents a high level
of mechanical vibrations due to the use of pulse tubes and the
effect of vibrations on the detector performance must be
investigated. In this paper we report the first test of the
CUPID-design bolometric light detectors with NTD-Ge sensors in a
dilution refrigerator equipped with a pulse tube in an above-ground
lab. Light detectors are characterized in terms of sensitivity,
energy resolution, pulse time constants, and noise power
spectrum. Despite the challenging noisy environment due to
pulse-tube-induced vibrations, we demonstrate that all the four
tested light detectors comply with the CUPID goal in terms of
intrinsic energy resolution of 100 eV RMS baseline noise. Indeed,
we have measured 70–90 eV RMS for the four devices, which show an
excellent reproducibility. We have also obtained high energy
resolutions at the 356 keV line from a
133
Ba source, as good
as Ge semiconductor
γ
detectors in this energy range.
Direct observation of the survival of 199Au residues after 2n transfer in the He8+Au197 system and the absence of the corresponding 67Cu in the He8+Cu65 system at various energies are reported. The ...measurements of the surprisingly large cross sections for 199Au, coupled with the integral cross sections for the various Au residues, is used to obtain the first model-independent lower limits on the ratio of 2n to 1n transfer cross sections from 8He to a heavy target. A comparison of the transfer cross sections for 6,8He on these targets highlights the differences in the interactions of these Borromean nuclei. These measurements for the most neutron-rich nuclei on different targets highlight the need to probe the reaction mechanism with various targets and represent an experimental advance towards understanding specific features of pairing in the dynamics of dilute nuclear systems.
Abstract
The CROSS experiment is proposing to use a new technology of surface sensitive bolometers for low-background neutrinoless double beta decay searches. Efficient rejection of surface
α
and
β
...events will allow to reach background in the region of interest below than 10
−4
cnts/keV/kg/yr. The isotopes of interest, which are
130
Te and
100
Mo, are investigated with TeO
2
and Li
2
MoO
4
bolometers. The surface sensitivity is achieved thanks to the evaporation of thin metallic film on the crystal surface that modifies the pulse shape of near-surface events. An investigation of various pulse shape parameters was performed. The analysis shows that one of the best parameters for discrimination is the integrated area of the raw signal both for TeO
2
and Li
2
MoO
4
with Pd-Al (10 nm - 100 nm) bi-layer.
Pairing and quartetting are competing phenomena in nuclei. In the selfconjugate nuclei from the fp-shell, the competition between T=0 pairing (deuteron-like) and alpha clusterisation is predicted to ...be a_ected by the spin-orbit interaction. In order to probe the α structure of fp-shell nuclei, the nuclear break-up of 40Ca and 40Ar has been measured at GANIL. The α spectroscopic factors obtained for the N=Z nucleus and the N≠Z nuclei do not reflect any difference. This might be an indication that the tail of the wave function in not sensitive to nuclear asymmetry. Perspectives for probing the deuteron-like pairing (T=0) are given.
The low-lying spectroscopy of 6He was investigated via the 2-neutron transfer reaction p (He 8 , t) with the 8He beam delivered by the SPIRAL facility at 15.4 A MeV . The light charged particles ...produced by the direct reactions were measured using the MUST2 Si-strip telescope array. Above the known 2 + state, two new resonances were observed: at E a = 2.6 +/- 0.3 MeV (width Phi = 1.6 +/- 0.4 MeV) and at 5.3 +/- 0.3 MeV with Phi = 2 +/- 1 MeV . Through the analysis of the angular distributions, they correspond to a 2 + state and to an L = 1 state, respectively. These new states, challenging the nuclear theories, could be used as benchmarks for checking the microscopic inputs of the newly improved structure models, and should trigger development of models including the treatments of both core excitation and continuum coupling effects.
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