1,014 research outputs found
Performance of the Fully Digital FPGA-based Front-End Electronics for the GALILEO Array
In this work we present the architecture and results of a fully digital Front
End Electronics (FEE) read out system developed for the GALILEO array. The FEE
system, developed in collaboration with the Advanced Gamma Tracking Array
(AGATA) collaboration, is composed of three main blocks: preamplifiers,
digitizers and preprocessing electronics. The slow control system contains a
custom Linux driver, a dynamic library and a server implementing network
services. The digital processing of the data from the GALILEO germanium
detectors has demonstrated the capability to achieve an energy resolution of
1.53 per mil at an energy of 1.33 MeV.Comment: 5 pages, 6 figures, preprint version of IEEE Transactions on Nuclear
Science paper submitted for the 19th IEEE Real Time Conferenc
Co-existing structures in 105Ru
New positive-parity states, having a band-like structure, were observed in
105Ru. The nucleus was produced in induced fission reaction and the prompt
gamma-rays, emitted from the fragments, were detected by the EUROBALL III
multi-detector array. The partial scheme of excited 105Ru levels is analyzed
within the Triaxial-Rotor-plus-Particle approach
On the production of ancient Egyptian blue: Multi-modal characterization and micronscale luminescence mapping
The ancient pigment Egyptian blue has long been studied for its historical significance; however, recent work has shown that its unique visible induced luminescent property can be used both to identify the pigment and to inspire new materials with this characteristic. In this study, a multi-modal characterization approach is used to explore variations in ancient production of Egyptian blue from shabti statuettes found in the village of Deir el-Medina in Egypt (Luxor, West Bank) dating back to the New Kingdom (18th-20th Dynasties; about 1550-1077 BCE). Using quantitative SEM-EDS analysis, we identify two possible production groups of the Egyptian blue and demonstrate the presence of multiple phases within samples using cluster analysis and ternary diagram representations. Using both macro-scale non-invasive (X-rays fluorescence and multi-spectral imaging) and micro-sampling (SEM-EDS and Raman confocal microspectroscopy) techniques, we correlate photoluminescence and chemical composition of the ancient samples. We introduce Raman spectroscopic imaging as a means to capture simultaneously visible-induced luminesce and crystal structure and utilize it to identify two classes of luminescing and non-luminescing silicate phases in the pigment that may be connected to production technologies. The results presented here provide a new framework through which Egyptian blue can be studied and inform the design of new materials based on its luminescent property
coupling determined beyond the chiral limit
Within the conventional QCD sum rules, we calculate the coupling
constant, , beyond the chiral limit using two-point correlation
function with a pion. We consider the Dirac structure, , at
order, which has clear dependence on the PS and PV coupling schemes
for the pion-nucleon interactions. For a consistent treatment of the sum rule,
we include the linear terms in quark mass as they constitute the same chiral
order as . Using the PS coupling scheme for the pion-nucleon
interaction, we obtain , which is very close to the
empirical coupling. This demonstrates that going beyond the chiral
limit is crucial in determining the coupling and the pseudoscalar coupling
scheme is preferable from the QCD point of view.Comment: 8 pages, revtex, some errors are corrected, substantially revise
Extending the dynamic range of nuclear pulse spectrometers
Using an innovative time-varying front-end electronics in conjunction with a bulky coaxial high-purity germanium detector, we were able to extend the range of the radionuclide spectra well beyond the analog to digital converter (ADC) saturation point. The electronics automatically conditions the signal for digital-filtering optimization if it is in the ADC voltage range and for time-over-threshold analysis if it exceeds the ADC range. A high spectroscopic resolution has been achieved in both operation ranges. An unprecedented wide energy range from 5 keV to 150 MeV of equivalent energy, or 90 dB, has been obtained using a single acquisition chain, while maintaining a high-energy resolution in the whole spectrum. For example, with an ADC range of 3 MeV a resolution has been obtained of 1.3/2.2 keV full width at half maximum on the 122/1332 keV gamma-ray lines of Co-57 and Co-60, and of <0.4% in the time-over-threshold region, or for energy deposits beyond 3 MeV. (C) 2008 American Institute of Physics
Identification and rejection of scattered neutrons in AGATA
Gamma rays and neutrons, emitted following spontaneous fission of 252Cf, were
measured in an AGATA experiment performed at INFN Laboratori Nazionali di
Legnaro in Italy. The setup consisted of four AGATA triple cluster detectors
(12 36-fold segmented high-purity germanium crystals), placed at a distance of
50 cm from the source, and 16 HELENA BaF2 detectors. The aim of the experiment
was to study the interaction of neutrons in the segmented high-purity germanium
detectors of AGATA and to investigate the possibility to discriminate neutrons
and gamma rays with the gamma-ray tracking technique. The BaF2 detectors were
used for a time-of-flight measurement, which gave an independent discrimination
of neutrons and gamma rays and which was used to optimise the gamma-ray
tracking-based neutron rejection methods. It was found that standard gamma-ray
tracking, without any additional neutron rejection features, eliminates
effectively most of the interaction points due to recoiling Ge nuclei after
elastic scattering of neutrons. Standard tracking rejects also a significant
amount of the events due to inelastic scattering of neutrons in the germanium
crystals. Further enhancements of the neutron rejection was obtained by setting
conditions on the following quantities, which were evaluated for each event by
the tracking algorithm: energy of the first and second interaction point,
difference in the calculated incoming direction of the gamma ray,
figure-of-merit value. The experimental results of tracking with neutron
rejection agree rather well with Geant4 simulations
Electromagnetic transitions and structure in the Z = N nucleus 46 V
The nucleus 46V has been studied in the reaction 24Mg(28Si,apn) 46V at 115 MeV beam energy, using both Au and Pb backed targets. Lifetimes were obtained for 14 levels with DSAM analysis. Experimental B (E2) reduced transition probabilities are well reproduced by the large scale shell model. The observed levels could be organizied in bands with a rather good
K value.DGES PB96-5
Band termination in the N=Z Odd-Odd Nucleus 46V
High spin states in the odd-odd N=Z nucleus 46V have been identified. At low
spin, the T=1 isobaric analogue states of 46Ti are established up to I = 6+.
Other high spin states, including the band terminating state, are tentatively
assigned to the same T=1 band. The T=0 band built on the low-lying 3+ isomer is
observed up to the 1f7/2-shell termination at I=15. Both signatures of a
negative parity T=0 band are observed up to the terminating states at I = 16-
and I = 17-, respectively. The structure of this band is interpreted as a
particle-hole excitation from the 1d3/2 shell. Spherical shell model
calculations are found to be in excellent agreement with the experimental
results.Comment: 5 pages, 4 figure
Transition probabilities in the X(5) candidate Ba
To investigate the possible X(5) character of 122Ba, suggested by the ground
state band energy pattern, the lifetimes of the lowest yrast states of 122Ba
have been measured, via the Recoil Distance Doppler-Shift method. The relevant
levels have been populated by using the 108Cd(16O,2n)122Ba and the
112Sn(13C,3n)122Ba reactions. The B(E2) values deduced in the present work are
compared to the predictions of the X(5) model and to calculations performed in
the framework of the IBA-1 and IBA-2 models
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