541 research outputs found
Observation of large scissors resonance strength in actinides
The orbital M1-scissors resonance (SR) has been measured for the first time
in the quasi-continuum of actinides. Particle-gamma coincidences are recorded
with deuteron and 3He induced reactions on 232Th. The residual nuclei
231,232,233Th and 232,233Pa show an unexpectedly strong integrated strength of
in the Egamma=1.0 - 3.5 MeV region. The increased
gamma-decay probability in actinides due to the SR is important for
cross-section calculations for future fuel cycles of fast nuclear reactors and
may also have impact on stellar nucleosynthesis.Comment: 5 pages and 4 figure
Scissors resonance in the quasi-continuum of Th, Pa and U isotopes
The gamma-ray strength function in the quasi-continuum has been measured for
231-233Th, 232,233Pa and 237-239U using the Oslo method. All eight nuclei show
a pronounced increase in gamma strength at omega_SR approx 2.4 MeV, which is
interpreted as the low-energy M1 scissors resonance (SR). The total strength is
found to be B_SR = 9-11 mu_N^2 when integrated over the 1 - 4 MeV gamma-energy
region. The SR displays a double-hump structure that is theoretically not
understood. Our results are compared with data from (gamma, gamma') experiments
and theoretical sum-rule estimates for a nuclear rigid-body moment of inertia.Comment: 11 pages, 9 figure
Pulse processing routines for neutron time-of-flight data
A pulse shape analysis framework is described, which was developed for
n_TOF-Phase3, the third phase in the operation of the n_TOF facility at CERN.
The most notable feature of this new framework is the adoption of generic pulse
shape analysis routines, characterized by a minimal number of explicit
assumptions about the nature of pulses. The aim of these routines is to be
applicable to a wide variety of detectors, thus facilitating the introduction
of the new detectors or types of detectors into the analysis framework. The
operational details of the routines are suited to the specific requirements of
particular detectors by adjusting the set of external input parameters. Pulse
recognition, baseline calculation and the pulse shape fitting procedure are
described. Special emphasis is put on their computational efficiency, since the
most basic implementations of these conceptually simple methods are often
computationally inefficient.Comment: 13 pages, 10 figures, 5 table
Pulse processing routines for neutron time-of-flight data
A pulse shape analysis framework is described, which was developed for n_TOF-Phase3, the third phase in the operation of the n_TOF facility at CERN. The most notable feature of this new framework is the adoption of generic pulse shape analysis routines, characterized by a minimal number of explicit assumptions about the nature of pulses. The aim of these routines is to be applicable to a wide variety of detectors, thus facilitating the introduction of the new detectors or types of detectors into the analysis framework. The operational details of the routines are suited to the specific requirements of particular detectors by adjusting the set of external input parameters. Pulse recognition, baseline calculation and the pulse shape fitting procedure are described. Special emphasis is put on their computational efficiency, since the most basic implementations of these conceptually simple methods are often computationally inefficient.Croatian Science Foundation - Project No. 168
New developments in Micromegas Microbulk detectors
A new Micromegas manufacturing technique, based on kapton etching technology,
has been recently developed, improving the uniformity and stability of this
kind of readouts. Excellent energy resolutions have been obtained, reaching 11%
FWHM for the 5.9 keV photon peak of 55Fe source and 1.8% FWHM for the 5.5 MeV
alpha peak of the 241Am source. The new detector has other advantages like its
flexible structure, low material and high radio-purity. The two actual
approaches of this technique will be described and the features of these
readouts in argon-isobutane mixtures will be presented. Moreover, the low
material present in the amplification gap makes these detectors approximate the
Rose and Korff model for the avalanche amplification, which will be discussed
for the same type of mixtures. Finally, we will present several applications of
the microbulk technique.Comment: To be published in the Proceedings of the TIPP2011 conference
(Physics Procedia
First Light Measurements of Capella with the Low Energy Transmission Grating Spectrometer aboard the Chandra X-ray Observatory
We present the first X-ray spectrum obtained by the Low Energy Transmission
Grating Spectrometer (LETGS) aboard the Chandra X-ray Observatory. The spectrum
is of Capella and covers a wavelength range of 5-175 A (2.5-0.07 keV). The
measured wavelength resolution, which is in good agreement with ground
calibration, is 0.06 A (FWHM). Although in-flight
calibration of the LETGS is in progress, the high spectral resolution and
unique wavelength coverage of the LETGS are well demonstrated by the results
from Capella, a coronal source rich in spectral emission lines. While the
primary purpose of this letter is to demonstrate the spectroscopic potential of
the LETGS, we also briefly present some preliminary astrophysical results. We
discuss plasma parameters derived from line ratios in narrow spectral bands,
such as the electron density diagnostics of the He-like triplets of carbon,
nitrogen, and oxygen, as well as resonance scattering of the strong Fe XVII
line at 15.014 A.Comment: 4 pages (ApJ letter LaTeX), 2 PostScript figures, accepted for
publication in ApJ Letters, 200
Development of a novel segmented mesh MicroMegas detector for neutron beam profiling
A novel MicroMegas detector based on microbulk technology with an embedded XY strip structure was developed, obtained by segmenting both the mesh and the anode in perpendicular directions. This results in a very low-mass device with good energy and spatial resolution capabilities. Such a detector is practically âtransparentâ to neutrons, being ideal for in-beam neutron measurements and can be used as a quasi-online neutron beam profiler at neutron time-of-flight facilities. A dedicated front end electronics and acquisition system has been developed and used. The first studies of this new detection system are presented and discussed
Neutron cross-sections for advanced nuclear systems : The n-TOF project at CERN
© Owned by the authors, published by EDP Sciences, 2014 This is an Open Access article distributed under the terms of the Creative Commons Attribution License 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly citedThe study of neutron-induced reactions is of high relevance in a wide variety of fields, ranging from stellar nucleosynthesis and fundamental nuclear physics to applications of nuclear technology. In nuclear energy, high accuracy neutron data are needed for the development of Generation IV fast reactors and accelerator driven systems, these last aimed specifically at nuclear waste incineration, as well as for research on innovative fuel cycles. In this context, a high luminosity Neutron Time Of Flight facility, n-TOF, is operating at CERN since more than a decade, with the aim of providing new, high accuracy and high resolution neutron cross-sections. Thanks to the features of the neutron beam, a rich experimental program relevant to nuclear technology has been carried out so far. The program will be further expanded in the near future, thanks in particular to a new high-flux experimental area, now under construction.Peer reviewedFinal Published versio
The measurement programme at the neutron time-of-flight facility n-TOF at CERN
Neutron-induced reaction cross sections are important for a wide variety of research fields ranging from the study of nuclear level densities, nucleosynthesis to applications of nuclear technology like design, and criticality and safety assessment of existing and future nuclear reactors, radiation dosimetry, medical applications, nuclear waste transmutation, accelerator-driven systems and fuel cycle investigations. Simulations and calculations of nuclear technology applications largely rely on evaluated nuclear data libraries. The evaluations in these libraries are based both on experimental data and theoretical models. CERN's neutron time-of-flight facility n-TOF has produced a considerable amount of experimental data since it has become fully operational with the start of its scientific measurement programme in 2001. While for a long period a single measurement station (EAR1) located at 185 m from the neutron production target was available, the construction of a second beam line at 20 m (EAR2) in 2014 has substantially increased the measurement capabilities of the facility. An outline of the experimental nuclear data activities at n-TOF will be presented
- âŠ