78 research outputs found
Iron and Nickel spectral opacity calculations in conditions relevant for pulsating stellar envelopes and experiments
Seismology of stars is strongly developing. To address this question we have
formed an international collaboration OPAC to perform specific experimental
measurements, compare opacity calculations and improve the opacity calculations
in the stellar codes [1]. We consider the following opacity codes: SCO,
CASSANDRA, STA, OPAS, LEDCOP, OP, SCO-RCG. Their comparison has shown large
differences for Fe and Ni in equivalent conditions of envelopes of type II
supernova precursors, temperatures between 15 and 40 eV and densities of a few
mg/cm3 [2, 3, 4]. LEDCOP, OPAS, SCO-RCG structure codes and STA give similar
results and differ from OP ones for the lower temperatures and for spectral
interval values [3]. In this work we discuss the role of Configuration
Interaction (CI) and the influence of the number of used configurations. We
present and include in the opacity code comparisons new HULLAC-v9 calculations
[5, 6] that include full CI. To illustrate the importance of this effect we
compare different CI approximations (modes) available in HULLAC-v9 [7]. These
results are compared to previous predictions and to experimental data.
Differences with OP results are discussed.Comment: 4 pages, 3 figures, conference Inertial Fusion Sciences and
Applications, Bordeaux, 12th to 16th September 2011; EPJ web of Conferences
201
Covariant description of inelastic electron--deuteron scattering:predictions of the relativistic impulse approximation
Using the covariant spectator theory and the transversity formalism, the
unpolarized, coincidence cross section for deuteron electrodisintegration,
, is studied. The relativistic kinematics are reviewed, and simple
theoretical formulae for the relativistic impulse approximation (RIA) are
derived and discussed. Numerical predictions for the scattering in the high
region obtained from the RIA and five other approximations are presented
and compared. We conclude that measurements of the unpolarized coincidence
cross section and the asymmetry , to an accuracy that will distinguish
between different theoretical models, is feasible over most of the wide
kinematic range accessible at Jefferson Lab.Comment: 54 pages and 24 figure
Measurement of the analyzing power Ay0 for the reaction H(p⃗,d)π+ between 1000 and 1300 MeV
The analyzing power Ay0 of the reaction H(p⃗,d)π+ has been measured at a fixed value of the Mandelstam variable ud=-0.17GeV2 for nine proton energies between 1000 and 1300 MeV. The experiment was performed at SATURNE with the SPES1 spectrometer. The data exhibit structure around √s≃2.37GeV. The origin of this structure could be related to a resonancelike behavior of the 1S0P or 1G4F partial amplitudes
Mass measurement and isoscaling in Sn+Sn and Sn+Sn reactions at 600 AMeV
Isotopic effects in projectile spectator fragmentation at 600 AMeV have been investigated using data collected in recent experiments with SIS beams at the GSI laboratory and with the ALADiN forward-spectrometer. For this purpose, primary beams of 124Sn, as well as secondary beams of 124La and 107Sn produced at the FRS fragment separator have been used. Isoscaling in 124,107Sn+Sn reactions is investigated and results are compared with data taken with the INDRA multidetector for 12C+112,124Sn reactions
Dynamics of the O(e,e'p) cross section at high missing energies
We measured the cross section and response functions (R_L, R_T, and R_LT) for the 16O(e,e'p) reaction in quasielastic kinematics for missing energies 25 60 MeV and P_miss > 200 MeV/c, the cross section is relatively constant. Calculations which include contributions from pion exchange currents, isobar currents and short-range correlations account for the shape and the transversity but only for half of the magnitude of the measured cross section
Addressing the two-step scenario of high-energy ion collisions with Xe + p and Xe +C at 1 A.GeV in inverse kinematics, at the SPALADiN setup of GSI
International audienceWe have measured at GSI-Darmstadt (Germany) the reactions 136Xe + p and 136Xe +12 C, using the inverse-kinematics technique at 1 A.GeV and the large acceptance SPALADiN setup. The combination of both provides a very good coverage of the phase-space of the excited system decay channels, allowing the study of the relative importance of those decay channels, as well as a very efficient filter to reject from the detection the particles and nuclear fragments of high energy in the projectile centre-of-mass frame, essentially produced in the first-instant nucleon-nucleon collisions, prior to the decay of the excited nuclear system. Our analysis in the two-step scenario permits one to estimate on an event basis E*/A, the excitation energy per nucleon of the decaying nuclear system, and to study the E*/A dependence of the different decay channels. The E*/A range of overlap of the 136Xe + p and 136Xe+12C reactions is large and allows for an extensive comparison between both reactions, and therefore provides a strong test bench of the entrance-channel-independence hypothesis of the excited-system decay. We address the two-step-scenario assumption in the light of our data and their comparison with different up-to-date model
ICAN: High power neutral beam generation
During the last few years there is an increasing interest on the development of alternative high power new negative ion source for Tokamak applications. The proposed new neutral beam device presents a number of advantages with respect to: the density current, the acceleration voltage, the relative compact dimension of the negative ion source, and the coupling of a high power laser beam for photo-neutralization of the negative ion beam. Here we numerically investigate, using a multi-fluid 1-D code, the acceleration and the extraction of high power ion beam from a Magnetically Insulated Diode (MID). The diode configuration will be coupled to a high power device capable of extracting a current up to few kA with an accelerating voltage up to MeV. An efficiency of up to 92% of the coupling of the laser beam, is required in order to obtain a high power, up to GW, neutral beam. The new high energy, high average power, high efficiency (up to 30%) ICAN fiber laser is proposed for both the plasma generation and the photo-neutralizer configuration [1]
First beams at neutrons for science
International audienceThe neutrons for science facility (NFS), the firstoperational experimental area of the new GANIL/SPIRAL-2facility, received its first beams in December 2019. Protoninducedreaction cross-sections as well as neutron beam characteristicswere measured during the first commissioningphases. The first results, showing the features of the facility,are presented here and compared with previously publisheddata. The physics cases and the first accepted experimentsare presented as well
Chemical constituents in the air and snow at Dye 3, Greenland—II. Analysis of episodes in April 1989
International audienc
Chemical constituents in the air and snow at Dye 3, Greenland—I. Seasonal variations
International audienc
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