420 research outputs found
The PREFER (Polarization REsearch for Fusion Experiments and Reactors) - Collaboration: Purposes and present status
No full textThe possibility to exploit spin physics in fusion science opens new impressive panorama and challenging fields to be explored. In addition to the fundamental interesting topics the PREFER collaboration is trying with synergistic efforts to make the well known behavior of spin-dependent nuclear reactions available for feasibility studies and experimental tests for fusion programs. In this contribution the main challenges of the different collaborating groups will be put in evidence, and recent developments with the respective references will be provided
Advantages of nuclear fusion with polarized fuel
No full textThe use of nuclear polarized fuel, i.e. polarized D, T or 3He, for coming fusion reactors promises to increase their energy output and to optimize the complete fusion process in various ways. But before these advantages can be utilized, several questions must be answered and technical issues must be overcome. Among others, the members of the PREFER collaboration started to investigate the different challenges of “polarized fusion”
Advantages of Nuclear Fusion with Polarized Fuel
No full textThe use of nuclear polarized fuel, i.e. polarized D, T or 3He, for coming fusion reactors promises to increase their energy output and to optimize the complete fusion process in various ways. But before these advantages can be utilized, several questions must be answered and technical issues must be overcome. Among others, the members of the PREFER collaboration started to investigate the different challenges of “polarized fusion”
Polarization REsearch for Fusion Experiments and Reactors - The PREFER Collaboration: Purposes and Present Status
No full textThe PREFER (Polarization REsearch for Fusion Experiments and Reactors) collaboration aims to address the know–hows in different fields and techniques to the challenging bet on fusion with polarized fuel. The efforts on a variety of duties and goals are shared between different research groups, indicated here by underlining in the authors’ list the scientific responsibles. Starting from still open questions of fusion reaction physics, as for example the study of D+D spin–dependent cross–sections (Vasilyev) to the acceleration of polarized ions from laser-induced plasmas (Büscher), there are many connections between the involved research groups. The collaboration is also tackling the production of nuclear polarized molecules, recombined from a polarized atomic beam (Engels), and its cryogenic condensation and transport (Ciullo). Other options for the production of polarized fuel are investigated in parallel, like spin separation of molecules in polarized molecular beam sources (Toporkov), or via photodissociation of molecules into polarized hydrogen/deuterium atoms (Rakitzis). The status of the different fields under investigation and the connections between these topics and the different research groups will be provided
Production of e(+)e(-) pairs accompanied by nuclear dissociation in ultraperipheral heavy-ion collisions
No full textWe present data on e(+)e(-) pair production accompanied by nuclear breakup in ultraperipheral gold-gold collisions at a center of mass energy of 200 GeV per nucleon pair. The nuclear breakup requirement selects events at small impact parameters, where higher-order diagrams for pair production should be enhanced. We compare the data with two calculations: one based on the equivalent photon approximation, and the other using lowest-order quantum electrodynamics (QED). The data distributions agree with both calculations, except that the pair transverse momentum spectrum disagrees with the equivalent photon approach. We set limits on higher-order contributions to the cross section
Measurements of pairs from open heavy flavor in + and + collisions at GeV
No full textInternational audienceWe report a measurement of e+e− pairs from semileptonic heavy-flavor decays in p+p collisions at sNN=200 GeV. The e+e− pair yield from bb¯ and cc¯ is separated by exploiting a double differential fit done simultaneously in dielectron invariant mass and pT. We used three different event generators, pythia, mc@nlo, and powheg, to simulate the e+e− spectra from cc¯ and bb¯ production. The data can be well described by all three generators within the detector acceptance. However, when using the generators to extrapolate to 4π, significant differences are observed for the total cross section. These difference are less pronounced for bb¯ than for cc¯. The same model dependence was observed in already published d+A data. The p+p data are also directly compared with d+A data in mass and pT, and within the statistical accuracy no nuclear modification is seen
Production of pairs accompanied by nuclear dissociation in ultraperipheral heavy-ion collisions
No full textWe present the first data on e{sup +}e{sup -} pair production accompanied by nuclear breakup in ultra-peripheral gold-gold collisions at a center of mass energy of 200 GeV per nucleon pair. The nuclear breakup requirement selects events at small impact parameters, where higher-order corrections to the pair production cross section should be enhanced. We compare the pair kinematic distributions with two calculations: one based on the equivalent photon approximation, and the other using lowest-order quantum electrodynamics (QED); the latter includes the photon virtuality. The cross section, pair mass, rapidity and angular distributions are in good agreement with both calculations. The pair transverse momentum, p{sub T}, spectrum agrees with the QED calculation, but not with the equivalent photon approach. We set limits on higher-order contributions to the cross section. The e{sup +} and e{sup -} p{sub T} spectra are similar, with no evidence for interference effects due to higher-order diagrams
Photoproduction of J/psi and of high mass e(+)e(-) in ultra-peripheral Au plus Au collisions at root s(NN)=200 GeV
No full textWe present the first measurement of photoproduction of J/psi and of two-photon production of high-mass e(+)e(-) pairs in electromagnetic (or ultra-peripheral) nucleus-nucleus interactions, using Au + Au data at root s(NN) = 200 GeV. The events are tagged with forward neutrons emitted following Coulomb excitation of one or both Au* nuclei. The event sample consists of 28 events with m(e+e-) > 2 GeV/c(2) with zero like-sign background. The measured cross sections at midrapidity of d sigma/dy (J/psi + Xn, y = 0) = 76 +/- 33 (stat) +/- 11 (syst) pb and d(2)sigma /dm dy (e(+) e(-) + Xn, y = 0) = 86 +/- 23(stat) +/- 16(syst) mu b/ (GeV/c(2)) for m(e+e-) epsilon vertical bar 2.0, 2.8 vertical bar GeV/c(2) have been compared and found to be consistent with models for photoproduction of J/psi and QED based calculations of two-photon production of e(+)e(-) pairs. (C) 2009 Elsevier B.V. All rights reserved.Office of Nuclear Physics in DOE Office of Science and NSF (USA)U.S. National Science Foundation (NSF)U.S. Department of Energy (DOE)MEXTMEXTJapan Society for the Promotion of Science (JSPS)JSPS OapanConselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)CNPqFundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)FAPESP (Brazil)Natural Science Foundation of China (NSFC)NSFC Natural Science Foundation (China)IN2P3/CNRSIN2P3/CNRSCEA (France)Commissariat à l énergie atomique et aux énergies alternatives (CEA)BIVIBF, DAADBIVIBFDeutscher Akademischer Austauschdienst (DAAD)Alexander von Humboldt Foundation (AvH)Alexander von Humboldt Foundation - AvH (Germany)Országos Tudományos Kutatási Alapprogramok (OTKA)OTKA (Hungary)DAE (India)Department of Atomic Energy of India (DAE)ISF (Israel)ISF (Israel)KRFKRFKOSEF (Korea)KOSEF (Korea)MESMESRASRASFAAE (Russia)FAAE (Russia)VRVRKAW (Sweden)KAW (Sweden)US CRDF for the FSUUS CRDF for the FSUUS-Hungarian NSF-OTKA-MTAUS-Hungarian NSF-OTKA-MTAUS-Israel BSFUS-Israel BS
Design and operation of a cryogenic charge-integrating preamplifier for the MuSun experiment
No full textThe central detector in the MuSun experiment is a pad-plane time projection ionization chamber that operates without gas amplification in deuterium at 31 K; it is used to measure the rate of the muon capture process μ-+dn+n+νμ. A new charge-sensitive preamplifier, operated at 140 K, has been developed for this detector. It achieved a resolution of 4.5 keV(D2) or 120 e- RMS with zero detector capacitance at 1.1 μ s integration time in laboratory tests. In the experimental environment, the electronic resolution is 10 keV(D2) or 250 e- RMS at a 0.5 μ s integration time. The excellent energy resolution of this amplifier has enabled discrimination between signals from muon-catalyzed fusion and muon capture on chemical impurities, which will precisely determine systematic corrections due to these processes. It is also expected to improve the muon tracking and determination of the stopping location. © 2014 IOP Publishing Ltd and Sissa Medialab srl
Multipole neodymium magnets for polarized atom source
No full textA possibility of high gradient magnets construction from the commercially available NdFeB dipole magnets for the polarized atomic beam sources is described. Radial component of the magnetic field for quadrupole and six-pole magnets is measured at the middle plane of the magnet as function of the angle and along the magnet axis. Characteristics of magnetic field of the magnets calculated using COMSOL MultiPhysics software are compared to the experimental results. The feasibility to effectively use the software for 3D-simulation of the gradient multipole magnet systems to be developed is demonstrated
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