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Sample records for suppress fermi acceleration

  1. Suppressing Fermi acceleration in two-dimensional driven billiards.

    Science.gov (United States)

    Leonel, Edson D; Bunimovich, Leonid A

    2010-07-01

    We consider a dissipative oval-like shaped billiard with a periodically moving boundary. The dissipation considered is proportional to a power of the velocity V of the particle. The three specific types of power laws used are: (i) F∝-V ; (ii) F∝-V(2) and (iii) F∝-V(δ) with 1unlimited energy gain for cases (ii) and (iii). The critical exponents obtained for the phase transition in the case (ii) are the same as those obtained for the dissipative bouncer model. Therefore near this phase transition, these two rather different models belong to the same class of universality. For all types of dissipation, the results obtained allow us to conclude that suppression of the unlimited energy growth is indeed observed.

  2. Decay of energy and suppression of Fermi acceleration in a dissipative driven stadium-like billiard.

    Science.gov (United States)

    Livorati, André L P; Caldas, Iberê L; Leonel, Edson D

    2012-06-01

    The behavior of the average energy for an ensemble of non-interacting particles is studied using scaling arguments in a dissipative time-dependent stadium-like billiard. The dynamics of the system is described by a four dimensional nonlinear mapping. The dissipation is introduced via inelastic collisions between the particles and the moving boundary. For different combinations of initial velocities and damping coefficients, the long time dynamics of the particles leads them to reach different states of final energy and to visit different attractors, which change as the dissipation is varied. The decay of the average energy of the particles, which is observed for a large range of restitution coefficients and different initial velocities, is described using scaling arguments. Since this system exhibits unlimited energy growth in the absence of dissipation, our results for the dissipative case give support to the principle that Fermi acceleration seems not to be a robust phenomenon.

  3. In-flight and collisional dissipation as a mechanism to suppress Fermi acceleration in a breathing Lorentz gas.

    Science.gov (United States)

    Oliveira, Diego F M; Leonel, Edson D

    2012-06-01

    Some dynamical properties for a time dependent Lorentz gas considering both the dissipative and non dissipative dynamics are studied. The model is described by using a four-dimensional nonlinear mapping. For the conservative dynamics, scaling laws are obtained for the behavior of the average velocity for an ensemble of non interacting particles and the unlimited energy growth is confirmed. For the dissipative case, four different kinds of damping forces are considered namely: (i) restitution coefficient which makes the particle experiences a loss of energy upon collisions; and in-flight dissipation given by (ii) F=-ηV(2); (iii) F=-ηV(μ) with μ≠1 and μ≠2 and; (iv) F=-ηV, where η is the dissipation parameter. Extensive numerical simulations were made and our results confirm that the unlimited energy growth, observed for the conservative dynamics, is suppressed for the dissipative case. The behaviour of the average velocity is described using scaling arguments and classes of universalities are defined.

  4. Fermi acceleration in non-autonomous billiards

    International Nuclear Information System (INIS)

    Gelfreich, V; Turaev, D

    2008-01-01

    Fermi acceleration can be modelled by a classical particle moving inside a time-dependent domain and elastically reflecting from its boundary. In this paper, we describe how the results from the dynamical system theory can be used to explain the existence of trajectories with unbounded energy. In particular, we show for slowly oscillating boundaries that the energy of the particle may increase exponentially fast in time. (fast track communication)

  5. The peculiarities of particle dynamics in the Fermi acceleration scheme

    International Nuclear Information System (INIS)

    Buts, V.A.

    2015-01-01

    With examples of discrete and distributed mathematical models of the Fermi acceleration mechanism, a usefulness, or even necessity, of taking into account of singular solutions is demonstrated. Also the role is shown of those parts of phase space where the uniqueness theorem conditions to form the dynamics of physical systems are broken. It was found that the dynamics of particles in discrete and distributed mathematical schemes of Fermi acceleration can be significantly different. The difference is due to the fact that the distributed model takes into account the effects of phase space where conditions do not correspond to those necessary for application of the uniqueness theorem. The role of singular solutions is under discussion as well.

  6. Fast Fermi acceleration in the plasma sheet boundary layer

    International Nuclear Information System (INIS)

    Wu, C.S.; Lui, A.T.Y.

    1989-01-01

    A longstanding question in the field of magnetospheric physics is the source of the energetic particles which are commonly observed along the plasma sheet boundary layer (PSBL). Several models have been suggested for the acceleration of these particles. We suggest a means by which the fast Fermi acceleration mechanism [Wu, 1984] can accelerate electrons at the plasma sheet and perhaps account for some of the observations. We propose the following: A localized hydromagnetic disturbance propagating through the tail lobe region impinges upon the PSBL deforming it and displacing it in towards the central plasma sheet. The boundary layer can then act like a moving magnetic mirror. If the disturbance is propagating nearly perpendicular to the layer then its velocity projected parallel to the layer (and the magnetic field) can be very large resulting in significant acceleration of reflected particles. copyright American Geophysical Union 1989

  7. A family of crisis in a dissipative Fermi accelerator model

    International Nuclear Information System (INIS)

    Leonel, Edson D.; Egydio de Carvalho, R.

    2007-01-01

    The Fermi accelerator model is studied in the framework of inelastic collisions. The dynamics of this problem is obtained by use of a two-dimensional nonlinear area-contracting map. We consider that the collisions of the particle with both periodically time varying and fixed walls are inelastic. We have shown that the dissipation destroys the mixed phase space structure of the nondissipative case and in special, we have obtained and characterized in this problem a family of two damping coefficients for which a boundary crisis occurs

  8. TIME-DEPENDENT STOCHASTIC ACCELERATION MODEL FOR FERMI BUBBLES

    Energy Technology Data Exchange (ETDEWEB)

    Sasaki, Kento; Asano, Katsuaki; Terasawa, Toshio, E-mail: kentos@icrr.u-tokyo.ac.jp, E-mail: asanok@icrr.u-tokyo.ac.jp, E-mail: terasawa@icrr.u-tokyo.ac.jp [Institute for Cosmic Ray Research, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8582 (Japan)

    2015-12-01

    We study stochastic acceleration models for the Fermi bubbles. Turbulence is excited just behind the shock front via Kelvin–Helmholtz, Rayleigh–Taylor, or Richtmyer–Meshkov instabilities, and plasma particles are continuously accelerated by the interaction with the turbulence. The turbulence gradually decays as it goes away from the shock fronts. Adopting a phenomenological model for the stochastic acceleration, we explicitly solve the temporal evolution of the particle energy distribution in the turbulence. Our results show that the spatial distribution of high-energy particles is different from those for a steady solution. We also show that the contribution of electrons that escaped from the acceleration regions significantly softens the photon spectrum. The photon spectrum and surface brightness profile are reproduced by our models. If the escape efficiency is very high, the radio flux from the escaped low-energy electrons can be comparable to that of the WMAP haze. We also demonstrate hadronic models with the stochastic acceleration, but they are unlikely in the viewpoint of the energy budget.

  9. Environmental Survey preliminary report, Fermi National Accelerator Laboratory, Batavia, Illinois

    International Nuclear Information System (INIS)

    1988-10-01

    This report presents the preliminary findings from the first phase of the Environmental Survey of the US Department of Energy (DOE) Fermi National Accelerator Laboratory (Fermilab), conducted September 14 through 25, 1987. The Survey is being conducted by an interdisciplinary team of environmental specialists led and managed by the Office of Environment, Safety and Health's Office of Environmental Audit. Individual participants for the Survey team are being supplied by a private contractor. The objective of the Survey is to identify environmental problems and areas of environmental risk associated with Fermilab. The Survey covers all environmental media and all areas of environmental regulation. It is being performed in accordance with the DOE Environmental Survey Manual. This phase of the Survey involves the review of existing site environmental data, observations of the operations performed at Fermilab, and interviews with site personnel. 110 refs., 26 figs., 41 tabs

  10. Environmental Survey preliminary report, Fermi National Accelerator Laboratory, Batavia, Illinois

    Energy Technology Data Exchange (ETDEWEB)

    1988-10-01

    This report presents the preliminary findings from the first phase of the Environmental Survey of the US Department of Energy (DOE) Fermi National Accelerator Laboratory (Fermilab), conducted September 14 through 25, 1987. The Survey is being conducted by an interdisciplinary team of environmental specialists led and managed by the Office of Environment, Safety and Health's Office of Environmental Audit. Individual participants for the Survey team are being supplied by a private contractor. The objective of the Survey is to identify environmental problems and areas of environmental risk associated with Fermilab. The Survey covers all environmental media and all areas of environmental regulation. It is being performed in accordance with the DOE Environmental Survey Manual. This phase of the Survey involves the review of existing site environmental data, observations of the operations performed at Fermilab, and interviews with site personnel. 110 refs., 26 figs., 41 tabs.

  11. Proposed Casey's Pond Improvement Project, Fermi National Accelerator Laboratory

    International Nuclear Information System (INIS)

    1995-05-01

    The U.S. Department of Energy (DOE) has prepared an Environmental Assessment (EA), evaluating the impacts associated with the proposed Casey's Pond Improvement Project at the Fermi National Accelerator Laboratory (Fermilab) in Batavia, Illinois. The improvement project would maximize the efficiency of the Fermilab Industrial Cooling Water (ICW) distribution system, which removes (via evaporation) the thermal load from experimental and other support equipment supporting the high energy physics program at Fermilab. The project would eliminate the risk of overheating during fixed target experiments, ensure that the Illinois Water Quality Standards are consistently achieved and provide needed additional water storage for fire protection. Based on the analysis in the EA, the DOE has determined that the proposed action does not constitute a major Federal action significantly affecting the quality of the human environment, within the meaning of the National Environmental Policy Act (NEPA) of 1969. Therefore, the preparation of an Environmental Impact Statement is not required

  12. Waves and particles in the Fermi accelerator model. Numerical simulation

    International Nuclear Information System (INIS)

    Meplan, O.

    1996-01-01

    This thesis is devoted to a numerical study of the quantum dynamics of the Fermi accelerator which is classically chaotic: it is particle in a one dimensional box with a oscillating wall. First, we study the classical dynamics: we show that the time of impact of the particle with the moving wall and its energy in the wall frame are conjugated variables and that Poincare surface of sections in these variables are more understandable than the usual stroboscopic sections. Then, the quantum dynamics of this systems is studied by the means of two numerical methods. The first one is a generalization of the KKR method in the space-time; it is enough to solve an integral equation on the boundary of a space-time billiard. The second method is faster and is based on successive free propagations and kicks of potential. This allows us to obtain Floquet states which we can on one hand, compare to the classical dynamics with the help of Husimi distributions and on the other hand, study as a function of parameters of the system. This study leads us to nice illustrations of phenomenons such as spatial localizations of a wave packet in a vibrating well or tunnel effects. In the adiabatic situation, we give a formula for quasi-energies which exhibits a phase term independent of states. In this regime, there exist some particular situations where the quasi-energy spectrum presents a total quasi-degeneracy. Then, the wave packet energy can increase significantly. This phenomenon is quite surprising for smooth motion of the wall. The third part deals with the evolution of a classical wave in the Fermi accelerator. Using generalized KKR method, we show a surprising phenomenon: in most of situations (so long as the wall motion is periodic), a wave is localized exponentially in the well and its energy increases in a geometric way. (author). 107 refs., 66 figs., 5 tabs. 2 appends

  13. FERMI and Elettra Accelerator Technical Optimization Final Report

    International Nuclear Information System (INIS)

    Cornacchia, M.; Craievich, P.; Di Mitri, S.; Pogorelov, I.; Qiang, J.; Venturini, M.; Zholents, A.; Wang, D.; Warnock, R.

    2006-01-01

    This report describes the accelerator physics aspects, the engineering considerations and the choice of parameters that led to the accelerator design of the FERMI Free-Electron-Laser. The accelerator (also called the ''electron beam delivery system'') covers the region from the exit of the injector to the entrance of the first FEL undulator. The considerations that led to the proposed configuration were made on the basis of a study that explored various options and performance limits. This work follows previous studies of x-ray FEL facilities (SLAC LCLS[1], DESY XFEL [2], PAL XFEL [3], MIT [4], BESSY FEL[5], LBNL LUX [6], Daresbury 4GLS [7]) and integrates many of the ideas that were developed there. Several issues specific to harmonic cascade FELs, and that had not yet been comprehensively studied, were also encountered and tackled. A particularly difficult issue was the need to meet the requirement for high peak current and small slice energy spread, as the specification for the ratio of these two parameters (that defines the peak brightness of the electron beam) is almost a factor of two higher than that of the LCLS's SASE FEL. Another challenging aspect was the demand to produce an electron beam with as uniform as possible peak current and energy distributions along the bunch, a condition that was met by introducing novel beam dynamics techniques. Part of the challenge was due to the fact that there were no readily available computational tools to carry out reliable calculations, and these had to be developed. Most of the information reported in this study is available in the form of scientific publications, and is partly reproduced here for the convenience of the reader

  14. Impact of compressibility and a guide field on Fermi acceleration during magnetic island coalescence

    Science.gov (United States)

    Montag, Peter; Egedal, Jan; Lichko, Emily; Wetherton, Blake

    2017-10-01

    Previous work has shown that Fermi acceleration can be an effective heating mechanism during magnetic island coalescence, where electrons may undergo repeated reflections as the magnetic field lines contract. This energization has the potential to account for the power-law distributions of particle energy inferred from observations of solar flares. Here, we develop a generalized framework for the analysis of Fermi acceleration that can incorporate the effects of compressibility and non-uniformity along field lines, which have commonly been neglected in previous treatments of the problem. Applying this framework to the simplified case of the uniform flux tube allows us to find both the power-law scaling of the distribution function and the rate at which the power-law behavior develops. We find that a guide magnetic field of order unity effectively suppresses the development of power-law distributions. The work was supported by NASA Grant No. NNX14AC68G, NSF GEM Grant No. 1405166, NSF Award 1404166, and NASA Award NNX15AJ73G.

  15. Tunneling dynamics of superfluid Fermi gases in an accelerating optical lattice

    International Nuclear Information System (INIS)

    Tie Lu; Xue Jukui

    2010-01-01

    The nonlinear Landau-Zener tunneling and the nonlinear Rabi oscillations of superfluid Fermi gases between Bloch bands in an accelerating optical lattice are discussed. Within the hydrodynamic theory and a two-level model, the tunneling probability of superfluid Fermi gases between Bloch bands is obtained. We find that, as the system crosses from the Bose-Einstein condensation (BEC) side to the BCS side, the tunneling rate is closely related to the particle density: when the density is smaller (larger) than a critical value, the tunneling rate at unitarity is larger (smaller) than that in the BEC limit. This is well explained in terms of an effective interaction and an effective potential. Furthermore, the nonlinear Rabi oscillations of superfluid Fermi gases between the bands are discussed by imposing a periodic modulation on the level bias and the strength of the lattice. Analytical expressions of the critical density for suppressing or enhancing the Rabi oscillations are obtained. It is shown that, as the system crosses from the BEC side to the BCS side, the critical density strongly depends on the modulation parameters (i.e., the modulation amplitude and the modulation frequency). For a fixed density, a high-frequency or low-frequency modulation can suppress or enhance the Rabi oscillations both at unitarity and in the BEC limit. For an intermediate modulation frequency, the Rabi oscillations are chaotic along the entire BEC-BCS crossover, especially, on the BCS side. Interestingly, we find that the modulation of the lattice strength only with an intermediate modulation frequency has significant effect on the Rabi oscillations both in the BEC limit and at unitarity; that is, an intermediate-frequency modulation can enhance the Rabi oscillations, especially on the BCS side.

  16. Tiger Team Assessment of the Fermi National Accelerator Laboratory

    International Nuclear Information System (INIS)

    1992-06-01

    This draft report documents the Tiger Team Assessment of the Fermi National Accelerator Laboratory (Fermilab) located in Batavia, Illinois. Fermilab is a program-dedicated national laboratory managed by the Universities Research Association, Inc. (URA) for the US Department of Energy (DOE). The Tiger Team Assessment was conducted from May 11 to June 8, 1992, under the auspices of DOE's Office of Special Projects (OSP) under the Office of the Assistant Secretary for Environment, Safety and Health (EH). The assessment was comprehensive, encompassing environmental, safety and health (ES ampersand H), and quality assurance (QA) disciplines; site remediation; facilities management; and waste management operations. Compliance with applicable Federal , State of Illinois, and local regulations; applicable DOE Orders; best management practices; and internal Fermilab requirements was addressed. In addition, an evaluation of the effectiveness of DOE and Fermilab management of the ES ampersand H/QA and self-assessment programs was conducted. The Fermilab Tiger Team Assessment is part a larger, comprehensive DOE Tiger Team Independent Assessment Program planned for DOE facilities. The objective of the initiative is to provide the Secretary of Energy with information on the compliance status of DOE facilities with regard to ES ampersand H requirements, root causes for noncompliance, adequacy of DOE and contractor ES ampersand H management programs, response actions to address the identified problem areas, and DOE-wide ES ampersand H compliance trends and root causes

  17. First order and second order fermi acceleration of energetic charged particles by shock waves

    International Nuclear Information System (INIS)

    Webb, G.M.

    1983-01-01

    Steady state solutions of the cosmic ray transport equation describing first order Fermi acceleration of energetic charged particles at a plane shock (without losses) and second order Fermi acceleration in the downstream region of the shock are derived. The solutions for the isotropic part of the phase space distribution function are expressible as eigenfunction expansions, being superpositions of series of power law momentum spectra, with the power law indices being the roots of an eigenvalue equation. The above exact analytic solutions are for the case where the spatial diffusion coefficient kappa is independent of momentum. The solutions in general depend on the shock compression ratio, the modulation parameters V 1 L/kappa 1 , V 2 L/kappa 2 (V is the plasma velocity, kappa is the energetic particle diffusion coefficient, and L a characteristic length over which second order Fermi acceleration is effective) in the upstream and downstream regions of the shock, respectively, and also on a further dimensionless parameter, zeta, characterizing second order Fermi acceleration. In the limit as zeta→0 (no second order Fermi acceleration) the power law momentum spectrum characteristic of first order Fermi acceleration (depending only on the shock compression ratio) obtained previously is recovered. Perturbation solutions for the case where second order Fermi effects are small, and for realistic diffusion coefficients (kappainfinityp/sup a/, a>0, p = particle momentum), applicable at high momenta, are also obtained

  18. Fermi

    Data.gov (United States)

    National Aeronautics and Space Administration — Fermi is a powerful space observatory that will open a wide window on the universe. Gamma rays are the highest-energy form of light, and the gamma-ray sky is...

  19. Myc suppression of Nfkb2 accelerates lymphomagenesis

    International Nuclear Information System (INIS)

    Keller, Ulrich; Huber, Jürgen; Nilsson, Jonas A; Fallahi, Mohammad; Hall, Mark A; Peschel, Christian; Cleveland, John L

    2010-01-01

    Deregulated c-Myc expression is a hallmark of several human cancers where it promotes proliferation and an aggressive tumour phenotype. Myc overexpression is associated with reduced activity of Rel/NF-κB, transcription factors that control the immune response, cell survival, and transformation, and that are frequently altered in cancer. The Rel/NF-κB family member NFKB2 is altered by chromosomal translocations or deletions in lymphoid malignancies and deletion of the C-terminal ankyrin domain of NF-κB2 augments lymphocyte proliferation. Precancerous Eμ-Myc-transgenic B cells, Eμ-Myc lymphomas and human Burkitt lymphoma samples were assessed for Nfkb2 expression. The contribution of Nfkb2 to Myc-driven apoptosis, proliferation, and lymphomagenesis was tested genetically in vivo. Here we report that the Myc oncoprotein suppresses Nfkb2 expression in vitro in primary mouse fibroblasts and B cells, and in vivo in the Eμ-Myc transgenic mouse model of human Burkitt lymphoma (BL). NFKB2 suppression by Myc was also confirmed in primary human BL. Promoter-reporter assays indicate that Myc-mediated suppression of Nfkb2 occurs at the level of transcription. The contribution of Nfkb2 to Myc-driven lymphomagenesis was tested in vivo, where Nfkb2 loss was shown to accelerate lymphoma development in Eμ-Myc transgenic mice, by impairing Myc's apoptotic response. Nfkb2 is suppressed by c-Myc and harnesses Myc-driven lymphomagenesis. These data thus link Myc-driven lymphomagenesis to the non-canonical NF-κB pathway

  20. 179th International School of Physics "Enrico Fermi" : Laser-Plasma Acceleration

    CERN Document Server

    Gizzi, L A; Faccini, R

    2012-01-01

    Impressive progress has been made in the field of laser-plasma acceleration in the last decade, with outstanding achievements from both experimental and theoretical viewpoints. Closely exploiting the development of ultra-intense, ultrashort pulse lasers, laser-plasma acceleration has developed rapidly, achieving accelerating gradients of the order of tens of GeV/m, and making the prospect of miniature accelerators a more realistic possibility. This book presents the lectures delivered at the Enrico Fermi International School of Physics and summer school: "Laser-Plasma Acceleration" , held in Varenna, Italy, in June 2011. The school provided an opportunity for young scientists to experience the best from the worlds of laser-plasma and accelerator physics, with intensive training and hands-on opportunities related to key aspects of laser-plasma acceleration. Subjects covered include: the secrets of lasers; the power of numerical simulations; beam dynamics; and the elusive world of laboratory plasmas. The object...

  1. Overview of Fermi National Accelerator Lab Control System

    International Nuclear Information System (INIS)

    Lucas, P.W.

    1990-01-01

    Various facets of the control of the Fermilab accelerators, in particular the Tevatron, are presented. Since Fermilab contains a superconducting machine and a sophisticated injection complex, much of the controls functionality will of necessity be the same at the SSC. The various functions required at a large laboratory are discussed; these include computer-based fire and security alarms and a cable television system, as well as computer networks connected to accelerator hardware components. A description is given of that hardware, of which much is Camac but with considerable computer backplane bus equipment also present. A large fraction of the controls hardware has access to high precision real-time clocks. Our various networks are introduced, with the physical layer being a combination of copper and more modern optic cables, with the primary intercomputer link being Token Ring. A description of the computers is presented - basically these consist of operators' consoles, host VAXs, and link driving front ends. The software effort is detailed, with emphasis on consoles and microprocessors where the majority of effort has been placed. Future plans for the system are presented briefly. 3 refs., 2 figs., 2 tabs

  2. Linear accelerator accelerating module to suppress back-acceleration of field-emitted particles

    Science.gov (United States)

    Benson, Stephen V.; Marhauser, Frank; Douglas, David R.; Ament, Lucas J. P.

    2017-12-05

    A method for the suppression of upstream-directed field emission in RF accelerators. The method is not restricted to a certain number of cavity cells, but requires similar operating field levels in all cavities to efficiently annihilate the once accumulated energy. Such a field balance is desirable to minimize dynamic RF losses, but not necessarily achievable in reality depending on individual cavity performance, such as early Q.sub.0-drop or quench field. The method enables a significant energy reduction for upstream-directed electrons within a relatively short distance. As a result of the suppression of upstream-directed field emission, electrons will impact surfaces at rather low energies leading to reduction of dark current and less issues with heating and damage of accelerator components as well as radiation levels including neutron generation and thus radio-activation.

  3. One-dimensional Fermi accelerator model with moving wall described by a nonlinear van der Pol oscillator.

    Science.gov (United States)

    Botari, Tiago; Leonel, Edson D

    2013-01-01

    A modification of the one-dimensional Fermi accelerator model is considered in this work. The dynamics of a classical particle of mass m, confined to bounce elastically between two rigid walls where one is described by a nonlinear van der Pol type oscillator while the other one is fixed, working as a reinjection mechanism of the particle for a next collision, is carefully made by the use of a two-dimensional nonlinear mapping. Two cases are considered: (i) the situation where the particle has mass negligible as compared to the mass of the moving wall and does not affect the motion of it; and (ii) the case where collisions of the particle do affect the movement of the moving wall. For case (i) the phase space is of mixed type leading us to observe a scaling of the average velocity as a function of the parameter (χ) controlling the nonlinearity of the moving wall. For large χ, a diffusion on the velocity is observed leading to the conclusion that Fermi acceleration is taking place. On the other hand, for case (ii), the motion of the moving wall is affected by collisions with the particle. However, due to the properties of the van der Pol oscillator, the moving wall relaxes again to a limit cycle. Such kind of motion absorbs part of the energy of the particle leading to a suppression of the unlimited energy gain as observed in case (i). The phase space shows a set of attractors of different periods whose basin of attraction has a complicated organization.

  4. An aerial radiological survey of the Fermi National Accelerator Laboratory and surrounding area, Batavia, Illinois

    International Nuclear Information System (INIS)

    Fritzsche, A.E.

    1990-11-01

    An aerial radiological gamma survey was conducted over the Fermi National Accelerator Laboratory during 1 through 6 June 1989. Flight lines at 150-foot altitude and 250-foot line spacings assured nearly 100% coverage. The terrestrial exposure at about 6 μR/h was nearly the same as that measured by the previous survey of this area (May 1977). Ten anomalous areas, mostly Na-22 and Mn-54, were detected within buildings and laboratories in the area. Although these locations have changed somewhat from the 1977 survey, the aerial data shows good agreement with the ground-based ion chamber and soil sample data. 7 refs., 15 figs., 1 tab

  5. An improved 8 GeV beam transport system for the Fermi National Accelerator Laboratory

    International Nuclear Information System (INIS)

    Syphers, M.J.

    1987-06-01

    A new 8 GeV beam transport system between the Booster and Main Ring synchrotrons at the Fermi National Accelerator Laboratory is presented. The system was developed in an effort to improve the transverse phase space area occupied by the proton beam upon injection into the Main Ring accelerator. Problems with the original system are described and general methods of beamline design are formulated. Errors in the transverse properties of a beamline at the injection point of the second synchrotron and their effects on the region in transverse phase space occupied by a beam of particles are discussed. Results from the commissioning phase of the project are presented as well as measurements of the degree of phase space dilution generated by the transfer of 8 GeV protons from the Booster synchrotron to the Main Ring synchrotron

  6. A cocoon of freshly accelerated cosmic rays detected by Fermi in the Cygnus Superbubble

    International Nuclear Information System (INIS)

    Ackermann, M.; Ajello, A.; Allafort, A.; Berenji, B.; Blandford, R.D.; Bloom, E.D.; Borgland, A.W.; Bottacini, E.; Buehler, R.; Cameron, R.A.; Chiang, J.; Claus, R.; Do Couto e Silva, E.; Drell, P.S.; Focke, W.B.; Glanzman, T.; Godfrey, G.; Hayashida, M.; Johnson, A.S.; Kamae, T.; Kerr, M.; Lande, J.; Michelson, P.F.; Mitthumsiri, W.; Monzani, M.E.; Moskalenko, I.V.; Murgia, S.; Nolan, P.L.; Okumura, A.; Orlando, E.; Paneque, D.; Prokhorov, D.; Tanaka, T.; Thayer, J.G.; Thayer, J.B.; Tramacere, A.; Uchiyama, Y.; Vandenbroucke, J.; Vianello, G.; Waite, A.P.; Wang, P.; Baldini, L.; Bellazzini, R.; Kuss, M.; Latronico, L.; Pesce-Rollins, M.; Razzano, M.; Sgro, C.; Ballet, J.; Casandjian, J.M.; Grenier, I.A.; Naumann-Godo, M.; Pierbattista, M.; Tibaldo, L.

    2011-01-01

    The origin of Galactic cosmic rays is a century-long puzzle. Indirect evidence points to their acceleration by supernova shock waves, but we know little of their escape from the shock and their evolution through the turbulent medium surrounding massive stars. Gamma rays can probe their spreading through the ambient gas and radiation fields. The Fermi Large Area Telescope (LAT) has observed the star-forming region of Cygnus X. The 1- to 100-giga-electron-volt images reveal a 50-parsec-wide cocoon of freshly accelerated cosmic rays that flood the cavities carved by the stellar winds and ionization fronts from young stellar clusters. It provides an example to study the youth of cosmic rays in a superbubble environment before they merge into the older Galactic population. (authors)

  7. Doubling Beam Intensity Unlocks Rare Opportunities for Discovery at Fermi National Accelerator Laboratory

    International Nuclear Information System (INIS)

    Segui, Jennifer A.

    2014-01-01

    Particle accelerators such as the Booster synchrotron at the Fermi National Accelerator Laboratory (FNAL) produce high-intensity proton beams for particle physics experiments that can ultimately reveal the secrets of the universe. High-intensity proton beams are required by experiments at the ''intensity frontier'' of particle physics research, where the availability of more particles improves the chances of observing extremely rare physical processes. In addition to their central role in particle physics experiments, particle accelerators have found widespread use in industrial, nuclear, environmental, and medical applications. RF cavities are essential components of particle accelerators that, depending on the design, can perform multiple functions, including bunching, focusing, decelerating, and accelerating a beam of charged particles. Engineers are working to model the RF cavities required for upgrading the 40-year old Booster synchrotron. It is a rather complicated process to refurbish, test, and qualify the upgraded RF cavities to sustain an increased repetition rate of the RF field required to produce proton beams at double the current intensity. Both multiphysics simulation and physical measurements are used to evaluate the RF, thermal, and mechanical properties of the Booster RF cavities.

  8. The MARS15-based FermiCORD code system for calculation of the accelerator-induced residual dose

    Science.gov (United States)

    Grebe, A.; Leveling, A.; Lu, T.; Mokhov, N.; Pronskikh, V.

    2018-01-01

    The FermiCORD code system, a set of codes based on MARS15 that calculates the accelerator-induced residual doses at experimental facilities of arbitrary configurations, has been developed. FermiCORD is written in C++ as an add-on to Fortran-based MARS15. The FermiCORD algorithm consists of two stages: 1) simulation of residual doses on contact with the surfaces surrounding the studied location and of radionuclide inventories in the structures surrounding those locations using MARS15, and 2) simulation of the emission of the nuclear decay γ-quanta by the residuals in the activated structures and scoring the prompt doses of these γ-quanta at arbitrary distances from those structures. The FermiCORD code system has been benchmarked against similar algorithms based on other code systems and against experimental data from the CERF facility at CERN, and FermiCORD showed reasonable agreement with these. The code system has been applied for calculation of the residual dose of the target station for the Mu2e experiment and the results have been compared to approximate dosimetric approaches.

  9. Waves and particles in the Fermi accelerator model. Numerical simulation; Ondes et particules dans le modele de l`accelerateur de Fermi. Simulation numerique

    Energy Technology Data Exchange (ETDEWEB)

    Meplan, O

    1996-01-01

    This thesis is devoted to a numerical study of the quantum dynamics of the Fermi accelerator which is classically chaotic: it is particle in a one dimensional box with a oscillating wall. First, we study the classical dynamics: we show that the time of impact of the particle with the moving wall and its energy in the wall frame are conjugated variables and that Poincare surface of sections in these variables are more understandable than the usual stroboscopic sections. Then, the quantum dynamics of this systems is studied by the means of two numerical methods. The first one is a generalization of the KKR method in the space-time; it is enough to solve an integral equation on the boundary of a space-time billiard. The second method is faster and is based on successive free propagations and kicks of potential. This allows us to obtain Floquet states which we can on one hand, compare to the classical dynamics with the help of Husimi distributions and on the other hand, study as a function of parameters of the system. This study leads us to nice illustrations of phenomenons such as spatial localizations of a wave packet in a vibrating well or tunnel effects. In the adiabatic situation, we give a formula for quasi-energies which exhibits a phase term independent of states. In this regime, there exist some particular situations where the quasi-energy spectrum presents a total quasi-degeneracy. Then, the wave packet energy can increase significantly. This phenomenon is quite surprising for smooth motion of the wall. The third part deals with the evolution of a classical wave in the Fermi accelerator. Using generalized KKR method, we show a surprising phenomenon: in most of situations (so long as the wall motion is periodic), a wave is localized exponentially in the well and its energy increases in a geometric way. (author). 107 refs., 66 figs., 5 tabs. 2 appends.

  10. The MARS15-based FermiCORD code system for calculation of the accelerator-induced residual dose

    Energy Technology Data Exchange (ETDEWEB)

    Grebe, A.; Leveling, A.; Lu, T.; Mokhov, N.; Pronskikh, V.

    2018-01-01

    The FermiCORD code system, a set of codes based on MARS15 that calculates the accelerator-induced residual doses at experimental facilities of arbitrary configurations, has been developed. FermiCORD is written in C++ as an add-on to Fortran-based MARS15. The FermiCORD algorithm consists of two stages: 1) simulation of residual doses on contact with the surfaces surrounding the studied location and of radionuclide inventories in the structures surrounding those locations using MARS15, and 2) simulation of the emission of the nuclear decay gamma-quanta by the residuals in the activated structures and scoring the prompt doses of these gamma-quanta at arbitrary distances from those structures. The FermiCORD code system has been benchmarked against similar algorithms based on other code systems and showed a good agreement. The code system has been applied for calculation of the residual dose of the target station for the Mu2e experiment and the results have been compared to approximate dosimetric approaches.

  11. Thin Film Coatings for Suppressing Electron Multipacting in Particle Accelerators

    CERN Document Server

    Costa Pinto, P; Chiggiato, P; Neupert, H; Shaposhnikova, E N; Taborelli, M; Vollenberg, W; Yin Vallgren, C

    2011-01-01

    Thin film coatings are an effective way for suppressing electron multipacting in particle accelerators. For bakeable beam pipes, the TiZrV Non Evaporable Getter (NEG) developed at CERN can provide a Secondary Electron Yield (SEY) of 1.1 after activation at 180oC (24h). The coating process was implemented in large scale to coat the long straight sections and the experimental beam pipes for the Large Hadron Collider (LHC). For non bakeable beam pipes, as those of the Super Proton Synchrotron (SPS), CERN started a campaign to develop a coating having a low SEY without need of in situ heating. Magnetron sputtered carbon thin films have shown SEY of 1 with marginal deterioration when exposed in air for months. This material is now being tested in both laboratory and accelerator environment. At CERN’s SPS, tests with electron cloud monitors attached to carbon coated chambers show no degradation of the coating after two years of operation interleaved with a total of 3 months of air exposure during shutdown periods...

  12. Design study of high gradient, low impedance accelerating structures for the FERMI free electron laser linac upgrade

    Science.gov (United States)

    Shafqat, N.; Di Mitri, S.; Serpico, C.; Nicastro, S.

    2017-09-01

    The FERMI free-electron laser (FEL) of Elettra Sincrotrone Trieste, Italy, is a user facility driven by a 1.5 GeV 10-50 Hz S-band radiofrequency linear accelerator (linac), and it is based on an external laser seeding scheme that allows lasing at the shortest fundamental wavelength of 4 nm. An increase of the beam energy to 1.8 GeV at a tolerable breakdown rate, and an improvement of the final beam quality is desired in order to allow either lasing at 4 nm with a higher flux, or lasing at shorter wavelengths. This article presents the impedance analysis of newly designed S-band accelerating structures, for replacement of the existing backward travelling wave structures (BTWS) in the last portion of the FERMI linac. The new structure design promises higher accelerating gradient and lower impedance than those of the existing BTWS. Particle tracking simulations show that, with the linac upgrade, the beam relative energy spread, its linear and nonlinear z-correlation internal to the bunch, and the beam transverse emittances can be made smaller than the ones in the present configuration, with expected advantage to the FEL performance. The repercussion of the upgrade on the linac quadrupole magnets setting, for a pre-determined electron beam optics, is also considered.

  13. Experience with copper oxide production in antiproton source components at Fermi National Accelerator Laboratory

    International Nuclear Information System (INIS)

    Ader, Christine R.; Harms, Elvin R. Jr; Morgan, James P.

    2000-01-01

    The Antiproton (Pbar) Source at Fermi National Accelerator Laboratory is a facility comprised of a target station, two rings called the Debuncher and Accumulator and the transport lines between those rings and the remainder of the particle accelerator complex. Water is by far the most common medium for carrying excess heat away from components, primarily electromagnets, in this facility. The largest of the water systems found in Pbar is the 95 degree Fahrenheit Low Conductivity Water (LCW) system. LCW is water which has had free ions removed, increasing its resistance to electrical current. This water circuit is used to cool magnets, power supplies, and stochastic cooling components and typically has a resistivity of 11--18 megaohms-cm. For more than ten years the Antiproton rings were plagued with overheating magnets due to plugged water-cooling channels. Various repairs have been tried over the years with no permanent success. Throughout all of this time, water samples have indicated copper oxide, CuO, as the source of the contamination. Matters came to a head in early 1997 following a major underground LCW leak between the Central Utilities Building and the Antiproton Rings enclosures. Over a span of several weeks following system turn-on, some twenty magnets overheated leading to unreliable Pbar source operation. Although it was known that oxygen in the system reacts with the copper tubing to form CuO, work to remedy this problem was not undertaken until this time period. Leaks, large quantities of make-up water, infrequent filter replacement, and thermal cycling also result in an increase in the corrosion product release rate. A three-pronged approach has been implemented to minimize the amount of copper oxide available to plug the magnets: (1) installation of an oxygen removal system capable of achieving dissolved oxygen concentrations in the parts per billion (ppb) range; (2) regular closed-loop filter/flushing of the copper headers and magnets and stainless

  14. Construction and Performance of a Liquid Argon Calorimeter for use in Experiment E-706 at the Fermi National Accelerator Laboratory

    Energy Technology Data Exchange (ETDEWEB)

    DeSoi, William Edward [Rochester U.

    1990-01-01

    The subject of this thesis is a liquid argon calorimeter developed by the E-706 collaboration. This device was used in measuring the energy content of showers produced by the interaction of nucleons with 530 GeV/c pions at the Fermi National Accelerator Laboratory. A description of the calorimeter's construction and design considerations precedes the analysis of its performance, which is the central topic to be discussed. The calorimeter was found to have an intrinsic energy for electromagnetic showers of 14.5%/$\\sqrt{E}$ and for hadronic showers a resolution of 183%/$\\sqrt{E}$. The position resolution of showers for the calorimeter was found to be 1.0 mm or better for energies greater than 2.0 GeV.

  15. Non-thermal electron acceleration in low Mach number collisionless shocks. II. Firehose-mediated Fermi acceleration and its dependence on pre-shock conditions

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Xinyi; Narayan, Ramesh [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Sironi, Lorenzo [NASA Einstein Postdoctoral Fellow. (United States)

    2014-12-10

    Electron acceleration to non-thermal energies is known to occur in low Mach number (M{sub s} ≲ 5) shocks in galaxy clusters and solar flares, but the electron acceleration mechanism remains poorly understood. Using two-dimensional (2D) particle-in-cell (PIC) plasma simulations, we showed in Paper I that electrons are efficiently accelerated in low Mach number (M{sub s} = 3) quasi-perpendicular shocks via a Fermi-like process. The electrons bounce between the upstream region and the shock front, with each reflection at the shock resulting in energy gain via shock drift acceleration. The upstream scattering is provided by oblique magnetic waves that are self-generated by the electrons escaping ahead of the shock. In the present work, we employ additional 2D PIC simulations to address the nature of the upstream oblique waves. We find that the waves are generated by the shock-reflected electrons via the firehose instability, which is driven by an anisotropy in the electron velocity distribution. We systematically explore how the efficiency of wave generation and of electron acceleration depend on the magnetic field obliquity, the flow magnetization (or equivalently, the plasma beta), and the upstream electron temperature. We find that the mechanism works for shocks with high plasma beta (≳ 20) at nearly all magnetic field obliquities, and for electron temperatures in the range relevant for galaxy clusters. Our findings offer a natural solution to the conflict between the bright radio synchrotron emission observed from the outskirts of galaxy clusters and the low electron acceleration efficiency usually expected in low Mach number shocks.

  16. Representing Value as Digital Object: A Discussion of Transferability and Anonymity; Digital Library Initiatives of the Deutsche Forschungsgemeinschaft; CrossRef Turns One; Fermi National Accelerator Laboratory (Fermilab).

    Science.gov (United States)

    Kahn, Robert E.; Lyons, Patrice A.; Brahms, Ewald; Brand, Amy; van den Bergen, Mieke

    2001-01-01

    Includes four articles that discuss the use of digital objects to represent value in a network environment; digital library initiatives at the central public funding organization for academic research in Germany; an application of the Digital Object Identifier System; and the Web site of the Fermi National Accelerator Laboratory. (LRW)

  17. Effect of X-ray suppression system upon parameters of electrostatic accelerator ion beam

    Directory of Open Access Journals (Sweden)

    I. G. Ignat'ev

    2014-12-01

    Full Text Available Experimental study results are presented for a beam profile and emittance of an electrostatic accelerator “Sokol” before and after being equipped with magnet X-ray suppression system.

  18. A Novel Method for Vertical Acceleration Noise Suppression of a Thrust-Vectored VTOL UAV.

    Science.gov (United States)

    Li, Huanyu; Wu, Linfeng; Li, Yingjie; Li, Chunwen; Li, Hangyu

    2016-12-02

    Acceleration is of great importance in motion control for unmanned aerial vehicles (UAVs), especially during the takeoff and landing stages. However, the measured acceleration is inevitably polluted by severe noise. Therefore, a proper noise suppression procedure is required. This paper presents a novel method to reduce the noise in the measured vertical acceleration for a thrust-vectored tail-sitter vertical takeoff and landing (VTOL) UAV. In the new procedure, a Kalman filter is first applied to estimate the UAV mass by using the information in the vertical thrust and measured acceleration. The UAV mass is then used to compute an estimate of UAV vertical acceleration. The estimated acceleration is finally fused with the measured acceleration to obtain the minimum variance estimate of vertical acceleration. By doing this, the new approach incorporates the thrust information into the acceleration estimate. The method is applied to the data measured in a VTOL UAV takeoff experiment. Two other denoising approaches developed by former researchers are also tested for comparison. The results demonstrate that the new method is able to suppress the acceleration noise substantially. It also maintains the real-time performance in the final estimated acceleration, which is not seen in the former denoising approaches. The acceleration treated with the new method can be readily used in the motion control applications for UAVs to achieve improved accuracy.

  19. A Novel Method for Vertical Acceleration Noise Suppression of a Thrust-Vectored VTOL UAV

    Directory of Open Access Journals (Sweden)

    Huanyu Li

    2016-12-01

    Full Text Available Acceleration is of great importance in motion control for unmanned aerial vehicles (UAVs, especially during the takeoff and landing stages. However, the measured acceleration is inevitably polluted by severe noise. Therefore, a proper noise suppression procedure is required. This paper presents a novel method to reduce the noise in the measured vertical acceleration for a thrust-vectored tail-sitter vertical takeoff and landing (VTOL UAV. In the new procedure, a Kalman filter is first applied to estimate the UAV mass by using the information in the vertical thrust and measured acceleration. The UAV mass is then used to compute an estimate of UAV vertical acceleration. The estimated acceleration is finally fused with the measured acceleration to obtain the minimum variance estimate of vertical acceleration. By doing this, the new approach incorporates the thrust information into the acceleration estimate. The method is applied to the data measured in a VTOL UAV takeoff experiment. Two other denoising approaches developed by former researchers are also tested for comparison. The results demonstrate that the new method is able to suppress the acceleration noise substantially. It also maintains the real-time performance in the final estimated acceleration, which is not seen in the former denoising approaches. The acceleration treated with the new method can be readily used in the motion control applications for UAVs to achieve improved accuracy.

  20. First-order Fermi acceleration of the diffuse ion population near the earth's bow shock

    Science.gov (United States)

    Forman, M. A.

    1981-01-01

    The flux of 30-65 keV particles observed by the ISEE-3 200 earth radii upstream is shown to be an upstream escape of the energetic ions in the earth's bow shock. A formal solution to the transport equation for the distribution function of energetic particles upstream from an isotropic monoenergetic source of particles/sq cm at a plane shock where the plasma changes speed is found, and escape conditions are defined. The efficiency of the acceleration is calculated to depend on the charge/particle, and fluxes near and far upstream of the shock are described analytically. Any model which takes into account shock acceleration by diffusive scattering with significant escape losses produces the observed spectrum close to the shock. The escape loss upstream is demonstrated to control the spectrum and the variation of flux and anisotropy with distance from the shock.

  1. Electron Fermi acceleration in collapsing magnetic traps: Computational and analytical models

    International Nuclear Information System (INIS)

    Gisler, G.; Lemons, D.

    1990-01-01

    The authors consider the heating and acceleration of electrons trapped on magnetic field lines between approaching magnetic mirrors. Such a collapsing magnetic trap and consequent electron energization can occur whenever a curved (or straight) flux tube drifts into a relatively straight (or curved) perpendicular shock. The relativistic, three-dimensional, collisionless test particle simulations show that an initial thermal electron distribution is bulk heated while a few individual electrons are accelerated to many times their original energy before they escape the trap. Upstream field-aligned beams and downstream pancake distributions perpendicular to the field are predicted. In the appropriate limit the simulation results agree well with a nonrelativistic analytic model of the distribution of escaping electrons which is based on the first adiabatic invariant and energy conservation between collisions with the mirrors. Space science and astrophysical applications are discussed

  2. Identification of cosmic accelerators: search for GeV pulsar nebulae with the Large Area Fermi telescope

    International Nuclear Information System (INIS)

    Rousseau, R.

    2013-01-01

    The Fermi Gamma-ray Space Telescope was launched on 2008 June 11, carrying the Large Area Telescope (LAT), sensitive to gamma-rays from 20 MeV to more than 300 GeV. Its constantly improving sensitivity and performance offer a new opportunity to understand the sources of the gamma-ray sky including Pulsar Wind Nebulae (PWNe). PWNe are powered by the constant injection of a relativistic wind of electrons and positrons from their central pulsars. These charged particles are accelerated at the shock front forming the PWN and emit photons which can be observed along the entire electromagnetic spectrum, including the high energy gamma-ray domain via inverse Compton scattering. This thesis presents the detailed analysis of two sources of gamma-ray emission potentially associated to PWNe: MSH 11-62 and HESS J1857+026. The combination of the spatial and spectral analyses provide new elements to confirm these associations. In a second step, we describe a search for counterparts to sources detected by Cerenkov telescopes. This search led to the detection of six new LAT sources potentially associated with PWNe. These studies bring new insights and constraints on the physical properties of the sources as well as on emitting processes by constraining the models and allowing population studies. (author)

  3. Aerial radiological survey of the Fermi National accelerator Laboratory and surrounding area, Batavia, Illinois. Data of survey: 12-14 May 1977

    International Nuclear Information System (INIS)

    Jobst, J.E.

    1981-01-01

    An aerial radiological survey was conducted over the facilities of the Fermi National Accelerator Laboratory (Fermilab) near Batavia, Illinois on 12-14 May 1977. The survey was flown at an altitude of 91 m by a helicopter containing 20 sodium iodide detectors. The line spacing was also 91 m. Enhanced gamma exposure rate levels, which could be attributed to Fermilab operations, were observed at seven locations. One additional anomaly, not related to the Laboratory, was also discovered

  4. Rapamycin suppresses brain aging in senescence-accelerated OXYS rats.

    Science.gov (United States)

    Kolosova, Nataliya G; Vitovtov, Anton O; Muraleva, Natalia A; Akulov, Andrey E; Stefanova, Natalia A; Blagosklonny, Mikhail V

    2013-06-01

    Cellular and organismal aging are driven in part by the MTOR (mechanistic target of rapamycin) pathway and rapamycin extends life span inC elegans, Drosophila and mice. Herein, we investigated effects of rapamycin on brain aging in OXYS rats. Previously we found, in OXYS rats, an early development of age-associated pathological phenotypes similar to several geriatric disorders in humans, including cerebral dysfunctions. Behavioral alterations as well as learning and memory deficits develop by 3 months. Here we show that rapamycin treatment (0.1 or 0.5 mg/kg as a food mixture daily from the age of 1.5 to 3.5 months) decreased anxiety and improved locomotor and exploratory behavior in OXYS rats. In untreated OXYS rats, MRI revealed an increase of the area of hippocampus, substantial hydrocephalus and 2-fold increased area of the lateral ventricles. Rapamycin treatment prevented these abnormalities, erasing the difference between OXYS and Wister rats (used as control). All untreated OXYS rats showed signs of neurodegeneration, manifested by loci of demyelination. Rapamycin decreased the percentage of animals with demyelination and the number of loci. Levels of Tau and phospho-Tau (T181) were increased in OXYS rats (compared with Wistar). Rapamycin significantly decreased Tau and inhibited its phosphorylation in the hippocampus of OXYS and Wistar rats. Importantly, rapamycin treatment caused a compensatory increase in levels of S6 and correspondingly levels of phospo-S6 in the frontal cortex, indicating that some downstream events were compensatory preserved, explaining the lack of toxicity. We conclude that rapamycin in low chronic doses can suppress brain aging.

  5. Design consideration of relativistic klystron two-beam accelerator for suppression of beam-break-up

    International Nuclear Information System (INIS)

    Li, H.; Houck, T.L.; Yu, S.; Goffeney, N.

    1994-03-01

    It is demonstrated in this simulation study that by using the scheme of operating rf extraction structures on the betatron nodes of electron drive beam in conjunction with adequate de-Q-ing, appropriate choice of geometries for the rf structures (reducing transverse impedence) and/or staggered tuning we can suppress the overall growth of transverse instabilities to 4 e-folds in a relativistic klystron two-beam accelerator with 200 extraction cavities

  6. Stable radiation pressure acceleration of ions by suppressing transverse Rayleigh-Taylor instability with multiple Gaussian pulses

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, M. L.; Liu, B.; Hu, R. H.; Shou, Y. R.; Lin, C.; Lu, H. Y.; Lu, Y. R.; Ma, W. J., E-mail: wenjun.ma@pku.edu.cn [State Key Laboratory of Nuclear Physics and Technology, and Key Laboratory of HEDP of the Ministry of Education, CAPT, Peking University, Beijing 100871 (China); Gu, Y. Q. [Laser Fusion Research Center, China Academy of Engineering Physics, Mianyang, Sichuan 621900 (China); Yan, X. Q., E-mail: x.yan@pku.edu.cn [State Key Laboratory of Nuclear Physics and Technology, and Key Laboratory of HEDP of the Ministry of Education, CAPT, Peking University, Beijing 100871 (China); Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, Shanxi 030006 (China)

    2016-08-15

    In the case of a thin plasma slab accelerated by the radiation pressure of an ultra-intense laser pulse, the development of Rayleigh-Taylor instability (RTI) will destroy the acceleration structure and terminate the acceleration process much sooner than theoretical limit. In this paper, a new scheme using multiple Gaussian pulses for ion acceleration in a radiation pressure acceleration regime is investigated with particle-in-cell simulation. We found that with multiple Gaussian pulses, the instability could be efficiently suppressed and the divergence of the ion bunch is greatly reduced, resulting in a longer acceleration time and much more collimated ion bunch with higher energy than using a single Gaussian pulse. An analytical model is developed to describe the suppression of RTI at the laser-plasma interface. The model shows that the suppression of RTI is due to the introduction of the long wavelength mode RTI by the multiple Gaussian pulses.

  7. Twist1 suppresses senescence programs and thereby accelerates and maintains mutant Kras-induced lung tumorigenesis.

    Directory of Open Access Journals (Sweden)

    Phuoc T Tran

    Full Text Available KRAS mutant lung cancers are generally refractory to chemotherapy as well targeted agents. To date, the identification of drugs to therapeutically inhibit K-RAS have been unsuccessful, suggesting that other approaches are required. We demonstrate in both a novel transgenic mutant Kras lung cancer mouse model and in human lung tumors that the inhibition of Twist1 restores a senescence program inducing the loss of a neoplastic phenotype. The Twist1 gene encodes for a transcription factor that is essential during embryogenesis. Twist1 has been suggested to play an important role during tumor progression. However, there is no in vivo evidence that Twist1 plays a role in autochthonous tumorigenesis. Through two novel transgenic mouse models, we show that Twist1 cooperates with Kras(G12D to markedly accelerate lung tumorigenesis by abrogating cellular senescence programs and promoting the progression from benign adenomas to adenocarcinomas. Moreover, the suppression of Twist1 to physiological levels is sufficient to cause Kras mutant lung tumors to undergo senescence and lose their neoplastic features. Finally, we analyzed more than 500 human tumors to demonstrate that TWIST1 is frequently overexpressed in primary human lung tumors. The suppression of TWIST1 in human lung cancer cells also induced cellular senescence. Hence, TWIST1 is a critical regulator of cellular senescence programs, and the suppression of TWIST1 in human tumors may be an effective example of pro-senescence therapy.

  8. Observational test of shock drift and Fermi acceleration on a seed particle population upstream of earth's bow shock

    Science.gov (United States)

    Anagnostopoulos, G. C.; Sarris, E. T.; Krimigis, S. M.

    1988-01-01

    The efficiency of proposed shock acceleration mechanisms as they operate at the bow shock in the presence of a seed energetic particle population was examined using data from simultaneous observations of energetic solar-origin protons, carried out by the IMP 7 and 8 spacecraft in the vicinity of the quasi-parallel (dawn) and quasi-perpendicular (dusk) regions of the earth's bow shock, respectively. The results of observations (which include acceleration effects in the intensities of the energetic protons with energies as high as 4 MeV observed at the vicinity of the dusk bow shock, but no evidence for any particle acceleration at the energy equal to or above 50 keV at the dawn side of the bow shock) indicate that the acceleration of a seed particle population occurs only at the quasi-perpendicular bow shock through shock drift acceleration and that the major source of observed upstream ion populations is the leakage of magnetospheric ions of energies not less than 50 keV, rather than in situ acceleration.

  9. Observation of multipactor suppression in a dielectric-loaded accelerating structure using an applied axial magnetic field

    International Nuclear Information System (INIS)

    Jing, C.; Konecny, R.; Antipov, S.; Chang, C.; Gold, S. H.; Schoessow, P.; Kanareykin, A.; Gai, W.

    2013-01-01

    Efforts by a number of institutions to develop a Dielectric-Loaded Accelerating (DLA) structure capable of supporting high gradient acceleration when driven by an external radio frequency source have been ongoing over the past decade. Single surface resonant multipactor has been previously identified as one of the major limitations on the practical application of DLA structures in electron accelerators. In this paper, we report the results of an experiment that demonstrated suppression of multipactor growth in an X-band DLA structure through the use of an applied axial magnetic field. This represents an advance toward the practical use of DLA structures in many accelerator applications

  10. E Fermi

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education. E Fermi. Articles written in Resonance – Journal of Science Education. Volume 19 Issue 1 January 2014 pp 82-96 Classics. Quantization of an Ideal Monoatomic Gas · E Fermi · More Details Fulltext PDF ...

  11. Suppression of beam-break-up in a standing wave free electron laser two-beam accelerator

    International Nuclear Information System (INIS)

    Li, H.; Kim, J.S.

    1994-03-01

    Various schemes are examined in this study on the suppression of beam break-up (BBU) in a standing wave free electron laser two-beam accelerator (SWFEL/TBA). Two schemes are found to be not only able to effectively suppress the BBU but at the same time have minimum effect on the microwave generation process inside the SWFEL cavities. One is making the cavity-iris junction sufficiently gradual and the other is stagger-tuning the cavities

  12. Cosmic ray acceleration mechanisms

    International Nuclear Information System (INIS)

    Cesarsky, C.J.

    1982-09-01

    We present a brief summary of some of the most popular theories of cosmic ray acceleration: Fermi acceleration, its application to acceleration by shocks in a scattering medium, and impulsive acceleration by relativistic shocks

  13. Suppression of X-radiation from 2 MeV ion electrostatic accelerator

    International Nuclear Information System (INIS)

    Ignat'ev, I.G.; Miroshnichenko, V.I.; Sirenko, A.M.; Storizhko, V.E.

    2008-01-01

    The paper presents results concerning studies of X-radiation from 2 MeV ion electrostatic accelerator 'Sokol' used for nuclear microprobe analysis. The radiation protection system of the accelerator was developed and tested. Tests of the system of the accelerator show that it reduces doses rate by two orders of magnitude

  14. The Calculation and Design of Fire suppression system in the proton accelerator research center

    International Nuclear Information System (INIS)

    Jeon, G. P.; Kim, J. Y.; Cho, J. H.; Min, Y. S.; Mun, K. J.; Cho, J. S.; Nam, J. M.; Park, S. S.; Joo, H. G.

    2010-01-01

    The fire protection system is composed of various fire suppression systems and fire detection and alarm systems. The primary function of the fire protection system is to protect life and property from a fire through detecting fires quickly and suppressing those fires that occur. In this paper, we described the fire suppression system only. The fire suppression system capacity for fire hydrant, the water mist system, sprinkler system and clean agent system is calculated and designed in compliance with the applicable Korean Acts that are applicable to fire protection and the NFSC code

  15. Fermi Large Area Telescope

    Science.gov (United States)

    are available to the public, along with standard analysis software, from NASA's Fermi Science Support Center. For general questions about Fermi, Fermi science, or Fermi classroom materials, please contact Fermi has its own music: a prelude and a symphony. Gamma Ray Bursts trasformed into visual music

  16. Analysis of a three-cell cavity which suppresses instabilities associated with the accelerating mode

    International Nuclear Information System (INIS)

    Yamazaki, Y.; Kageyama, T.

    1994-01-01

    In a large ring with extremely heavy beam loading such as a B-factory it is possible that the accelerating mode, itself, gives rise to a longitudinal coupled-bunch instability. In order to solve this problem Shintake proposed to attach a storage cavity to an accelerating cavity. The present paper shows that the system can be put into practical use, if one adds a coupling cavity in between the two cavities. (author)

  17. Instabilities of a Fermi gas with nested Fermi surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Schlottmann, Pedro [Department of Physics, Florida State University, Tallahassee, FL (United States)

    2018-01-15

    The nesting of the Fermi surfaces of an electron and a hole pocket separated by a vector Q commensurate with the lattice in conjunction with the interaction between the quasiparticles can give rise to a rich phase diagram. Of particular importance is itinerant antiferromagnetic order in the context of pnictides and heavy fermion compounds. By mismatching the nesting the order can gradually be suppressed and as the Neel temperature tends to zero a quantum critical point is obtained. A superconducting dome above the quantum critical point can be induced by the transfer of pairs of electrons between the pockets. The conditions under which such a dome arises are studied. In addition numerous other phases may arise, e.g. charge density waves, non-Fermi liquid behavior, non-s-wave superconductivity, Pomeranchuk instabilities of the Fermi surface, nematic order, and phases with persistent orbital currents. (copyright 2017 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  18. Endogenous activation of adenosine A(1) receptors accelerates ischemic suppression of spontaneous electrocortical activity

    DEFF Research Database (Denmark)

    Ilie, Andrei; Ciocan, Dragos; Zagrean, Ana-Maria

    2006-01-01

    Cerebral ischemia induces a rapid suppression of spontaneous brain rhythms prior to major alterations in ionic homeostasis. It was found in vitro during ischemia that the rapidly formed adenosine, resulting from the intracellular breakdown of ATP, may inhibit synaptic transmission via the A(1......) receptor subtype. The link between endogenous A(1) receptor activation during ischemia and the suppression of spontaneous electrocortical activity has not yet been established in the intact brain. The aim of this study was to investigate in vivo the effects of A(1) receptor antagonism by 8-cyclopentyl-1...

  19. Suppressing beam-centroid motion in a long-pulse linear induction accelerator

    Directory of Open Access Journals (Sweden)

    Carl Ekdahl

    2011-12-01

    Full Text Available The second axis of the dual-axis radiography of hydrodynamic testing (DARHT facility produces up to four radiographs within an interval of 1.6  μs. It does this by slicing four micropulses out of a 2-μs long electron beam pulse and focusing them onto a bremsstrahlung converter target. The 1.8-kA beam pulse is created by a dispenser cathode diode and accelerated to more than 16 MeV by the unique DARHT Axis-II linear induction accelerator (LIA. Beam motion in the accelerator would be a problem for multipulse flash radiography. High-frequency motion, such as from beam-breakup (BBU instability, would blur the individual spots. Low-frequency motion, such as produced by pulsed-power variation, would produce spot-to-spot differences. In this article, we describe these sources of beam motion, and the measures we have taken to minimize it. Using the methods discussed, we have reduced beam motion at the accelerator exit to less than 2% of the beam envelope radius for the high-frequency BBU, and less than 1/3 of the envelope radius for the low-frequency sweep.

  20. 7th International Fermi Symposium

    Science.gov (United States)

    2017-10-01

    The two Fermi instruments have been surveying the high-energy sky since August 2008. The Large Area Telescope (LAT) has discovered more than three thousand gamma-ray sources and many new source classes, bringing the importance of gamma-ray astrophysics to an ever-broadening community. The LAT catalog includes supernova remnants, pulsar wind nebulae, pulsars, binary systems, novae, several classes of active galaxies, starburst galaxies, normal galaxies, and a large number of unidentified sources. Continuous monitoring of the high-energy gamma-ray sky has uncovered numerous outbursts from a wide range of transients. Fermi LAT's study of diffuse gamma-ray emission in our Galaxy revealed giant bubbles, as well as an excess of gamma-rays from the Galactic center region, both observations have become exciting puzzles for the astrophysics community. The direct measurement of a harder-than- expected cosmic-ray electron spectrum may imply the presence of nearby cosmic-ray accelerators. LAT data have provided stringent constraints on new phenomena such as supersymmetric dark-matter annihilations as well as tests of fundamental physics. The full reprocessing of the entire mission dataset with Pass 8 includes improved event reconstruction, a wider energy range, better energy measurements, and significantly increased effective area, all them boosting the discovery potential and the ability to do precision observations with LAT. The Gamma-ray Burst Monitor (GBM) continues to be a prolific detector of gamma-ray transients: magnetars, solar flares, terrestrial gamma-ray flashes and gamma-ray bursts at keV to MeV energies, complementing the higher energy LAT observations of those sources in addition to providing valuable science return in their own right. All gamma-ray data are made immediately available at the Fermi Science Support Center (http://fermi.gsfc.nasa.gov/ssc). These publicly available data and Fermi analysis tools have enabled a large number of important studies. We

  1. Chronic stress accelerates ligature-induced periodontitis by suppressing glucocorticoid receptor-α signaling.

    Science.gov (United States)

    Lu, Huaixiu; Xu, Minguang; Wang, Feng; Liu, Shisen; Gu, Jing; Lin, Songshan; Zhao, Lisheng

    2016-03-25

    Periodontitis is a common chronic inflammatory disease. Recent studies have shown that chronic stress (CS) might modulate periodontal disease, but there are few models of CS-induced periodontitis, and the underlying mechanisms are unclear. The present study established a rat model of periodontitis associated with CS induced by nylon thread ligatures. The severity of periodontitis was evaluated in this model by radiographic and pathological examination. The inflammatory reaction indicated by the elevated serum levels of interleukin (IL)-1β, IL-6 and IL-8 was assessed by enzyme-linked immunosorbent assay. Toll-like receptor-4 (TLR4) and glucocorticoid receptor-α (GR-α) expressions were detected by reverse transcriptase-PCR and western blotting. Open-field tests and serum corticosterone were used to evaluate CS. The results showed that CS induced behavioral changes and increased corticosterone levels of the animals with periodontitis. CS stimulation markedly increased alveolar bone loss, periodontal pocket depth and the number of plaques. It also enhanced the inflammatory reaction. These results suggest that CS accelerated the ligature-induced pathological changes associated with periodontitis. Further analysis of the mechanisms involved showed that GR-α expression was significantly downregulated in periodontal tissues of the animals undergoing CS. Blocking GR-α signaling in lipopolysaccharide and corticosteroid-treated human periodontal ligament fibroblast cells in vitro significantly upregulated the expression of p-Akt (protein kinase B) and TLR4, promoted nuclear factor-κB activity and increased levels of IL-1β, IL-6 and IL-8. This research suggests that CS might accelerate the pathological progression of periodontitis by a GR-α signaling-mediated inflammatory response and that this may be a potential therapeutic target for the treatment of periodontal disease, particularly in patients with CS.

  2. Sox4 Links Tumor Suppression to Accelerated Aging in Mice by Modulating Stem Cell Activation

    Directory of Open Access Journals (Sweden)

    Miguel Foronda

    2014-07-01

    Full Text Available Sox4 expression is restricted in mammals to embryonic structures and some adult tissues, such as lymphoid organs, pancreas, intestine, and skin. During embryogenesis, Sox4 regulates mesenchymal and neural progenitor survival, as well as lymphocyte and myeloid differentiation, and contributes to pancreas, bone, and heart development. Aberrant Sox4 expression is linked to malignant transformation and metastasis in several types of cancer. To understand the role of Sox4 in the adult organism, we first generated mice with reduced whole-body Sox4 expression. These mice display accelerated aging and reduced cancer incidence. To specifically address a role for Sox4 in adult stem cells, we conditionally deleted Sox4 (Sox4cKO in stratified epithelia. Sox4cKO mice show increased skin stem cell quiescence and resistance to chemical carcinogenesis concomitantly with downregulation of cell cycle, DNA repair, and activated hair follicle stem cell pathways. Altogether, these findings highlight the importance of Sox4 in regulating adult tissue homeostasis and cancer.

  3. Accelerators

    CERN Multimedia

    CERN. Geneva

    2001-01-01

    The talk summarizes the principles of particle acceleration and addresses problems related to storage rings like LEP and LHC. Special emphasis will be given to orbit stability, long term stability of the particle motion, collective effects and synchrotron radiation.

  4. Inhibition of nuclear factor of activated T-cells (NFAT suppresses accelerated atherosclerosis in diabetic mice.

    Directory of Open Access Journals (Sweden)

    Anna V Zetterqvist

    Full Text Available OBJECTIVE OF THE STUDY: Diabetic patients have a much more widespread and aggressive form of atherosclerosis and therefore, higher risk for myocardial infarction, peripheral vascular disease and stroke, but the molecular mechanisms leading to accelerated damage are still unclear. Recently, we showed that hyperglycemia activates the transcription factor NFAT in the arterial wall, inducing the expression of the pro-atherosclerotic protein osteopontin. Here we investigate whether NFAT activation may be a link between diabetes and atherogenesis. METHODOLOGY AND PRINCIPAL FINDINGS: Streptozotocin (STZ-induced diabetes in apolipoprotein E(-/- mice resulted in 2.2 fold increased aortic atherosclerosis and enhanced pro-inflammatory burden, as evidenced by elevated blood monocytes, endothelial activation- and inflammatory markers in aorta, and pro-inflammatory cytokines in plasma. In vivo treatment with the NFAT blocker A-285222 for 4 weeks completely inhibited the diabetes-induced aggravation of atherosclerosis, having no effect in non-diabetic mice. STZ-treated mice exhibited hyperglycemia and higher plasma cholesterol and triglycerides, but these were unaffected by A-285222. NFAT-dependent transcriptional activity was examined in aorta, spleen, thymus, brain, heart, liver and kidney, but only augmented in the aorta of diabetic mice. A-285222 completely blocked this diabetes-driven NFAT activation, but had no impact on the other organs or on splenocyte proliferation or cytokine secretion, ruling out systemic immunosuppression as the mechanism behind reduced atherosclerosis. Instead, NFAT inhibition effectively reduced IL-6, osteopontin, monocyte chemotactic protein 1, intercellular adhesion molecule 1, CD68 and tissue factor expression in the arterial wall and lowered plasma IL-6 in diabetic mice. CONCLUSIONS: Targeting NFAT signaling may be a novel and attractive approach for the treatment of diabetic macrovascular complications.

  5. Stochastic acceleration by hydromagnetic turbulence

    International Nuclear Information System (INIS)

    Kulsrud, R.M.

    1979-03-01

    A general theory for particle acceleration by weak hydromagnetic turbulence with a given spectrum of waves is described. Various limiting cases, corresponding to Fermi acceleration and magnetic pumping, are discussed and two numerical examples illustrating them are given. An attempt is made to show that the expression for the rate of Fermi acceleration is valid for finite amplitudes

  6. Supernova Remnants with Fermi Large Area Telescope

    Directory of Open Access Journals (Sweden)

    Caragiulo M.

    2017-01-01

    Full Text Available The Large Area Telescope (LAT, on-board the Fermi satellite, proved to be, after 8 years of data taking, an excellent instrument to detect and observe Supernova Remnants (SNRs in a range of energies running from few hundred MeV up to few hundred GeV. It provides essential information on physical processes that occur at the source, involving both accelerated leptons and hadrons, in order to understand the mechanisms responsible for the primary Cosmic Ray (CR acceleration. We show the latest results in the observation of Galactic SNRs by Fermi-LAT.

  7. A microscope for Fermi gases

    International Nuclear Information System (INIS)

    Omran, Ahmed

    2016-01-01

    evaluate the local number statistics on an ensemble of band-insulating clouds. In the central region of high filling, the atom number fluctuations are suppressed by an order of magnitude compared to classical gases, which is a manifestation of Pauli blocking. Occupation probabilities are used to measure the local entropy on each individual site. The entropy per atom is found to be as low as 0.34 kB in the band-insulating core. The extension of quantum gas microscopy to degenerate Fermi gases opens up new avenues in quantum simulation of strongly correlated many-body systems and can yield unprecedented insight into fermionic systems in and out of equilibrium, quantum magnetism and different phases of the Fermi-Hubbard model.

  8. Accelerated development in Johnsongrass seedlings (Sorghum halepense suppresses the growth of native grasses through size-asymmetric competition.

    Directory of Open Access Journals (Sweden)

    Susanne Schwinning

    Full Text Available Invasive plant species often dominate native species in competition, augmenting other potential advantages such as release from natural enemies. Resource pre-emption may be a particularly important mechanism for establishing dominance over competitors of the same functional type. We hypothesized that competitive success of an exotic grass against native grasses is mediated by establishing an early size advantage. We tested this prediction among four perennial C4 warm-season grasses: the exotic weed Johnsongrass (Sorghum halepense, big bluestem (Andropogon gerardii, little bluestem (Schizachyrium scoparius and switchgrass (Panicum virgatum. We predicted that a the competitive effect of Johnsongrass on target species would be proportional to their initial biomass difference, b competitive effect and response would be negatively correlated and c soil fertility would have little effect on competitive relationships. In a greenhouse, plants of the four species were grown from seed either alone or with one Johnsongrass neighbor at two fertilizer levels and periodically harvested. The first two hypotheses were supported: The seedling biomass of single plants at first harvest (50 days after seeding ranked the same way as the competitive effect of Johnsongrass on target species: Johnsongrass < big bluestem < little bluestem/switchgrass, while Johnsongrass responded more strongly to competition from Johnsongrass than from native species. At final harvest, native plants growing with Johnsongrass attained between 2-5% of their single-plant non-root biomass, while Johnsongrass growing with native species attained 89% of single-plant non-root biomass. Fertilization enhanced Johnsongrass' competitive effects on native species, but added little to the already severe competitive suppression. Accelerated early growth of Johnsongrass seedlings relative to native seedlings appeared to enable subsequent resource pre-emption. Size-asymmetric competition and resource

  9. Whole-brain background-suppressed pCASL MRI with 1D-accelerated 3D RARE Stack-Of-Spirals readout.

    Directory of Open Access Journals (Sweden)

    Marta Vidorreta

    Full Text Available Arterial Spin Labeled (ASL perfusion MRI enables non-invasive, quantitative measurements of tissue perfusion, and has a broad range of applications including brain functional imaging. However, ASL suffers from low signal-to-noise ratio (SNR, limiting image resolution. Acquisitions using 3D readouts are optimal for background-suppression of static signals, but can be SAR intensive and typically suffer from through-plane blurring. In this study, we investigated the use of accelerated 3D readouts to obtain whole-brain, high-SNR ASL perfusion maps and reduce SAR deposition. Parallel imaging was implemented along the partition-encoding direction in a pseudo-continuous ASL sequence with background-suppression and 3D RARE Stack-Of-Spirals readout, and its performance was evaluated in three small cohorts. First, both non-accelerated and two-fold accelerated single-shot versions of the sequence were evaluated in healthy volunteers during a motor-photic task, and the performance was compared in terms of temporal SNR, GM-WM contrast, and statistical significance of the detected activation. Secondly, single-shot 1D-accelerated imaging was compared to a two-shot accelerated version to assess benefits of SNR and spatial resolution for applications in which temporal resolution is not paramount. Third, the efficacy of this approach in clinical populations was assessed by applying the single-shot 1D-accelerated version to a larger cohort of elderly volunteers. Accelerated data demonstrated the ability to detect functional activation at the subject level, including cerebellar activity, without loss in the perfusion signal temporal stability and the statistical power of the activations. The use of acceleration also resulted in increased GM-WM contrast, likely due to reduced through-plane partial volume effects, that were further attenuated with the use of two-shot readouts. In a clinical cohort, image quality remained excellent, and expected effects of age and sex

  10. Fermi comes to CERN

    CERN Multimedia

    NASA

    2009-01-01

    1. This view from NASA's Fermi Gamma-ray Space Telescope is the deepest and best-resolved portrait of the gamma-ray sky to date. The image shows how the sky appears at energies more than 150 million times greater than that of visible light. Among the signatures of bright pulsars and active galaxies is something familiar -- a faint path traced by the sun. (Credit: NASA/DOE/Fermi LAT Collaboration) 2. The Large Area Telescope (LAT) on Fermi detects gamma-rays through matter (electrons) and antimatter (positrons) they produce after striking layers of tungsten. (Credit: NASA/Goddard Space Flight Center Conceptual Image Lab)

  11. Fermi GBM Trigger Catalog

    Data.gov (United States)

    National Aeronautics and Space Administration — Fermi is a powerful space observatory that will open a wide window on the universe. Gamma rays are the highest-energy form of light, and the gamma-ray sky is...

  12. Enrico Fermi centenary exhibition seminar

    CERN Multimedia

    Maximilien Brice

    2002-01-01

    Photo 01: Dr. Juan Antonio Rubio, Leader of the Education and Technology Transfer Division and CERN Director General, Prof. Luciano Maiani. Photo 03: Luciano Maiani, Welcome and Introduction Photo 09: Antonino Zichichi, The New 'Centro Enrico Fermi' at Via Panisperna Photos 10, 13: Ugo Amaldi, Fermi at Via Panisperna and the birth of Nuclear Medicine Photo 14: Jack Steinberger, Fermi in Chicago Photo 18: Valentin Telegdi, A close-up of Fermi Photo 21: Arnaldo Stefanini, Celebrating Fermi's Centenary in Documents and Pictures.

  13. Diatomic molecules in ultracold Fermi gases - Novel composite bosons

    OpenAIRE

    Petrov, D. S.; Salomon, C.; Shlyapnikov, G. V.

    2005-01-01

    We give a brief overview of recent studies of weakly bound homonuclear molecules in ultracold two-component Fermi gases. It is emphasized that they represent novel composite bosons, which exhibit features of Fermi statistics at short intermolecular distances. In particular, Pauli exclusion principle for identical fermionic atoms provides a strong suppression of collisional relaxation of such molecules into deep bound states. We then analyze heteronuclear molecules which are expected to be for...

  14. Enrico Fermi exhibition at CERN

    CERN Multimedia

    2002-01-01

    A touring exhibition celebrating the centenary of Enrico Fermi's birth in 1901 will be on display at CERN (Main Building, Mezzanine) from 12-27 September. You are cordially invited to the opening celebration on Thursday 12 September at 16:00 (Main Building, Council Chamber), which will include speechs from: Luciano Maiani Welcome and Introduction Arnaldo Stefanini Celebrating Fermi's Centenary in Documents and Pictures Antonino Zichichi The New 'Centro Enrico Fermi' at Via Panisperna Ugo Amaldi Fermi at Via Panisperna and the birth of Nuclear Medicine Jack Steinberger Fermi in Chicago Valentin Telegdi A Close-up of Fermi and the screening of a documentary video about Fermi: Scienziati a Pisa: Enrico Fermi (Scientists at Pisa: Enrico Fermi) created by Francesco Andreotti for La Limonaia from early film, photographs and sound recordings (In Italian, with English subtitles - c. 30 mins). This will be followed by an aperitif on the Mezz...

  15. Fermi comes to CERN

    CERN Multimedia

    2009-01-01

    In only 10 months of scientific activity, the Fermi space observatory has already collected an unprecedented wealth of information on some of the most amazing objects in the sky. In a recent talk at CERN, Luca Latronico, a member of the Fermi collaboration, explained some of their findings and emphasized the strong links between High Energy Physics (HEP) and High Energy Astrophysics (HEA). The Fermi gamma-ray telescope was launched by NASA in June 2008. After about two months of commissioning it started sending significant data back to the Earth. Since then, it has made observations that are changing our view of the sky: from discovering a whole new set of pulsars, the greatest total energy gamma-ray burst ever, to detecting an unexplained abundance of high-energy electrons that could be a signature of dark matter, to producing a uniquely rich and high definition sky map in gamma-rays. The high performance of the instrument comes as ...

  16. Fermi and nuclear security

    International Nuclear Information System (INIS)

    Alcober Bosch, V.

    2003-01-01

    Following the scientific life of Fermi the article reviews the historical evolution of nuclear security from the base of the first system foreseen for the CP-1 critical pile, which made it possible to demonstrate self-sustaining fission reaction, until the mid-fifties by which time the subsequent importance of this concept was perceived. Technological advances have gone hand in hand with the development of the concept of security, and have become a further point to be taken into account in any nuclear installation, and which Fermi always kept in mind during his professional life. (Author) 12 refs

  17. Berry Fermi liquid theory

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Jing-Yuan, E-mail: chjy@uchicago.edu [Kadanoff Center for Theoretical Physics, University of Chicago, Chicago, IL 60637 (United States); Stanford Institute for Theoretical Physics, Stanford University, CA 94305 (United States); Son, Dam Thanh, E-mail: dtson@uchicago.edu [Kadanoff Center for Theoretical Physics, University of Chicago, Chicago, IL 60637 (United States)

    2017-02-15

    We develop an extension of the Landau Fermi liquid theory to systems of interacting fermions with non-trivial Berry curvature. We propose a kinetic equation and a constitutive relation for the electromagnetic current that together encode the linear response of such systems to external electromagnetic perturbations, to leading and next-to-leading orders in the expansion over the frequency and wave number of the perturbations. We analyze the Feynman diagrams in a large class of interacting quantum field theories and show that, after summing up all orders in perturbation theory, the current–current correlator exactly matches with the result obtained from the kinetic theory. - Highlights: • We extend Landau’s kinetic theory of Fermi liquid to incorporate Berry phase. • Berry phase effects in Fermi liquid take exactly the same form as in Fermi gas. • There is a new “emergent electric dipole” contribution to the anomalous Hall effect. • Our kinetic theory is matched to field theory to all orders in Feynman diagrams.

  18. A tribute to Enrico Fermi

    Energy Technology Data Exchange (ETDEWEB)

    Kubbinga, H. [Groningen Univ. (Netherlands)

    2009-07-01

    This article is a short biography of Enrico Fermi 'The Pope of physics'. His main contributions in theoretical physics have paved the way to quantum electrodynamics and the quantization of the fields. Fermi got also great achievements on beta decay process and on nuclear reactions brought about by slow neutrons. Fermi was awarded the Nobel prize of physics in 1938

  19. Suppressing Thermal Energy Drift In The LLNL Flash X-Ray Accelerator Using Linear Disk Resistor Stacks

    Energy Technology Data Exchange (ETDEWEB)

    Kreitzer, B R; Houck, T L; Luchterhand, O C

    2011-07-19

    This paper addresses thermal drift in sodium thiosulfate liquid resistors and their replacement with linear disk resistors from HVR Advanced Power Components. Sodium thiosulfate resistors in the FXR induction linear accelerator application have a temperature coefficient of {approx}1.8%/C. The FXR Marx banks send an 8kJ pulse through eight 524 cm{sup 3} liquid resistors at a repetition rate of up to 1 every 45 seconds. Every pulse increases the temperature of the solution by {approx}0.4 C which produces a 0.7% change in resistance. The typical cooling rate is {approx}0.4 C per minute which results in {approx}0.1% energy drop per pulse during continuous pulsed operations. A radiographic accelerator is extraordinarily sensitive to energy variations. Changes in beam energy produce movement in beam transport, changes in spot size, and large dose variations. If self-heating were the only problem, we could predict the increase in input voltage required to compensate for the energy loss. However, there are other variables that influence the temperature of the resistors such as focus magnet heating, changes in room temperature, changes in cooling water, where the cell is located, etc. Additionally not all of the resistors have equivalent cooling rates and as many as 32 resistors are driven from a single power source. The FXR accelerator group elected to replace the sodium thiosulfate resistors with HVR Linear Disk Resistors in a stack type configuration. With data limited for these resistors when used in oil and at low resistance values, a full characterization needed to be performed. High currents (up to 15kA), high voltages (up to 400kV), and Fast Rise times (<10ns) made a resistor choice difficult. Other solid resistors have been tried and had problems at the connection points and with the fact that the resistivity changed as they absorbed oil. The selected HVR resistors have the advantage of being manufactured with the oil impregnated in to them so this characteristic

  20. Suppressing Thermal Energy Drift In The LLNL Flash X-Ray Accelerator Using Linear Disk Resistor Stacks

    International Nuclear Information System (INIS)

    Kreitzer, B.R.; Houck, T.L.; Luchterhand, O.C.

    2011-01-01

    This paper addresses thermal drift in sodium thiosulfate liquid resistors and their replacement with linear disk resistors from HVR Advanced Power Components. Sodium thiosulfate resistors in the FXR induction linear accelerator application have a temperature coefficient of ∼1.8%/C. The FXR Marx banks send an 8kJ pulse through eight 524 cm 3 liquid resistors at a repetition rate of up to 1 every 45 seconds. Every pulse increases the temperature of the solution by ∼0.4 C which produces a 0.7% change in resistance. The typical cooling rate is ∼0.4 C per minute which results in ∼0.1% energy drop per pulse during continuous pulsed operations. A radiographic accelerator is extraordinarily sensitive to energy variations. Changes in beam energy produce movement in beam transport, changes in spot size, and large dose variations. If self-heating were the only problem, we could predict the increase in input voltage required to compensate for the energy loss. However, there are other variables that influence the temperature of the resistors such as focus magnet heating, changes in room temperature, changes in cooling water, where the cell is located, etc. Additionally not all of the resistors have equivalent cooling rates and as many as 32 resistors are driven from a single power source. The FXR accelerator group elected to replace the sodium thiosulfate resistors with HVR Linear Disk Resistors in a stack type configuration. With data limited for these resistors when used in oil and at low resistance values, a full characterization needed to be performed. High currents (up to 15kA), high voltages (up to 400kV), and Fast Rise times (<10ns) made a resistor choice difficult. Other solid resistors have been tried and had problems at the connection points and with the fact that the resistivity changed as they absorbed oil. The selected HVR resistors have the advantage of being manufactured with the oil impregnated in to them so this characteristic is minimized while still

  1. High-energy cosmic-ray acceleration

    OpenAIRE

    Bustamante, M; Carrillo Montoya, G; de Paula, W; Duarte Chavez, J A; Gago, A M; Hakobyan, H; Jez, P; Monroy Montañez, J A; Ortiz Velasquez, A; Padilla Cabal, F; Pino Rozas, M; Rodriguez Patarroyo, D J; Romeo, G L; Saldaña-Salazar , U J; Velasquez, M

    2010-01-01

    We briefly review the basics of ultrahigh-energy cosmic-ray acceleration. The Hillas criterion is introduced as a geometrical criterion that must be fulfilled by potential acceleration sites, and energy losses are taken into account in order to obtain a more realistic scenario. The different available acceleration mechanisms are presented, with special emphasis on Fermi shock acceleration and its prediction of a power-law cosmic-ray energy spectrum. We conclude that first-order Fermi accelera...

  2. Strongly interacting Fermi gases

    Directory of Open Access Journals (Sweden)

    Bakr W.

    2013-08-01

    Full Text Available Strongly interacting gases of ultracold fermions have become an amazingly rich test-bed for many-body theories of fermionic matter. Here we present our recent experiments on these systems. Firstly, we discuss high-precision measurements on the thermodynamics of a strongly interacting Fermi gas across the superfluid transition. The onset of superfluidity is directly observed in the compressibility, the chemical potential, the entropy, and the heat capacity. Our measurements provide benchmarks for current many-body theories on strongly interacting fermions. Secondly, we have studied the evolution of fermion pairing from three to two dimensions in these gases, relating to the physics of layered superconductors. In the presence of p-wave interactions, Fermi gases are predicted to display toplogical superfluidity carrying Majorana edge states. Two possible avenues in this direction are discussed, our creation and direct observation of spin-orbit coupling in Fermi gases and the creation of fermionic molecules of 23Na 40K that will feature strong dipolar interactions in their absolute ground state.

  3. Illinois Accelerator Research Center

    Science.gov (United States)

    Kroc, Thomas K.; Cooper, Charlie A.

    The Illinois Accelerator Research Center (IARC) hosts a new accelerator development program at Fermi National Accelerator Laboratory. IARC provides access to Fermi's state-of-the-art facilities and technologies for research, development and industrialization of particle accelerator technology. In addition to facilitating access to available existing Fermi infrastructure, the IARC Campus has a dedicated 36,000 ft2 Heavy Assembly Building (HAB) with all the infrastructure needed to develop, commission and operate new accelerators. Connected to the HAB is a 47,000 ft2 Office, Technology and Engineering (OTE) building, paid for by the state, that has office, meeting, and light technical space. The OTE building, which contains the Accelerator Physics Center, and nearby Accelerator and Technical divisions provide IARC collaborators with unique access to world class expertise in a wide array of accelerator technologies. At IARC scientists and engineers from Fermilab and academia work side by side with industrial partners to develop breakthroughs in accelerator science and translate them into applications for the nation's health, wealth and security.

  4. Fermi surfaces in Kondo insulators

    Science.gov (United States)

    Liu, Hsu; Hartstein, Máté; Wallace, Gregory J.; Davies, Alexander J.; Ciomaga Hatnean, Monica; Johannes, Michelle D.; Shitsevalova, Natalya; Balakrishnan, Geetha; Sebastian, Suchitra E.

    2018-04-01

    We report magnetic quantum oscillations measured using torque magnetisation in the Kondo insulator YbB12 and discuss the potential origin of the underlying Fermi surface. Observed quantum oscillations as well as complementary quantities such as a finite linear specific heat capacity in YbB12 exhibit similarities with the Kondo insulator SmB6, yet also crucial differences. Small heavy Fermi sections are observed in YbB12 with similarities to the neighbouring heavy fermion semimetallic Fermi surface, in contrast to large light Fermi surface sections in SmB6 which are more similar to the conduction electron Fermi surface. A rich spectrum of theoretical models is suggested to explain the origin across different Kondo insulating families of a bulk Fermi surface potentially from novel itinerant quasiparticles that couple to magnetic fields, yet do not couple to weak DC electric fields.

  5. Suppression of WIF-1 through promoter hypermethylation causes accelerated proliferation of the aryl hydrocarbon receptor (AHR) overexpressing MCF10AT1 breast cancer cells

    International Nuclear Information System (INIS)

    Wu, Dalei; Wong, Patrick; Li, Wen; Vogel, Christoph F.; Matsumura, Fumio

    2011-01-01

    Highlights: → 5-Aza-2'-deoxycytidine (AZ) causes proliferation suppression and ERα recovery. → AZ down-regulates Wnt/β-catenin pathway mainly by increasing WIF-1 expression. → Both ERα and AhR have some effects on DNA methylation in breast cancer cells. → Artificial overexpression of ERα in ER negative cells increases WIF-1 expression. → WIF-1 promoter hypermethylation is one of the major causes for accelerated proliferation. -- Abstract: The cause for increased cell proliferation in AHR overexpressing breast cancer cells still remains unknown. Here we studied the molecular basis of aggressive cell proliferation of an AHR overexpressing and ERα functionally down-regulated MCF10AT1 cell line, designated as P20E, in comparison to a matched sub-line, P20C with normal AHR expression and ERα function. We found that a 4-day treatment of P20E cells with 5-aza-2'-deoxycytidine (AZ) caused a significant suppression of cell proliferation. Such an effect of AZ was accompanied with the significant recovery of ERα function. Among diagnostic markers of AZ-induced cellular changes we found conspicuous up-regulation of mRNA expression of Wnt inhibitory factor-1 (WIF-1), particularly in P20E. The possibility of AZ-induced demethylation on the promoter of WIF-1 gene was confirmed through methylation specific PCR assay. Such AZ-induced changes in P20E cells were also accompanied with the decrease in the binding of nuclear proteins to the 32 P labeled TRE (TCF response element) and the reduced accumulation of β-catenin protein in the cell nucleus, indicating the importance of Wnt/β-catenin pathway in maintaining the increased cell proliferation in P20E line over P20C line. The importance of WIF-1 in this regard has been validated by transfecting cells with siRNA against WIF-1, which caused an increase in cell proliferation. Moreover, artificial overexpression of ERα in both P20E as well as MDA-MB-231 cells increased the mRNA expression of WIF-1. Together these

  6. Pulsar Polar Cap and Slot Gap Models: Confronting Fermi Data

    Science.gov (United States)

    Harding, Alice K.

    2012-01-01

    Rotation-powered pulsars are excellent laboratories for studying particle acceleration as well as fundamental physics of strong gravity, strong magnetic fields and relativity. I will review acceleration and gamma-ray emission from the pulsar polar cap and slot gap. Predictions of these models can be tested with the data set on pulsars collected by the Large Area Telescope on the Fermi Gamma-Ray Telescope over the last four years, using both detailed light curve fitting and population synthesis.

  7. Fermi Large Area Telescope Operations: Progress Over 4 Years

    Energy Technology Data Exchange (ETDEWEB)

    Cameron, Robert A.; /SLAC

    2012-06-28

    The Fermi Gamma-ray Space Telescope was launched into orbit in June 2008, and is conducting a multi-year gamma-ray all-sky survey, using the main instrument on Fermi, the Large Area Telescope (LAT). Fermi began its science mission in August 2008, and has now been operating for almost 4 years. The SLAC National Accelerator Laboratory hosts the LAT Instrument Science Operations Center (ISOC), which supports the operation of the LAT in conjunction with the Mission Operations Center (MOC) and the Fermi Science Support Center (FSSC), both at NASA's Goddard Space Flight Center. The LAT has a continuous output data rate of about 1.5 Mbits per second, and data from the LAT are stored on Fermi and transmitted to the ground through TDRS and the MOC to the ISOC about 10 times per day. Several hundred computers at SLAC are used to process LAT data to perform event reconstruction, and gamma-ray photon data are subsequently delivered to the FSSC for public release with a few hours of being detected by the LAT. We summarize the current status of the LAT, and the evolution of the data processing and monitoring performed by the ISOC during the first 4 years of the Fermi mission, together with future plans for further changes to detected event data processing and instrument operations and monitoring.

  8. FERMI multi-chip module

    CERN Multimedia

    This FERMI multi-chip module contains five million transistors. 25 000 of these modules will handle the flood of information through parts of the ATLAS and CMS detectors at the LHC. To select interesting events for recording, crucial decisions are taken before the data leaves the detector. FERMI modules are being developed at CERN in partnership with European industry.

  9. Enrico Fermi and uranium fission

    International Nuclear Information System (INIS)

    Hahn, O.

    1962-01-01

    The author describes the part of his scientific work connected to the research made by Enrico Fermi in the field of nuclear reactions. He said that 'Our gratitude to Fermi today is therefore due less perhaps for his reactor than for his experiments using uncharged neutrons in order to bring about artificial nuclear processes'

  10. Superallowed Fermi β decay studies at TRIUMF-ISAC

    Science.gov (United States)

    Svensson, C. E.; Dunlop, R.; Finlay, P.; Ball, G. C.; Ettenauer, S.; Leslie, J. R.; Towner, I. S.; Andreoiu, C.; Austin, R. A. E.; Bandyopadhyay, D.; Chagnon-Lessard, S.; Chester, A.; Cross, D. S.; Demand, G.; Djongolov, M.; Garnsworthy, A. B.; Garrett, P. E.; Green, K. L.; Glister, J.; Grinyer, G. F.; Hackman, G.; Hadinia, B.; Leach, K. G.; Pearson, C. J.; Phillips, A. A.; Rand, E. T.; Starosta, K.; Sumithrarachchi, C. S.; Tardiff, E. R.; Triambak, S.; Williams, S. J.; Wong, J.; Yates, S. W.; Zganjar, E. F.

    2013-10-01

    A program of high-precision superallowed Fermi β decay studies is being carried out at the Isotope Separator and Accelerator (ISAC) radioactive ion beam facility at TRIUMF. Recent high-precision branching ratio measurements for the superallowed decays of 74Rb and 26Alm, as well as a half-life measurement for 26Alm that is the most precise half-life measurement for any superallowed emitter to date, are reported. These results provide demanding tests of the theoretical isospin symmetry breaking corrections in superallowed Fermi β decays.

  11. Enrico Fermi Symposium at CERN : opening celebration

    CERN Multimedia

    CERN. Geneva. Audiovisual Unit

    2002-01-01

    You are cordially invited to the opening celebration on Thursday 12 September at 16:00 (Main Building, Council Chamber), which will include speechs from: Luciano Maiani - Welcome and Introduction Antonino Zichichi - The New 'Centro Enrico Fermi' at Via Panisperna Ugo Amaldi - Fermi at Via Panisperna and the birth of Nuclear Medicine Jack Steinberger - Fermi in Chicago Valentin Telegdi - A Close-up of Fermi Arnaldo Stefanini - Celebrating Fermi's Centenary in Documents and Pictures and the screening of a documentary video about Fermi: Scienziati a Pisa: Enrico Fermi (Scientists at Pisa: Enrico Fermi) created by Francesco Andreotti for La Limonaia from early film, photographs and sound recordings (English version - c. 30 mins).

  12. Fermi, Heisenberg y Lawrence

    Directory of Open Access Journals (Sweden)

    Ynduráin, Francisco J.

    2002-01-01

    Full Text Available Not available

    Los azares de las onomásticas hacen coincidir en este año el centenario del nacimiento de tres de los más grandes físicos del siglo XX. Dos de ellos, Fermi y Heisenberg, dejaron una marca fundamental en la ciencia (ambos, pero sobre todo el segundo y, el primero, también en la tecnología. Lawrence, indudablemente de un nivel inferior al de los otros dos, estuvo sin embargo en el origen de uno de los desarrollos tecnológicos que han sido básicos para la exploración del universo subnuclear en la segunda mitad del siglo que ha terminado hace poco, el de los aceleradores de partículas.

  13. Anisotropic non-Fermi liquids

    Science.gov (United States)

    Sur, Shouvik; Lee, Sung-Sik

    2016-11-01

    We study non-Fermi-liquid states that arise at the quantum critical points associated with the spin density wave (SDW) and charge density wave (CDW) transitions in metals with twofold rotational symmetry. We use the dimensional regularization scheme, where a one-dimensional Fermi surface is embedded in (3 -ɛ ) -dimensional momentum space. In three dimensions, quasilocal marginal Fermi liquids arise both at the SDW and CDW critical points: the speed of the collective mode along the ordering wave vector is logarithmically renormalized to zero compared to that of Fermi velocity. Below three dimensions, however, the SDW and CDW critical points exhibit drastically different behaviors. At the SDW critical point, a stable anisotropic non-Fermi-liquid state is realized for small ɛ , where not only time but also different spatial coordinates develop distinct anomalous dimensions. The non-Fermi liquid exhibits an emergent algebraic nesting as the patches of Fermi surface are deformed into a universal power-law shape near the hot spots. Due to the anisotropic scaling, the energy of incoherent spin fluctuations disperse with different power laws in different momentum directions. At the CDW critical point, on the other hand, the perturbative expansion breaks down immediately below three dimensions as the interaction renormalizes the speed of charge fluctuations to zero within a finite renormalization group scale through a two-loop effect. The difference originates from the fact that the vertex correction antiscreens the coupling at the SDW critical point whereas it screens at the CDW critical point.

  14. Pulsar Polar Cap and Slot Gap Models: Confronting Fermi Data

    Directory of Open Access Journals (Sweden)

    Alice K. Harding

    2013-09-01

    Full Text Available Rotation-powered pulsars are excellent laboratories for studying particle acceleration as well as fundamental physics of strong gravity, strong magnetic fields and relativity. Particle acceleration and high-energy emission from the polar caps is expected to occur in connection with electron-positron pair cascades. I will review acceleration and gamma-ray emission from the pulsar polar cap and associated slot gap. Predictions of these models can be tested with the data set on pulsars collected by the Large Area Telescope on the Fermi Gamma-Ray Telescope over the last four years, using both detailed light curve fitting, population synthesis and phase-resolved spectroscopy.

  15. The Statistical Fermi Paradox

    Science.gov (United States)

    Maccone, C.

    In this paper is provided the statistical generalization of the Fermi paradox. The statistics of habitable planets may be based on a set of ten (and possibly more) astrobiological requirements first pointed out by Stephen H. Dole in his book Habitable planets for man (1964). The statistical generalization of the original and by now too simplistic Dole equation is provided by replacing a product of ten positive numbers by the product of ten positive random variables. This is denoted the SEH, an acronym standing for “Statistical Equation for Habitables”. The proof in this paper is based on the Central Limit Theorem (CLT) of Statistics, stating that the sum of any number of independent random variables, each of which may be ARBITRARILY distributed, approaches a Gaussian (i.e. normal) random variable (Lyapunov form of the CLT). It is then shown that: 1. The new random variable NHab, yielding the number of habitables (i.e. habitable planets) in the Galaxy, follows the log- normal distribution. By construction, the mean value of this log-normal distribution is the total number of habitable planets as given by the statistical Dole equation. 2. The ten (or more) astrobiological factors are now positive random variables. The probability distribution of each random variable may be arbitrary. The CLT in the so-called Lyapunov or Lindeberg forms (that both do not assume the factors to be identically distributed) allows for that. In other words, the CLT "translates" into the SEH by allowing an arbitrary probability distribution for each factor. This is both astrobiologically realistic and useful for any further investigations. 3. By applying the SEH it is shown that the (average) distance between any two nearby habitable planets in the Galaxy may be shown to be inversely proportional to the cubic root of NHab. This distance is denoted by new random variable D. The relevant probability density function is derived, which was named the "Maccone distribution" by Paul Davies in

  16. Enrico Fermi the obedient genius

    CERN Document Server

    Bruzzaniti, Giuseppe

    2016-01-01

    This biography explores the life and career of the Italian physicist Enrico Fermi, which is also the story of thirty years that transformed physics and forever changed our understanding of matter and the universe: nuclear physics and elementary particle physics were born, nuclear fission was discovered, the Manhattan Project was developed, the atomic bombs were dropped, and the era of “big science” began. It would be impossible to capture the full essence of this revolutionary period without first understanding Fermi, without whom it would not have been possible. Enrico Fermi: The Obedient Genius attempts to shed light on all aspects of Fermi’s life - his work, motivation, influences, achievements, and personal thoughts - beginning with the publication of his first paper in 1921 through his death in 1954. During this time, Fermi demonstrated that he was indeed following in the footsteps of Galileo, excelling in his work both theoretically and experimentally by deepening our understanding of the Pauli e...

  17. High-energy cosmic-ray acceleration

    CERN Document Server

    Bustamante, M; de Paula, W; Duarte Chavez, J A; Gago, A M; Hakobyan, H; Jez, P; Monroy Montañez, J A; Ortiz Velasquez, A; Padilla Cabal, F; Pino Rozas, M; Rodriguez Patarroyo, D J; Romeo, G L; Saldaña-Salazar , U J; Velasquez, M; von Steinkirch, M

    2010-01-01

    We briefly review the basics of ultrahigh-energy cosmic-ray acceleration. The Hillas criterion is introduced as a geometrical criterion that must be fulfilled by potential acceleration sites, and energy losses are taken into account in order to obtain a more realistic scenario. The different available acceleration mechanisms are presented, with special emphasis on Fermi shock acceleration and its prediction of a power-law cosmic-ray energy spectrum. We conclude that first-order Fermi acceleration, though not entirely satisfactory, is the most promising mechanism for explaining the ultra-high-energy cosmic-ray flux.

  18. Superconducting magnets technologies for large accelerator

    International Nuclear Information System (INIS)

    Ogitsu, Toru

    2017-01-01

    The first hadron collider with superconducting magnet technologies was built at Fermi National Accelerator Laboratory as TEVATRON. Since then, the superconducting magnet technologies are widely used in large accelerator applications. The paper summarizes the superconducting magnet technologies used for large accelerators. (author)

  19. The Fermiac or Fermi's Trolley

    Science.gov (United States)

    Coccetti, F.

    2016-03-01

    The Fermiac, known also as Fermi's trolley or Monte Carlo trolley, is an analog computer used to determine the change in time of the neutron population in a nuclear device, via the Monte Carlo method. It was invented by Enrico Fermi and constructed by Percy King at Los Alamos in 1947, and used for about two years. A replica of the Fermiac was built at INFN mechanical workshops of Bologna in 2015, on behalf of the Museo Storico della Fisica e Centro Studi e Ricerche "Enrico Fermi", thanks to the original drawings made available by Los Alamos National Laboratory (LANL). This reproduction of the Fermiac was put in use, and a simulation was developed.

  20. Thomas-Fermi molecular dynamics

    International Nuclear Information System (INIS)

    Clerouin, J.; Pollock, E.L.; Zerah, G.

    1992-01-01

    A three-dimensional density-functional molecular-dynamics code is developed for the Thomas-Fermi density functional as a prototype for density functionals using only the density. Following Car and Parrinello [Phys. Rev. Lett. 55, 2471 (1985)], the electronic density is treated as a dynamical variable. The electronic densities are verified against a multi-ion Thomas-Fermi algorithm due to Parker [Phys. Rev. A 38, 2205 (1988)]. As an initial application, the effect of electronic polarization in enhancing ionic diffusion in strongly coupled plasmas is demonstrated

  1. Fermi and the Art of Estimation

    Indian Academy of Sciences (India)

    IAS Admin

    The balance wheel will now shed some ... work best when used by someone with the ... [1] Laura Fermi, Atoms in the Family: My Life with Enrico Fermi, The. University of Chicago ... Geneva, European Organization for Nuclear Research, 1969.

  2. Spin interaction with an ideal fermi gas

    International Nuclear Information System (INIS)

    Aizenstadt, V.V.; Malyshev, V.A.

    1987-01-01

    The authors consider the equilibrium dynamics of a system consisting of a spin interacting with an ideal Fermi gas on the lattice Z/sup v, v ≥ 3. They present two examples; when this system is unitarily equivalent to an ideal Fermi gas or to a spin in an ideal Fermi gas without interactions between them

  3. Giant Viscosity Enhancement in a Spin-Polarized Fermi Liquid

    International Nuclear Information System (INIS)

    Akimoto, H.; Xia, J. S.; Adams, E. D.; Sullivan, N. S.; Candela, D.; Mullin, W. J.

    2007-01-01

    The viscosity is measured for a Fermi liquid, a dilute 3 He- 4 He mixture, under extremely high magnetic field/temperature conditions (B≤14.8 T, T≥1.5 mK). The spin-splitting energy μB is substantially greater than the Fermi energy k B T F ; as a consequence the polarization tends to unity and s-wave quasiparticle scattering is suppressed for T F . Using a novel composite vibrating-wire viscometer an enhancement of the viscosity is observed by a factor of more than 500 over its low-field value. Good agreement is found between the measured viscosity and theoretical predictions based upon a t-matrix formalism

  4. Universal behavior of strongly correlated Fermi systems

    Energy Technology Data Exchange (ETDEWEB)

    Shaginyan, Vasilii R [B.P. Konstantinov St. Petersburg Institute of Nuclear Physics, Russian Academy of Sciences, Gatchina, Leningrad region, Rusian Federation (Russian Federation); Amusia, M Ya [A.F. Ioffe Physico-Technical Institute, Russian Academy of Sciences, St. Petersburg (Russian Federation); Popov, Konstantin G [Komi Scientific Center, Ural Branch of the Russian Academy of Sciences, Syktyvkar (Russian Federation)

    2007-06-30

    This review discusses the construction of a theory and the analysis of phenomena occurring in strongly correlated Fermi systems such as high-T{sub c} superconductors, heavy-fermion metals, and quasi-two-dimensional Fermi systems. It is shown that the basic properties and the universal behavior of strongly correlated Fermi systems can be described in the framework of the Fermi-condensate quantum phase transition and the well-known Landau paradigm of quasiparticles and the order parameter. The concept of fermion condensation may be fruitful in studying neutron stars, finite Fermi systems, ultra-cold gases in traps, and quark plasma. (reviews of topical problems)

  5. Universal behavior of strongly correlated Fermi systems

    International Nuclear Information System (INIS)

    Shaginyan, Vasilii R; Amusia, M Ya; Popov, Konstantin G

    2007-01-01

    This review discusses the construction of a theory and the analysis of phenomena occurring in strongly correlated Fermi systems such as high-T c superconductors, heavy-fermion metals, and quasi-two-dimensional Fermi systems. It is shown that the basic properties and the universal behavior of strongly correlated Fermi systems can be described in the framework of the Fermi-condensate quantum phase transition and the well-known Landau paradigm of quasiparticles and the order parameter. The concept of fermion condensation may be fruitful in studying neutron stars, finite Fermi systems, ultra-cold gases in traps, and quark plasma. (reviews of topical problems)

  6. Thermal gravitational radiation of Fermi gases and Fermi liquids

    International Nuclear Information System (INIS)

    Schafer, G.; Dehnen, H.

    1983-01-01

    In view of neutron stars the gravitational radiation power of the thermal ''zero-sound'' phonons of a Fermi liquid and the gravitational bremsstrahlung of a degenerate Fermi gas is calculated on the basis of a hard-sphere Fermi particle model. We find for the gravitational radiation power per unit volume P/sub( s/)approx. =[(9π)/sup 1/3//5] x GQ n/sup 5/3/(kT) 4 h 2 c 5 and P/sub( g/)approx. =(4 5 /5 3 )(3/π)/sup 2/3/ G a 2 n/sup 5/3/(kT) 4 /h 2 c 5 for the cases of ''zero sound'' and bremsstrahlung, respectively. Here Q = 4πa 2 is the total cross section of the hard-sphere fermions, where a represents the radius of their hard-core potential. The application to very young neutron stars results in a total gravitational luminosity of about 10 31 erg/sec

  7. Model for paramagnetic Fermi systems

    International Nuclear Information System (INIS)

    Ainsworth, T.L.; Bedell, K.S.; Brown, G.E.; Quader, K.F.

    1983-01-01

    We develop a mode for paramagnetic Fermi liquids. This model has both direct and induced interactions, the latter including both density-density and current-current response. The direct interactions are chosen to reproduce the Fermi liquid parameters F/sup s/ 0 , F/sup a/ 0 , F/sup s/ 1 and to satify the forward scattering sum rule. The F/sup a/ 1 and F/sup s/,a/sub l/ for l>1 are determined self-consistently by the induced interactions; they are checked aginst experimental determinations. The model is applied in detail to liquid 3 He, using data from spin-echo experiments, sound attenuation, and the velocities of first and zero sound. Consistency with experiments gives definite preferences for values of m. The model is also applied to paramagnetic metals. Arguments are given that this model should provide a basis for calculating effects of magnetic fields

  8. Thermodynamics of ultracold Fermi gases

    International Nuclear Information System (INIS)

    Nascimbene, Sylvain

    2010-01-01

    Complex Hamiltonians from condensed matter, such as the Fermi-Hubbard model, can be experimentally studied using ultracold gases. This thesis describes a new method for determining the equation of state of an ultracold gas, making the comparison with many-body theories straightforward. It is based on the measurement of the local pressure inside a trapped gas from the analysis of its in situ image. We first apply this method to the study of a Fermi gas with resonant interactions, a weakly-interacting 7 Li gas acting as a thermometer. Surprisingly, none of the existing many-body theories of the unitary gas accounts for the equation of state deduced from our study over its full range. The virial expansion extracted from the high-temperature data agrees with the resolution of the three-body problem. At low temperature, we observe, contrary to some previous studies, that the normal phase behaves as a Fermi liquid. Finally we obtain the critical temperature for superfluidity from a clear signature on the equation of state. We also measure the pressure of the ground state as a function of spin imbalance and interaction strength - measure directly relevant to describe the crust of neutron stars. Our data validate Monte-Carlo simulations and quantify the Lee-Huang-Yang corrections to mean-field interactions in low-density fermionic or bosonic superfluids. We show that, in most cases, the partially polarized normal phase can be described as a Fermi liquid of polarons. The polaron effective mass extracted from the equation of state is in agreement with a study of collective modes. (author)

  9. Shot-noise at a Fermi-edge singularity: Non-Markovian dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Ubbelohde, N.; Maire, N.; Haug, R. J. [Institut für Festkörperphysik, Leibniz Universität Hannover, Appelstraße 2, D-30167 Hannover (Germany); Roszak, K. [Institute of Physics, Wrocław University of Technology, PL-50370 Wrocław (Poland); Hohls, F. [Physikalisch-Technische Bundesanstalt, D-38116 Braunschweig (Germany); Novotný, T. [Department of Condensed Matter Physics, Faculty of Mathematics and Physics, Charles University, CZ-12116 Prague (Czech Republic)

    2013-12-04

    For an InAs quantum dot we study the current shot noise at a Fermi-edge singularity in low temperature cross-correlation measurements. In the regime of the interaction effect the strong suppression of noise observed at zero magnetic field and the sequence of enhancement and suppression in magnetic field go beyond a Markovian master equation model. Qualitative and quantitative agreement can however be achieved by a generalized master equation model taking non-Markovian dynamics into account.

  10. Fermi Timing and Synchronization System

    International Nuclear Information System (INIS)

    Wilcox, R.; Staples, J.; Doolittle, L.; Byrd, J.; Ratti, A.; Kaertner, F.X.; Kim, J.; Chen, J.; Ilday, F.O.; Ludwig, F.; Winter, A.; Ferianis, M.; Danailov, M.; D'Auria, G.

    2006-01-01

    The Fermi FEL will depend critically on precise timing of its RF, laser and diagnostic subsystems. The timing subsystem to coordinate these functions will need to reliably maintain sub-100fs synchronicity between distant points up to 300m apart in the Fermi facility. The technology to do this is not commercially available, and has not been experimentally demonstrated in a working facility. Therefore, new technology must be developed to meet these needs. Two approaches have been researched by different groups working with the Fermi staff. At MIT, a pulse transmission scheme has been developed for synchronization of RF and laser devices. And at LBL, a CW transmission scheme has been developed for RF and laser synchronization. These respective schemes have advantages and disadvantages that will become better understood in coming years. This document presents the work done by both teams, and suggests a possible system design which integrates them both. The integrated system design provides an example of how choices can be made between the different approaches without significantly changing the basic infrastructure of the system. Overall system issues common to any synchronization scheme are also discussed

  11. Fermi Timing and Synchronization System

    Energy Technology Data Exchange (ETDEWEB)

    Wilcox, R.; Staples, J.; Doolittle, L.; Byrd, J.; Ratti, A.; Kaertner, F.X.; Kim, J.; Chen, J.; Ilday, F.O.; Ludwig, F.; Winter, A.; Ferianis, M.; Danailov, M.; D' Auria, G.

    2006-07-19

    The Fermi FEL will depend critically on precise timing of its RF, laser and diagnostic subsystems. The timing subsystem to coordinate these functions will need to reliably maintain sub-100fs synchronicity between distant points up to 300m apart in the Fermi facility. The technology to do this is not commercially available, and has not been experimentally demonstrated in a working facility. Therefore, new technology must be developed to meet these needs. Two approaches have been researched by different groups working with the Fermi staff. At MIT, a pulse transmission scheme has been developed for synchronization of RF and laser devices. And at LBL, a CW transmission scheme has been developed for RF and laser synchronization. These respective schemes have advantages and disadvantages that will become better understood in coming years. This document presents the work done by both teams, and suggests a possible system design which integrates them both. The integrated system design provides an example of how choices can be made between the different approaches without significantly changing the basic infrastructure of the system. Overall system issues common to any synchronization scheme are also discussed.

  12. Effects of acceleration through the Dirac sea

    International Nuclear Information System (INIS)

    Hacyan, S.

    1986-01-01

    The effects of acceleration through massive scalar and spin-1/2 fields are investigated. It is shown that the density-of-states factor in a uniformly accelerated frame takes a complicated form, but the energy spectrum exhibits a Bose-Einstein or Fermi-Dirac distribution function. In particular, the Dirac sea shows thermal-like effects

  13. Modeling high-energy gamma-rays from the Fermi Bubbles

    Energy Technology Data Exchange (ETDEWEB)

    Splettstoesser, Megan

    2015-09-17

    In 2010, the Fermi Bubbles were discovered at the galactic center of the Milky Way. These giant gamma-ray structures, extending 55° in galactic latitude and 20°-30° in galactic longitude, were not predicted. We wish to develop a model for the gamma-ray emission of the Fermi Bubbles. To do so, we assume that second order Fermi acceleration requires charged particles and irregular magnetic fields- both of which are present in the disk of the Milky Way galaxy. By solving the steady-state case of the transport equation, I compute the proton spectrum due to second order Fermi acceleration. I compare the analytical solutions of the proton spectrum to a numerical solution. I find that the numerical solution to the transport equation converges to the analytical solution in all cases. The gamma-ray spectrum due to proton-proton interaction is compared to Fermi Bubble data (from Ackermann et al. 2014), and I find that second order Fermi acceleration is a good fit for the gamma-ray spectrum of the Fermi Bubbles at low energies with an injection source term of S = 1.5 x 10⁻¹⁰ GeV⁻¹cm⁻³yr⁻¹. I find that a non-steady-state solution to the gamma-ray spectrum with an injection source term of S = 2 x 10⁻¹⁰ GeV⁻¹cm⁻³yr⁻¹ matches the bubble data at high energies.

  14. SSC accelerator availability allocation

    International Nuclear Information System (INIS)

    Dixon, K.T.; Franciscovich, J.

    1991-03-01

    Superconducting Super Collider (SSC) operational availability is an area of major concern, judged by the Central Design Group to present such risk that use of modern engineering tools would be essential to program success. Experience has shown that as accelerator beam availability falls below about 80%, efficiency of physics experiments degrades rapidly due to inability to maintain adequate coincident accelerator and detector operation. For this reason, the SSC availability goal has been set at 80%, even though the Fermi National Accelerator Laboratory accelerator, with a fraction of the SSC's complexity, has only recently approached that level. This paper describes the allocation of the top-level goal to part-level reliability and maintainability requirements, and it gives the results of parameter sensitivity studies designed to help identify the best approach to achieve the needed system availability within funding and schedule constraints. 1 ref., 12 figs., 4 tabs

  15. Attack-Induced Entanglement of Noninteracting Fermi Gas

    International Nuclear Information System (INIS)

    Ren Jie; Zhu Shiqun

    2008-01-01

    The bipartite entanglement in Fermi gas without interaction is investigated when there are three fermions in the system. The negativity and the von Neumann entropy are employed to measure the entanglement of the system. The position of the third fermion can affect the entanglement between the first and the second fermions. The entanglement can be enhanced or suppressed when the third fermion changes its position. When the two fermions are at the same position or when their distance is more than 2.0/k F , the third fermion cannot affect them

  16. Circular orbits in cosmic string and Schwarzschild-AdS spacetime with Fermi-Walker transport

    International Nuclear Information System (INIS)

    Bakke, K.; Furtado, C.; Carvalho, A.M. de

    2009-01-01

    In this paper we discuss the Fermi-Walker transport of vectors along orbits in cosmic string and Schwarzschild-AdS spacetimes. We analyze the influence of acceleration on these holonomies. An effect similar to Thomas precession is observed within the process of Fermi-Walker transport along these circular orbits which are studied in the limit of vanishing cosmological constant in Schwarzschild-AdS case; also we obtain Fermi-Walker transport in a Schwarzschild background. In the case of a Schwarzschild spacetime, we analyze the quantized band holonomy invariance. In the limit of zero acceleration we recover the well-known results for holonomy matrix obtained by parallel transport in all these spacetimes. (orig.)

  17. Beam-induced back-streaming electron suppression analysis for an accelerator type neutron generator designed for 40Ar/39Ar geochronology.

    Science.gov (United States)

    Waltz, Cory; Ayllon, Mauricio; Becker, Tim; Bernstein, Lee; Leung, Ka-Ngo; Kirsch, Leo; Renne, Paul; Bibber, Karl Van

    2017-07-01

    A facility based on a next-generation, high-flux D-D neutron generator has been commissioned and it is now operational at the University of California, Berkeley. The current generator designed for 40 Ar/ 39 Ar dating of geological materials produces nearly monoenergetic 2.45MeV neutrons at outputs of 10 8 n/s. The narrow energy range is advantageous relative to the 235 U fission spectrum neutrons due to (i) reduced 39 Ar recoil energy, (ii) minimized production of interfering argon isotopes from K, Ca, and Cl, and (iii) reduced total activity for radiological safety and waste generation. Calculations provided show that future conditioning at higher currents and voltages will allow for a neutron output of over 10 10 n/s, which is a necessary requirement for production of measurable quantities of 39 Ar through the reaction 39 K(n,p) 39 Ar. A significant problem encountered with increasing deuteron current was beam-induced electron backstreaming. Two methods of suppressing secondary electrons resulting from the deuterium beam striking the target were tested: the application of static electric and magnetic fields. Computational simulations of both techniques were done using a finite element analysis in COMSOL Multiphysics ® . Experimental tests verified these simulations. The most reliable suppression was achieved via the implementation of an electrostatic shroud with a voltage offset of -800V relative to the target. Copyright © 2017. Published by Elsevier Ltd.

  18. Early history of physics with accelerators

    International Nuclear Information System (INIS)

    Anderson, H.L.

    1982-01-01

    The early history of physics at accelerators is reviewed, with emphasis on three experiments which have had a profound influence on our veiw of the structure of matter: The Franck and Hertz experiment opening practical ways of studying nuclear disintegration, and the discovery of the del ++ isobar of the proton by Fermi and collaborators, revealing structure in the nucleon. Fermi's work is illustrated by pages from his notebooks

  19. Pseudogap phenomena in ultracold atomic Fermi gases

    OpenAIRE

    Chen, Qijin; Wang, Jibiao

    2014-01-01

    The pairing and superfluid phenomena in a two-component ultracold atomic Fermi gas is an analogue of Cooper pairing and superconductivity in an electron system, in particular, the high $T_c$ superconductors. Owing to the various tunable parameters that have been made accessible experimentally in recent years, atomic Fermi gases can be explored as a prototype or quantum simulator of superconductors. It is hoped that, utilizing such an analogy, the study of atomic Fermi gases may shed light to ...

  20. Pulsar Timing with the Fermi LAT

    Science.gov (United States)

    2010-12-01

    Pulsar Timing with the Fermi LAT Paul S. Ray∗, Matthew Kerr†, Damien Parent∗∗ and the Fermi PSC‡ ∗Naval Research Laboratory, 4555 Overlook Ave., SW...Laboratory, Washington, DC 20375, USA ‡Fermi Pulsar Search Consortium Abstract. We present an overview of precise pulsar timing using data from the Large...unbinned photon data. In addition to determining the spindown behavior of the pulsars and detecting glitches and timing noise, such timing analyses al

  1. Phase diagram of strongly correlated Fermi systems

    International Nuclear Information System (INIS)

    Zverev, M.V.; Khodel', V.A.; Baldo, M.

    2000-01-01

    Phase transitions in uniform Fermi systems with repulsive forces between the particles caused by restructuring of quasiparticle filling n(p) are analyzed. It is found that in terms of variables, i.e. density ρ, nondimensional binding constant η, phase diagram of a strongly correlated Fermi system for rather a wide class of interactions reminds of a puff-pastry pie. Its upper part is filled with fermion condensate, the lower one - with normal Fermi-liquid. They are separated by a narrow interlayer - the Lifshits phase, characterized by the Fermi multibound surface [ru

  2. Thermal radiation of fermions by an accelerated wall

    International Nuclear Information System (INIS)

    Horibe, Minoru

    1979-01-01

    The theory of particle production by an accelerated wall is extended to the massless Dirac particle. It is shown that the mean occupation number of fermions (anti-fermions) is given by the Fermi distribution function. (author)

  3. Compositeness and the Fermi scale

    International Nuclear Information System (INIS)

    Peccei, R.D.

    1984-01-01

    The positive attitude adopted up to now, due to the non-observation of effects of substructure, is that the compositeness scale Λ must be large: Λ > or approx. 1 TeV. Such a large value of Λ gives rise to two theoretical problems which I examine here, namely: 1) What dynamics yields light composite quarks and leptons (msub(f) < < Λ) and 2) What relation does the compositeness scale Λ have with the Fermi scale Λsub(F) = (√2 Gsub(F))sup(-1/2) approx.= 250 GeV. (orig./HSI)

  4. Fermi problem in disordered systems

    Science.gov (United States)

    Menezes, G.; Svaiter, N. F.; de Mello, H. R.; Zarro, C. A. D.

    2017-10-01

    We revisit the Fermi two-atom problem in the framework of disordered systems. In our model, we consider a two-qubit system linearly coupled with a quantum massless scalar field. We analyze the energy transfer between the qubits under different experimental perspectives. In addition, we assume that the coefficients of the Klein-Gordon equation are random functions of the spatial coordinates. The disordered medium is modeled by a centered, stationary, and Gaussian process. We demonstrate that the classical notion of causality emerges only in the wave zone in the presence of random fluctuations of the light cone. Possible repercussions are discussed.

  5. Relativistic shocks and particle acceleration

    International Nuclear Information System (INIS)

    Heavens, A.F.

    1988-01-01

    In this paper, we investigate the fluid dynamics of relativistic shock waves, and use the results to calculate the spectral index of particles accelerated by the Fermi process in such shocks. We have calculated the distributions of Fermi-accelerated particles at shocks propagating into cold proton-electron plasma and also cold electron-positron plasma. We have considered two different power spectra for the scattering waves, and find, in contrast to the non-relativistic case, that the spectral index of the accelerated particles depends on the wave power spectrum. On the assumption of thermal equilibrium both upstream and downstream, we present some useful fits for the compression ratio of shocks propagating at arbitrary speeds into gas of any temperature. (author)

  6. Fermilab 1982. Annual report of the Fermi National Accelerator Laboratory

    International Nuclear Information System (INIS)

    The state of Fermilab is reviewed for 1982, and summaries are given in the following areas: fabricating energy saver superconducting magnets; present knowledge and future directions in particle physics; accomplishments of Fermilab in a decade of operation 1972 to 1982; a photo essay on the energy saver installation work in the Main Ring Tunnel; a listing of 1982 Fermilab experimental, general, and theoretical publications; and a listing of the 1982 workshop and seminar series

  7. Fermi National Accelerator Laboratory Annual Program Review 2000

    Energy Technology Data Exchange (ETDEWEB)

    2000-03-01

    This book is submitted as one written part of the 2000 Annual DOE High Energy Physics Program Review of Fermilab, scheduled March 22-24, 2000. In it are Director's Overview, some experimental highlights, discussions of several projects, and descriptions of the functions and activities of the four laboratory divisions. This book should be read in conjunction with the 2000 Fermilab Workbook and the review presentations (both in formal sessions and at the poster session).

  8. Fermi National Accelerator Laboratory Annual Program Review 1999

    Energy Technology Data Exchange (ETDEWEB)

    1999-05-01

    This book is submitted as one written part of the 1999 Annual DOE High Energy Physics Program Review of Fermilab, scheduled May 5-7,1999. This book should be read in conjunction with the 1999 Fermilab Workbook and the review presentations.

  9. Fermi National Accelerator Laboratory Annual Program Review 1993

    Energy Technology Data Exchange (ETDEWEB)

    1993-01-01

    This book is submitted as a written adjunct to the 1993 Annual DOE High Energy Physics Program Review of Fermilab, scheduled for March 31-April 3. In it are described the functions and activities of the various Laboratory Divisions and Sections plus statements of plans and goals for the coming year. The Review Committee, as this goes to press, consists of·

  10. Fermi National Accelerator Laboratory Annual Program Review 1991

    Energy Technology Data Exchange (ETDEWEB)

    Appel, Jeffrey A. [Fermilab; Jovanovic, Drasko [Fermilab; Pordes, Stephen [Fermilab

    1991-01-01

    This book is submitted as a written adjunct to the Annual DOE High Energy Physics Program Review of Fermilab, scheduled this year for April 10-12, 1991. In it are described the functions and activities of the various Laboratory areas plus statements of plans and goals for the coming year.

  11. Theoretical problems in accelerator physics

    International Nuclear Information System (INIS)

    1992-01-01

    This report discusses the following research on accelerators: computational methods; higher order mode suppression in accelerators structures; overmoded waveguide components and application to SLED II and power transport; rf sources; accelerator cavity design for a B factory asymmetric collider; and photonic band gap cavities

  12. Nonextensive Thomas-Fermi model

    Science.gov (United States)

    Shivamoggi, Bhimsen; Martinenko, Evgeny

    2007-11-01

    Nonextensive Thomas-Fermi model was father investigated in the following directions: Heavy atom in strong magnetic field. following Shivamoggi work on the extension of Kadomtsev equation we applied nonextensive formalism to father generalize TF model for the very strong magnetic fields (of order 10e12 G). The generalized TF equation and the binding energy of atom were calculated which contain a new nonextensive term dominating the classical one. The binding energy of a heavy atom was also evaluated. Thomas-Fermi equations in N dimensions which is technically the same as in Shivamoggi (1998) ,but behavior is different and in interesting 2 D case nonextesivity prevents from becoming linear ODE as in classical case. Effect of nonextensivity on dielectrical screening reveals itself in the reduction of the envelope radius. It was shown that nonextesivity in each case is responsible for new term dominating classical thermal correction term by order of magnitude, which is vanishing in a limit q->1. Therefore it appears that nonextensive term is ubiquitous for a wide range of systems and father work is needed to understand the origin of it.

  13. Detecting superlight dark matter with Fermi-degenerate materials

    Energy Technology Data Exchange (ETDEWEB)

    Hochberg, Yonit [Theory Group, Lawrence Berkeley National Laboratory,Berkeley, CA 94709 (United States); Berkeley Center for Theoretical Physics, University of California, Berkeley, CA 94709 (United States); Pyle, Matt [Physics Department, University of California,Berkeley, CA 94709 (United States); Zhao, Yue [Michigan Center for Theoretical Physics, University of Michigan,Ann Arbor, MI 48109 (United States); Zurek, Kathryn M. [Theory Group, Lawrence Berkeley National Laboratory,Berkeley, CA 94709 (United States); Berkeley Center for Theoretical Physics, University of California,Berkeley, CA 94709 (United States)

    2016-08-08

    We examine in greater detail the recent proposal of using superconductors for detecting dark matter as light as the warm dark matter limit of O(keV). Detection of such light dark matter is possible if the entire kinetic energy of the dark matter is extracted in the scattering, and if the experiment is sensitive to O(meV) energy depositions. This is the case for Fermi-degenerate materials in which the Fermi velocity exceeds the dark matter velocity dispersion in the Milky Way of ∼10{sup −3}. We focus on a concrete experimental proposal using a superconducting target with a transition edge sensor in order to detect the small energy deposits from the dark matter scatterings. Considering a wide variety of constraints, from dark matter self-interactions to the cosmic microwave background, we show that models consistent with cosmological/astrophysical and terrestrial constraints are observable with such detectors. A wider range of viable models with dark matter mass below an MeV is available if dark matter or mediator properties (such as couplings or masses) differ at BBN epoch or in stellar interiors from those in superconductors. We also show that metal targets pay a strong in-medium suppression for kinetically mixed mediators; this suppression is alleviated with insulating targets.

  14. Suppression of the ferromagnetic state by disorder in the Kondo lattice

    International Nuclear Information System (INIS)

    Crisan, M.; Popoviciu, C.

    1992-01-01

    This paper reports that ferromagnetic ground state of a Kondo lattice with a low concentration of conduction electrons is ferromagnetic. Assuming the existence of disorder in the Fermi liquid of the conduction electrons the authors show that the ferromagnetic state can be suppressed by the effect of the spin fluctuations of the disordered Fermi liquid

  15. Enrico Fermi significato di una scoperta

    CERN Document Server

    2001-01-01

    Questo volume è la riedizione, rinnovata ed ampliata, del volume "Enrico Fermi. Significato di una scoperta" edito dal FIEN (Forum Italiano dell'Energia Nucleare) nel 1982 e nel 1992 in occasione, rispettivamente, del 40mo e del 50mo anniversario della pila di Fermi.

  16. Vacuum alignment and radiatively induced Fermi scale

    Directory of Open Access Journals (Sweden)

    Alanne Tommi

    2017-01-01

    Full Text Available We extend the discussion about vacuum misalignment by quantum corrections in models with composite pseudo-Goldstone Higgs boson to renormalisable models with elementary scalars. As a concrete example, we propose a framework, where the hierarchy between the unification and the Fermi scale emerges radiatively. This scenario provides an interesting link between the unification and Fermi scale physics.

  17. Reversible beam heater for suppression of microbunching instability by transverse gradient undulators

    Science.gov (United States)

    Liu, Tao; Qin, Weilun; Wang, Dong; Huang, Zhirong

    2017-08-01

    The microbunching instability driven by beam collective effects in a linear accelerator of a free-electron laser (FEL) facility significantly degrades the electron beam quality and FEL performance. A conventional method to suppress this instability is to introduce an additional uncorrelated energy spread by laser-electron interaction, which has been successfully operated in the Linac Coherent Light Source and Fermi@Elettra, etc. Some other ideas are recently proposed to suppress the instability without increasing energy spread, which could benefit the seeded FEL schemes. In this paper, we propose a reversible electron beam heater using two transverse gradient undulators to suppress the microbunching instability. This scheme introduces both an energy spread increase and a transverse-to-longitudinal phase space coupling, which suppress the microbunching instabilities driven by both longitudinal space charge and coherent synchrotron radiation before and within the system. Finally the induced energy spread increase and emittance growth are reversed. Theoretical analysis and numerical simulations are presented to verify the feasibility of the scheme and indicate the capability to improve the seeded FEL radiation performance.

  18. Transverse to longitudinal phase space coupling in an electron beam for suppression of microbunching instability

    Directory of Open Access Journals (Sweden)

    Dazhang Huang

    2016-10-01

    Full Text Available The microbunching instability developed during the beam compression process in the linear accelerator (LINAC of a free-electron laser (FEL facility has always been a problem that degrades the lasing performance, and even no FEL is able to be produced if the beam quality is destroyed too much by the instability. A common way to suppress the microbunching instability is to introduce extra uncorrelated energy spread by the laser heater that heats the beam through the interaction between the electron and laser beam, as what has been successfully implemented in the Linac Coherent Light Source and Fermi@Elettra. In this paper, a simple and effective scheme is proposed to suppress the microbunching instability by adding two transverse gradient undulators (TGU before and after the magnetic bunch compressor. The additional uncorrelated energy spread and the density mixing from the transverse spread brought up by the first TGU results in significant suppression of the instability. Meanwhile, the extra slice energy spread and the transverse emittance can also be effectively recovered by the second TGU. The magnitude of the suppression can be easily controlled by varying the strength of the magnetic fields of the TGUs. Theoretical analysis and numerical simulations demonstrate the capability of the proposed technique in the LINAC of an x-ray free-electron laser facility.

  19. IceCube Constraints on the Fermi Bubbles

    Energy Technology Data Exchange (ETDEWEB)

    Sherf, Nimrod; Keshet, Uri [Physics Department, Ben-Gurion University of the Negev, POB 653, Be’er-Sheva 84105 (Israel); Gurwich, Ilya, E-mail: sherfnim@post.bgu.ac.il, E-mail: ukeshet@bgu.ac.il, E-mail: gurwichphys@gmail.com [Department of Physics, NRCN, POB 9001, Beer-Sheva 84190 (Israel)

    2017-10-01

    We analyze the IceCube four-year neutrino data in search of a signal from the Fermi bubbles. No signal is found from the bubbles or from their dense shell, even when taking into account the softer background. This imposes a conservative ξ {sub i} < 8% upper limit on the cosmic-ray ion (CRI) acceleration efficiency, and an η ≡ ξ {sub e} / ξ {sub i} ≳ 0.006 lower limit on the electron-to-ion ratio of acceleration efficiencies (at the 2 σ confidence level). For typical ξ {sub i} , a signal should surface once the number of IceCube neutrinos increases by ∼an order of magnitude, unless there is a

  20. Using of new possibilities of Fermi architecture by development og GPGPU programs

    International Nuclear Information System (INIS)

    Dudnik, V.A.; Kudryavtsev, V.I.; Us, S.A.; Shestakov, M.V.

    2013-01-01

    Description of additional functions of hardware and software, which are presented in the structure of new architecture of FERMI graphic processors made by company NVIDIA, was given. Recommendations of their use within the realization of algorithms of scientific and technical calculations by means of the graphic processors were given. Application of the new possibilities of FERMI architecture and CUDA technologies (Compute Unified Device Architecture - unified hardware-software decision for parallel calculations on GPU) of NVIDIA Company was described. It was done for time reduction of applications' development which is using possibilities of GPGPU for acceleration of data processing

  1. A possible origin of gamma rays from the Fermi Bubbles

    Science.gov (United States)

    Thoudam, Satyendra

    2014-11-01

    One of the most exciting discoveries of recent years is a pair of gigantic gamma-ray emission regions, the so-called Fermi bubbles, above and below the Galactic center. The bubbles, discovered by the Fermi space telescope, extend up to ∼50° in Galactic latitude and are ∼40° wide in Galactic longitude. The gamma-ray emission is also found to correlate with radio, microwave and X-rays emission. The origin of the bubbles and the associated non-thermal emissions are still not clearly understood. Possible explanations for the non-thermal emission include cosmic-ray injection from the Galactic center by high speed Galactic winds/jets, acceleration by multiple shocks or plasma turbulence present inside the bubbles, and acceleration by strong shock waves associated with the expansion of the bubbles. In this paper, I will discuss the possibility that the gamma-ray emission is produced by the injection of Galactic cosmic-rays mainly protons during their diffusive propagation through the Galaxy. The protons interact with the bubble plasma producing π°-decay gamma rays, while at the same time, radio and microwave synchrotron emissions are produced by the secondary electrons/positrons resulting from the π± decays.

  2. A possible origin of gamma rays from the Fermi Bubbles

    International Nuclear Information System (INIS)

    Thoudam, Satyendra

    2014-01-01

    One of the most exciting discoveries of recent years is a pair of gigantic gamma-ray emission regions, the so-called Fermi bubbles, above and below the Galactic center. The bubbles, discovered by the Fermi space telescope, extend up to ∼50 ° in Galactic latitude and are ∼40 ° wide in Galactic longitude. The gamma-ray emission is also found to correlate with radio, microwave and X-rays emission. The origin of the bubbles and the associated non-thermal emissions are still not clearly understood. Possible explanations for the non-thermal emission include cosmic-ray injection from the Galactic center by high speed Galactic winds/jets, acceleration by multiple shocks or plasma turbulence present inside the bubbles, and acceleration by strong shock waves associated with the expansion of the bubbles. In this paper, I will discuss the possibility that the gamma-ray emission is produced by the injection of Galactic cosmic-rays mainly protons during their diffusive propagation through the Galaxy. The protons interact with the bubble plasma producing π ° -decay gamma rays, while at the same time, radio and microwave synchrotron emissions are produced by the secondary electrons/positrons resulting from the π ± decays

  3. Turbulence and particle acceleration

    International Nuclear Information System (INIS)

    Scott, J.S.

    1975-01-01

    A model for the production of high energy particles in the supernova remnant Cas A is considered. The ordered expansion of the fast moving knots produce turbulent cells in the ambient interstellar medium. The turbulent cells act as magnetic scattering centers and charged particles are accelerated to large energies by the second order Fermi mechanism. Model predictions are shown to be consistent with the observed shape and time dependence of the radio spectrum, and with the scale size of magnetic field irregularities. Assuming a galactic supernova rate at 1/50 yr -1 , this mechanism is capable of producing the observed galactic cosmic ray flux and spectrum below 10 16 eV/nucleon. Several observed features of galactic cosmic rays are shown to be consistent with model predictions. A model for the objects known as radio tall galaxies is also presented. Independent blobs of magnetized plasma emerging from an active radio galaxy into an intracluster medium become turbulent due to Rayleigh--Taylor and Kelvin--Helmholz instabilities. The turbulence produces both in situ betatron and 2nd order Fermi accelerations. Predictions of the dependence of spectral index and flux on distance along the tail match observations well. Fitting provides values of physical parameters in the blobs. The relevance of this method of particle acceleration for the problem of the origin of x-ray emission in clusters of galaxies is discussed

  4. Mean free path of nucleons in a Fermi gas at finite temperature

    International Nuclear Information System (INIS)

    Collins, M.T.; Griffin, J.J.

    1980-01-01

    The mean free path of a nucleon in a nuclear Fermi gas at finite temperature is calculated by utilizing the free nucleon-nucleon cross section modified to suppress final states excluded by the Pauli principle. The results agree with an earlier zero-temperature calculation but yield substantially smaller values than a previous finite-temperature analysis. The Fermi gas mean free paths are some two to four times shorter than those implied by phenomenological imaginary optical potentials, suggesting that the present Fermi gas model fails to adequately describe the physical processes determining the mean free path. Even so, the present results, taken as lower bounds on te mean free path, require temperatures of some 4.5 MeV before the mean free path of bound nucleons becomes as short as the nuclear diameter. It follows that very high excitation energies are prerequisite to any short mean free path assumption in nuclear heavy-ion collisions. (orig.)

  5. In situ acceleration in extragalactic radio jets

    International Nuclear Information System (INIS)

    Bicknell, G.V.; Melrose, D.B.

    1982-01-01

    We have examined the energy dissipated by large-scale turbulence in an extragalactic jet. The turbulence is driven by a shear instability which does not disrupt the jet. Fluid theory should be used to treat the evolution of the turbulence, and this allows us to estimate the rate of dissipation without detailed knowledge of the dissipation process. Dissipation occurs due to Fermi acceleration at a scale length approx.10 -3 R and that resonant acceleration plays no role. The Alfvenic component in the turbulent spectrum is dissipated by first being converted into magneto-acoustic waves. An alternative dissipation process due to formation of weak shocks is shown to be equivalent in some respects to Fermi acceleration. Dissipation in the thermal gas should not exceed that due to Fermi acceleration. The effect of Fermi acceleration, adiabatic losses, and radiative losses on an initial power-law distribution with an upper cutoff is studied. Radio emission extending to at least 100 GHz is shown to be possible, and no spectral index gradients are introduced by the acceleration. The upper cutoff can increase due to the acceleration alone or when the acceleration is balanced by radiative losses. The northern jet in NGC 315 is studied in detail. Using our model for the acceleration, we estimate a jet velocity > or approx. =5000 km s -1 with Mach number not much greater than 1, and a density -4 f -1 cm -3 at the turn-on of the jet at 6 cm, where 0.05 5 yr, and it is predicted that the radius of the jet at the turn-on point should vary with frequency either as ν/sup 2/3/ or as ν/sup 3/2/, or there may be no frequency dependence, contingent upon the details of the acceleration

  6. Fermi liquids from D-branes

    OpenAIRE

    Moshe RozaliDepartment of Physics and Astronomy, University of British Columbia, Vancouver, BC V6T 1Z1, Canada; Darren Smyth(Department of Physics and Astronomy, University of British Columbia, Vancouver, BC V6T 1Z1, Canada)

    2014-01-01

    We discuss finite density configurations on probe D-branes, in the presence of worldvolume fermions. To this end we consider a phenomenological model whose bosonic sector is governed by the DBI action, and whose charged sector is purely fermionic. In this model, we demonstrate the existence of a compact worldvolume embedding, stabilized by a Fermi surface on the D- brane. The finite density state in the boundary QFT is a Fermi-like liquid. We comment on the possibility of realizing non-Fermi ...

  7. Quantum mechanical models for the Fermi shuttle

    Science.gov (United States)

    Sternberg, James; Ovchinnikov, S. Yu.; Macek, J. H.

    2009-05-01

    Although the Fermi shuttle was originally proposed as an explanation for highly energetic cosmic rays, it is also a mechanism for the production of high energy electrons in atomic collisions [1]. The Fermi shuttle is usually thought of as a classical effect and most models of this process rely on classical or semi-classical approximations. In this work we explore several quantum mechanical models for ion-atom collisions and examine the evidence for the Fermi shuttle in these models. [4pt] [1] B. Sulik, Cs. Koncz, K. Tok'esi, A. Orb'an, and D. Ber'enyi, Phys Rev. Lett. 88 073201 (2002)

  8. SHEAR ACCELERATION IN EXPANDING FLOWS

    Energy Technology Data Exchange (ETDEWEB)

    Rieger, F. M. [ZAH, Institut für Theoretische Astrophysik, Universität Heidelberg, Philosophenweg 12, D-69120 Heidelberg (Germany); Duffy, P., E-mail: frank.rieger@mpi-hd.mpg.de, E-mail: peter.duffy@ucd.ie [University College Dublin, Belfield, Dublin 4 (Ireland)

    2016-12-10

    Shear flows are naturally expected to occur in astrophysical environments and potential sites of continuous non-thermal Fermi-type particle acceleration. Here we investigate the efficiency of expanding relativistic outflows to facilitate the acceleration of energetic charged particles to higher energies. To this end, the gradual shear acceleration coefficient is derived based on an analytical treatment. The results are applied to the context of the relativistic jets from active galactic nuclei. The inferred acceleration timescale is investigated for a variety of conical flow profiles (i.e., power law, Gaussian, Fermi–Dirac) and compared to the relevant radiative and non-radiative loss timescales. The results exemplify that relativistic shear flows are capable of boosting cosmic-rays to extreme energies. Efficient electron acceleration, on the other hand, requires weak magnetic fields and may thus be accompanied by a delayed onset of particle energization and affect the overall jet appearance (e.g., core, ridge line, and limb-brightening).

  9. Fermi: a physicist in the upheaval

    International Nuclear Information System (INIS)

    Maria, M. de

    2002-01-01

    This book summarizes the life, works and complex personality of the Italian physicist Enrico Fermi (1901-1954) whose myth is linked with the political upheaval of the 2. world war: the youth of an autodidact, the theorician and the quantum mechanics, his invention of a quantum statistics, the weak interaction theory, his works on artificial radioactivity, the end of the Fermi team and his exile in the USA, the secrete researches at the university of Columbia and the birth of the first atomic 'pile' (December 2, 1942), the building of Los Alamos center and the Alamogordo explosion test, the disagreements among the physicists of the Manhattan project and the position of Fermi, Fermi's contribution in the H-bomb construction, the creation of the physics school of Chicago, the Oppenheimer spying affair. (J.S.)

  10. Fermi's Conundrum: Proliferation and Closed Societies

    Science.gov (United States)

    Teller, Wendy; Westfall, Catherine

    2007-04-01

    On January 1, 1946 Emily Taft Douglas, a freshman Representative at Large for Illinois, sent a letter to Enrico Fermi. She wanted to know whether, if atomic energy was used for peaceful purposes, it might be possible to clandestinely divert some material for bombs. Douglas first learned about the bomb not quite five months before when Hiroshima was bombed. Even though she was not a scientist she identified a key problem of the nuclear age. Fermi responded with requirements to allow peaceful uses of atomic energy and still outlaw nuclear weapons. First, free interchange of information between people was required, and second, people who reported possible violations had to be protected. Fermi had lived in Mussolini's Italy and worked under the war time secrecy restrictions of the Manhattan Project. He was not optimistic that these conditions could be met. This paper discusses how Douglas came to recognize the proliferation issue and what led Fermi to his solution and his pessimism about its practicality.

  11. Fermi and the Theory of Weak Interactions

    Indian Academy of Sciences (India)

    IAS Admin

    Quantum Field Theory created by Dirac and used by Fermi to describe weak ... of classical electrodynamics (from which the electric field and magnetic field can be obtained .... Universe. However, thanks to weak interactions, this can be done.

  12. Bright solitons in Bose-Fermi mixtures

    International Nuclear Information System (INIS)

    Karpiuk, Tomasz; Brewczyk, Miroslaw; RzaPewski, Kazimierz

    2006-01-01

    We consider the formation of bright solitons in a mixture of Bose and Fermi degenerate gases confined in a three-dimensional elongated harmonic trap. The Bose and Fermi atoms are assumed to effectively attract each other whereas bosonic atoms repel each other. Strong enough attraction between bosonic and fermionic components can change the character of the interaction within the bosonic cloud from repulsive to attractive making thus possible the generation of bright solitons in the mixture. On the other hand, such structures might be in danger due to the collapse phenomenon existing in attractive gases. We show, however, that under some conditions (defined by the strength of the Bose-Fermi components attraction) the structures which neither spread nor collapse can be generated. For elongated enough traps the formation of solitons is possible even at the 'natural' value of the mutual Bose-Fermi ( 87 Rb- 40 K in our case) scattering length

  13. Suppressed Belief

    Directory of Open Access Journals (Sweden)

    Komarine Romdenh-Romluc

    2009-12-01

    Full Text Available Moran’s revised conception of conscious belief requires us to reconceptualise suppressed belief. The work of Merleau-Ponty offers a way to do this. His account of motor-skills allows us to understand suppressed beliefs as pre-reflective ways of dealing with the world.

  14. Thomas Fermi model of finite nuclei

    International Nuclear Information System (INIS)

    Boguta, J.; Rafelski, J.

    1977-01-01

    A relativistic Thomas-Fermi model of finite-nuclei is considered. The effective nuclear interaction is mediated by exchanges of isoscalar scalar and vector mesons. The authors include also a self-interaction of the scalar meson field and the Coulomb repulsion of the protons. The parameters of the model are constrained by the average nuclear properties. The Thomas-Fermi equations are solved numerically for finite, stable nuclei. The particular case of 208 82 Pb is considered in more detail. (Auth.)

  15. Conoscere Fermi nel centenario della nascita : 29 settembre 1901 - 2001

    CERN Document Server

    Bonolis, Luisa

    2001-01-01

    Il lavoro scientifico di Fermi riguarda molti campi disparati, ciascuno dei quali ha avuto uno sviluppo peculiare in tempi successivi alla morte. In questo volume un certo numero di specialisti contemporanei di ciascun settore espone in forma semplice l'idea originaria e la sua successiva evoluzione. INDICE. Carlo Bernardini, "Introduzione"; Giorgio Salvini, "Enrico Fermi. La sua vita, ed un commento alla sua opera"; Edoardo Amaldi, "Commemorazione del Socio Enrico Fermi"; Enrico Persico, "Commemorazione di Enrico Fermi"; Franco Rasetti, "Enrico Fermi e la Fisica Italiana"; Franco Bassani, "Enrico Fermi e la Fisica dello Stato Solido"; Giorgio Parisi, "La statistica di Fermi"; Giovanni Gallavotti, "La meccanica classica e la rivoluzione quantistica nei lavori giovanili di Fermi"; Tullio Levi-Civita, "Sugli invarianti adiabatici"; Bruno Bertotti, "Le coordinate di Fermi e il Principio di Equivalenza"; Marcello Cini, "Fermi e l'elettrodinamica quantistica"; Nicola Cabibbo. "Le interazioni deboli"; Ugo Amaldi, "...

  16. Tunable heat conduction through coupled Fermi-Pasta-Ulam chains

    Science.gov (United States)

    Su, Ruixia; Yuan, Zongqiang; Wang, Jun; Zheng, Zhigang

    2015-01-01

    We conduct a study on heat conduction through coupled Fermi-Pasta-Ulam (FPU) chains by using classical molecular dynamics simulations. Our attention is dedicated to showing how the phonon transport is affected by the interchain coupling. It has been well accepted that the heat conduction could be impeded by the interchain interaction due to the interface phonon scattering. However, recent theoretical and experimental studies suggest that the thermal conductivity of nanoscale materials can be counterintuitively enhanced by the interaction with the substrate. In the present paper, by consecutively varying the interchain coupling intensity, we observed both enhancement and suppression of thermal transport through the coupled FPU chains. For weak interchain couplings, it is found that the heat flux increases with the coupling intensity, whereas in the case of strong interchain couplings, the energy transport is found to be suppressed by the interchain interaction. Based on the phonon spectral energy density method, we attribute the enhancement of the energy transport to the excited phonon modes (in addition to the intrinsic phonon modes), while the upward shift of the high-frequency phonon branch and the interface phonon-phonon scattering account for the suppressed heat conduction.

  17. Status report of the FERMI-Elettra control system

    International Nuclear Information System (INIS)

    Lonza, M.; Abrami, A.; Asnicar, F.; Battistello, L.; Bogani, A.I.; Borghes, R.; Chenda, V.; Cleva, S.; Curri, A.; Marco, M. de; Dos Santos, M.; Gaio, G.; Giacuzzo, F.; Kourousias, G.; Passos, G.; Passuello, R.; Pivetta, L.; Prica, M.; Pugliese, R.; Scafuri, C.; Scalamera, G.; Strangolino, G.; Vittor, D.; Zambon, L.

    2012-01-01

    FERMI-Elettra is a new fourth-generation light source based on a seeded Free Electron Laser (FEL) presently under commissioning in Trieste, Italy. It is the first seeded FEL ever designed to produce fundamental output wavelength down to 4 nm with High Gain Harmonic Generation (HGHG). FERMI-Elettra is a linac-based FEL whose 200 m long accelerator consists of a high brightness photo-cathode gun working at up to 50 Hz repetition rate, a 1.5 GeV normal conducting linac and 2 bunch compressors. Unlike storage ring based synchrotron light sources that are well known machines, the commissioning of a new-concept FEL is a complex and time-consuming process consisting in thorough testing, understanding and optimization, in which a reliable and powerful control system is mandatory. In particular, integrated shot-by-shot beam manipulation capabilities and easy-to-use high level applications are crucial to allow an effective and smooth machine commissioning. This paper reports the status of the control system and the experience gained in two years of alternating construction and commissioning phases. (authors)

  18. Interplay between magnetic quantum criticality, Fermi surface and unconventional superconductivity in UCoGe, URhGe and URu2Si2

    International Nuclear Information System (INIS)

    Bastien, Gael

    2017-01-01

    This thesis is concentrated on the ferromagnetic superconductors UCoGe and URhGe and on the hidden order state in URu 2 Si 2 . In the first part the pressure temperature phase diagram of UCoGe was studied up to 10.5 GPa. Ferromagnetism vanishes at the critical pressure pc≅1 GPa. Unconventional superconductivity and non Fermi liquid behavior can be observed in a broad pressure range around pc. The superconducting upper critical field properties were explained by the suppression of the magnetic fluctuations under field. In the second part the Fermi surfaces of UCoGe and URhGe were investigated by quantum oscillations. In UCoGe four Fermi surface pockets were observed. Under magnetic field successive Lifshitz transitions of the Fermi surface have been detected. The observed Fermi surface pockets in UCoGe evolve smoothly with pressure up to 2.5 GPa and do not show any Fermi surface reconstruction at the critical pressure pc. In URhGe, three heavy Fermi surface pockets were detected by quantum oscillations. In the last part the quantum oscillation study in the hidden order state of URu 2 Si 2 shows a strong g factor anisotropy for two Fermi surface pockets, which is compared to the macroscopic g factor anisotropy extracted from the upper critical field study. (author) [fr

  19. The FERMI-Elettra distributed real-time framework

    International Nuclear Information System (INIS)

    Pivetta, L.; Gaio, G.; Passuello, R.; Scalamera, G.

    2012-01-01

    FERMI-Elettra is a Free Electron Laser (FEL) based on a 1.5 GeV linac. The pulsed operation of the accelerator and the necessity to characterize and control each electron bunch requires synchronous acquisition of the beam diagnostics together with the ability to drive actuators in real-time at the linac repetition rate. The Adeos/Xenomai real-time extensions have been adopted in order to add real-time capabilities to the Linux based control system computers running the Tango software. A software communication protocol based on Gigabit Ethernet and known as Network Reflective Memory (NRM) has been developed to implement a shared memory across the whole control system, allowing computers to communicate in real-time. The NRM architecture, the real-time performance and the integration in the control system are described. (authors)

  20. Operational status display and automation tools for FERMI-Elettra

    International Nuclear Information System (INIS)

    Scafuri, C.

    2012-01-01

    Detecting and locating faults and malfunctions of an accelerator is a difficult and time consuming task. The situation is even more difficult during the commissioning phase of a new accelerator, when the plants are not yet well known. Faults involving single devices are easy to detect, however a fault free machine does not imply that it is ready to run: the definition of malfunction depends on what is the expected behavior of the plant. In the case of FERMI-Elettra, in which the electron beam goes to different branches of the machine depending on the programmed activity, the configuration of the plant determines the rules for detecting malfunctions. In order to help the detection of faults and malfunctions and to display the status of the plant, a tool, known as the 'Matrix', has been developed. It is composed by a graphical front-end which displays a synthetic view of the plant status grouped by subsystem and location along the accelerator, and by a back-end calculation engine. The graphical front-end gives also the possibility, once a problem is detected, to focus on its details. The calculation engine is composed by a set of objects known as Sequencers. The calculation rules have been determined by analyzing the various subsystems and global working of the accelerator with plant and operations experts. The Sequencer is designed so that it can also issue commands to the plant. This will be used in the next releases of the Matrix for actively switching from one accelerator configuration to another. (author)

  1. Can Accelerators Accelerate Learning?

    International Nuclear Information System (INIS)

    Santos, A. C. F.; Fonseca, P.; Coelho, L. F. S.

    2009-01-01

    The 'Young Talented' education program developed by the Brazilian State Funding Agency (FAPERJ)[1] makes it possible for high-schools students from public high schools to perform activities in scientific laboratories. In the Atomic and Molecular Physics Laboratory at Federal University of Rio de Janeiro (UFRJ), the students are confronted with modern research tools like the 1.7 MV ion accelerator. Being a user-friendly machine, the accelerator is easily manageable by the students, who can perform simple hands-on activities, stimulating interest in physics, and getting the students close to modern laboratory techniques.

  2. Can Accelerators Accelerate Learning?

    Science.gov (United States)

    Santos, A. C. F.; Fonseca, P.; Coelho, L. F. S.

    2009-03-01

    The 'Young Talented' education program developed by the Brazilian State Funding Agency (FAPERJ) [1] makes it possible for high-schools students from public high schools to perform activities in scientific laboratories. In the Atomic and Molecular Physics Laboratory at Federal University of Rio de Janeiro (UFRJ), the students are confronted with modern research tools like the 1.7 MV ion accelerator. Being a user-friendly machine, the accelerator is easily manageable by the students, who can perform simple hands-on activities, stimulating interest in physics, and getting the students close to modern laboratory techniques.

  3. Topology of Fermi surfaces and anomaly inflows

    Energy Technology Data Exchange (ETDEWEB)

    Adem, Alejandro; Camarena, Omar Antolín [Department of Mathematics, University of British Columbia,1984 Mathematics Road, Vancouver, V6T 1Z2 (Canada); Semenoff, Gordon W. [Department of Physics and Astronomy, University of British Columbia,6224 Agricultural Road, Vancouver, V6T 1Z1 (Canada); Sheinbaum, Daniel [Department of Mathematics, University of British Columbia,1984 Mathematics Road, Vancouver, V6T 1Z2 (Canada)

    2016-11-14

    We derive a rigorous classification of topologically stable Fermi surfaces of non-interacting, discrete translation-invariant systems from electronic band theory, adiabatic evolution and their topological interpretations. For systems on an infinite crystal it is shown that there can only be topologically unstable Fermi surfaces. For systems on a half-space and with a gapped bulk, our derivation naturally yields a K-theory classification. Given the d−1-dimensional surface Brillouin zone X{sub s} of a d-dimensional half-space, our result implies that different classes of globally stable Fermi surfaces belong in K{sup −1}(X{sub s}) for systems with only discrete translation-invariance. This result has a chiral anomaly inflow interpretation, as it reduces to the spectral flow for d=2. Through equivariant homotopy methods we extend these results for symmetry classes AI, AII, C and D and discuss their corresponding anomaly inflow interpretation.

  4. Dark lump excitations in superfluid Fermi gases

    Science.gov (United States)

    Xu, Yan-Xia; Duan, Wen-Shan

    2012-11-01

    We study the linear and nonlinear properties of two-dimensional matter-wave pulses in disk-shaped superfluid Fermi gases. A Kadomtsev—Petviashvili I (KPI) solitary wave has been realized for superfluid Fermi gases in the limited cases of Bardeen—Cooper—Schrieffer (BCS) regime, Bose—Einstein condensate (BEC) regime, and unitarity regime. One-lump solution as well as one-line soliton solutions for the KPI equation are obtained, and two-line soliton solutions with the same amplitude are also studied in the limited cases. The dependence of the lump propagating velocity and the sound speed of two-dimensional superfluid Fermi gases on the interaction parameter are investigated for the limited cases of BEC and unitarity.

  5. Dark lump excitations in superfluid Fermi gases

    International Nuclear Information System (INIS)

    Xu Yan-Xia; Duan Wen-Shan

    2012-01-01

    We study the linear and nonlinear properties of two-dimensional matter-wave pulses in disk-shaped superfluid Fermi gases. A Kadomtsev—Petviashvili I (KPI) solitary wave has been realized for superfluid Fermi gases in the limited cases of Bardeen—Cooper—Schrieffer (BCS) regime, Bose—Einstein condensate (BEC) regime, and unitarity regime. One-lump solution as well as one-line soliton solutions for the KPI equation are obtained, and two-line soliton solutions with the same amplitude are also studied in the limited cases. The dependence of the lump propagating velocity and the sound speed of two-dimensional superfluid Fermi gases on the interaction parameter are investigated for the limited cases of BEC and unitarity

  6. Pseudogap-generated a coexistence of Fermi arcs and Fermi pockets in cuprate superconductors

    Science.gov (United States)

    Zhao, Huaisong; Gao, Deheng; Feng, Shiping

    2017-03-01

    One of the most intriguing puzzle is why there is a coexistence of Fermi arcs and Fermi pockets in the pseudogap phase of cuprate superconductors? This puzzle is calling for an explanation. Based on the t - J model in the fermion-spin representation, the coexistence of the Fermi arcs and Fermi pockets in cuprate superconductors is studied by taking into account the pseudogap effect. It is shown that the pseudogap induces an energy band splitting, and then the poles of the electron Green's function at zero energy form two contours in momentum space, however, the electron spectral weight on these two contours around the antinodal region is gapped out by the pseudogap, leaving behind the low-energy electron spectral weight only located at the disconnected segments around the nodal region. In particular, the tips of these disconnected segments converge on the hot spots to form the closed Fermi pockets, generating a coexistence of the Fermi arcs and Fermi pockets. Moreover, the single-particle coherent weight is directly related to the pseudogap, and grows linearly with doping. The calculated result of the overall dispersion of the electron excitations is in qualitative agreement with the experimental data. The theory also predicts that the pseudogap-induced peak-dip-hump structure in the electron spectrum is absent from the hot-spot directions.

  7. The Fermi surface of CeSb

    International Nuclear Information System (INIS)

    Crabtree, G.W.; Aoki, H.; Joss, W.; Hulliger, F.

    1987-01-01

    This paper uses accurate Fermi surface measurements as a test of hybridization models in CeSb. Detailed measurements of the Fermi surface geometry and effective masses are presented which show a number of unusual properties associated with the magnetic structure and anisotropy. Measurements are compared with predictions of a band structure in which the f-electron is assumed to be local, interacting with the conduction electrons only through anisotropic Coulomb and exchange interactions. This model reproduces all the unusual features observed in the measurements and suggests that hybridization is not essential to describing the electronic properties of CeSb

  8. Itinerant Ferromagnetism in Ultracold Fermi Gases

    DEFF Research Database (Denmark)

    Heiselberg, Henning

    2012-01-01

    Itinerant ferromagnetism in cold Fermi gases with repulsive interactions is studied applying the Jastrow-Slater approximation generalized to finite polarization and temperature. For two components at zero temperature a second order transition is found at akF ≃ 0.90 compatible with QMC. Thermodyna......Itinerant ferromagnetism in cold Fermi gases with repulsive interactions is studied applying the Jastrow-Slater approximation generalized to finite polarization and temperature. For two components at zero temperature a second order transition is found at akF ≃ 0.90 compatible with QMC...

  9. Quantum simulation of a Fermi-Hubbard model using a semiconductor quantum dot array.

    Science.gov (United States)

    Hensgens, T; Fujita, T; Janssen, L; Li, Xiao; Van Diepen, C J; Reichl, C; Wegscheider, W; Das Sarma, S; Vandersypen, L M K

    2017-08-02

    Interacting fermions on a lattice can develop strong quantum correlations, which are the cause of the classical intractability of many exotic phases of matter. Current efforts are directed towards the control of artificial quantum systems that can be made to emulate the underlying Fermi-Hubbard models. Electrostatically confined conduction-band electrons define interacting quantum coherent spin and charge degrees of freedom that allow all-electrical initialization of low-entropy states and readily adhere to the Fermi-Hubbard Hamiltonian. Until now, however, the substantial electrostatic disorder of the solid state has meant that only a few attempts at emulating Fermi-Hubbard physics on solid-state platforms have been made. Here we show that for gate-defined quantum dots this disorder can be suppressed in a controlled manner. Using a semi-automated and scalable set of experimental tools, we homogeneously and independently set up the electron filling and nearest-neighbour tunnel coupling in a semiconductor quantum dot array so as to simulate a Fermi-Hubbard system. With this set-up, we realize a detailed characterization of the collective Coulomb blockade transition, which is the finite-size analogue of the interaction-driven Mott metal-to-insulator transition. As automation and device fabrication of semiconductor quantum dots continue to improve, the ideas presented here will enable the investigation of the physics of ever more complex many-body states using quantum dots.

  10. Quantum simulation of a Fermi-Hubbard model using a semiconductor quantum dot array

    Science.gov (United States)

    Hensgens, T.; Fujita, T.; Janssen, L.; Li, Xiao; van Diepen, C. J.; Reichl, C.; Wegscheider, W.; Das Sarma, S.; Vandersypen, L. M. K.

    2017-08-01

    Interacting fermions on a lattice can develop strong quantum correlations, which are the cause of the classical intractability of many exotic phases of matter. Current efforts are directed towards the control of artificial quantum systems that can be made to emulate the underlying Fermi-Hubbard models. Electrostatically confined conduction-band electrons define interacting quantum coherent spin and charge degrees of freedom that allow all-electrical initialization of low-entropy states and readily adhere to the Fermi-Hubbard Hamiltonian. Until now, however, the substantial electrostatic disorder of the solid state has meant that only a few attempts at emulating Fermi-Hubbard physics on solid-state platforms have been made. Here we show that for gate-defined quantum dots this disorder can be suppressed in a controlled manner. Using a semi-automated and scalable set of experimental tools, we homogeneously and independently set up the electron filling and nearest-neighbour tunnel coupling in a semiconductor quantum dot array so as to simulate a Fermi-Hubbard system. With this set-up, we realize a detailed characterization of the collective Coulomb blockade transition, which is the finite-size analogue of the interaction-driven Mott metal-to-insulator transition. As automation and device fabrication of semiconductor quantum dots continue to improve, the ideas presented here will enable the investigation of the physics of ever more complex many-body states using quantum dots.

  11. Thermoelectric Properties in Fermi Level Tuned Topological Materials (Bi1-xSnx)2Te3

    Science.gov (United States)

    Lin, Chan-Chieh; Shon, Won Hyuk; Rathnam, Lydia; Rhyee, Jong-Soo

    2018-03-01

    We investigated the thermoelectric properties of Sn-doped (Bi1-xSnx)2Te3 (x = 0, 0.1, 0.3, 0.5, and 0.7%) compounds, which is known as topological insulators. Fermi level tuning by Sn-doping can be justified by the n- to p-type transition with increasing Sn-doping concentration, as confirmed by Seebeck coefficient and Hall coefficient. Near x = 0.3 and 0.5%, the Fermi level resides inside the bulk band gap, resulting in a low Seebeck coefficient and increase of electrical resistivity. The magnetoconductivity with applying magnetic field showed weak antilocalization (WAL) effect for pristine Bi2Te3 while Sn-doped compounds do not follow the WAL behavior of magneto-conductivity, implying that the topological surface Dirac band contribution in magneto-conductivity is suppressed with decreasing the Fermi level by Sn-doping. This research can be applied to the topological composite of p-type/n-type topological materials by Fermi level tuning via Sn-doping in Bi2Te3 compounds.

  12. Interocular suppression

    Science.gov (United States)

    Tuna, Ana Rita; Almeida Neves Carrega, Filipa; Nunes, Amélia Fernandes

    2017-08-01

    The objective of this work is to quantify the suppressive imbalance, based on the manipulation of ocular luminance, between a group of subjects with normal binocular vision and a group of subjects with amblyopia. The result reveals that there are statistically significant differences in interocular dominance between two groups, evidencing a greater suppressive imbalance in amblyopic subjects. The technique used, proved to be a simple, easy to apply and economic method, for quantified ocular dominance. It is presented as a technique with the potential to accompany subjects with a marked dominance in one of the eyes that makes fusion difficult.

  13. Plasma accelerators

    International Nuclear Information System (INIS)

    Bingham, R.; Angelis, U. de; Johnston, T.W.

    1991-01-01

    Recently attention has focused on charged particle acceleration in a plasma by a fast, large amplitude, longitudinal electron plasma wave. The plasma beat wave and plasma wakefield accelerators are two efficient ways of producing ultra-high accelerating gradients. Starting with the plasma beat wave accelerator (PBWA) and laser wakefield accelerator (LWFA) schemes and the plasma wakefield accelerator (PWFA) steady progress has been made in theory, simulations and experiments. Computations are presented for the study of LWFA. (author)

  14. Linear Accelerators

    International Nuclear Information System (INIS)

    Vretenar, M

    2014-01-01

    The main features of radio-frequency linear accelerators are introduced, reviewing the different types of accelerating structures and presenting the main characteristics aspects of linac beam dynamics

  15. Ground-state pressure of an ideal Fermi gas

    International Nuclear Information System (INIS)

    Delsante, A.E.; Frankel, N.E.

    1979-01-01

    A simple relationship between the pressure, internal energy and Fermi energy of an ideal ultra-degenerate Fermi gas is derived in two ways. The conditions for its validity and its use in simplifying calculations are discussed

  16. Large optical conductivity of Dirac semimetal Fermi arc surface states

    Science.gov (United States)

    Shi, Li-kun; Song, Justin C. W.

    2017-08-01

    Fermi arc surface states, a hallmark of topological Dirac semimetals, can host carriers that exhibit unusual dynamics distinct from that of their parent bulk. Here we find that Fermi arc carriers in intrinsic Dirac semimetals possess a strong and anisotropic light-matter interaction. This is characterized by a large Fermi arc optical conductivity when light is polarized transverse to the Fermi arc; when light is polarized along the Fermi arc, Fermi arc optical conductivity is significantly muted. The large surface spectral weight is locked to the wide separation between Dirac nodes and persists as a large Drude weight of Fermi arc carriers when the system is doped. As a result, large and anisotropic Fermi arc conductivity provides a novel means of optically interrogating the topological surfaces states of Dirac semimetals.

  17. High-precision half-life and branching-ratio measurements for superallowed Fermi β+ emitters at TRIUMF - ISAC

    Science.gov (United States)

    Laffoley, A. T.; Dunlop, R.; Finlay, P.; Grinyer, G. F.; Andreoiu, C.; Austin, R. A. E.; Ball, G. C.; Bandyopadhyay, D.; Blank, B.; Bouzomita, H.; Chagnon-Lessard, S.; Chester, A.; Cross, D. S.; Demand, G.; Diaz Varela, A.; Djongolov, M.; Ettenauer, S.; Garnsworthy, A. B.; Garrett, P. E.; Giovinazzo, J.; Glister, J.; Green, K. L.; Hackman, G.; Hadinia, B.; Jamieson, D. S.; Ketelhut, S.; Leach, K. G.; Leslie, J. R.; Pearson, C. J.; Phillips, A. A.; Rand, E. T.; Starosta, K.; Sumithrarachchi, C. S.; Svensson, C. E.; Tardiff, E. R.; Thomas, J. C.; Towner, I. S.; Triambak, S.; Unsworth, C.; Williams, S. J.; Wong, J.; Yates, S. W.; Zganjar, E. F.

    2014-03-01

    A program of high-precision half-life and branching-ratio measurements for superallowed Fermi β emitters is being carried out at TRIUMF's Isotope Separator and Accelerator (ISAC) radioactive ion beam facility. Recent half-life measurements for the superallowed decays of 14O, 18Ne, and 26Alm, as well as branching-ratio measurements for 26Alm and 74Rb are reported. These results provide demanding tests of the Standard Model and the theoretical isospin symmetry breaking (ISB) corrections in superallowed Fermi β decays.

  18. The Fermi GBM catalog (Paciesas+, 2012) [Dataset

    NARCIS (Netherlands)

    Paciesas, W.S.; Meegan, C.A.; von Kienlin, A.; Bhat, P.N.; Bissaldi, E.; Briggs, M.S.; Burgess, J.M.; Chaplin, V.; Connaughton, V.; Diehl, R.; Fishman, G.J.; Fitzpatrick, G.; Foley, S.; H. Gibby, M.; Giles, M.; Goldstein, A.; Greiner, J.; Gruber, D.; Guiriec, S.; van der Horst, A.J.; Kippen, R.M.; Kouveliotou, C.; Lichti, G.; Lin, L.; McBreen, S.; Preece, R.D.; Rau, A.; Tierney, D.; Wilson-Hodge, C.

    2012-01-01

    The Fermi Gamma-ray Space Telescope was launched on 2008 June 11 on a mission to study the universe at high energies. The onboard Gamma-ray Burst Monitor (GBM) trigger system for detecting GRBs was first enabled on 2008 July 12. In this paper, we provide a catalog of GRBs that triggered the GBM

  19. Modelling of Graphene Nanoribbon Fermi Energy

    International Nuclear Information System (INIS)

    Johari, Z.; Ahmadi, M.T.; Chek, D.C.Y.; Amin, N.A.; Ismail, R.

    2010-01-01

    Graphene nano ribbon (GNR) is a promising alternative to carbon nano tube (CNT) to overcome the chirality challenge as a nano scale device channel. Due to the one-dimensional behavior of plane GNR, the carrier statistic study is attractive. Research works have been done on carrier statistic study of GNR especially in the parabolic part of the band structure using Boltzmann approximation (nondegenerate regime). Based on the quantum confinement effect, we have improved the fundamental study in degenerate regime for both the parabolic and non parabolic parts of GNR band energy. Our results demonstrate that the band energy of GNR near to the minimum band energy is parabolic. In this part of the band structure, the Fermi-Dirac integrals are sufficient for the carrier concentration study. The Fermi energy showed the temperature-dependent behavior similar to any other one-dimensional device in nondegenerate regime. However in the degenerate regime, the normalized Fermi energy with respect to the band edge is a function of carrier concentration. The numerical solution of Fermi-Dirac integrals for non parabolic region, which is away from the minimum energy band structure of GNR, is also presented.

  20. Scattering resonances in a degenerate Fermi gas

    DEFF Research Database (Denmark)

    Challis, Katharine; Nygaard, Nicolai; Mølmer, Klaus

    2009-01-01

    We consider elastic single-particle scattering from a one-dimensional trapped two-component superfluid Fermi gas when the incoming projectile particle is identical to one of the confined species. Our theoretical treatment is based on the Hartree-Fock ground state of the trapped gas...

  1. Fermi Surface and Antiferromagnetism in Europium Metal

    DEFF Research Database (Denmark)

    Andersen, O. Krogh; Loucks, T. L.

    1968-01-01

    of the nearly cubical part of the hole surface at P, and we also discuss the effects of the electron surface at H. Since it is likely that barium and europium have similar Fermi surfaces, we have presented several extremal areas and the corresponding de Haas-van Alphen frequencies in the hope that experimental...

  2. Thomas-Fermi model of warm nuclei

    International Nuclear Information System (INIS)

    Buchler, J.R.; Epstein, R.I.

    1980-01-01

    The average nuclear level density of spherical nuclei is computed with a finite temperature Thomas-Fermi model. More than 80% of the low energy nuclear excitations can be accounted for in terms of this statistical model. The relevance for stellar collapse is discussed

  3. Vacuum alignment and radiatively induced Fermi scale

    DEFF Research Database (Denmark)

    Alanne, Tommi

    2017-01-01

    We extend the discussion about vacuum misalignment by quantum corrections in models with composite pseudo-Goldstone Higgs boson to renormalisable models with elementary scalars. As a concrete example, we propose a framework, where the hierarchy between the unification and the Fermi scale emerges ...

  4. Fermi: a physicist in the upheaval; Fermi: un physicien dans la tourmente

    Energy Technology Data Exchange (ETDEWEB)

    Maria, M. de

    2002-07-01

    This book summarizes the life, works and complex personality of the Italian physicist Enrico Fermi (1901-1954) whose myth is linked with the political upheaval of the 2. world war: the youth of an autodidact, the theorician and the quantum mechanics, his invention of a quantum statistics, the weak interaction theory, his works on artificial radioactivity, the end of the Fermi team and his exile in the USA, the secrete researches at the university of Columbia and the birth of the first atomic 'pile' (December 2, 1942), the building of Los Alamos center and the Alamogordo explosion test, the disagreements among the physicists of the Manhattan project and the position of Fermi, Fermi's contribution in the H-bomb construction, the creation of the physics school of Chicago, the Oppenheimer spying affair. (J.S.)

  5. Seebeck effect on a weak link between Fermi and non-Fermi liquids

    Science.gov (United States)

    Nguyen, T. K. T.; Kiselev, M. N.

    2018-02-01

    We propose a model describing Seebeck effect on a weak link between two quantum systems with fine-tunable ground states of Fermi and non-Fermi liquid origin. The experimental realization of the model can be achieved by utilizing the quantum devices operating in the integer quantum Hall regime [Z. Iftikhar et al., Nature (London) 526, 233 (2015), 10.1038/nature15384] designed for detection of macroscopic quantum charged states in multichannel Kondo systems. We present a theory of thermoelectric transport through hybrid quantum devices constructed from quantum-dot-quantum-point-contact building blocks. We discuss pronounced effects in the temperature and gate voltage dependence of thermoelectric power associated with a competition between Fermi and non-Fermi liquid behaviors. High controllability of the device allows to fine tune the system to different regimes described by multichannel and multi-impurity Kondo models.

  6. Radio core dominance of Fermi blazars

    Science.gov (United States)

    Pei, Zhi-Yuan; Fan, Jun-Hui; Liu, Yi; Yuan, Yi-Hai; Cai, Wei; Xiao, Hu-Bing; Lin, Chao; Yang, Jiang-He

    2016-07-01

    During the first 4 years of mission, Fermi/LAT detected 1444 blazars (3FGL) (Ackermann et al. in Astrophys. J. 810:14, 2015). Fermi/LAT observations of blazars indicate that Fermi blazars are luminous and strongly variable with variability time scales, for some cases, as short as hours. Those observations suggest a strong beaming effect in Fermi/LAT blazars. In the present work, we will investigate the beaming effect in Fermi/LAT blazars using a core-dominance parameter, R = S_{core}/ S_{ext.}, where S_{core} is the core emission, while S_{ext.} is the extended emission. We compiled 1335 blazars with available core-dominance parameter, out of which 169 blazars have γ-ray emission (from 3FGL). We compared the core-dominance parameters, log R, between the 169 Fermi-detected blazars (FDBs) and the rest non-Fermi-detected blazars (non-FDBs), and we found that the averaged values are R+(2.25±0.10), suggesting that a source with larger log R has larger V.I. value. Thirdly, we compared the mean values of radio spectral index for FDBs and non-FDBs, and we obtained < α_{radio}rangle =0.06±0.35 for FDBs and < α_{radio}rangle =0.57±0.46 for non-FDBs. If γ-rays are composed of two components like radio emission (core and extended components), then we can expect a correlation between log R and the γ-ray spectral index. When we used the radio core-dominance parameter, log R, to investigate the relationship, we found that the spectral index for the core component is α_{γ}|_{core} = 1.11 (a photon spectral index of α_{γ}^{ph}|_{core} = 2.11) and that for the extended component is α_{γ}|_{ext.} = 0.70 (a photon spectral index of α_{γ}^{ph}|_{ext.} = 1.70). Some discussions are also presented.

  7. Relativistic effects in the Thomas--Fermi atom

    International Nuclear Information System (INIS)

    Waber, J.T.; Canfield, J.M.

    1975-01-01

    Two methods of applying relativistic corrections to the Thomas--Fermi atom are considered, and numerical calculations are discussed. Radial charge distributions calculated from a relativistic Thomas--Fermi equation agree in gross form with those from more complicated self-consistent calculations. Energy eigenvalues for mercury, as determined from the relativistic Thomas--Fermi solution, are compared with other calculated and experimental values

  8. Expansions of Fermi and symmetrized Fermi integrals and applications in nuclear physics

    International Nuclear Information System (INIS)

    Grypeos, M.; Koutroulos, C.; Luk'yanov, V.; Shebeko, A.

    1998-01-01

    A detailed study is undertaken, using various techniques, in deriving expansions of integrals containing the Fermi or the symmetrized Fermi distributions. The results are presented in a mathematically compact form and consist of generalizations and extensions of previously known expansions. The relevance of the results to quantities of interest in nuclear physics is recalled and particular attention is paid to the so-called exponentially small terms which may play an essential role in certain cases

  9. FermiGrid—experience and future plans

    Science.gov (United States)

    Chadwick, K.; Berman, E.; Canal, P.; Hesselroth, T.; Garzoglio, G.; Levshina, T.; Sergeev, V.; Sfiligoi, I.; Sharma, N.; Timm, S.; Yocum, D. R.

    2008-07-01

    Fermilab supports a scientific program that includes experiments and scientists located across the globe. In order to better serve this community, Fermilab has placed its production computer resources in a Campus Grid infrastructure called 'FermiGrid'. The FermiGrid infrastructure allows the large experiments at Fermilab to have priority access to their own resources, enables sharing of these resources in an opportunistic fashion, and movement of work (jobs, data) between the Campus Grid and National Grids such as Open Science Grid (OSG) and the Worldwide LHC Computing Grid Collaboration (WLCG). FermiGrid resources support multiple Virtual Organizations (VOs), including VOs from the OSG, EGEE, and the WLCG. Fermilab also makes leading contributions to the Open Science Grid in the areas of accounting, batch computing, grid security, job management, resource selection, site infrastructure, storage management, and VO services. Through the FermiGrid interfaces, authenticated and authorized VOs and individuals may access our core grid services, the 10,000+ Fermilab resident CPUs, near-petabyte (including CMS) online disk pools and the multi-petabyte Fermilab Mass Storage System. These core grid services include a site wide Globus gatekeeper, VO management services for several VOs, Fermilab site authorization services, grid user mapping services, as well as job accounting and monitoring, resource selection and data movement services. Access to these services is via standard and well-supported grid interfaces. We will report on the user experience of using the FermiGrid campus infrastructure interfaced to a national cyberinfrastructure - the successes and the problems.

  10. FermiGrid - experience and future plans

    International Nuclear Information System (INIS)

    Chadwick, K.; Berman, E.; Canal, P.; Hesselroth, T.; Garzoglio, G.; Levshina, T.; Sergeev, V.; Sfiligoi, I.; Timm, S.; Yocum, D.

    2007-01-01

    Fermilab supports a scientific program that includes experiments and scientists located across the globe. In order to better serve this community, Fermilab has placed its production computer resources in a Campus Grid infrastructure called 'FermiGrid'. The FermiGrid infrastructure allows the large experiments at Fermilab to have priority access to their own resources, enables sharing of these resources in an opportunistic fashion, and movement of work (jobs, data) between the Campus Grid and National Grids such as Open Science Grid and the WLCG. FermiGrid resources support multiple Virtual Organizations (VOs), including VOs from the Open Science Grid (OSG), EGEE and the Worldwide LHC Computing Grid Collaboration (WLCG). Fermilab also makes leading contributions to the Open Science Grid in the areas of accounting, batch computing, grid security, job management, resource selection, site infrastructure, storage management, and VO services. Through the FermiGrid interfaces, authenticated and authorized VOs and individuals may access our core grid services, the 10,000+ Fermilab resident CPUs, near-petabyte (including CMS) online disk pools and the multi-petabyte Fermilab Mass Storage System. These core grid services include a site wide Globus gatekeeper, VO management services for several VOs, Fermilab site authorization services, grid user mapping services, as well as job accounting and monitoring, resource selection and data movement services. Access to these services is via standard and well-supported grid interfaces. We will report on the user experience of using the FermiGrid campus infrastructure interfaced to a national cyberinfrastructure--the successes and the problems

  11. FermiGrid-experience and future plans

    International Nuclear Information System (INIS)

    Chadwick, K; Berman, E; Canal, P; Hesselroth, T; Garzoglio, G; Levshina, T; Sergeev, V; Sfiligoi, I; Sharma, N; Timm, S; Yocum, D R

    2008-01-01

    Fermilab supports a scientific program that includes experiments and scientists located across the globe. In order to better serve this community, Fermilab has placed its production computer resources in a Campus Grid infrastructure called 'FermiGrid'. The FermiGrid infrastructure allows the large experiments at Fermilab to have priority access to their own resources, enables sharing of these resources in an opportunistic fashion, and movement of work (jobs, data) between the Campus Grid and National Grids such as Open Science Grid (OSG) and the Worldwide LHC Computing Grid Collaboration (WLCG). FermiGrid resources support multiple Virtual Organizations (VOs), including VOs from the OSG, EGEE, and the WLCG. Fermilab also makes leading contributions to the Open Science Grid in the areas of accounting, batch computing, grid security, job management, resource selection, site infrastructure, storage management, and VO services. Through the FermiGrid interfaces, authenticated and authorized VOs and individuals may access our core grid services, the 10,000+ Fermilab resident CPUs, near-petabyte (including CMS) online disk pools and the multi-petabyte Fermilab Mass Storage System. These core grid services include a site wide Globus gatekeeper, VO management services for several VOs, Fermilab site authorization services, grid user mapping services, as well as job accounting and monitoring, resource selection and data movement services. Access to these services is via standard and well-supported grid interfaces. We will report on the user experience of using the FermiGrid campus infrastructure interfaced to a national cyberinfrastructure - the successes and the problems

  12. Fermi-surface reconstruction by stripe order in cuprate superconductors

    Science.gov (United States)

    Laliberté, Francis

    2012-02-01

    The origin of pairing in a superconductor resides in the underlying normal state. In the cuprate high-temperature superconductor YBCO, application of a magnetic field to suppress superconductivity reveals a ground state that appears to break the translational symmetry of the lattice, pointing to some density-wave order [1,2,3]. In another cuprate, Eu-LSCO, the onset of stripe order - a modulation of spin and charge densities - at low temperature is well established [4]. By a comparative study of thermoelectric transport in the cuprates YBCO and Eu-LSCO, we show that the two materials exhibit a very similar process of Fermi-surface reconstruction as a function of temperature and doping [5,6]. This strongly suggests that Fermi-surface reconstruction is caused by stripe order in both cases, compelling evidence that stripe order is a generic tendency of hole-doped cuprates.[4pt] Work done in collaboration with J. Chang, N. Doiron-Leyraud, E. Hassinger, R. Daou, D. LeBoeuf, M. Rondeau, B. J. Ramshaw, R. Liang, D. A. Bonn, W. N. Hardy, S. Pyon, T. Takayama, H. Takagi, I. Sheikin, L. Malone, C. Proust, K. Behnia and L. Taillefer.[4pt] [1] N. Doiron-Leyraud et al., Nature 447, 565 (2007).[0pt] [2] D. LeBoeuf et al., Nature 450, 533 (2007).[0pt] [3] D. LeBoeuf et al., Phys. Rev. B 83, 054506 (2011).[0pt] [4] J. Fink et al., Phys. Rev. B 83, 092503 (2011).[0pt] [5] J. Chang et al., Phys. Rev. Lett. 104, 057005 (2010).[0pt] [6] F. Lalibert'e et al., Nat. Commun. 2, 432 (2011).

  13. Accelerator Service

    International Nuclear Information System (INIS)

    Champelovier, Y.; Ferrari, M.; Gardon, A.; Hadinger, G.; Martin, J.; Plantier, A.

    1998-01-01

    Since the cessation of the operation of hydrogen cluster accelerator in July 1996, four electrostatic accelerators were in operation and used by the peri-nuclear teams working in multidisciplinary collaborations. These are the 4 MV Van de Graaff accelerator, 2,5 MV Van de Graaff accelerator, 400 kV ion implanter as well as the 120 kV isotope separator

  14. Collective ion acceleration

    International Nuclear Information System (INIS)

    Godfrey, B.B.; Faehl, R.J.; Newberger, B.S.; Shanahan, W.R.; Thode, L.E.

    1977-01-01

    Progress achieved in the understanding and development of collective ion acceleration is presented. Extensive analytic and computational studies of slow cyclotron wave growth on an electron beam in a helix amplifier were performed. Research included precise determination of linear coupling between beam and helix, suppression of undesired transients and end effects, and two-dimensional simulations of wave growth in physically realizable systems. Electrostatic well depths produced exceed requirements for the Autoresonant Ion Acceleration feasibility experiment. Acceleration of test ions to modest energies in the troughs of such waves was also demonstrated. Smaller efforts were devoted to alternative acceleration mechanisms. Langmuir wave phase velocity in Converging Guide Acceleration was calculated as a function of the ratio of electron beam current to space-charge limiting current. A new collective acceleration approach, in which cyclotron wave phase velocity is varied by modulation of electron beam voltage, is proposed. Acceleration by traveling Virtual Cathode or Localized Pinch was considered, but appears less promising. In support of this research, fundamental investigations of beam propagation in evacuated waveguides, of nonneutral beam linear eigenmodes, and of beam stability were carried out. Several computer programs were developed or enhanced. Plans for future work are discussed

  15. Magnetar Observations with Fermi/GBM

    Science.gov (United States)

    Kouveliotou, Chryssa

    2009-01-01

    NASA's Fermi Observatory was launched June 11, 2009; the Fermi Gamma Ray Burst Monitor (GBM) began normal operations on July 14, about a month after launch, when the trigger algorithms were enabled. In the first year of operations we recorded emission from four magnetar sources; of these, only one was an old magnetar: SGR 1806+20. The other three detections were: SGR J0501+4516, newly discovered with Swift and extensively monitored with both Swift and GBM, SGR J1550-5418, a source originally classified as an Anomalous X-ray Pulsar (AXP) and a very recently discovered new source, SGR 0418+5729. I report below on the current status of the analyses efforts of the GBM data.

  16. Excited Dark Matter versus PAMELA/Fermi

    CERN Document Server

    Cline, James M

    2010-01-01

    Excitation of multicomponent dark matter in the galactic center has been proposed as the source of low-energy positrons that produce the excess 511 keV gamma rays that have been observed by INTEGRAL. Such models have also been promoted to explain excess high-energy electrons/positrons observed by the PAMELA, Fermi/LAT and H.E.S.S. experiments. We investigate whether one model can simultaneously fit all three anomalies, in addition to further constraints from inverse Compton scattering by the high-energy leptons. We find models that fit both the 511 keV and PAMELA excesses at dark matter masses M < 400 GeV, but not the Fermi lepton excess. The conflict arises because a more cuspy DM halo profile is needed to match the observed 511 keV signal than is compatible with inverse Compton constraints at larger DM masses.

  17. Statistical mechanics of magnetized pair Fermi gas

    International Nuclear Information System (INIS)

    Daicic, J.; Frankel, N.E.; Kowalenko, V.

    1993-01-01

    Following previous work on the magnetized pair Bose gas this contribution presents the statistical mechanics of the charged relativistic Fermi gas with pair creation in d spatial dimensions. Initially, the gas in no external fields is studied. As a result, expansions for the various thermodynamic functions are obtained in both the μ/m→0 (neutrino) limit, and about the point μ/m =1, where μ is the chemical potential. The thermodynamics of a gas of quantum-number conserving massless fermions is also discussed. Then a complete study of the pair Fermi gas in a homogeneous magnetic field, is presented investigating the behavior of the magnetization over a wide range of field strengths. The inclusion of pairs leads to new results for the net magnetization due to the paramagnetic moment of the spins and the diamagnetic Landau orbits. 20 refs

  18. Two-Dimensional Homogeneous Fermi Gases

    Science.gov (United States)

    Hueck, Klaus; Luick, Niclas; Sobirey, Lennart; Siegl, Jonas; Lompe, Thomas; Moritz, Henning

    2018-02-01

    We report on the experimental realization of homogeneous two-dimensional (2D) Fermi gases trapped in a box potential. In contrast to harmonically trapped gases, these homogeneous 2D systems are ideally suited to probe local as well as nonlocal properties of strongly interacting many-body systems. As a first benchmark experiment, we use a local probe to measure the density of a noninteracting 2D Fermi gas as a function of the chemical potential and find excellent agreement with the corresponding equation of state. We then perform matter wave focusing to extract the momentum distribution of the system and directly observe Pauli blocking in a near unity occupation of momentum states. Finally, we measure the momentum distribution of an interacting homogeneous 2D gas in the crossover between attractively interacting fermions and bosonic dimers.

  19. Super-allowed Fermi beta-decay

    International Nuclear Information System (INIS)

    Wilkinson, D.H.

    2005-01-01

    A final analysis of J π =0 + ->0 + super-allowed Fermi transitions yields vertical bar V ud vertical bar 2 =0.9500±0.0007; vertical bar V ud vertical bar 2 + vertical bar V us vertical bar 2 + vertical bar V ub vertical bar 2 =0.9999±0.0011 with the operational vector coupling constant G V */(-bar c) 3 =(1.15052±0.00021)x10 -5 GeV -2

  20. Fermi/GBM Results of Magnetars

    Science.gov (United States)

    Kouveliotou, chryssa

    2011-01-01

    Magnetars are magnetically powered rotating neutron stars with extreme magnetic fields (over 10(exp 14) Gauss). They were discovered in the X- and gamma-rays where they predominantly emit their radiation. Very few sources (roughly 18) have been found since their discovery in 1987. NASA's Fermi Gamma-ray Space Telescope was launched June 11,2009; since then the Fermi Gamma-ray Burst Monitor (GBM) recorded emission from four magnetar sources. Two of these were brand new sources, SGR J0501 +4516, discovered with Swift and extensively monitored with Swift and GBM, SGR J0418+5729, discovered with GBM and the Interplanetary Network (IPN). A third was SGR Jl550-5418, a source originally classified as an Anomalous X-ray Pulsar (AXP IEI547.0-5408), but exhibiting a very prolific outburst with over 400 events recorded in January 2009. In my talk I will give a short history of magnetars and describe how this, once relatively esoteric field, has emerged as a link between several astrophysical areas including Gamma-Ray Bursts. Finally, I will describe the exciting new results of Fermi in this field and the current status of our knowledge of the magnetar population properties and magnetic fields.

  1. Future accelerators (?)

    Energy Technology Data Exchange (ETDEWEB)

    John Womersley

    2003-08-21

    I describe the future accelerator facilities that are currently foreseen for electroweak scale physics, neutrino physics, and nuclear structure. I will explore the physics justification for these machines, and suggest how the case for future accelerators can be made.

  2. Superconductivity and non-Fermi liquid behavior on the border of itinerant ferromagnetism

    Energy Technology Data Exchange (ETDEWEB)

    Ritz, Robert

    2013-10-04

    When magnetic order is suppressed under pressure, a superconducting (SC) phase emerges in the ferromagnet UGe{sub 2} and an extended non-Fermi liquid (NFL) regime is observed in the helimagnet MnSi. We report thermal expansion measurements of UGe{sub 2} under pressure by means of neutron Larmor diffraction. We find a new, putatively non-magnetic transition at the temperature TL at pressures close to the SC phase. In MnSi we report Hall effect measurements under pressure. We find a topological Hall effect, as the signature of a topologically non-trivial spin texture, above the critical pressure in the NFL regime.

  3. Strongly correlated Fermi-systems: Non-Fermi liquid behavior, quasiparticle effective mass and their interplay

    Energy Technology Data Exchange (ETDEWEB)

    Shaginyan, V.R. [Petersburg Nuclear Physics Institute, RAS, Gatchina 188300 (Russian Federation); Racah Institute of Physics, Hebrew University, Jerusalem 91904 (Israel)], E-mail: vrshag@thd.pnpi.spb.ru; Amusia, M.Ya. [Racah Institute of Physics, Hebrew University, Jerusalem 91904 (Israel); Popov, K.G. [Komi Science Center, Ural Division, RAS, Syktyvkar 167982 (Russian Federation)

    2009-06-15

    Basing on the density functional theory of fermion condensation, we analyze the non-Fermi liquid behavior of strongly correlated Fermi-systems such as heavy-fermion metals. When deriving equations for the effective mass of quasiparticles, we consider solids with a lattice and homogeneous systems. We show that the low-temperature thermodynamic and transport properties are formed by quasiparticles, while the dependence of the effective mass on temperature, number density, magnetic fields, etc., gives rise to the non-Fermi liquid behavior. Our theoretical study of the heat capacity, magnetization, energy scales, the longitudinal magnetoresistance and magnetic entropy are in good agreement with the remarkable recent facts collected on the heavy-fermion metal YbRh{sub 2}Si{sub 2}.

  4. Strongly correlated Fermi-systems: Non-Fermi liquid behavior, quasiparticle effective mass and their interplay

    International Nuclear Information System (INIS)

    Shaginyan, V.R.; Amusia, M.Ya.; Popov, K.G.

    2009-01-01

    Basing on the density functional theory of fermion condensation, we analyze the non-Fermi liquid behavior of strongly correlated Fermi-systems such as heavy-fermion metals. When deriving equations for the effective mass of quasiparticles, we consider solids with a lattice and homogeneous systems. We show that the low-temperature thermodynamic and transport properties are formed by quasiparticles, while the dependence of the effective mass on temperature, number density, magnetic fields, etc., gives rise to the non-Fermi liquid behavior. Our theoretical study of the heat capacity, magnetization, energy scales, the longitudinal magnetoresistance and magnetic entropy are in good agreement with the remarkable recent facts collected on the heavy-fermion metal YbRh 2 Si 2 .

  5. Fermi wave vector for the partially spin-polarized composite-fermion Fermi sea

    Science.gov (United States)

    Balram, Ajit C.; Jain, J. K.

    2017-12-01

    The fully spin-polarized composite-fermion (CF) Fermi sea at the half-filled lowest Landau level has a Fermi wave vector kF*=√{4 π ρe } , where ρe is the density of electrons or composite fermions, supporting the notion that the interaction between composite fermions can be treated perturbatively. Away from ν =1 /2 , the area is seen to be consistent with kF*=√{4 π ρe } for ν 1 /2 , where ρh is the density of holes in the lowest Landau level. This result is consistent with particle-hole symmetry in the lowest Landau level. We investigate in this article the Fermi wave vector of the spin-singlet CF Fermi sea (CFFS) at ν =1 /2 , for which particle-hole symmetry is not a consideration. Using the microscopic CF theory, we find that for the spin-singlet CFFS the Fermi wave vectors for up- and down-spin CFFSs at ν =1 /2 are consistent with kF*↑,↓=√{4 π ρe↑,↓ } , where ρe↑=ρe↓=ρe/2 , which implies that the residual interactions between composite fermions do not cause a nonperturbative correction for spin-singlet CFFS either. Our results suggest the natural conjecture that for arbitrary spin polarization the CF Fermi wave vectors are given by kF*↑=√{4 π ρe↑ } and kF*↓=√{4 π ρe↓ } .

  6. Quasiparticle lifetime in a mixture of Bose and Fermi superfluids.

    Science.gov (United States)

    Zheng, Wei; Zhai, Hui

    2014-12-31

    In this Letter, we study the effect of quasiparticle interactions in a Bose-Fermi superfluid mixture. We consider the lifetime of a quasiparticle of the Bose superfluid due to its interaction with quasiparticles in the Fermi superfluid. We find that this damping rate, i.e., the inverse of the lifetime, has quite a different threshold behavior at the BCS and the BEC side of the Fermi superfluid. The damping rate is a constant near the threshold momentum in the BCS side, while it increases rapidly in the BEC side. This is because, in the BCS side, the decay process is restricted by the constraint that the fermion quasiparticle is located near the Fermi surface, while such a restriction does not exist in the BEC side where the damping process is dominated by bosonic quasiparticles of the Fermi superfluid. Our results are related to the collective mode experiment in the recently realized Bose-Fermi superfluid mixture.

  7. Induced interactions in a superfluid Bose-Fermi mixture

    DEFF Research Database (Denmark)

    Kinnunen, Jami; Bruun, Georg

    2015-01-01

    We analyze a Bose-Einstein condensate (BEC) mixed with a superfluid two-component Fermi gas in the whole BCS-BEC crossover. Using a quasiparticle random-phase approximation combined with Beliaev theory to describe the Fermi superfluid and the BEC, respectively, we show that the single-particle an......We analyze a Bose-Einstein condensate (BEC) mixed with a superfluid two-component Fermi gas in the whole BCS-BEC crossover. Using a quasiparticle random-phase approximation combined with Beliaev theory to describe the Fermi superfluid and the BEC, respectively, we show that the single...... shift in the excitation spectrum of the BEC. In addition, the excitation of quasiparticles in the Fermi superfluid leads to damping of the excitations in the BEC. Besides studying induced interactions themselves, we can use these prominent effects to systematically probe the strongly interacting Fermi...

  8. Fermi -LAT Observations of High-energy Behind-the-limb Solar Flares

    Energy Technology Data Exchange (ETDEWEB)

    Ackermann, M.; Buehler, R. [Deutsches Elektronen Synchrotron DESY, D-15738 Zeuthen (Germany); Allafort, A.; Bottacini, E.; Cameron, R. A.; Charles, E. [W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States); Baldini, L. [Università di Pisa and Istituto Nazionale di Fisica Nucleare, Sezione di Pisa I-56127 Pisa (Italy); Barbiellini, G. [Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, I-34127 Trieste (Italy); Bastieri, D. [Istituto Nazionale di Fisica Nucleare, Sezione di Padova, I-35131 Padova (Italy); Bellazzini, R. [Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, I-56127 Pisa (Italy); Bissaldi, E.; Caragiulo, M.; Costanza, F. [Istituto Nazionale di Fisica Nucleare, Sezione di Bari, I-70126 Bari (Italy); Bonino, R. [Istituto Nazionale di Fisica Nucleare, Sezione di Torino, I-10125 Torino (Italy); Bregeon, J. [Laboratoire Univers et Particules de Montpellier, Université Montpellier, CNRS/IN2P3, F-34095 Montpellier (France); Bruel, P. [Laboratoire Leprince-Ringuet, École polytechnique, CNRS/IN2P3, F-91128 Palaiseau (France); Caraveo, P. A. [INAF-Istituto di Astrofisica Spaziale e Fisica Cosmica Milano, via E. Bassini 15, I-20133 Milano (Italy); Cavazzuti, E.; Ciprini, S. [Agenzia Spaziale Italiana (ASI) Science Data Center, I-00133 Roma (Italy); Cecchi, C., E-mail: nicola.omodei@stanford.edu, E-mail: vahep@stanford.edu, E-mail: melissa.pesce.rollins@pi.infn.it [Istituto Nazionale di Fisica Nucleare, Sezione di Perugia, I-06123 Perugia (Italy); and others

    2017-02-01

    We report on the Fermi -LAT detection of high-energy emission from the behind-the-limb (BTL) solar flares that occurred on 2013 October 11, and 2014 January 6 and September 1. The Fermi -LAT observations are associated with flares from active regions originating behind both the eastern and western limbs, as determined by STEREO . All three flares are associated with very fast coronal mass ejections (CMEs) and strong solar energetic particle events. We present updated localizations of the >100 MeV photon emission, hard X-ray (HXR) and EUV images, and broadband spectra from 10 keV to 10 GeV, as well as microwave spectra. We also provide a comparison of the BTL flares detected by Fermi -LAT with three on-disk flares and present a study of some of the significant quantities of these flares as an attempt to better understand the acceleration mechanisms at work during these occulted flares. We interpret the HXR emission to be due to electron bremsstrahlung from a coronal thin-target loop top with the accelerated electron spectra steepening at semirelativistic energies. The >100 MeV gamma-rays are best described by a pion-decay model resulting from the interaction of protons (and other ions) in a thick-target photospheric source. The protons are believed to have been accelerated (to energies >10 GeV) in the CME environment and precipitate down to the photosphere from the downstream side of the CME shock and landed on the front side of the Sun, away from the original flare site and the HXR emission.

  9. Nonlinear Excitations in Strongly-Coupled Fermi-Dirac Plasmas

    OpenAIRE

    Akbari-Moghanjoughi, M.

    2012-01-01

    In this paper we use the conventional quantum hydrodynamics (QHD) model in combination with the Sagdeev pseudopotential method to explore the effects of Thomas-Fermi nonuniform electron distribution, Coulomb interactions, electron exchange and ion correlation on the large-amplitude nonlinear soliton dynamics in Fermi-Dirac plasmas. It is found that in the presence of strong interactions significant differences in nonlinear wave dynamics of Fermi-Dirac plasmas in the two distinct regimes of no...

  10. Four-fermi anomalous dimension with adjoint fermions

    CERN Document Server

    Del Debbio, Luigi; Ruano, Carlos Pena

    2014-01-01

    The four-fermi interaction can play an important role in models of strong dynamical EW sym- metry breaking if the anomalous dimensions of the four-fermi operators become large in the IR. We discuss a number of issues that are relevant for the nonperturbative computation of the four- fermi anomalous dimensions for the SU(2) gauge theory with two flavors of Dirac fermions in the adjoint representation, using a Schrödinger functional formalism.

  11. New particle accelerations by magnetized plasma shock waves

    International Nuclear Information System (INIS)

    Takeuchi, Satoshi

    2005-01-01

    Three mechanisms concerning particle accelerations are proposed to account for the high energy of cosmic rays. A model of magnetized plasma clouds is used to simulate a shock-type wave. The attainable energies of test particles colliding with the moving magnetic clouds are investigated by analytical and numerical methods for the three mechanisms. The magnetic trapping acceleration is a new type of particle trapping and acceleration in which, in principle, the test particle is accelerated indefinitely; hence, this mechanism surpasses the Fermi-type acceleration. In the single-step acceleration, the test particle obtains a significant energy gain even though it only experiences a single collision. Lastly, there is the bouncing acceleration by which the test particle is substantially accelerated due to repeated collisions

  12. Phase structure of strongly correlated Fermi gases

    International Nuclear Information System (INIS)

    Roscher, Dietrich

    2015-01-01

    Strongly correlated fermionic many-body systems are ubiquitous in nature. Their theoretical description poses challenging problems which are further complicated when imbalances in, e.g., the particle numbers of the involved species or their masses are introduced. In this thesis, a number of different approaches is developed and applied in order to obtain predictions for physical observables of such systems that mutually support and confirm each other. In a first step, analytically well-founded mean-field analyses are carried through. One- and three-dimensional ultracold Fermi gases with spin and mass imbalance as well as Gross-Neveu and NJL-type relativistic models at finite baryon chemical potential are investigated with respect to their analytic properties in general and the occurrence of spontaneous breaking of translational invariance in particular. Based on these studies, further methods are devised or adapted allowing for investigations also beyond the mean-field approximation. Lattice Monte Carlo simulations with imaginary imbalance parameters are employed to surmount the infamous sign problem and compute the equation of state of the respective unitary Fermi gases. Moreover, in-medium two-body analyses are used to confirm and explain the characteristics of inhomogeneously ordered phases. Finally, functional RG methods are applied to the unitary Fermi gas with spin and mass imbalance. Besides quantitatively competitive predictions for critical temperatures for the superfluid state, strong hints on the stability of inhomogeneous phases with respect to order parameter fluctuations in the regime of large mass imbalance are obtained. Combining the findings from these different theoretical studies suggests the possibility to find such phases in experiments presently in preparation.

  13. FERMI LARGE AREA TELESCOPE FIRST SOURCE CATALOG

    International Nuclear Information System (INIS)

    Abdo, A. A.; Ackermann, M.; Ajello, M.; Allafort, A.; Bechtol, K.; Berenji, B.; Blandford, R. D.; Bloom, E. D.; Antolini, E.; Bonamente, E.; Atwood, W. B.; Axelsson, M.; Baldini, L.; Bellazzini, R.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bisello, D.; Baughman, B. M.; Belli, F.

    2010-01-01

    We present a catalog of high-energy gamma-ray sources detected by the Large Area Telescope (LAT), the primary science instrument on the Fermi Gamma-ray Space Telescope (Fermi), during the first 11 months of the science phase of the mission, which began on 2008 August 4. The First Fermi-LAT catalog (1FGL) contains 1451 sources detected and characterized in the 100 MeV to 100 GeV range. Source detection was based on the average flux over the 11 month period, and the threshold likelihood Test Statistic is 25, corresponding to a significance of just over 4σ. The 1FGL catalog includes source location regions, defined in terms of elliptical fits to the 95% confidence regions and power-law spectral fits as well as flux measurements in five energy bands for each source. In addition, monthly light curves are provided. Using a protocol defined before launch we have tested for several populations of gamma-ray sources among the sources in the catalog. For individual LAT-detected sources we provide firm identifications or plausible associations with sources in other astronomical catalogs. Identifications are based on correlated variability with counterparts at other wavelengths, or on spin or orbital periodicity. For the catalogs and association criteria that we have selected, 630 of the sources are unassociated. Care was taken to characterize the sensitivity of the results to the model of interstellar diffuse gamma-ray emission used to model the bright foreground, with the result that 161 sources at low Galactic latitudes and toward bright local interstellar clouds are flagged as having properties that are strongly dependent on the model or as potentially being due to incorrectly modeled structure in the Galactic diffuse emission.

  14. Fermi-LAT Observations of the Gamma-Ray Burst GRB 130427A

    Science.gov (United States)

    Ackermann, M.; Ajello, M.; Asano, K.; Atwood, W. B.; Axelsson, M.; Baldini, L.; Ballet, J.; Barbiellini, G.; Baring, M. G.; Bastieri, D.; hide

    2013-01-01

    The observations of the exceptionally bright gamma-ray burst (GRB) 130427A by the Large Area Telescope aboard the Fermi Gamma-ray Space Telescope provide constraints on the nature of these unique astrophysical sources. GRB 130427A had the largest fluence, highest-energy photon (95 GeV), longest gamma-ray duration (20 hours), and one of the largest isotropic energy releases ever observed from a GRB. Temporal and spectral analyses of GRB 130427A challenge the widely accepted model that the nonthermal high-energy emission in the afterglow phase of GRBs is synchrotron emission radiated by electrons accelerated at an external shock.

  15. Exploring the Extreme Universe with the Fermi Gamma-Ray Space Telescope

    Science.gov (United States)

    Thompson, David J.; Digel, Seth W.; Racusin, Judith L.

    2012-01-01

    In ways similar to experiments in nuclear and particle physics, high-energy astrophysics usesgamma rays and energetic charged particles toprobe processes that involve large energy transfers.Since its launch in 2008, the international Fermi Gamma-Ray Space Telescope has been exploringnatural particle accelerators and the interactionsof high-energy particles in the universe. Withsources ranging from thunderstorms on Earth to galaxies and exploding stars in distant parts of the cosmos, the telescopes subjects of study are almostas diverse as were those of the scientist whose name it bears.

  16. Search for Fermi shuttle mechanisms in electron emission from atomic collision sequences

    International Nuclear Information System (INIS)

    Suarez, S.; Jung, M.; Rothard, H.; Schosnig, M.; Maier, R.; Clouvas, A.; Groeneveld, K.O.

    1994-01-01

    In electron spectra induced by slow heavy ion bombardment of solids a high energy tail can be observed, which is suggested to be explained by multiple collision sequences. In order to find those multiple collision effects like the ''Fermi shuttle'' acceleration mechanism we measured doubly differential electron emission cross sections for H + (33.5-700 keV) impact on different targets (He, Ne, C and Au) as a function of projectile energy and electron emission angle. We observed a surprising target dependence of the electron emission within the range of electron energies close to that of the binary encounter electrons for all observed angles of emission. (orig.)

  17. Nonlocal Poisson-Fermi model for ionic solvent.

    Science.gov (United States)

    Xie, Dexuan; Liu, Jinn-Liang; Eisenberg, Bob

    2016-07-01

    We propose a nonlocal Poisson-Fermi model for ionic solvent that includes ion size effects and polarization correlations among water molecules in the calculation of electrostatic potential. It includes the previous Poisson-Fermi models as special cases, and its solution is the convolution of a solution of the corresponding nonlocal Poisson dielectric model with a Yukawa-like kernel function. The Fermi distribution is shown to be a set of optimal ionic concentration functions in the sense of minimizing an electrostatic potential free energy. Numerical results are reported to show the difference between a Poisson-Fermi solution and a corresponding Poisson solution.

  18. Fermi states of Bose systems in three space dimensions

    International Nuclear Information System (INIS)

    Garbaczewski, P.

    1985-01-01

    Recently an exact spectral solution was constructed by Sudarshan and Tata for the (NTHETA) Fermi version of the Lee model. We demonstrate that it provides a partial solution for the related pure Bose spectral problems. Moreover, the (NTHETA) Bose (Bolsterli--Nelson) version of the Lee model is shown to possess Fermi partners, both exhibiting the partial solubility interplay: finding solutions in the Fermi case would presumably be easier than in the original Bose model. Fermi states of the underlying Bose systems in three space dimensions are explicitly identified

  19. Particle acceleration near Halley's comet

    International Nuclear Information System (INIS)

    Somogyi, Antal

    1987-01-01

    Vega and Giotto space probes observed energetic ions of cometary origin near Halley's comet. The water molecules evaporating from the cometary nucleus were ionized by the solar UV radiation. These 'standing' ions were accelerated from 1 km/s to a few 1000 km/s. Present paper analyses the possible mechanisms of acceleration based on the data of TUENDE detector (constructed by CRIP, Hungary) working on board of Vega probes. The basic mechanism is the ExB Lorentz acceleration by interplanetary magnetic field and electric field induced by magnetic field frozen into solar wind plasma. It is followed by an acceleration caused by the adiabatic compression of the plasma at shock wave front. These processes can not explain the observed velocity of ions. It is shown that the second order Fermi acceleration which dissipates the ion distribution in the velocity space can lead to the observed velocities. The circumstances required to the occurrence of this process are present at the cometary environment. (D.G.) 2 figs

  20. Cosmic Accelerators: Engines of the Extreme Universe

    Energy Technology Data Exchange (ETDEWEB)

    Funk, Stefan

    2009-06-23

    The universe is home to numerous exotic and beautiful phenomena, some of which can generate almost inconceivable amounts of energy. While the night sky appears calm, it is populated by colossal explosions, jets from supermassive black holes, rapidly rotating neutron stars, and shock waves of gas moving at supersonic speeds. These accelerators in the sky boost particles to energies far beyond those we can produce on earth. New types of telescopes, including the Fermi Gamma-ray Space Telescope orbiting in space, are now discovering a host of new and more powerful accelerators. Please come and see how these observations are revising our picture of the most energetic phenomena in the universe.

  1. Optimization Studies of the FERMI at ELETTRA FEL Design

    CERN Document Server

    De Ninno, G

    2005-01-01

    The FERMI at ELETTRA project at Sincotrone Trieste involves two FEL's, each based upon the principle of a seeded harmonic cascade and using the existing ELETTRA injection linac at 1.2 GeV beam energy. Scheduled to be completed in 2008, FEL-1 will operate in the 40-100 nm wavelength range and will involve one stage of harmonic up-conversion. The second phase, FEL-2, will begin operation two years later in the 10-40 nm wavelength range and will involve two cascade stages. FEL design assumes wavelength tunability over the full wavelength range and polarization tunability of the output radiation including helical polarization. The design considers focusing properties and segmentation of realizable undulators and available input seed lasers. We discuss how the interplay between various limitations and self-consistent accelerator simulations [1,2] have led to our current design. We present results of simulations using GENESIS and GINGER simulation codes including studies of various shot-to-shot fluctuations and und...

  2. Fermi GBM: Highlights from the First Year

    Science.gov (United States)

    Wilson-Hodge, Colleen A.

    2009-01-01

    The Fermi Gamma ray Burst Monitor is an all-sky instrument sensitive to photons from about 8 keV to 40 MeV. I will summarize highlights from the first year, including triggered observations of gamma ray bursts, soft gamma ray repeaters, and terrestrial gamma flashes, and observations in the continuous data of X-ray binaries and accreting X-ray pulsars. GBM provides complementary observations to Swift/BAT, observing many of the same sources, but over a wider energy range.

  3. Fermi GBM Observations of Terrestrial Gamma Flashes

    Science.gov (United States)

    Wilson-Hodge, Colleen A.; Briggs, M. S.; Connaughton, V.; Fishman, G. J.; Bhat, P. N.; Paciesas, W. S.; Preece, R. D.; Kippen, R. M.; vonKienlin, A.; Dwyer, J. R.; hide

    2010-01-01

    In its first two years of operation, the Fermi Gamma Ray Burst Monitor (GBM) has observed 79 Terrestrial Gamma Flashes (TGFs). The thick Bismuth Germanate (BGO) detectors are excellent for TGF spectroscopy, having a high probability of recording the full energy of an incident photon, spanning a broad energy range from 150 keV to 40 MeV, and recording a large number of photons per TGF. Correlations between GBM TGF triggers and lightning sferics detected with the World-Wide Lightning Location Network indicate that TGFs and lightning are simultaneous to within tens of microseconds.

  4. Pairing fluctuations in trapped Fermi gases

    International Nuclear Information System (INIS)

    Viverit, Luciano; Bruun, Georg M.; Minguzzi, Anna; Fazio, Rosario

    2004-01-01

    We examine the contribution of pairing fluctuations to the superfluid order parameter for harmonically trapped atomic Fermi gases in the BCS regime. In the limit of small systems we consider, both analytically and numerically, their space and temperature dependence. We predict a parity effect, i.e., that pairing fluctuations show a maximum or a minimum at the center of the trap, depending on the value of the last occupied shell being even or odd. We propose to detect pairing fluctuations by measuring the density-density correlation function after a ballistic expansion of the gas

  5. Millisecond Pulsars at Gamma-Ray Energies: Fermi Detections and Implications

    Science.gov (United States)

    Harding, Alice K.

    2011-01-01

    The Fermi Gamma-Ray Space Telescope has revolutionized the study of pulsar physics with the discovery of new populations of radio quiet and millisecond gamma-ray pulsars. The Fermi Large Area Telescope has so far discovered approx.20 new gamma-ray millisecond pulsars (MSPs) by both folding at periods of known radio MSPs or by detecting them as gamma-ray sources that are followed up by radio pulsar searches. The second method has resulted in a phenomenally successful synergy, with -30 new radio MSPs (to date) having been discovered at Fermi unidentified source locations and the gamma-ray pulsations having then been detected in a number of these using the radio timing solutions. Many of the newly discovered MSPs may be suitable for addition to the collection of very stable MSPs used for gravitational wave detection. Detection of such a large number of MSPs was surprising, given that most have relatively low spin-down luminosity and surface field strength. I will discuss their properties and the implications for pulsar particle acceleration and emission, as well as their potential contribution to gamma-ray backgrounds and Galactic cosmic rays.

  6. Atomic Fermi-Bose mixtures in inhomogeneous and random lattices: From Fermi glass to quantum spin glass and quantum percolation

    International Nuclear Information System (INIS)

    Sanpera, A.; Lewenstein, M.; Kantian, A.; Sanchez-Palencia, L.; Zakrzewski, J.

    2004-01-01

    We investigate strongly interacting atomic Fermi-Bose mixtures in inhomogeneous and random optical lattices. We derive an effective Hamiltonian for the system and discuss its low temperature physics. We demonstrate the possibility of controlling the interactions at local level in inhomogeneous but regular lattices. Such a control leads to the achievement of Fermi glass, quantum Fermi spin-glass, and quantum percolation regimes involving bare and/or composite fermions in random lattices

  7. Electrostatic accelerators

    OpenAIRE

    Hinterberger, F

    2006-01-01

    The principle of electrostatic accelerators is presented. We consider Cockcroft– Walton, Van de Graaff and Tandem Van de Graaff accelerators. We resume high voltage generators such as cascade generators, Van de Graaff band generators, Pelletron generators, Laddertron generators and Dynamitron generators. The speci c features of accelerating tubes, ion optics and methods of voltage stabilization are described. We discuss the characteristic beam properties and the variety of possible beams. We ...

  8. Electrostatic accelerators

    CERN Document Server

    Hinterberger, F

    2006-01-01

    The principle of electrostatic accelerators is presented. We consider Cockcroft– Walton, Van de Graaff and Tandem Van de Graaff accelerators. We resume high voltage generators such as cascade generators, Van de Graaff band generators, Pelletron generators, Laddertron generators and Dynamitron generators. The speci c features of accelerating tubes, ion optics and methods of voltage stabilization are described. We discuss the characteristic beam properties and the variety of possible beams. We sketch possible applications and the progress in the development of electrostatic accelerators.

  9. Accelerator development

    International Nuclear Information System (INIS)

    Anon.

    1975-01-01

    Because the use of accelerated heavy ions would provide many opportunities for new and important studies in nuclear physics and nuclear chemistry, as well as other disciplines, both the Chemistry and Physics Divisions are supporting the development of a heavy-ion accelerator. The design of greatest current interest includes a tandem accelerator with a terminal voltage of approximately 25 MV injecting into a linear accelerator with rf superconducting resonators. This combined accelerator facility would be capable of accelerating ions of masses ranging over the entire periodic table to an energy corresponding to approximately 10 MeV/nucleon. This approach, as compared to other concepts, has the advantages of lower construction costs, lower operating power, 100 percent duty factor, and high beam quality (good energy resolution, good timing resolution, small beam size, and small beam divergence). The included sections describe the concept of the proposed heavy-ion accelerator, and the development program aiming at: (1) investigation of the individual questions concerning the superconducting accelerating resonators; (2) construction and testing of prototype accelerator systems; and (3) search for economical solutions to engineering problems. (U.S.)

  10. Fermilab and Berkeley Lab Collaborate with Meyer Tool on Key Component for European Particle Accelerator

    CERN Multimedia

    2004-01-01

    Officials of the U.S. Department of Energy's Fermi National Accelerator Laboratory and Lawrence Berkeley National Laboratory announced yesterday the completion of a key component of the U.S. contribution to the Large Hadron Collider, a particle accelerator under construction at CERN, in Geneva, Switzerland

  11. FERMI/LAT OBSERVATIONS OF LS 5039

    International Nuclear Information System (INIS)

    Abdo, A. A.; Ackermann, M.; Ajello, M.; Bechtol, K.; Berenji, B.; Blandford, R. D.; Bloom, E. D.; Borgland, A. W.; Atwood, W. B.; Axelsson, M.; Baldini, L.; Bellazzini, R.; Bregeon, J.; Brez, A.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Baughman, B. M.; Bonamente, E.; Brigida, M.

    2009-01-01

    The first results from observations of the high-mass X-ray binary LS 5039 using the Fermi Gamma-ray Space Telescope data between 2008 August and 2009 June are presented. Our results indicate variability that is consistent with the binary period, with the emission being modulated with a period of 3.903 ± 0.005 days; the first detection of this modulation at GeV energies. The light curve is characterized by a broad peak around superior conjunction in agreement with inverse Compton scattering models. The spectrum is represented by a power law with an exponential cutoff, yielding an overall flux (100 MeV-300 GeV) of 4.9 ± 0.5(stat) ± 1.8(syst) x10 -7 photon cm -2 s -1 , with a cutoff at 2.1 ± 0.3(stat) ± 1.1(syst) GeV and photon index Γ = 1.9 ± 0.1(stat) ± 0.3(syst). The spectrum is observed to vary with orbital phase, specifically between inferior and superior conjunction. We suggest that the presence of a cutoff in the spectrum may be indicative of magnetospheric emission similar to the emission seen in many pulsars by Fermi.

  12. THE FIRST FERMI LAT SUPERNOVA REMNANT CATALOG

    Energy Technology Data Exchange (ETDEWEB)

    Acero, F.; Ballet, J. [Laboratoire AIM, CEA-IRFU/CNRS/Université Paris Diderot, Service d’Astrophysique, CEA Saclay, F-91191 Gif sur Yvette (France); Ackermann, M.; Buehler, R. [Deutsches Elektronen Synchrotron DESY, D-15738 Zeuthen (Germany); Ajello, M. [Department of Physics and Astronomy, Clemson University, Kinard Lab of Physics, Clemson, SC 29634-0978 (United States); Baldini, L. [Università di Pisa and Istituto Nazionale di Fisica Nucleare, Sezione di Pisa I-56127 Pisa (Italy); Barbiellini, G. [Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, I-34127 Trieste (Italy); Bastieri, D.; Buson, S. [Istituto Nazionale di Fisica Nucleare, Sezione di Padova, I-35131 Padova (Italy); Bellazzini, R. [Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, I-56127 Pisa (Italy); Bissaldi, E. [Istituto Nazionale di Fisica Nucleare, Sezione di Bari, I-70126 Bari (Italy); Blandford, R. D.; Bloom, E. D.; Bottacini, E.; Caliandro, G. A.; Cameron, R. A. [W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States); Bonino, R. [Istituto Nazionale di Fisica Nucleare, Sezione di Torino, I-10125 Torino (Italy); Brandt, T. J. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Bregeon, J. [Laboratoire Univers et Particules de Montpellier, Université Montpellier, CNRS/IN2P3, Montpellier (France); Bruel, P., E-mail: francesco.depalma@ba.infn.it, E-mail: t.j.brandt@nasa.gov, E-mail: john.w.hewitt@unf.edu [Laboratoire Leprince-Ringuet, École polytechnique, CNRS/IN2P3, Palaiseau (France); and others

    2016-05-01

    To uniformly determine the properties of supernova remnants (SNRs) at high energies, we have developed the first systematic survey at energies from 1 to 100 GeV using data from the Fermi Large Area Telescope (LAT). Based on the spatial overlap of sources detected at GeV energies with SNRs known from radio surveys, we classify 30 sources as likely GeV SNRs. We also report 14 marginal associations and 245 flux upper limits. A mock catalog in which the positions of known remnants are scrambled in Galactic longitude allows us to determine an upper limit of 22% on the number of GeV candidates falsely identified as SNRs. We have also developed a method to estimate spectral and spatial systematic errors arising from the diffuse interstellar emission model, a key component of all Galactic Fermi LAT analyses. By studying remnants uniformly in aggregate, we measure the GeV properties common to these objects and provide a crucial context for the detailed modeling of individual SNRs. Combining our GeV results with multiwavelength (MW) data, including radio, X-ray, and TeV, we demonstrate the need for improvements to previously sufficient, simple models describing the GeV and radio emission from these objects. We model the GeV and MW emission from SNRs in aggregate to constrain their maximal contribution to observed Galactic cosmic rays.

  13. Fermi's Paradox - The Last Challenge For Copernicanism?

    Directory of Open Access Journals (Sweden)

    Ćirković, M. M.

    2009-06-01

    Full Text Available We review Fermi's paradox (or the "Great Silence" problem, not only arguably the oldest and crucial problem for the Search for ExtraTerrestrial Intelligence (SETI, but also a conundrum of profound scientific, philosophical and cultural importance. By a simple analysis of observation selection effects, the correct resolution of Fermi's paradox is certain to tell us something about the future of humanity. Already more than three quarters of century old puzzle -- and a quarter of century since the last major review paper in the field by G. David Brin -- has generated many ingenious discussions and hypotheses. We analyze the often tacit methodological assumptions built in various answers to this puzzle and attempt a new classification of the numerous solutions proposed in an already huge literatureon the subject. Finally, we consider the ramifications of variousclasses of hypotheses for the practical SETI projects. Somewhatparadoxically, it seems that the class of (neocatastrophichypotheses gives, on the balance, the strongest justification tooptimism regarding our current and near-future SETI efforts.

  14. Bosonic Analogue of Dirac Composite Fermi Liquid

    Science.gov (United States)

    Mross, David; Alicea, Jason; Motrunich, Olexei

    The status of particle-hole symmetry has long posed a challenge to the theory of the quantum Hall effect. It is expected to be present in the half-filled Landau level, but is absent in the conventional field theory, i.e., the composite Fermi liquid. Recently, Son proposed an alternative, explicitly particle-hole symmetric theory which features composite fermions that exhibit a Dirac dispersion. In my talk, I will introduce an analogous particle-hole-symmetric metallic state of bosons at odd-integer filling. This state hosts composite fermions whose energy dispersion features a quadratic band touching and corresponding 2 Ï Berry flux, protected by particle-hole and discrete rotation symmetries. As in the Dirac composite Fermi liquid introduced by Son, breaking particle-hole symmetry recovers the familiar Chern-Simons theory. I will discuss realizations of this phase both in 2D and on bosonic topological insulator surfaces, as well as its signatures in experiments and simulations.

  15. Orientifolding of the ABJ Fermi gas

    International Nuclear Information System (INIS)

    Okuyama, Kazumi

    2016-01-01

    The grand partition functions of ABJ theory can be factorized into even and odd parts under the reflection of fermion coordinate in the Fermi gas approach. In some cases, the even/odd part of ABJ grand partition function is equal to that of N=5O(n)×USp(n"′) theory, hence it is natural to think of the even/odd projection of grand partition function as an orientifolding of ABJ Fermi gas system. By a systematic WKB analysis, we determine the coefficients in the perturbative part of grand potential of such orientifold ABJ theory. We also find the exact form of the first few “half-instanton” corrections coming from the twisted sector of the reflection of fermion coordinate. For the Chern-Simons level k=2,4,8 we find closed form expressions of the grand partition functions of orientifold ABJ theory, and for k=2,4 we prove the functional relations among the grand partition functions conjectured in http://arxiv.org/abs/1410.7658.

  16. Orientifolding of the ABJ Fermi gas

    Science.gov (United States)

    Okuyama, Kazumi

    2016-03-01

    The grand partition functions of ABJ theory can be factorized into even and odd parts under the reflection of fermion coordinate in the Fermi gas approach. In some cases, the even/odd part of ABJ grand partition function is equal to that of {N}=5O(n)× USp({n}^') theory, hence it is natural to think of the even/odd projection of grand partition function as an orientifolding of ABJ Fermi gas system. By a systematic WKB analysis, we determine the coefficients in the perturbative part of grand potential of such orientifold ABJ theory. We also find the exact form of the first few "half-instanton" corrections coming from the twisted sector of the reflection of fermion coordinate. For the Chern-Simons level k = 2 ,4 ,8 we find closed form expressions of the grand partition functions of orientifold ABJ theory, and for k = 2 , 4 we prove the functional relations among the grand partition functions conjectured in arXiv:1410.7658.

  17. THE SPECTRAL INDEX PROPERTIES OF FERMI BLAZARS

    Energy Technology Data Exchange (ETDEWEB)

    Fan, J. H.; Yang, J. H.; Yuan, Y. H.; Wang, J.; Gao, Y., E-mail: jhfan_cn@yahoo.com.cn [Center for Astrophysics, Guangzhou University, Guangzhou 510006 (China)

    2012-12-20

    In this paper, a sample of 451 blazars (193 flat spectrum radio quasars (FSRQs), 258 BL Lacertae objects) with corresponding X-ray and Fermi {gamma}-ray data is compiled to investigate the correlation both between the X-ray spectral index and the {gamma}-ray spectral index and between the spectral index and the luminosity, and to compare the spectral indexes {alpha}{sub X}, {alpha}{sub {gamma}}, {alpha}{sub X{gamma}}, and {alpha}{sub {gamma}X{gamma}} for different subclasses. We also investigated the correlation between the X-ray and the {gamma}-ray luminosity. The following results have been obtained. Our analysis indicates that an anti-correlation exists between the X-ray and the {gamma}-ray spectral indexes for the whole sample. However, when we considered the subclasses of blazars (FSRQs, the low-peaked BL Lacertae objects (LBLs) and the high-peaked BL Lacertae objects (HBLs)) separately, there is not a clear relationship for each subclass. Based on the Fermi-detected sources, we can say that the HBLs are different from FSRQs, while the LBLs are similar to FSRQs.

  18. Massive Fermi gas in the expanding universe

    Energy Technology Data Exchange (ETDEWEB)

    Trautner, Andreas, E-mail: atrautner@uni-bonn.de [Bethe Center for Theoretical Physics and Physikalisches Institut der Universität Bonn, Nussallee 12, 53115 Bonn (Germany)

    2017-03-01

    The behavior of a decoupled ideal Fermi gas in a homogeneously expanding three-dimensional volume is investigated, starting from an equilibrium spectrum. In case the gas is massless and/or completely degenerate, the spectrum of the gas can be described by an effective temperature and/or an effective chemical potential, both of which scale down with the volume expansion. In contrast, the spectrum of a decoupled massive and non-degenerate gas can only be described by an effective temperature if there are strong enough self-interactions such as to maintain an equilibrium distribution. Assuming perpetual equilibration, we study a decoupled gas which is relativistic at decoupling and then is red-shifted until it becomes non-relativistic. We find expressions for the effective temperature and effective chemical potential which allow us to calculate the final spectrum for arbitrary initial conditions. This calculation is enabled by a new expansion of the Fermi-Dirac integral, which is for our purpose superior to the well-known Sommerfeld expansion. We also compute the behavior of the phase space density under expansion and compare it to the case of real temperature and real chemical potential. Using our results for the degenerate case, we also obtain the mean relic velocity of the recently proposed non-thermal cosmic neutrino background.

  19. Fermi's paradox: The last challenge for copernicanism?

    Directory of Open Access Journals (Sweden)

    Ćirković M.M.

    2009-01-01

    Full Text Available We review Fermi's paradox (or the 'Great Silence' problem, not only arguably the oldest and crucial problem for the Search for ExtraTerrestrial Intelligence (SETI, but also a conundrum of profound scientific, philosophical and cultural importance. By a simple analysis of observation selection effects, the correct resolution of Fermi's paradox is certain to tell us something about the future of humanity. Already more than three quarters of century old puzzle and a quarter of century since the last major review paper in the field by G. David Brin has generated many ingenious discussions and hypotheses. We analyze the often tacit methodological assumptions built in various answers to this puzzle and attempt a new classification of the numerous solutions proposed in an already huge literature on the subject. Finally, we consider the ramifications of various classes of hypotheses for the practical SETI projects. Somewhat paradoxically, it seems that the class of (neocatastrophic hypotheses gives, on the balance, the strongest justification to optimism regarding our current and near-future SETI efforts.

  20. Gamma-Ray Observations of Tycho’s Supernova Remnant with VERITAS and Fermi

    Energy Technology Data Exchange (ETDEWEB)

    Archambault, S.; Bourbeau, E.; Feng, Q.; Griffin, S. [Physics Department, McGill University, Montreal, QC H3A 2T8 (Canada); Archer, A.; Buckley, J. H.; Bugaev, V.; Errando, M. [Department of Physics, Washington University, St. Louis, MO 63130 (United States); Benbow, W.; Cerruti, M. [Fred Lawrence Whipple Observatory, Harvard-Smithsonian Center for Astrophysics, Amado, AZ 85645 (United States); Bird, R.; Buchovecky, M. [Department of Physics and Astronomy, University of California, Los Angeles, CA 90095 (United States); Connolly, M. P. [School of Physics, National University of Ireland Galway, University Road, Galway (Ireland); Cui, W.; Finley, J. P. [Department of Physics and Astronomy, Purdue University, West Lafayette, IN 47907 (United States); Dwarkadas, V. V. [Department of Astronomy and Astrophysics, University of Chicago, Chicago, IL 60637 (United States); Falcone, A. [Department of Astronomy and Astrophysics, 525 Davey Lab, Pennsylvania State University, University Park, PA 16802 (United States); Fleischhack, H. [DESY, Platanenallee 6, D-15738 Zeuthen (Germany); Fortson, L. [School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455 (United States); Furniss, A., E-mail: nahee@uchicago.edu [Department of Physics, California State University—East Bay, Hayward, CA 94542 (United States); and others

    2017-02-10

    High-energy gamma-ray emission from supernova remnants (SNRs) has provided a unique perspective for studies of Galactic cosmic-ray acceleration. Tycho’s SNR is a particularly good target because it is a young, type Ia SNR that has been well-studied over a wide range of energies and located in a relatively clean environment. Since the detection of gamma-ray emission from Tycho’s SNR by VERITAS and Fermi -LAT, there have been several theoretical models proposed to explain its broadband emission and high-energy morphology. We report on an update to the gamma-ray measurements of Tycho’s SNR with 147 hr of VERITAS and 84 months of Fermi -LAT observations, which represent about a factor of two increase in exposure over previously published data. About half of the VERITAS data benefited from a camera upgrade, which has made it possible to extend the TeV measurements toward lower energies. The TeV spectral index measured by VERITAS is consistent with previous results, but the expanded energy range softens a straight power-law fit. At energies higher than 400 GeV, the power-law index is 2.92 ± 0.42{sub stat} ± 0.20{sub sys}. It is also softer than the spectral index in the GeV energy range, 2.14 ± 0.09{sub stat} ± 0.02{sub sys}, measured in this study using Fermi -LAT data. The centroid position of the gamma-ray emission is coincident with the center of the remnant, as well as with the centroid measurement of Fermi -LAT above 1 GeV. The results are consistent with an SNR shell origin of the emission, as many models assume. The updated spectrum points to a lower maximum particle energy than has been suggested previously.

  1. RECIRCULATING ACCELERATION

    International Nuclear Information System (INIS)

    BERG, J.S.; GARREN, A.A.; JOHNSTONE, C.

    2000-01-01

    This paper compares various types of recirculating accelerators, outlining the advantages and disadvantages of various approaches. The accelerators are characterized according to the types of arcs they use: whether there is a single arc for the entire recirculator or there are multiple arcs, and whether the arc(s) are isochronous or non-isochronous

  2. LIBO accelerates

    CERN Multimedia

    2002-01-01

    The prototype module of LIBO, a linear accelerator project designed for cancer therapy, has passed its first proton-beam acceleration test. In parallel a new version - LIBO-30 - is being developed, which promises to open up even more interesting avenues.

  3. Effects of Shock and Turbulence Properties on Electron Acceleration

    Science.gov (United States)

    Qin, G.; Kong, F.-J.; Zhang, L.-H.

    2018-06-01

    Using test particle simulations, we study electron acceleration at collisionless shocks with a two-component model turbulent magnetic field with slab component including dissipation range. We investigate the importance of the shock-normal angle θ Bn, magnetic turbulence level {(b/{B}0)}2, and shock thickness on the acceleration efficiency of electrons. It is shown that at perpendicular shocks the electron acceleration efficiency is enhanced with the decrease of {(b/{B}0)}2, and at {(b/{B}0)}2=0.01 the acceleration becomes significant due to a strong drift electric field with long time particles staying near the shock front for shock drift acceleration (SDA). In addition, at parallel shocks the electron acceleration efficiency is increasing with the increase of {(b/{B}0)}2, and at {(b/{B}0)}2=10.0 the acceleration is very strong due to sufficient pitch-angle scattering for first-order Fermi acceleration, as well as due to the large local component of the magnetic field perpendicular to the shock-normal angle for SDA. On the other hand, the high perpendicular shock acceleration with {(b/{B}0)}2=0.01 is stronger than the high parallel shock acceleration with {(b/{B}0)}2=10.0, the reason might be the assumption that SDA is more efficient than first-order Fermi acceleration. Furthermore, for oblique shocks, the acceleration efficiency is small no matter whether the turbulence level is low or high. Moreover, for the effect of shock thickness on electron acceleration at perpendicular shocks, we show that there exists the bendover thickness, L diff,b. The acceleration efficiency does not noticeably change if the shock thickness is much smaller than L diff,b. However, if the shock thickness is much larger than L diff,b, the acceleration efficiency starts to drop abruptly.

  4. A FOCUSED TRANSPORT APPROACH TO THE TIME-DEPENDENT SHOCK ACCELERATION OF SOLAR ENERGETIC PARTICLES AT A FAST TRAVELING SHOCK

    International Nuclear Information System (INIS)

    Le Roux, J. A.; Webb, G. M.

    2012-01-01

    Some of the most sophisticated models for solar energetic particle (SEP) acceleration at coronal mass ejection driven shocks are based on standard diffusive shock acceleration theory. However, this theory, which only applies when SEP pitch-angle anisotropies are small, might have difficulty in describing first-order Fermi acceleration or the shock pre-heating and injection of SEPs into first-order Fermi acceleration accurately at lower SEP speeds where SEP pitch-angle anisotropies upstream near the shock can be large. To avoid this problem, we use a time-dependent focused transport model to reinvestigate first-order Fermi acceleration at planar parallel and quasi-parallel spherical traveling shocks between the Sun and Earth with high shock speeds associated with rare extreme gradual SEP events. The focused transport model is also used to investigate and compare three different shock pre-heating mechanisms associated with different aspects of the nonuniform cross-shock solar wind flow, namely, the convergence of the flow (adiabatic compression), the shear tensor of the flow, and the acceleration of the flow, and a fourth shock pre-heating mechanism associated with the cross-shock electric field, to determine which pre-heating mechanism contributes the most to injecting shock pre-heated source particles into the first-order Fermi acceleration process. The effects of variations in traveling shock conditions, such as increasing shock obliquity and shock slowdown, and variations in the SEP source with increasing shock distance from the Sun on the coupled processes of shock pre-heating, injection, and first-order Fermi acceleration are analyzed. Besides the finding that the cross-shock acceleration of the solar wind flow yields the dominant shock pre-heating mechanism at high shock speeds, we find that first-order Fermi acceleration at fast traveling shocks differs in a number of respects from the predictions and assumptions of standard steady-state diffusive shock

  5. Tan's distributions and Fermi-Huang pseudopotential in momentum space

    DEFF Research Database (Denmark)

    Valiente, Manuel

    2012-01-01

    form of the Fourier-transformed pseudopotential remains very simple. Operator forms for the so-called Tan's selectors, which, together with Fermi-Huang pseudopotential, largely simplify the derivation of Tan's universal relations for the Fermi gas, are here derived and are also very simple. A momentum...

  6. "Where is Everybody?" An Account of Fermi's Question

    Science.gov (United States)

    Jones, E. M.

    1985-03-01

    Enrico Fermi's famous question, now central to debates about the prevalence of extraterrestrial civilizations, arose during a luncheon conversation with Emil Konopinski, Edward Teller, and Herbert York in the summer of 1950. Fermi's companions on that day have provided accounts of the incident.

  7. Time domain astronomy with Swift and Fermi | Gehrels | Rwanda ...

    African Journals Online (AJOL)

    Swift and Fermi are unveiling an unexpectedly rich tapestry of behavior in the transient γ−ray sky. Sources which were already known to be transient − such as pulsars, gamma-ray bursts, and blazars − have been studied in ever-increasing detail. For example, Fermi/LAT has detected 117 pulsars of which 56 are new.

  8. On the quantization of spin systems and Fermi systems

    International Nuclear Information System (INIS)

    Combe, P.; Rodriguez, R.; Sirugue, M.

    1978-03-01

    It is shown that spin operators and Fermi operators can be interpreted as the Weyl quantization of some functions on a classical phase space which is a compact group. Moreover the transition from quantum spin to Fermi operators is an isomorphism of the classical phase space preserving the Haar measure

  9. Fermi-Dirac statistics and the number theory

    OpenAIRE

    Kubasiak, A.; Korbicz, J.; Zakrzewski, J.; Lewenstein, M.

    2005-01-01

    We relate the Fermi-Dirac statistics of an ideal Fermi gas in a harmonic trap to partitions of given integers into distinct parts, studied in number theory. Using methods of quantum statistical physics we derive analytic expressions for cumulants of the probability distribution of the number of different partitions.

  10. Fermi liquid description of relativistic high density matter

    Science.gov (United States)

    Pal, K.; Dutt-Mazumder, A. K.

    2011-06-01

    We calculate pionic contribution to the relativistic Fermi Liquid parameters (RFLPs) using Chiral Effective Lagrangian. The RFLPs so determined are then used to calculate chemical potential, exchange energy due to πN interaction. We also compare the results of exchange energy from two loop ring diagrams involving σ, ω and π meson with what one obtains from the relativistic Fermi Liquid theory (RFLT).

  11. Accelerating Inspire

    CERN Document Server

    AUTHOR|(CDS)2266999

    2017-01-01

    CERN has been involved in the dissemination of scientific results since its early days and has continuously updated the distribution channels. Currently, Inspire hosts catalogues of articles, authors, institutions, conferences, jobs, experiments, journals and more. Successful orientation among this amount of data requires comprehensive linking between the content. Inspire has lacked a system for linking experiments and articles together based on which accelerator they were conducted at. The purpose of this project has been to create such a system. Records for 156 accelerators were created and all 2913 experiments on Inspire were given corresponding MARC tags. Records of 18404 accelerator physics related bibliographic entries were also tagged with corresponding accelerator tags. Finally, as a part of the endeavour to broaden CERN's presence on Wikipedia, existing Wikipedia articles of accelerators were updated with short descriptions and links to Inspire. In total, 86 Wikipedia articles were updated. This repo...

  12. High-energy transients with Fermi/GBM

    International Nuclear Information System (INIS)

    Gruber, David

    2012-01-01

    project focuses on GRBs which triggered Swift but not GBM although the GRBs came from positions above the horizon, with a favorable orientation to at least one GBM detector. The properties of these GRBs are then compared to the full sample of GBM GRBs published in the GBM spectral catalogue. Although designed mainly for GRB studies, GBM observes solar flares as well. In Chapter 3, I made use of the high temporal quality of GBM data to perform a detailed timing analysis of four solar flares. Contrary to recent claims in the literature, where quasiperiodic pulsations (QPPs) have been allegedly identified in the γ-ray data of solar flares, I did not find any statistical significant signatures of such QPPs. When red-noise, an intrinsic source component, is accounted for, most of the claimed QPPs fall below the threshold of a significant detection. Moreover, I developed a new background estimation method for solar flares, called SOBER 2 (SOlar Background Employing Relative Rates). This method uses the count rate of the complementary and shaded BGO detector as an a priori information to determine the background fluctuations for the Sun-facing BGO detector. Such a method is especially useful and beneficial for solar flares because they are usually of very long duration and the standard GBM background subtraction fails in such cases. Finally, in Chapter 4, I present the log-parabolic model which I used to fit the spectra of SGR bursts. Even though the spectra of the latter are usually and preferentially fit by a sum of two blackbodies in the literature, I show that the log-parabolic model fits the data as least as well as the double blackbody function. Additionally, the log-parabolic model is based on a strong underlying physical mechanism, i.e. second order Fermi acceleration, which gives it even more credibility.

  13. Fermi-LAT upper limits on gamma-ray emission from colliding wind binaries

    International Nuclear Information System (INIS)

    Werner, Michael; Reimer, O.; Reimer, A.

    2013-01-01

    Here, colliding wind binaries (CWBs) are thought to give rise to a plethora of physical processes including acceleration and interaction of relativistic particles. Observation of synchrotron radiation in the radio band confirms there is a relativistic electron population in CWBs. Accordingly, CWBs have been suspected sources of high-energy γ-ray emission since the COS-B era. Theoretical models exist that characterize the underlying physical processes leading to particle acceleration and quantitatively predict the non-thermal energy emission observable at Earth. Furthermore, we strive to find evidence of γ-ray emission from a sample of seven CWB systems: WR 11, WR 70, WR 125, WR 137, WR 140, WR 146, and WR 147. Theoretical modelling identified these systems as the most favourable candidates for emitting γ-rays. We make a comparison with existing γ-ray flux predictions and investigate possible constraints. We used 24 months of data from the Large Area Telescope (LAT) on-board the Fermi Gamma Ray Space Telescope to perform a dedicated likelihood analysis of CWBs in the LAT energy range. As a result, we find no evidence of γ-ray emission from any of the studied CWB systems and determine corresponding flux upper limits. For some CWBs the interplay of orbital and stellar parameters renders the Fermi-LAT data not sensitive enough to constrain the parameter space of the emission models. In the cases of WR140 and WR147, the Fermi-LAT upper limits appear to rule out some model predictions entirely and constrain theoretical models over a significant parameter space. A comparison of our findings to the CWB η Car is made.

  14. NuSTAR Observations of Fermi-detected Novae, V339 Delphini and V5668 Sagitarii

    Science.gov (United States)

    Mukai, K.; Nelson, T.; Sokoloski, J.; Chomiuk, L.; Finzell, T.; Linford, J.; Weston, J.; Rupen, M.; Mioduszewski, A.

    2017-10-01

    Ten Galactic novae have been detected as transient GeV gamma-ray sources with Fermi/LAT to date, presumably due to shock acceleration that produces relativistic particles. This unexpected discovery highlights the complexity of the mass ejection process in novae. It has also added a new class of objects in which particle acceleration can be studied. We can in principle study the same shock in X-rays through their thermal emission and the lower energy extension of the non-thermal emission. Here we present our NuSTAR observations of two Fermi-detected novae, V339 Del and V5668 Sgr, that were carried out while they were being detected with the LAT. We did not detect thermal or non-thermal emissions from these novae. Our results place a tight limit on the properties of the putative shocks in V339 Del and V5668 Sgr. We also compare our results with previous reports of possible detection of non-thermal hard X-rays from novae, and discuss the implications in the context of our current understanding of the complicated process of mass ejection in novae.

  15. Holographic Fermi and Non-Fermi Liquids with Transitions in Dilaton Gravity

    CERN Document Server

    Iizuka, Norihiro; Narayan, Prithvi; Trivedi, Sandip P

    2012-01-01

    We study the two-point function for fermionic operators in a class of strongly coupled systems using the gauge-gravity correspondence. The gravity description includes a gauge field and a dilaton which determines the gauge coupling and the potential energy. Extremal black brane solutions in this system typically have vanishing entropy. By analyzing a charged fermion in these extremal black brane backgrounds we calculate the two-point function of the corresponding boundary fermionic operator. We find that in some region of parameter space it is of Fermi liquid type. Outside this region no well-defined quasi-particles exist, with the excitations acquiring a non-vanishing width at zero frequency. At the transition, the two-point function can exhibit non-Fermi liquid behaviour.

  16. Fermi liquid and non-Fermi liquid in M-channel N fold degenerate anderson lattice

    International Nuclear Information System (INIS)

    Tsuruta, Atsushi; Ono, Yoshiaki; Matsuura, Tamifusa; Kuroda, Yoshihiro; Kobayashi, Akito; Deguchi, Ken

    1999-01-01

    We investigate Fermi liquid in the single-channel U-infinite N fold degenerate Anderson lattice with use of the expansion from the large limit of the spin-orbital degeneracy N. By collecting all diagrams up to O(N -2 ) of the imaginary part of the self-energy of the conduction electrons, the sum of those is shown to be given by a form proportional to ω 2 + π 2 T 2 up to O(N -2 ) in the single-channel model. On the other hand, the imaginary part of the self-energy of O(N -1 ) in the multichannel model has more singular frequency-/temperature-dependence, so the system is regarded as non-Fermi liquid. (author)

  17. Two-beam accelerator

    International Nuclear Information System (INIS)

    Sessler, A.M.; Hopkins, D.B.

    1986-06-01

    The Two-Beam Accelerator (TBA) consists of a long high-gradient accelerator structure (HGS) adjacent to an equal-length Free Electron Laser (FEL). In the FEL, a beam propagates through a long series of undulators. At regular intervals, waveguides couple microwave power out of the FEL into the HGS. To replenish energy given up by the FEL beam to the microwave field, induction accelerator units are placed periodically along the length of the FEL. In this manner it is expected to achieve gradients of more than 250 MV/m and thus have a serious option for a 1 TeV x 1 TeV linear collider. The state of present theoretical understanding of the TBA is presented with particular emphasis upon operation of the ''steady-state'' FEL, phase and amplitude control of the rf wave, and suppression of sideband instabilities. Experimental work has focused upon the development of a suitable HGS and the testing of this structure using the Electron Laser Facility (ELF). Description is given of a first test at ELF with a seven-cell 2π/3 mode structure which without preconditioning and with a not-very-good vacuum nevertheless at 35 GHz yielded an average accelerating gradient of 180 MV/m

  18. Fermi Observation of GRB 080916C

    International Nuclear Information System (INIS)

    Piron, F.

    2009-01-01

    We present the observations of the long-duration Gamma-Ray Burst GRB 080916C by the Fermi Gamma-ray Burst Monitor (GBM) and Large Area Telescope (LAT). This event was observed from 8 keV to a photon with an energy of 13.2 GeV. It develops over a 1400 s interval during which the highest number of photons with energy above 100 MeV are detected from a burst. The onset of the high-energy (>100 MeV) emission is delayed by ∼4.5 s with respect to the low-energy (<1 MeV) emission, which is not detected past 200 s. The broad-band spectrum of the burst is consistent with a single spectral form.

  19. The Gamma-ray Sky with Fermi

    Science.gov (United States)

    Thompson, David

    2012-01-01

    Gamma rays reveal extreme, nonthermal conditions in the Universe. The Fermi Gamma-ray Space Telescope has been exploring the gamma-ray sky for more than four years, enabling a search for powerful transients like gamma-ray bursts, novae, solar flares, and flaring active galactic nuclei, as well as long-term studies including pulsars, binary systems, supernova remnants, and searches for predicted sources of gamma rays such as dark matter annihilation. Some results include a stringent limit on Lorentz invariance derived from a gamma-ray burst, unexpected gamma-ray variability from the Crab Nebula, a huge gamma-ray structure associated with the center of our galaxy, surprising behavior from some gamma-ray binary systems, and a possible constraint on some WIMP models for dark matter.

  20. FermiLib v0.1

    Energy Technology Data Exchange (ETDEWEB)

    2017-02-27

    FermiLib is an open source software package designed to facilitate the development and testing of algorithms for simulations of fermionic systems on quantum computers. Fermionic simulations represent an important application of early quantum devices with a lot of potential high value targets, such as quantum chemistry for the development of new catalysts. This software strives to provide a link between the required domain expertise in specific fermionic applications and quantum computing to enable more users to directly interface with, and develop for, these applications. It is an extensible Python library designed to interface with the high performance quantum simulator, ProjectQ, as well as application specific software such as PSI4 from the domain of quantum chemistry. Such software is key to enabling effective user facilities in quantum computation research.

  1. Fermi-LAT observation of nonblazar AGNs

    Science.gov (United States)

    Sahakyan, N.; Baghmanyan, V.; Zargaryan, D.

    2018-06-01

    Context. Fermi Large Area Telescope (Fermi-LAT) has recently detected γ-ray emission from active galactic nuclei (AGN) that do not show clear evidence for optical blazar characteristics or have jets pointing away from the observer (nonblazar AGNs). These are interesting γ-ray emitters providing an alternative approach to studying high energy emission processes. Aims: This paper investigates the spectral and temporal properties of γ-ray emission from nonblazar AGNs using the recent Fermi-LAT observational data. Methods: The data collected by Fermi-LAT during 2008-2015, from the observations of 26 nonblazar AGNs, including 11 Fanaroff-Riley Type I (FRI) and ten FRII radio galaxies and steep spectrum radio quasars (SSRQs) and five narrow line seyfert 1s (NLSy1s) are analysed using the new PASS 8 event selection and instrument response function. Possible spectral changes above GeV energies are investigated with a detailed spectral analysis. Light curves generated with normal and adaptive time bins are used to study the γ-ray flux variability. Results: Non-blazar AGNs have a γ-ray photon index in the range of 1.84-2.86 and a flux varying from a few times 10-9 photon cm-2 s-1 to 10-7 photon cm-2 s-1. Over long time periods, the power law provides an adequate description of the γ-ray spectra of almost all sources. Significant curvature is observed in the γ-ray spectra of NGC 1275, NGC 6251, SBS 0846 + 513, and PMN J0948 + 0022 and their spectra are better described by log parabola or by the power law with exponential cut-off models. The γ-ray spectra of PKS 0625-25 and 3C 380 show a possible deviation from a simple power-law shape, indicating a spectral cut-off around the observed photon energy of Ecut = 131.2 ± 88.04 GeV and Ecut = 55.57 ± 50.74 GeV, respectively. Our analysis confirms the previous finding of an unusual spectral turnover in the γ-ray spectrum of Cen A: the photon index changes from Γ = 2.75 ± 0.02 to 2.31 ± 0.1 at 2.35 ± 0.08 GeV. In the

  2. Detecting Friedel oscillations in ultracold Fermi gases

    Science.gov (United States)

    Riechers, Keno; Hueck, Klaus; Luick, Niclas; Lompe, Thomas; Moritz, Henning

    2017-09-01

    Investigating Friedel oscillations in ultracold gases would complement the studies performed on solid state samples with scanning-tunneling microscopes. In atomic quantum gases interactions and external potentials can be tuned freely and the inherently slower dynamics allow to access non-equilibrium dynamics following a potential or interaction quench. Here, we examine how Friedel oscillations can be observed in current ultracold gas experiments under realistic conditions. To this aim we numerically calculate the amplitude of the Friedel oscillations which are induced by a potential barrier in a 1D Fermi gas and compare it to the expected atomic and photonic shot noise in a density measurement. We find that to detect Friedel oscillations the signal from several thousand one-dimensional systems has to be averaged. However, as up to 100 parallel one-dimensional systems can be prepared in a single run with present experiments, averaging over about 100 images is sufficient.

  3. Entanglement rules for holographic Fermi surfaces

    Directory of Open Access Journals (Sweden)

    Dibakar Roychowdhury

    2016-08-01

    Full Text Available In this paper, based on the notion of Gauge/Gravity duality, we explore the laws of entanglement thermodynamics for most generic classes of Quantum Field Theories with hyperscaling violation. In our analysis, we note that for Quantum Field Theories with compressible quark like excitation, the first law of entanglement thermodynamics gets modified due to the presence of an additional term that could be identified as the entanglement chemical potential associated with hidden Fermi surfaces of the boundary theory. Most notably, we find that the so called entanglement chemical potential does not depend on the size of the entangling region and is purely determined by the quark d.o.f. encoded within the entangling region.

  4. Theory of Fermi Liquid with Flat Bands

    Science.gov (United States)

    Khodel, V. A.

    2018-04-01

    A self-consistent theory of Fermi systems hosting flat bands is developed. Compared with an original model of fermion condensation, its key point consists in proper accounting for mixing between condensate and non-condensate degrees of freedom that leads to formation of a non-BCS gap Υ (p) in the single-particle spectrum. The results obtained explain: (1) the two-gap structure of spectra of single-particle excitations of electron systems of copper oxides, revealed in ARPES studies, (2) the role of violation of the topological stability of the Landau state in the arrangement of the T-x phase diagram of this family of high-T_c superconductors, (3) the topological nature of a metal-insulator transition, discovered in homogeneous two-dimensional low-density electron liquid of MOSFETs more than 20 years ago.

  5. Electroweak interactions in a relativistic Fermi gas

    International Nuclear Information System (INIS)

    Vantournhout, K.; Jachowicz, N.; Ryckebusch, J.

    2006-01-01

    We present a relativistic model for computing the neutrino mean free path in neutron matter. In this model, neutron matter is described as a noninteracting Fermi gas in β equilibrium. We present results for the neutrino mean free path for temperatures of 0 to 50 MeV and a broad range of neutrino energies. We show that relativistic effects cause a considerable enhancement of neutrino-scattering cross sections in neutron matter. The influence of the Q 2 dependence in the electroweak form factors and the inclusion of a weak-magnetic term in the hadron current is discussed. The weak-magnetic term in the hadron current is at the origin of some selective spin dependence for the nucleons that are subject to neutrino interactions

  6. Entanglement rules for holographic Fermi surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Roychowdhury, Dibakar, E-mail: dibakarphys@gmail.com

    2016-08-15

    In this paper, based on the notion of Gauge/Gravity duality, we explore the laws of entanglement thermodynamics for most generic classes of Quantum Field Theories with hyperscaling violation. In our analysis, we note that for Quantum Field Theories with compressible quark like excitation, the first law of entanglement thermodynamics gets modified due to the presence of an additional term that could be identified as the entanglement chemical potential associated with hidden Fermi surfaces of the boundary theory. Most notably, we find that the so called entanglement chemical potential does not depend on the size of the entangling region and is purely determined by the quark d.o.f. encoded within the entangling region.

  7. The Gamma-ray Universe through Fermi

    Science.gov (United States)

    Thompson, David J.

    2012-01-01

    Gamma rays, the most powerful form of light, reveal extreme conditions in the Universe. The Fermi Gamma-ray Space Telescope and its smaller cousin AGILE have been exploring the gamma-ray sky for several years, enabling a search for powerful transients like gamma-ray bursts, novae, solar flares, and flaring active galactic nuclei, as well as long-term studies including pulsars, binary systems, supernova remnants, and searches for predicted sources of gamma rays such as dark matter annihilation. Some results include a stringent limit on Lorentz invariance derived from a gamma-ray burst, unexpected gamma-ray variability from the Crab Nebula, a huge ga.nuna-ray structure associated with the center of our galaxy, surprising behavior from some gamma-ray binary systems, and a possible constraint on some WIMP models for dark matter.

  8. Momentum sharing in imbalanced Fermi systems

    Science.gov (United States)

    Hen, O.; Sargsian, M.; Weinstein, L. B.; Piasetzky, E.; Hakobyan, H.; Higinbotham, D. W.; Braverman, M.; Brooks, W. K.; Gilad, S.; Adhikari, K. P.; Arrington, J.; Asryan, G.; Avakian, H.; Ball, J.; Baltzell, N. A.; Battaglieri, M.; Beck, A.; Beck, S. May-Tal; Bedlinskiy, I.; Bertozzi, W.; Biselli, A.; Burkert, V. D.; Cao, T.; Carman, D. S.; Celentano, A.; Chandavar, S.; Colaneri, L.; Cole, P. L.; Crede, V.; D'Angelo, A.; De Vita, R.; Deur, A.; Djalali, C.; Doughty, D.; Dugger, M.; Dupre, R.; Egiyan, H.; El Alaoui, A.; El Fassi, L.; Elouadrhiri, L.; Fedotov, G.; Fegan, S.; Forest, T.; Garillon, B.; Garcon, M.; Gevorgyan, N.; Ghandilyan, Y.; Gilfoyle, G. P.; Girod, F. X.; Goetz, J. T.; Gothe, R. W.; Griffioen, K. A.; Guidal, M.; Guo, L.; Hafidi, K.; Hanretty, C.; Hattawy, M.; Hicks, K.; Holtrop, M.; Hyde, C. E.; Ilieva, Y.; Ireland, D. G.; Ishkanov, B. I.; Isupov, E. L.; Jiang, H.; Jo, H. S.; Joo, K.; Keller, D.; Khandaker, M.; Kim, A.; Kim, W.; Klein, F. J.; Koirala, S.; Korover, I.; Kuhn, S. E.; Kubarovsky, V.; Lenisa, P.; Levine, W. I.; Livingston, K.; Lowry, M.; Lu, H. Y.; MacGregor, I. J. D.; Markov, N.; Mayer, M.; McKinnon, B.; Mineeva, T.; Mokeev, V.; Movsisyan, A.; Camacho, C. Munoz; Mustapha, B.; Nadel-Turonski, P.; Niccolai, S.; Niculescu, G.; Niculescu, I.; Osipenko, M.; Pappalardo, L. L.; Paremuzyan, R.; Park, K.; Pasyuk, E.; Phelps, W.; Pisano, S.; Pogorelko, O.; Price, J. W.; Procureur, S.; Prok, Y.; Protopopescu, D.; Puckett, A. J. R.; Rimal, D.; Ripani, M.; Ritchie, B. G.; Rizzo, A.; Rosner, G.; Roy, P.; Rossi, P.; Sabatié, F.; Schott, D.; Schumacher, R. A.; Sharabian, Y. G.; Smith, G. D.; Shneor, R.; Sokhan, D.; Stepanyan, S. S.; Stepanyan, S.; Stoler, P.; Strauch, S.; Sytnik, V.; Taiuti, M.; Tkachenko, S.; Ungaro, M.; Vlassov, A. V.; Voutier, E.; Walford, N. K.; Wei, X.; Wood, M. H.; Wood, S. A.; Zachariou, N.; Zana, L.; Zhao, Z. W.; Zheng, X.; Zonta, I.; aff16

    2014-10-01

    The atomic nucleus is composed of two different kinds of fermions: protons and neutrons. If the protons and neutrons did not interact, the Pauli exclusion principle would force the majority of fermions (usually neutrons) to have a higher average momentum. Our high-energy electron-scattering measurements using 12C, 27Al, 56Fe, and 208Pb targets show that even in heavy, neutron-rich nuclei, short-range interactions between the fermions form correlated high-momentum neutron-proton pairs. Thus, in neutron-rich nuclei, protons have a greater probability than neutrons to have momentum greater than the Fermi momentum. This finding has implications ranging from nuclear few-body systems to neutron stars and may also be observable experimentally in two-spin-state, ultracold atomic gas systems.

  9. Momentum sharing in imbalanced Fermi systems

    Energy Technology Data Exchange (ETDEWEB)

    Hen, O.; Sargsian, M.; Weinstein, L. B.; Piasetzky, E.; Hakobyan, H.; Higinbotham, D. W.; Braverman, M.; Brooks, W. K.; Gilad, S.; Adhikari, K. P.; Arrington, J.; Asryan, G.; Avakian, H.; Ball, J.; Baltzell, N. A.; Battaglieri, M.; Beck, A.; Beck, S. M. -T.; Bedlinskiy, I.; Bertozzi, W.; Biselli, A.; Burkert, V. D.; Cao, T.; Carman, D. S.; Celentano, A.; Chandavar, S.; Colaneri, L.; Cole, P. L.; Crede, V.; D' Angelo, A.; De Vita, R.; Deur, A.; Djalali, C.; Doughty, D.; Dugger, M.; Dupre, R.; Egiyan, H.; El Alaoui, A.; El Fassi, L.; Elouadrhiri, L.; Fedotov, G.; Fegan, S.; Forest, T.; Garillon, B.; Garcon, M.; Gevorgyan, N.; Ghandilyan, Y.; Gilfoyle, G. P.; Girod, F. X.; Goetz, J. T.; Gothe, R. W.; Griffioen, K. A.; Guidal, M.; Guo, L.; Hafidi, K.; Hanretty, C.; Hattawy, M.; Hicks, K.; Holtrop, M.; Hyde, C. E.; Ilieva, Y.; Ireland, D. G.; Ishkanov, B. I.; Isupov, E. L.; Jiang, H.; Jo, H. S.; Joo, K.; Keller, D.; Khandaker, M.; Kim, A.; Kim, W.; Klein, F. J.; Koirala, S.; Korover, I.; Kuhn, S. E.; Kubarovsky, V.; Lenisa, P.; Levine, W. I.; Livingston, K.; Lowry, M.; Lu, H. Y.; MacGregor, I. J. D.; Markov, N.; Mayer, M.; McKinnon, B.; Mineeva, T.; Mokeev, V.; Movsisyan, A.; Camacho, C. M.; Mustapha, B.; Nadel-Turonski, P.; Niccolai, S.; Niculescu, G.; Niculescu, I.; Osipenko, M.; Pappalardo, L. L.; Paremuzyan, R.; Park, K.; Pasyuk, E.; Phelps, W.; Pisano, S.; Pogorelko, O.; Price, J. W.; Procureur, S.; Prok, Y.; Protopopescu, D.; Puckett, A. J. R.; Rimal, D.; Ripani, M.; Ritchie, B. G.; Rizzo, A.; Rosner, G.; Roy, P.; Rossi, P.; Sabatie, F.; Schott, D.; Schumacher, R. A.; Sharabian, Y. G.; Smith, G. D.; Shneor, R.; Sokhan, D.; Stepanyan, S. S.; Stepanyan, S.; Stoler, P.; Strauch, S.; Sytnik, V.; Taiuti, M.; Tkachenko, S.; Ungaro, M.; Vlassov, A. V.; Voutier, E.; Walford, N. K.; Wei, X.; Wood, M. H.; Wood, S. A.; Zachariou, N.; Zana, L.; Zhao, Z. W.; Zheng, X.; Zonta, I.

    2014-10-16

    The atomic nucleus is composed of two different kinds of fermions: protons and neutrons. If the protons and neutrons did not interact, the Pauli exclusion principle would force the majority of fermions (usually neutrons) to have a higher average momentum. Our high-energy electron-scattering measurements using C-12, Al-27, Fe-56, and Pb-208 targets show that even in heavy, neutron-rich nuclei, short-range interactions between the fermions form correlated high-momentum neutron-proton pairs. Thus, in neutron-rich nuclei, protons have a greater probability than neutrons to have momentum greater than the Fermi momentum. This finding has implications ranging from nuclear few-body systems to neutron stars and may also be observable experimentally in two-spin-state, ultracold atomic gas systems.

  10. Adaptationism fails to resolve Fermi's paradox

    Directory of Open Access Journals (Sweden)

    Ćirković Milan M.

    2005-01-01

    Full Text Available One of the most interesting problems in the nascent discipline of astrobiology is more than half-century old Fermi's paradox: why, considering extraordinary young age of Earth and the Solar System in the Galactic context, don't we perceive much older intelligent communities or signposts of their activity? In spite of a vigorous research activity in recent years, especially bolstered by successes of astrobiology in finding extrasolar planets and extremophiles, this problem (also known as the "Great Silence" or "astrosociological" paradox remains as open as ever. In a previous paper, we have discussed a particular evolutionary solution suggested by Karl Schroeder based on the currently dominant evolutionary doctrine of adaptationism. Here, we extend that discussion with emphasis on the problems such a solution is bound to face, and conclude that it is ultimately quite unlikely. .

  11. FMIT accelerator

    International Nuclear Information System (INIS)

    Armstrong, D.D.

    1983-01-01

    A 35-MeV 100-mA cw linear accelerator is being designed by Los Alamos for use in the Fusion Materials Irradiation Test (FMIT) Facility. Essential to this program is the design, construction, and evaluation of performance of the accelerator's injector, low-energy beam transport, and radio-frequency quadrupole sections before they are shipped to the facility site. The installation and testing of some of these sections have begun as well as the testing of the rf, noninterceptive beam diagnostics, computer control, dc power, and vacuum systems. An overview of the accelerator systems and the performance to date is given

  12. Electron accelerator

    International Nuclear Information System (INIS)

    Abramyan.

    1981-01-01

    The USSR produces an electron accelerator family of a simple design powered straight from the mains. The specifications are given of accelerators ELITA-400, ELITA-3, ELT-2, TEUS-3 and RIUS-5 with maximum electron energies of 0.3 to 5 MeV, a mean power of 10 to 70 kW operating in both the pulsed and the continuous (TEUS-3) modes. Pulsed accelerators ELITA-400 and ELITA-3 and RIUS-5 in which TESLA resonance transformers are used are characterized by their compact size. (Ha)

  13. From ultracold Fermi Gases to Neutron Stars

    Science.gov (United States)

    Salomon, Christophe

    2012-02-01

    Ultracold dilute atomic gases can be considered as model systems to address some pending problem in Many-Body physics that occur in condensed matter systems, nuclear physics, and astrophysics. We have developed a general method to probe with high precision the thermodynamics of locally homogeneous ultracold Bose and Fermi gases [1,2,3]. This method allows stringent tests of recent many-body theories. For attractive spin 1/2 fermions with tunable interaction (^6Li), we will show that the gas thermodynamic properties can continuously change from those of weakly interacting Cooper pairs described by Bardeen-Cooper-Schrieffer theory to those of strongly bound molecules undergoing Bose-Einstein condensation. First, we focus on the finite-temperature Equation of State (EoS) of the unpolarized unitary gas. Surprisingly, the low-temperature properties of the strongly interacting normal phase are well described by Fermi liquid theory [3] and we localize the superfluid phase transition. A detailed comparison with theories including recent Monte-Carlo calculations will be presented. Moving away from the unitary gas, the Lee-Huang-Yang and Lee-Yang beyond-mean-field corrections for low density bosonic and fermionic superfluids are quantitatively measured for the first time. Despite orders of magnitude difference in density and temperature, our equation of state can be used to describe low density neutron matter such as the outer shell of neutron stars. [4pt] [1] S. Nascimbène, N. Navon, K. Jiang, F. Chevy, and C. Salomon, Nature 463, 1057 (2010) [0pt] [2] N. Navon, S. Nascimbène, F. Chevy, and C. Salomon, Science 328, 729 (2010) [0pt] [3] S. Nascimbène, N. Navon, S. Pilati, F. Chevy, S. Giorgini, A. Georges, and C. Salomon, Phys. Rev. Lett. 106, 215303 (2011)

  14. Generalization of the Fermi-Segre formula

    International Nuclear Information System (INIS)

    Froeman, N.; Froeman, P.O.

    1981-01-01

    A generalization of the non-relativistic Fermi-Segre formula into a formula which is valid also for angular momentum quantum numbers l different from zero, is derived by means of a phase-integral method. The formula thus obtained, which gives an expression for the limit of u(r)/rsup(l+1) as r→0, where u(r) is a normalized bound-state radial wavefunction, in terms of the derivative of the energy level Esub(n'), with respect to the radial quantum number n', is an improvement and generalization of a formula which has been obtained by M.A. Bouchiat and C. Bouchiat. It reduces to their formula for a particular class of potentials and highly excited states with not too large values of l, and it reduces to the Fermi-Segre formula when l=0. The accuracy of our formula, as well as that of the Bouchiat-Bouchiat formula, is investigated by application to an exactly soluble model. The formula obtained can also be written in another form by replacing dEsub(n')/dn' by an expression involving a closed-loop integral in the complex r-plane (around the generalized classical turning points), the integrand being a phase-integral quantity expressed in terms of the potential in which the particle moves. It is also shown that the exact value of the limit of u(r)/rsup(l+1) as r→0 can be expressed as an expectation value of a certain function depending on the physical potential V(r) and r a swell as on l and Esub(n')

  15. Collapse and revival of the Fermi sea in a Bose-Fermi mixture

    Science.gov (United States)

    Iyer, Deepak; Will, Sebastian; Rigol, Marcos

    2014-05-01

    The collapse and revival of quantum fields is one of the most pristine forms of coherent quantum dynamics far from equilibrium. Until now, it has only been observed in the dynamical evolution of bosonic systems. We report on the first observation of the boson mediated collapse and revival of the Fermi sea in a Bose-Fermi mixture. Specifically, we present a simple model which captures the experimental observations shown in the talk titled Observation of Collapse and Revival Dynamics in the Fermionic Component of a Lattice Bose-Fermi Mixture by Sebastian Will. Our theoretical analysis shows why the results are robust to the presence of harmonic traps during the loading or the time evolution phase. It also makes apparent that the fermionic dynamics is independent of whether the bosonic component consists of a coherent state or localized Fock states with random occupation numbers. Because of the robustness of the experimental results, we argue that this kind of collapse and revival experiment can be used to accurately characterize interactions between bosons and fermions in a lattice.

  16. Horizontal Accelerator

    Data.gov (United States)

    Federal Laboratory Consortium — The Horizontal Accelerator (HA) Facility is a versatile research tool available for use on projects requiring simulation of the crash environment. The HA Facility is...

  17. Acceleration theorems

    International Nuclear Information System (INIS)

    Palmer, R.

    1994-06-01

    Electromagnetic fields can be separated into near and far components. Near fields are extensions of static fields. They do not radiate, and they fall off more rapidly from a source than far fields. Near fields can accelerate particles, but the ratio of acceleration to source fields at a distance R, is always less than R/λ or 1, whichever is smaller. Far fields can be represented as sums of plane parallel, transversely polarized waves that travel at the velocity of light. A single such wave in a vacuum cannot give continuous acceleration, and it is shown that no sums of such waves can give net first order acceleration. This theorem is proven in three different ways; each method showing a different aspect of the situation

  18. LINEAR ACCELERATOR

    Science.gov (United States)

    Christofilos, N.C.; Polk, I.J.

    1959-02-17

    Improvements in linear particle accelerators are described. A drift tube system for a linear ion accelerator reduces gap capacity between adjacent drift tube ends. This is accomplished by reducing the ratio of the diameter of the drift tube to the diameter of the resonant cavity. Concentration of magnetic field intensity at the longitudinal midpoint of the external sunface of each drift tube is reduced by increasing the external drift tube diameter at the longitudinal center region.

  19. Recent Developments in Non-Fermi Liquid Theory

    Science.gov (United States)

    Lee, Sung-Sik

    2018-03-01

    Non-Fermi liquids are unconventional metals whose physical properties deviate qualitatively from those of noninteracting fermions due to strong quantum fluctuations near Fermi surfaces. They arise when metals are subject to singular interactions mediated by soft collective modes. In the absence of well-defined quasiparticles, universal physics of non-Fermi liquids is captured by interacting field theories which replace Landau Fermi liquid theory. However, it has been difficult to understand their universal low-energy physics due to a lack of theoretical methods that take into account strong quantum fluctuations in the presence of abundant low-energy degrees of freedom. In this review, we discuss two approaches that have been recently developed for non-Fermi liquid theory with emphasis on two space dimensions. The first is a perturbative scheme based on a dimensional regularization, which achieves a controlled access to the low-energy physics by tuning the codimension of Fermi surface. The second is a nonperturbative approach which treats the interaction ahead of the kinetic term through a non-Gaussian scaling called interaction-driven scaling. Examples of strongly coupled non-Fermi liquids amenable to exact treatments through the interaction-driven scaling are discussed.

  20. Turbulence, Magnetic Reconnection in Turbulent Fluids and Energetic Particle Acceleration

    Science.gov (United States)

    Lazarian, A.; Vlahos, L.; Kowal, G.; Yan, H.; Beresnyak, A.; de Gouveia Dal Pino, E. M.

    2012-11-01

    Turbulence is ubiquitous in astrophysics. It radically changes many astrophysical phenomena, in particular, the propagation and acceleration of cosmic rays. We present the modern understanding of compressible magnetohydrodynamic (MHD) turbulence, in particular its decomposition into Alfvén, slow and fast modes, discuss the density structure of turbulent subsonic and supersonic media, as well as other relevant regimes of astrophysical turbulence. All this information is essential for understanding the energetic particle acceleration that we discuss further in the review. For instance, we show how fast and slow modes accelerate energetic particles through the second order Fermi acceleration, while density fluctuations generate magnetic fields in pre-shock regions enabling the first order Fermi acceleration of high energy cosmic rays. Very importantly, however, the first order Fermi cosmic ray acceleration is also possible in sites of magnetic reconnection. In the presence of turbulence this reconnection gets fast and we present numerical evidence supporting the predictions of the Lazarian and Vishniac (Astrophys. J. 517:700-718, 1999) model of fast reconnection. The efficiency of this process suggests that magnetic reconnection can release substantial amounts of energy in short periods of time. As the particle tracing numerical simulations show that the particles can be efficiently accelerated during the reconnection, we argue that the process of magnetic reconnection may be much more important for particle acceleration than it is currently accepted. In particular, we discuss the acceleration arising from reconnection as a possible origin of the anomalous cosmic rays measured by Voyagers as well as the origin cosmic ray excess in the direction of Heliotail.

  1. Towards a complete Fermi surface in underdoped high Tc superconductors

    Science.gov (United States)

    Harrison, Neil

    The discovery of magnetic quantum oscillations in underdoped high Tc superconductors raised many questions, and initiated a quest to understand the origin of the Fermi surface the like of which had not been seen since the very first discovery of quantum oscillations in elemental bismuth. While studies of the Fermi surface of materials are today mostly assisted by computer codes for calculating the electronic band structure, this was not the case in the underdoped high Tc materials. The Fermi surface was shown to reconstructed into small pockets, yet there was no hint of a viable order parameter. Crucial clues to understanding the origin of the Fermi surface were provided by the small value of the observed Fermi surface cross-section, the negative Hall coefficient and the small electronic heat capacity at high magnetic fields. We also know that the magnetic fields were likely to be too weak to destroy the pseudogap and that vortex pinning effects could be seen to persist to high magnetic fields at low temperatures. I will show that the Fermi surface that appears to fit best with the experimental observations is a small electron pocket formed by connecting the nodal `Fermi arcs' seen in photoemission experiments, corresponding to a density-wave state with two different orthogonal ordering vectors. The existence of such order has subsequently been detected by x-ray scattering experiments, thereby strengthening the case for charge ordering being responsible for reconstructing the Fermi surface. I will discuss new efforts to understand the relationship between the charge ordering and the pseudogap state, discussing the fate of the quasiparticles in the antinodal region and the dimensionality of the Fermi surface. The author acknowledges contributions from Suchitra Sebastian, Brad Ramshaw, Mun Chan, Yu-Te Hsu, Mate Hartstein, Gil Lonzarich, Beng Tan, Arkady Shekhter, Fedor Balakirev, Ross McDonald, Jon Betts, Moaz Altarawneh, Zengwei Zhu, Chuck Mielke, James Day, Doug

  2. Accelerator structure work for NLC

    International Nuclear Information System (INIS)

    Miller, R.H.; Adolphsen, C.; Bane, K.L.F.; Deruyter, H.; Farkas, Z.D.; Hoag, H.A.; Holtkamp, N.; Lavine, T.; Loew, G.A.; Nelson, E.M.; Palmer, R.B.; Paterson, J.M.; Ruth, R.D.; Thompson, K.A.; Vlieks, A.; Wang, J.W.; Wilson, P.B.; Gluckstern, R.; Ko, K.; Kroll, N.; California Univ., San Diego, La Jolla, CA

    1992-07-01

    The NLC design achieves high luminosity with multiple bunches in each RF pulse. Acceleration of a train of bunches without emittance growth requires control of long range dipole wakefields. SLAC is pursuing a structure design which suppresses the effect of wakefields by varying the physical dimensions of successive cells of the disk-loaded traveling wave structure in a manner which spreads the frequencies of the higher mode while retaining the synchronism between the electrons and the accelerating mode. The wakefields of structures incorporating higher mode detuning have been measured at the Accelerator Test Facility at Argonne. Mechanical design and brazing techniques which avoid getting brazing alloy into the interior of the accelerator are being studied. A test facility for high-power testing of these structures is complete and high power testing has begun

  3. X.509 Authentication/Authorization in FermiCloud

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Hyunwoo [Fermilab; Timm, Steven [Fermilab

    2014-11-11

    We present a summary of how X.509 authentication and authorization are used with OpenNebula in FermiCloud. We also describe a history of why the X.509 authentication was needed in FermiCloud, and review X.509 authorization options, both internal and external to OpenNebula. We show how these options can be and have been used to successfully run scientific workflows on federated clouds, which include OpenNebula on FermiCloud and Amazon Web Services as well as other community clouds. We also outline federation options being used by other commercial and open-source clouds and cloud research projects.

  4. Neutron physics for nuclear reactors unpublished writings by Enrico Fermi

    CERN Document Server

    Fermi, Enrico; Pisanti, O

    2010-01-01

    This unique volume gives an accurate and very detailed description of the functioning and operation of basic nuclear reactors, as emerging from yet unpublished papers by Nobel Laureate Enrico Fermi. In the first part, the entire course of lectures on Neutron Physics delivered by Fermi at Los Alamos is reported, according to the version made by Anthony P French. Here, the fundamental physical phenomena are described very clearly and comprehensively, giving the appropriate physics grounds for the functioning of nuclear piles. In the second part, all the patents issued by Fermi (and coworkers) on

  5. Fermi Large Area Telescope Bright Gamma-ray Source List

    Energy Technology Data Exchange (ETDEWEB)

    Abdo, Aous A.; /Naval Research Lab, Wash., D.C.; Ackermann, M.; /KIPAC, Menlo Park /SLAC; Ajello, M.; /KIPAC, Menlo Park /SLAC; Atwood, W.B.; /UC, Santa Cruz; Axelsson, M.; /Stockholm U., OKC /Stockholm U.; Baldini, L.; /INFN, Pisa; Ballet, J.; /DAPNIA, Saclay; Band, D.L.; /NASA, Goddard /NASA, Goddard; Barbiellini, Guido; /INFN, Trieste /Trieste U.; Bastieri, Denis; /INFN, Padua /Padua U.; Bechtol, K.; /KIPAC, Menlo Park /SLAC; Bellazzini, R.; /INFN, Pisa; Berenji, B.; /KIPAC, Menlo Park /SLAC; Bignami, G.F.; /Pavia U.; Bloom, Elliott D.; /KIPAC, Menlo Park /SLAC; Bonamente, E.; /INFN, Perugia /Perugia U.; Borgland, A.W.; /KIPAC, Menlo Park /SLAC; Bregeon, J.; /INFN, Pisa; Brigida, M.; /Bari U. /INFN, Bari; Bruel, P.; /Ecole Polytechnique; Burnett, Thompson H.; /Washington U., Seattle /Bari U. /INFN, Bari /KIPAC, Menlo Park /SLAC /IASF, Milan /IASF, Milan /DAPNIA, Saclay /ASDC, Frascati /INFN, Perugia /Perugia U. /KIPAC, Menlo Park /SLAC /George Mason U. /Naval Research Lab, Wash., D.C. /NASA, Goddard /KIPAC, Menlo Park /SLAC /INFN, Perugia /Perugia U. /KIPAC, Menlo Park /SLAC /Montpellier U. /Sonoma State U. /Stockholm U., OKC /Royal Inst. Tech., Stockholm /Stockholm U. /KIPAC, Menlo Park /SLAC /ASDC, Frascati /NASA, Goddard /Maryland U. /Naval Research Lab, Wash., D.C. /INFN, Trieste /Pavia U. /Bari U. /INFN, Bari /KIPAC, Menlo Park /SLAC /UC, Santa Cruz /KIPAC, Menlo Park /SLAC /KIPAC, Menlo Park /SLAC /KIPAC, Menlo Park /SLAC /Montpellier U. /Bari U. /INFN, Bari /Ecole Polytechnique /NASA, Goddard; /more authors..

    2009-05-15

    Following its launch in 2008 June, the Fermi Gamma-ray Space Telescope (Fermi) began a sky survey in August. The Large Area Telescope (LAT) on Fermi in three months produced a deeper and better resolved map of the {gamma}-ray sky than any previous space mission. We present here initial results for energies above 100 MeV for the 205 most significant (statistical significance greater than {approx}10{sigma}) {gamma}-ray sources in these data. These are the best characterized and best localized point-like (i.e., spatially unresolved) {gamma}-ray sources in the early mission data.

  6. Role of drifts in diffusive shock acceleration

    International Nuclear Information System (INIS)

    Decker, R.B.

    1988-01-01

    The role played by shock-associated drifts during the diffusive acceleration of charged particles at collisionless MHD shocks is evaluated. In the rest frame of the shock, the total energy gained by a particle is shown to result from two coupled acceleration mechanisms, the usual first-order Fermi mechanism and the drift mechanism. When averaged over a distribution of particles, the ratio of the drift-associated energy gain to the total energy is found to be independent of the total energy at a given theta1 (the angle between the shock normal and the unperturbed upstream magnetic field) in agreement with theoretical predictions. No evidence is found for drift-associated deceleration, suggesting that drifts always augment acceleration. 35 references

  7. Accelerator microanalysis

    International Nuclear Information System (INIS)

    Tuniz, C.

    1997-01-01

    Particle accelerators have been developed more than sixty years ago to investigate nuclear and atomic phenomena. A major shift toward applications of accelerators in the study of materials structure and composition in inter-disciplinary projects has been witnessed in the last two decades. The Australian Nuclear Science and Technology Organisation (ANSTO) has developed advanced research programs based on the use of particle and photon beams. Atmospheric pollution problems are investigated at the 3 MV Van de Graff accelerator using ion beam analysis techniques to detect toxic elements in aerosol particles. High temperature superconductor and semiconductor materials are characterised using the recoil of iodine and other heavy ions produced at ANTARES, the 10-MV Tandem accelerator. A heavy-ion microprobe is presently being developed at ANTARES to map elemental concentrations of specific elements with micro-size resolution. An Accelerator mass Spectrometry (AMS) system has been developed at ANSTO for the ultra-sensitive detection of Carbon-14, Iodine-129 and other long-lived radioisotopes. This AMS spectrometer is a key instrument for climate change studies and international safeguards. ANSTO is also managing the Australian Synchrotron Research program based on facilities developed at the Photon Factory (Japan) and at the Advanced Photon Source (USA). Advanced projects in biology, materials chemistry, structural condensed matter and other disciplines are being promoted by a consortium involving Australian universities and research institutions. This paper will review recent advances in the use of particle accelerators, with a particular emphasis on applications developed at ANSTO and related to problems of international concern, such as global environmental change, public health and nuclear proliferation

  8. Continuum approximation of the Fermi-Pasta-Ulam lattice

    International Nuclear Information System (INIS)

    Martina, L.

    1979-01-01

    A continuum approximation method is applied in order to discuss the connection between some properties of the infinite Fermi-Pasta-Ulam lattice and the ones displayed by the Korteweg-de Vries equation

  9. Vortex Lattices in the Bose-Fermi Superfluid Mixture.

    Science.gov (United States)

    Jiang, Yuzhu; Qi, Ran; Shi, Zhe-Yu; Zhai, Hui

    2017-02-24

    In this Letter we show that the vortex lattice structure in the Bose-Fermi superfluid mixture can undergo a sequence of structure transitions when the Fermi superfluid is tuned from the BCS regime to the BEC regime. This is due to the difference in the vortex core structure of a Fermi superfluid in the BCS regime and in the BEC regime. In the BCS regime the vortex core is nearly filled, while the density at the vortex core gradually decreases until it empties out in the BEC regime. Therefore, with the density-density interaction between the Bose and the Fermi superfluids, interaction between the two sets of vortex lattices gets stronger in the BEC regime, which yields the structure transition of vortex lattices. In view of the recent realization of this superfluid mixture and vortices therein, our theoretical predication can be verified experimentally in the near future.

  10. Renormalization group and the superconducting susceptibility of a Fermi liquid

    International Nuclear Information System (INIS)

    Parameswaran, S. A.; Sondhi, S. L.; Shankar, R.

    2010-01-01

    A free Fermi gas has, famously, a superconducting susceptibility that diverges logarithmically at zero temperature. In this paper we ask whether this is still true for a Fermi liquid and find that the answer is that it does not. From the perspective of the renormalization group for interacting fermions, the question arises because a repulsive interaction in the Cooper channel is a marginally irrelevant operator at the Fermi liquid fixed point and thus is also expected to infect various physical quantities with logarithms. Somewhat surprisingly, at least from the renormalization group viewpoint, the result for the superconducting susceptibility is that two logarithms are not better than one. In the course of this investigation we derive a Callan-Symanzik equation for the repulsive Fermi liquid using the momentum-shell renormalization group, and use it to compute the long-wavelength behavior of the superconducting correlation function in the emergent low-energy theory. We expect this technique to be of broader interest.

  11. Joule-Thomson Coefficient for Strongly Interacting Unitary Fermi Gas

    International Nuclear Information System (INIS)

    Liao Kai; Chen Jisheng; Li Chao

    2010-01-01

    The Joule-Thomson effect reflects the interaction among constituent particles of macroscopic system. For classical ideal gas, the corresponding Joule-Thomson coefficient is vanishing while it is non-zero for ideal quantum gas due to the quantum degeneracy. In recent years, much attention is paid to the unitary Fermi gas with infinite two-body scattering length. According to universal analysis, the thermodynamical law of unitary Fermi gas is similar to that of non-interacting ideal gas, which can be explored by the virial theorem P = 2E/3V. Based on previous works, we further study the unitary Fermi gas properties. The effective chemical potential is introduced to characterize the nonlinear levels crossing effects in a strongly interacting medium. The changing behavior of the rescaled Joule-Thomson coefficient according to temperature manifests a quite different behavior from that for ideal Fermi gas. (general)

  12. Non-Fermi glasses: fractionalizing electrons at finite energy density

    Science.gov (United States)

    Parameswaran, Siddharth; Gopalakrishnan, Sarang

    Non-Fermi liquids are metals that cannot be adiabatically deformed into free fermion states. We argue for the existence of ``non-Fermi glasses,'' which are phases of interacting disordered fermions that are fully many-body localized, yet cannot be deformed into an Anderson insulator without an eigenstate phase transition. We explore the properties of such non-Fermi glasses, focusing on a specific solvable example. At high temperature, non-Fermi glasses have qualitatively similar spectral features to Anderson insulators. We identify a diagnostic, based on ratios of correlation functions, that sharply distinguishes between the two phases even at infinite temperature. We argue that our results and diagnostic should generically apply to the high-temperature behavior of the many-body localized descendants of fractionalized phases. S.A.P. is supported by NSF Grant DMR-1455366 and a UC President's Research Catalyst Award CA-15-327861, and S.G. by the Burke Institute at Caltech.

  13. Fermi surface of underdoped high-Tc superconducting cuprates

    International Nuclear Information System (INIS)

    Dai, X.; Su, Z.; Yu, L.

    1997-01-01

    The coexistence of a π-flux state and a d-wave resonant-valance-bond (RVB) state is considered in this paper within the slave-boson approach. A critical value of doping concentration δ c is found, below which the coexisting π-flux and d-wave RVB state is favored in energy. The pseudo-Fermi surface of spinons and the physical electron spectral function are calculated. A clear Fermi-level crossing is found along the (0,0) to (π, π) direction, but no such crossing is detected along the (π, 0) to (π, π) direction. Also, an energy gap of d-wave symmetry appears at the Fermi level in our calculation. The above results are in agreement with the angle-resolved photoemission experiments which indicate at a d-wave pseudogap and a half-pocket-like Fermi surface in underdoped cuprates. copyright 1997 The American Physical Society

  14. Effective field theories for superconducting systems with multiple Fermi surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Braga, P.R., E-mail: pedro.rangel.braga@gmail.com [Departamento de Física Teórica, Instituto de Física, UERJ - Universidade do Estado do Rio de Janeiro, Rua São Francisco Xavier 524, 20550-013 Maracanã, Rio de Janeiro (Brazil); Granado, D.R., E-mail: diegorochagrana@uerj.br [Departamento de Física Teórica, Instituto de Física, UERJ - Universidade do Estado do Rio de Janeiro, Rua São Francisco Xavier 524, 20550-013 Maracanã, Rio de Janeiro (Brazil); Department of Physics and Astronomy, Ghent University, Krijgslaan 281-S9, 9000 Gent (Belgium); Guimaraes, M.S., E-mail: msguimaraes@uerj.br [Departamento de Física Teórica, Instituto de Física, UERJ - Universidade do Estado do Rio de Janeiro, Rua São Francisco Xavier 524, 20550-013 Maracanã, Rio de Janeiro (Brazil); Wotzasek, C., E-mail: clovis@if.ufrj.br [Instituto de Física, Universidade Federal do Rio de Janeiro, 21941-972, Rio de Janeiro (Brazil)

    2016-11-15

    In this work we investigate the description of superconducting systems with multiple Fermi surfaces. For the case of one Fermi surface we re-obtain the result that the superconductor is more precisely described as a topological state of matter. Studying the case of more than one Fermi surface, we obtain the effective theory describing a time reversal symmetric topological superconductor. These results are obtained by employing a general procedure to construct effective low energy actions describing states of electromagnetic systems interacting with charges and defects. The procedure consists in taking into account the proliferation or dilution of these charges and defects and its consequences for the low energy description of the electromagnetic response of the system. We find that the main ingredient entering the low energy characterization of the system with more than one Fermi surface is a non-conservation of the canonical supercurrent triggered by particular vortex configurations.

  15. Angular correlations near the Fermi energy

    International Nuclear Information System (INIS)

    Fox, D.; Cebra, D.A.; Karn, J.

    1988-01-01

    Angular correlations between light particles have been studied to probe the extent to which a thermally equilibrated system is formed in heavy ion collisions near the Fermi energy. Single-light-particle inclusive energy spectra and two-particle large-angle correlations were measured for 40 and 50 MeV/nucleon C+C, Ag, and Au. The single-particle inclusive energy spectra are well fit by a three moving source parametrization. Two-particle large-angle correlations are shown to be consistent with emission from a thermally equilibrated source when the effects of momentum conservation are considered. Single-particle inclusive spectra and light-particle correlations at small relative momentum were measured for 35 MeV/nucleon N+Ag. Source radii were extracted from the two-particle correlation functions and were found to be consistent with previous measurements using two-particle correlations and the coalescence model. The temperature of the emitting source was extracted from the relative populations of states using the quantum statistical model and was found to be 4.8/sub -2.4//sup +2.8/ MeV, compared to the 14 MeV temperature extracted from the slopes of the kinetic energy spectra

  16. Three years of Transients with Fermi GBM

    Science.gov (United States)

    Wilson-Hodge, Colleen A.

    2012-01-01

    The Gamma-ray Burst Monitor (GBM) is an all-sky monitoring instrument, sensitive between 8 keV and 40 MeV, with a primary objective of supporting the Large Area Telescope (LAT) in observations of Gamma-Ray Bursts (GRBs). Both instruments are part of the Fermi Gamma-ray Space Telescope. Together, the GBM and LAT instruments have provided ground-breaking measurements of GRBs that have, after 10 years of focus on GRB afterglows, inspired renewed interest in the prompt emission phase of GRBs and the physical mechanisms that fuel them. In addition to GRB science, GBM has made significant contributions to the astrophysics of galactic transient sources including long-term variations in the Crab nebula, spin state transitions in accretion powered pulsars, state transitions in black hole X-ray binaries, and unprecedented time-resolved spectral studies of soft gamma-ray repeater bursts. Closer to home, GBM also contributes to solar flare and terrestrial gamma flash science.

  17. The nuclear Thomas-Fermi model

    International Nuclear Information System (INIS)

    Myers, W.D.; Swiatecki, W.J.

    1994-08-01

    The statistical Thomas-Fermi model is applied to a comprehensive survey of macroscopic nuclear properties. The model uses a Seyler-Blanchard effective nucleon-nucleon interaction, generalized by the addition of one momentum-dependent and one density-dependent term. The adjustable parameters of the interaction were fitted to shell-corrected masses of 1654 nuclei, to the diffuseness of the nuclear surface and to the measured depths of the optical model potential. With these parameters nuclear sizes are well reproduced, and only relatively minor deviations between measured and calculated fission barriers of 36 nuclei are found. The model determines the principal bulk and surface properties of nuclear matter and provides estimates for the more subtle, Droplet Model, properties. The predicted energy vs density relation for neutron matter is in striking correspondence with the 1981 theoretical estimate of Friedman and Pandharipande. Other extreme situations to which the model is applied are a study of Sn isotopes from 82 Sn to 170 Sn, and the rupture into a bubble configuration of a nucleus (constrained to spherical symmetry) which takes place when Z 2 /A exceeds about 100

  18. Dynamical Friedel oscillations of a Fermi sea

    Science.gov (United States)

    Zhang, J. M.; Liu, Y.

    2018-02-01

    We study the scenario of quenching an interaction-free Fermi sea on a one-dimensional lattice ring by suddenly changing the potential of a site. From the point-of-view of the conventional Friedel oscillation, which is a static or equilibrium problem, it is of interest what temporal and spatial oscillations the local sudden quench will induce. Numerically, the primary observation is that for a generic site, the local particle density switches between two plateaus periodically in time. Making use of the proximity of the realistic model to an exactly solvable model and employing the Abel regularization to assign a definite value to a divergent series, we obtain an analytical formula for the heights of the plateaus, which turns out to be very accurate for sites not too close to the quench site. The unexpect relevance and the incredible accuracy of the Abel regularization are yet to be understood. Eventually, when the contribution of the defect mode is also taken into account, the plateaus for those sites close to or on the quench site can also be accurately predicted. We have also studied the infinite lattice case. In this case, ensuing the quench, the out-going wave fronts leave behind a stable density oscillation pattern. Because of some interesting single-particle property, this dynamically generated Friedel oscillation differs from its conventional static counterpart only by the defect mode.

  19. Fermi surface study of CeSb

    International Nuclear Information System (INIS)

    Aoki, H.; Crabtree, G.W.; Joss, W.; Hulliger, F.

    1984-09-01

    A Fermi surface study of the ferromagnetic phase of CeSb is presented. The γ frequency branches arising from the electron surfaces at the X points, three separate frequency branches from the hole surfaces at the GAMMA point and the low frequency branch α have been observed. The effective mass ratios are low and range from approx. 0.2 for the α branch to approx. 1.0 for the high frequency branch of γ. The low effective mass ratios suggest that the admixture of the conduction states with the f state is small. We have observed a drastic change in the appearance of the dHvA signal at the phase transition between the ferromagnetic and lower field antiferromagnetic phases: The low frequency α oscillation suddenly disappears as the crystal enters the antiferromagnetic phase. By utilizing the change in the signal appearance, the transition field strength has been measured as a function of the field direction. The present experimental results, particularly the origin of the α oscillation, are discussed in the light of the p-f mixing theory and recent band structure calculations based on localized f orbitals

  20. Fermi surface study of CeSb

    International Nuclear Information System (INIS)

    Aoki, H.; Crabtree, G.; Joss, W.; Hulliger, F.

    1985-01-01

    A Fermi surface study of the ferromagnetic phase of CeSb is presented. The γ frequency branches arising from the electron surfaces at the X points, three separate frequency branches from the hole surfaces at the GAMMA point, and the low-frequency branch α have been observed. The effective mass ratios are low and range from approx.0.2 for the α branch to approx.1.0 for the high-frequency branch of γ. The low effective mass ratios suggest that the admixture of the conduction states with the f state is small. We have observed a drastic change in the appearance of the de Haas--van Alpen signal at the phase transition between the ferromagnetic and lower field antiferromagnetic phases: the low-frequency α oscillation suddenly disappears as the crystal enters the antiferromagnetic phase. By utilizing the change in the signal appearance, the transition field strength has been measured as a function of the field direction. The present experimental results particularly the origin of the α oscillation, are discussed in the light of the p-f mixing theory and recent band-structure calculations based on localized f orbitals

  1. Fermi surface mapping: Techniques and visualization

    International Nuclear Information System (INIS)

    Rotenberg, E.; Denlinger, J.D.; Kevan, S.D.

    1997-01-01

    Angle-resolved photoemission (ARP) of valence bands is a mature technique that has achieved spectacular success in band-mapping metals, semiconductors, and insulators. The purpose of the present study was the development of experimental and analytical techniques in ARP which take advantage of third generation light sources. Here the authors studied the relatively simple Cu surface in preparation for other metals. Copper and related metals themselves are of current interest, especially due to its role as an interlayer in spin valves and other magnetic heterostructures. A major goal of this study was the development of a systematic technique to quickly (i.e. in a few hours of synchrotron beamtime) measure the FS and separate it into bulk and surface FS's. Often, one needs to avoid bulk features altogether, which one can achieve by carefully mapping their locations in k-space. The authors will also show how they systematically map Fermi surfaces throughout large volumes of k-space, and, by processing the resulting volume data sets, provide intuitive pictures of FS's, both bulk and surface

  2. Dark matter at the Fermi scale

    International Nuclear Information System (INIS)

    Feng, Jonathan L

    2006-01-01

    Recent breakthroughs in cosmology reveal that a quarter of the Universe is composed of dark matter, but the microscopic identity of dark matter remains a deep mystery. I review recent progress in resolving this puzzle, focusing on two well-motivated classes of dark matter candidates: weakly interacting massive particles (WIMPs) and superWIMPs. These possibilities have similar motivations: they exist in the same well-motivated particle physics models, the observed dark matter relic density emerges naturally and dark matter particles have mass around 100 GeV, the energy scale identified as interesting over 70 years ago by Fermi. At the same time, they have widely varying implications for direct and indirect dark matter searches, particle colliders, Big Bang nucleosynthesis, the cosmic microwave background, and halo profiles and structure formation. If WIMPs or superWIMPs are a significant component of dark matter, we will soon be entering a golden era in which dark matter will be studied through diverse probes at the interface of particle physics, astroparticle physics and cosmology. I outline a programme of dark matter studies for each of these scenarios and discuss the prospects for identifying dark matter in the coming years. (topical review)

  3. The Nuclear Thomas-Fermi Model

    Science.gov (United States)

    Myers, W. D.; Swiatecki, W. J.

    1994-08-01

    The statistical Thomas-Fermi model is applied to a comprehensive survey of macroscopic nuclear properties. The model uses a Seyler-Blanchard effective nucleon-nucleon interaction, generalized by the addition of one momentum-dependent and one density-dependent term. The adjustable parameters of the interaction were fitted to shell-corrected masses of 1654 nuclei, to the diffuseness of the nuclear surface and to the measured depths of the optical model potential. With these parameters nuclear sizes are well reproduced, and only relatively minor deviations between measured and calculated fission barriers of 36 nuclei are found. The model determines the principal bulk and surface properties of nuclear matter and provides estimates for the more subtle, Droplet Model, properties. The predicted energy vs density relation for neutron matter is in striking correspondence with the 1981 theoretical estimate of Friedman and Pandharipande. Other extreme situations to which the model is applied are a study of Sn isotopes from {sup 82}Sn to {sup 170}Sn, and the rupture into a bubble configuration of a nucleus (constrained to spherical symmetry) which takes place when Z{sup 2}/A exceeds about 100.

  4. Theory of two-dimensional fermi liquids: Pt. 3

    International Nuclear Information System (INIS)

    Cui Shimin; Cai Jianhua

    1990-01-01

    The transport properties and sound propagation of 2-D Fermi liquids are discussed. Microscopic expressions for the coefficients of diffusion, viscosity and thermal conductivity are derived using Resibois method. Velocities of the zeroth and first sounds are calculated. Based on an analysis of collision integral, it is shown that a series of relaxtion time parameters is necessary to define precisely the sound propagation properties in 2-D Fermi liquids in contrast to the 3-D case

  5. Coulomb sum rules in the relativistic Fermi gas model

    International Nuclear Information System (INIS)

    Do Dang, G.; L'Huillier, M.; Nguyen Giai, Van.

    1986-11-01

    Coulomb sum rules are studied in the framework of the Fermi gas model. A distinction is made between mathematical and observable sum rules. Differences between non-relativistic and relativistic Fermi gas predictions are stressed. A method to deduce a Coulomb response function from the longitudinal response is proposed and tested numerically. This method is applied to the 40 Ca data to obtain the experimental Coulomb sum rule as a function of momentum transfer

  6. Fermi liquid description of relativistic high density matter

    International Nuclear Information System (INIS)

    Pal, K.; Dutt-Mazumder, A.K.

    2011-01-01

    We calculate pionic contribution to the relativistic Fermi Liquid parameters (RFLPs) using Chiral Effective Lagrangian. The RFLPs so determined are then used to calculate chemical potential, exchange energy due to πN interaction. We also compare the results of exchange energy from two loop ring diagrams involving σ, ω and π meson with what one obtains from the relativistic Fermi Liquid theory (RFLT). (author)

  7. Fermi arc mediated entropy transport in topological semimetals

    Science.gov (United States)

    McCormick, Timothy M.; Watzman, Sarah J.; Heremans, Joseph P.; Trivedi, Nandini

    2018-05-01

    The low-energy excitations of topological Weyl semimetals are composed of linearly dispersing Weyl fermions that act as monopoles of Berry curvature in the bulk momentum space. Furthermore, on the surface there exist topologically protected Fermi arcs at the projections of these Weyl points. We propose a pathway for entropy transport involving Fermi arcs on one surface connecting to Fermi arcs on the other surface via the bulk Weyl monopoles. We present results for the temperature and magnetic field dependence of the magnetothermal conductance of this conveyor belt channel. The circulating currents result in a net entropy transport without any net charge transport. We provide results for the Fermi arc mediated magnetothermal conductivity in the low-field semiclassical limit as well as in the high-field ultraquantum limit, where only chiral Landau levels are involved. Our work provides a proposed signature of Fermi arc mediated magnetothermal transport and sets the stage for utilizing and manipulating the topological Fermi arcs in thermal applications.

  8. Relativistic finite-temperature Thomas-Fermi model

    Science.gov (United States)

    Faussurier, Gérald

    2017-11-01

    We investigate the relativistic finite-temperature Thomas-Fermi model, which has been proposed recently in an astrophysical context. Assuming a constant distribution of protons inside the nucleus of finite size avoids severe divergence of the electron density with respect to a point-like nucleus. A formula for the nuclear radius is chosen to treat any element. The relativistic finite-temperature Thomas-Fermi model matches the two asymptotic regimes, i.e., the non-relativistic and the ultra-relativistic finite-temperature Thomas-Fermi models. The equation of state is considered in detail. For each version of the finite-temperature Thomas-Fermi model, the pressure, the kinetic energy, and the entropy are calculated. The internal energy and free energy are also considered. The thermodynamic consistency of the three models is considered by working from the free energy. The virial question is also studied in the three cases as well as the relationship with the density functional theory. The relativistic finite-temperature Thomas-Fermi model is far more involved than the non-relativistic and ultra-relativistic finite-temperature Thomas-Fermi models that are very close to each other from a mathematical point of view.

  9. On the origin of gamma rays in Fermi blazars: beyond the broad line region.

    Science.gov (United States)

    Costamante, L.; Cutini, S.; Tosti, G.; Antolini, E.; Tramacere, A.

    2018-05-01

    The gamma-ray emission in broad-line blazars is generally explained as inverse Compton (IC) radiation of relativistic electrons in the jet scattering optical-UV photons from the Broad Line Region (BLR), the so-called BLR External Compton scenario. We test this scenario on the Fermi gamma-ray spectra of 106 broad-line blazars detected with the highest significance or largest BLR, by looking for cut-off signatures at high energies compatible with γ-γ interactions with BLR photons. We do not find evidence for the expected BLR absorption. For 2/3 of the sources, we can exclude any significant absorption (τmax 5). We conclude that for 9 out of 10 objects, the jet does not interact with BLR photons. Gamma-rays seem either produced outside the BLR most of the time, or the BLR is ˜100 × larger than given by reverberation mapping. This means that i) External Compton on BLR photons is disfavoured as the main gamma-ray mechanism, vs IC on IR photons from the torus or synchrotron self-Compton; ii) the Fermi gamma-ray spectrum is mostly intrinsic, determined by the interaction of the particle distribution with the seed-photons spectrum; iii) without suppression by the BLR, broad-line blazars can become copious emitters above 100 GeV, as demonstrated by 3C 454.3. We expect the CTA sky to be much richer of broad-line blazars than previously thought.

  10. Accelerator operations

    International Nuclear Information System (INIS)

    Anon.

    1980-01-01

    This section is concerned with the operation of both the tandem-linac system and the Dynamitron, two accelerators that are used for entirely different research. Developmental activities associated with the tandem and the Dynamitron are also treated here, but developmental activities associated with the superconducting linac are covered separately because this work is a program of technology development in its own right

  11. CNSTN Accelerator

    International Nuclear Information System (INIS)

    Habbassi, Afifa; Trabelsi, Adel

    2010-01-01

    This project give a big idea about the measurement of the linear accelerator in the CNSTN. During this work we control dose distribution for different product. For this characterisation we have to make an installation qualification ,operational qualification,performance qualification and of course for every step we have to control temperature and the dose ,even the distribution of the last one.

  12. Accelerators course

    CERN Multimedia

    CERN. Geneva HR-RFA; Métral, E

    2006-01-01

    1a) Introduction and motivation 1b) History and accelerator types 2) Transverse beam dynamics 3a) Longitudinal beam dynamics 3b) Figure of merit of a synchrotron/collider 3c) Beam control 4) Main limiting factors 5) Technical challenges

  13. Accelerator operations

    International Nuclear Information System (INIS)

    Anon.

    1979-01-01

    Operations of the SuperHILAC, the Bevatron/Bevalac, and the 184-inch Synchrocyclotron during the period from October 1977 to September 1978 are discussed. These include ion source development, accelerator facilities, the Heavy Ion Spectrometer System, and Bevelac biomedical operations

  14. Accelerator update

    International Nuclear Information System (INIS)

    Anon.

    1995-01-01

    When the Accelerator Conference, combined International High Energy and US Particle versions, held in Dallas in May, was initially scheduled, progress nearby for the US Superconducting Supercollider was high on the preliminary agenda. With the SSC voted down by Congress in October 1993, this was no longer the case. However the content of the meeting, in terms of both its deep implications for ambitious new projects and the breadth of its scope, showed that the worldwide particle accelerator field is far from being moribund. A traditional feature of such accelerator conferences is the multiplicity of parallel sessions. No one person can attend all sessions, so that delegates can follow completely different paths and emerge with totally different impressions. Despite this overload, and despite the SSC cancellation, the general picture is one of encouraging progress over a wide range of major new projects throughout the world. At the same time, spinoff from, and applications of, accelerators and accelerator technology are becoming increasingly important. Centrestage is now CERN's LHC proton-proton collider, where a test string of superconducting magnets is operating over long periods at the nominal LHC field of 8.36 tesla or more. The assignment of the underground areas in the existing 27- kilometre LEP tunnel is now quasidefinitive (see page 3). For CERN's existing big machine, the LEP electron-positron collider, ongoing work concentrates on boosting performance using improved optics and bunch trains. But the main objective is the LEP2 scheme using superconducting accelerating cavities to boost the beam energy (see page 6). After some initial teething problems, production and operation of these cavities appears to have been mastered, at least under test conditions. A highlight at CERN last year was the first run with lead ions (December 1994, page 15). Handling these heavy particles with systems originally designed for protons calls for ingenuity. The SPS

  15. Accelerator update

    Energy Technology Data Exchange (ETDEWEB)

    Anon.

    1995-09-15

    When the Accelerator Conference, combined International High Energy and US Particle versions, held in Dallas in May, was initially scheduled, progress nearby for the US Superconducting Supercollider was high on the preliminary agenda. With the SSC voted down by Congress in October 1993, this was no longer the case. However the content of the meeting, in terms of both its deep implications for ambitious new projects and the breadth of its scope, showed that the worldwide particle accelerator field is far from being moribund. A traditional feature of such accelerator conferences is the multiplicity of parallel sessions. No one person can attend all sessions, so that delegates can follow completely different paths and emerge with totally different impressions. Despite this overload, and despite the SSC cancellation, the general picture is one of encouraging progress over a wide range of major new projects throughout the world. At the same time, spinoff from, and applications of, accelerators and accelerator technology are becoming increasingly important. Centrestage is now CERN's LHC proton-proton collider, where a test string of superconducting magnets is operating over long periods at the nominal LHC field of 8.36 tesla or more. The assignment of the underground areas in the existing 27- kilometre LEP tunnel is now quasidefinitive (see page 3). For CERN's existing big machine, the LEP electron-positron collider, ongoing work concentrates on boosting performance using improved optics and bunch trains. But the main objective is the LEP2 scheme using superconducting accelerating cavities to boost the beam energy (see page 6). After some initial teething problems, production and operation of these cavities appears to have been mastered, at least under test conditions. A highlight at CERN last year was the first run with lead ions (December 1994, page 15). Handling these heavy particles with systems originally designed for protons calls for ingenuity. The SPS has managed

  16. FERMI LAT DISCOVERY OF EXTENDED GAMMA-RAY EMISSIONS IN THE VICINITY OF THE HB 3 SUPERNOVA REMNANT

    Energy Technology Data Exchange (ETDEWEB)

    Katagiri, H.; Yoshida, K. [College of Science, Ibaraki University, 2-1-1, Bunkyo, Mito 310-8512 (Japan); Ballet, J. [Laboratoire AIM, CEA-IRFU/CNRS/Université Paris Diderot, Service d’Astrophysique, CEA Saclay, F-91191 Gif sur Yvette (France); Grondin, M.-H.; Lemoine-Goumard, M. [Centre d’Études Nucléaires de Bordeaux Gradignan, IN2P3/CNRS, Université Bordeaux 1, BP120, F-33175 Gradignan Cedex (France); Hanabata, Y. [Institute for Cosmic-Ray Research, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba, 277-8582 (Japan); Hewitt, J. W. [Department of Physics and Center for Space Sciences and Technology, University of Maryland Baltimore County, Baltimore, MD 21250 (United States); Kubo, H., E-mail: hideaki.katagiri.sci@vc.ibaraki.ac.jp, E-mail: 13nm169s@gmail.com [Department of Physics, Graduate School of Science, Kyoto University, Kyoto (Japan)

    2016-02-20

    We report the discovery of extended gamma-ray emission measured by the Large Area Telescope (LAT) onboard the Fermi Gamma-ray Space Telescope in the region of the supernova remnant (SNR) HB 3 (G132.7+1.3) and the W3 II complex adjacent to the southeast of the remnant. W3 is spatially associated with bright {sup 12}CO (J = 1–0) emission. The gamma-ray emission is spatially correlated with this gas and the SNR. We discuss the possibility that gamma rays originate in interactions between particles accelerated in the SNR and interstellar gas or radiation fields. The decay of neutral pions produced in nucleon–nucleon interactions between accelerated hadrons and interstellar gas provides a reasonable explanation for the gamma-ray emission. The emission from W3 is consistent with irradiation of the CO clouds by the cosmic rays accelerated in HB 3.

  17. First detections of nebula with the Fermi-Large Area Telescope and study of their pulsars

    International Nuclear Information System (INIS)

    Grondin, M.H.

    2010-07-01

    The Fermi Gamma-ray Space Telescope was launched on 2008 June 11, carrying the Large Area Telescope (LAT), sensitive to gamma-rays in the 20 MeV - 300 GeV energy range. The Crab Nebula had been detected and studied in the 70 MeV - 30 GeV band using the CGRO-EGRET experiment, but no pulsar wind nebula (PWN) had ever been firmly identified in the high energy gamma-ray domain. PWNe are powered by the constant injection of a relativistic wind of electrons and positrons from their central pulsars. These charged particles are accelerated at the shock front forming the PWN and emit photons which can be observed along the entire electromagnetic spectrum, including the high energy gamma-ray domain. Data provided by the Fermi-LAT during the first two years of the mission have allowed the detection and the identification of three PWNe and their associated pulsars (Crab Nebula, Vela X and MSH 15-52) as well as the PWN HESS J1825-137 discovered by ground-based experiments sensitive to very high energy gamma-rays. Results of temporal, spectral and morphological analyses of the pulsar/PWN systems detected by Fermi- LAT, as well as results of systematic studies performed first around every gamma-ray pulsar detected by the LAT and secondly around every very high energy source identified as a PWN or a PWN candidate are presented in this dissertation. These studies bring new insights and constraints on the physical properties of the sources as well as on emitting processes in pulsar magnetospheres and in PWNe. (author)

  18. Dexamethasone suppression test

    Science.gov (United States)

    DST; ACTH suppression test; Cortisol suppression test ... During this test, you will receive dexamethasone. This is a strong man-made (synthetic) glucocorticoid medicine. Afterward, your blood is drawn ...

  19. Peltier heat measurements at a junction between materials exhibiting Fermi gas and Fermi liquid behaviour

    International Nuclear Information System (INIS)

    Kuznetsov, V L; Kuznetsova, L A; Rowe, D M

    2003-01-01

    The feasibility of improving the conversion efficiency of a thermoelectric converter by employing interfaces between materials exhibiting Fermi gas (FG) and Fermi liquid (FL) behaviour has been studied. Thermocouples consisting of a semiconductor and a strongly correlated material have been fabricated and the Peltier heat measured over the temperature range 15 deg 330 K. A number of materials possessing different types of strong electron correlation have been synthesized including the heavy fermion compound YbAl 3 , manganite La 0.7 Ca 0.3 MnO 3 and high-T c superconductor YBa 2 Cu 3 O 7δ . n- and p-Bi 2 Te 3 -based solid solutions as well as n-Bi 0.85 Sb 0.15 solid solution have also been synthesized and used as materials exhibiting FG properties. Experimental measurements of the Peltier heat were compared to the results of calculations based on preliminary measured thermoelectric properties of materials and electrical contact resistance at the interfaces. The potential of employing FG/FL interfaces in thermoelectric energy conversion is discussed

  20. Local antiferromagnetic exchange and collaborative Fermi surface as key ingredients of high temperature superconductors

    Science.gov (United States)

    Hu, Jiangping; Ding, Hong

    2012-01-01

    Cuprates, ferropnictides and ferrochalcogenides are three classes of unconventional high temperature superconductors, who share similar phase diagrams in which superconductivity develops after a magnetic order is suppressed, suggesting a strong interplay between superconductivity and magnetism, although the exact picture of this interplay remains elusive. Here we show that there is a direct bridge connecting antiferromagnetic exchange interactions determined in the parent compounds of these materials to the superconducting gap functions observed in the corresponding superconducting materials: in all high temperature superconductors, the Fermi surface topology matches the form factor of the pairing symmetry favored by local magnetic exchange interactions. We suggest that this match offers a principle guide to search for new high temperature superconductors. PMID:22536479

  1. Nonequilibrium Spin Dynamics in a Trapped Fermi Gas with Effective Spin-Orbit Interactions

    International Nuclear Information System (INIS)

    Stanescu, Tudor D.; Zhang Chuanwei; Galitski, Victor

    2007-01-01

    We consider a trapped atomic system in the presence of spatially varying laser fields. The laser-atom interaction generates a pseudospin degree of freedom (referred to simply as spin) and leads to an effective spin-orbit coupling for the fermions in the trap. Reflections of the fermions from the trap boundaries provide a physical mechanism for effective momentum relaxation and nontrivial spin dynamics due to the emergent spin-orbit coupling. We explicitly consider evolution of an initially spin-polarized Fermi gas in a two-dimensional harmonic trap and derive nonequilibrium behavior of the spin polarization. It shows periodic echoes with a frequency equal to the harmonic trapping frequency. Perturbations, such as an asymmetry of the trap, lead to the suppression of the spin echo amplitudes. We discuss a possible experimental setup to observe spin dynamics and provide numerical estimates of relevant parameters

  2. Deconstructing continuous flash suppression

    OpenAIRE

    Yang, Eunice; Blake, Randolph

    2012-01-01

    In this paper, we asked to what extent the depth of interocular suppression engendered by continuous flash suppression (CFS) varies depending on spatiotemporal properties of the suppressed stimulus and CFS suppressor. An answer to this question could have implications for interpreting the results in which CFS influences the processing of different categories of stimuli to different extents. In a series of experiments, we measured the selectivity and depth of suppression (i.e., elevation in co...

  3. Statistical properties of Fermi GBM GRBs' spectra

    Science.gov (United States)

    Rácz, István I.; Balázs, Lajos G.; Horvath, Istvan; Tóth, L. Viktor; Bagoly, Zsolt

    2018-03-01

    Statistical studies of gamma-ray burst (GRB) spectra may result in important information on the physics of GRBs. The Fermi GBM catalogue contains GRB parameters (peak energy, spectral indices, and intensity) estimated fitting the gamma-ray spectral energy distribution of the total emission (fluence, flnc), and during the time of the peak flux (pflx). Using contingency tables, we studied the relationship of the models best-fitting pflx and flnc time intervals. Our analysis revealed an ordering of the spectra into a power law - Comptonized - smoothly broken power law - Band series. This result was further supported by a correspondence analysis of the pflx and flnc spectra categorical variables. We performed a linear discriminant analysis (LDA) to find a relationship between categorical (spectral) and model independent physical data. LDA resulted in highly significant physical differences among the spectral types, that is more pronounced in the case of the pflx spectra, than for the flnc spectra. We interpreted this difference as caused by the temporal variation of the spectrum during the outburst. This spectral variability is confirmed by the differences in the low-energy spectral index and peak energy, between the pflx and flnc spectra. We found that the synchrotron radiation is significant in GBM spectra. The mean low-energy spectral index is close to the canonical value of α = -2/3 during the peak flux. However, α is ˜ -0.9 for the spectra of the fluences. We interpret this difference as showing that the effect of cooling is important only for the fluence spectra.

  4. No indications of axionlike particles from Fermi

    International Nuclear Information System (INIS)

    Belikov, Alexander V.; Goodenough, Lisa; Hooper, Dan

    2011-01-01

    As very high energy (> or approx. 100 GeV) gamma rays travel over cosmological distances, their flux is attenuated through interactions with the extragalactic background light. Observations of distant gamma ray sources at energies between ∼200 GeV and a few TeV by ground-based gamma-ray telescopes such as HESS, however, have motivated the possibility that the universe is more transparent to very high energy photons than had been anticipated. One proposed explanation for this is the existence of axionlike particles (ALPs) which gamma rays can efficiently oscillate into, enabling them to travel cosmological distances without attenuation. In this article, we use a state-of-the-art model for the extragalactic background light (which is somewhat lower at ∼μm wavelengths than in previous models) and data from the Fermi Gamma Ray Space Telescope to calculate the spectra at 1-100 GeV of two gamma-ray sources, 1ES1101-232 at redshift z=0.186 and H2356-309 at z=0.165, in conjunction with the measurements of ground-based telescopes, to test the ALP hypothesis. We find that these observations can be well fit by an intrinsic power-law source spectrum with indices of -1.72 and -2.1 for 1ES1101-232 and H2356-309, respectively, and that no ALPs or other exotic physics is necessary to explain the observed degree of attenuation. While this does not exclude the possibility that ALPs are involved in the cosmological propagation of gamma rays, it does reduce the motivation for such new physics.

  5. Accelerating Value Creation with Accelerators

    DEFF Research Database (Denmark)

    Jonsson, Eythor Ivar

    2015-01-01

    and developing the best business ideas and support the due diligence process. Even universities are noticing that the learning experience of the action learning approach is an effective way to develop capabilities and change cultures. Accelerators related to what has historically been associated...

  6. Stochastic Fermi Energization of Coronal Plasma during Explosive Magnetic Energy Release

    Science.gov (United States)

    Pisokas, Theophilos; Vlahos, Loukas; Isliker, Heinz; Tsiolis, Vassilis; Anastasiadis, Anastasios

    2017-02-01

    The aim of this study is to analyze the interaction of charged particles (ions and electrons) with randomly formed particle scatterers (e.g., large-scale local “magnetic fluctuations” or “coherent magnetic irregularities”) using the setup proposed initially by Fermi. These scatterers are formed by the explosive magnetic energy release and propagate with the Alfvén speed along the irregular magnetic fields. They are large-scale local fluctuations (δB/B ≈ 1) randomly distributed inside the unstable magnetic topology and will here be called Alfvénic Scatterers (AS). We constructed a 3D grid on which a small fraction of randomly chosen grid points are acting as AS. In particular, we study how a large number of test particles evolves inside a collection of AS, analyzing the evolution of their energy distribution and their escape-time distribution. We use a well-established method to estimate the transport coefficients directly from the trajectories of the particles. Using the estimated transport coefficients and solving the Fokker-Planck equation numerically, we can recover the energy distribution of the particles. We have shown that the stochastic Fermi energization of mildly relativistic and relativistic plasma can heat and accelerate the tail of the ambient particle distribution as predicted by Parker & Tidman and Ramaty. The temperature of the hot plasma and the tail of the energetic particles depend on the mean free path (λsc) of the particles between the scatterers inside the energization volume.

  7. Stochastic Fermi Energization of Coronal Plasma during Explosive Magnetic Energy Release

    Energy Technology Data Exchange (ETDEWEB)

    Pisokas, Theophilos; Vlahos, Loukas; Isliker, Heinz; Tsiolis, Vassilis [Department of Physics, Aristotle University of Thessaloniki GR-52124 Thessaloniki (Greece); Anastasiadis, Anastasios [Institute for Astronomy, Astrophysics, Space Applications and Remote Sensing, National Observatory of Athens GR-15236 Penteli (Greece)

    2017-02-01

    The aim of this study is to analyze the interaction of charged particles (ions and electrons) with randomly formed particle scatterers (e.g., large-scale local “magnetic fluctuations” or “coherent magnetic irregularities”) using the setup proposed initially by Fermi. These scatterers are formed by the explosive magnetic energy release and propagate with the Alfvén speed along the irregular magnetic fields. They are large-scale local fluctuations ( δB / B ≈ 1) randomly distributed inside the unstable magnetic topology and will here be called Alfvénic Scatterers (AS). We constructed a 3D grid on which a small fraction of randomly chosen grid points are acting as AS. In particular, we study how a large number of test particles evolves inside a collection of AS, analyzing the evolution of their energy distribution and their escape-time distribution. We use a well-established method to estimate the transport coefficients directly from the trajectories of the particles. Using the estimated transport coefficients and solving the Fokker–Planck equation numerically, we can recover the energy distribution of the particles. We have shown that the stochastic Fermi energization of mildly relativistic and relativistic plasma can heat and accelerate the tail of the ambient particle distribution as predicted by Parker and Tidman and Ramaty. The temperature of the hot plasma and the tail of the energetic particles depend on the mean free path ( λ {sub sc}) of the particles between the scatterers inside the energization volume.

  8. On the intrinsic shape of the gamma-ray spectrum for Fermi blazars

    Science.gov (United States)

    Kang, Shi-Ju; Wu, Qingwen; Zheng, Yong-Gang; Yin, Yue; Song, Jia-Li; Zou, Hang; Feng, Jian-Chao; Dong, Ai-Jun; Wu, Zhong-Zu; Zhang, Zhi-Bin; Wu, Lin-Hui

    2018-05-01

    The curvature of the γ-ray spectrumin blazarsmay reflect the intrinsic distribution of emitting electrons, which will further give some information on the possible acceleration and cooling processes in the emitting region. The γ-ray spectra of Fermi blazars are normally fitted either by a single power-law (PL) or a log-normal (call Logarithmic Parabola, LP) form. The possible reason for this difference is not clear. We statistically explore this issue based on the different observational properties of 1419 Fermi blazars in the 3LAC Clean Sample.We find that the γ-ray flux (100MeV–100GeV) and variability index follow bimodal distributions for PL and LP blazars, where the γ-ray flux and variability index show a positive correlation. However, the distributions of γ-ray luminosity and redshift follow a unimodal distribution. Our results suggest that the bimodal distribution of γ-ray fluxes for LP and PL blazars may not be intrinsic and all blazars may have an intrinsically curved γ-ray spectrum, and the PL spectrum is just caused by the fitting effect due to less photons.

  9. Laser acceleration

    Science.gov (United States)

    Tajima, T.; Nakajima, K.; Mourou, G.

    2017-02-01

    The fundamental idea of Laser Wakefield Acceleration (LWFA) is reviewed. An ultrafast intense laser pulse drives coherent wakefield with a relativistic amplitude robustly supported by the plasma. While the large amplitude of wakefields involves collective resonant oscillations of the eigenmode of the entire plasma electrons, the wake phase velocity ˜ c and ultrafastness of the laser pulse introduce the wake stability and rigidity. A large number of worldwide experiments show a rapid progress of this concept realization toward both the high-energy accelerator prospect and broad applications. The strong interest in this has been spurring and stimulating novel laser technologies, including the Chirped Pulse Amplification, the Thin Film Compression, the Coherent Amplification Network, and the Relativistic Mirror Compression. These in turn have created a conglomerate of novel science and technology with LWFA to form a new genre of high field science with many parameters of merit in this field increasing exponentially lately. This science has triggered a number of worldwide research centers and initiatives. Associated physics of ion acceleration, X-ray generation, and astrophysical processes of ultrahigh energy cosmic rays are reviewed. Applications such as X-ray free electron laser, cancer therapy, and radioisotope production etc. are considered. A new avenue of LWFA using nanomaterials is also emerging.

  10. Laser acceleration

    International Nuclear Information System (INIS)

    Tajima, T.; Nakajima, K.; Mourou, G.

    2017-01-01

    The fundamental idea of LaserWakefield Acceleration (LWFA) is reviewed. An ultrafast intense laser pulse drives coherent wakefield with a relativistic amplitude robustly supported by the plasma. While the large amplitude of wake fields involves collective resonant oscillations of the eigenmode of the entire plasma electrons, the wake phase velocity ∼ c and ultra fastness of the laser pulse introduce the wake stability and rigidity. A large number of worldwide experiments show a rapid progress of this concept realization toward both the high-energy accelerator prospect and broad applications. The strong interest in this has been spurring and stimulating novel laser technologies, including the Chirped Pulse Amplification, the Thin Film Compression, the Coherent Amplification Network, and the Relativistic Mirror Compression. These in turn have created a conglomerate of novel science and technology with LWFA to form a new genre of high field science with many parameters of merit in this field increasing exponentially lately. This science has triggered a number of worldwide research centers and initiatives. Associated physics of ion acceleration, X-ray generation, and astrophysical processes of ultrahigh energy cosmic rays are reviewed. Applications such as X-ray free electron laser, cancer therapy, and radioisotope production etc. are considered. A new avenue of LWFA using nano materials is also emerging.

  11. Accelerating networks

    International Nuclear Information System (INIS)

    Smith, David M D; Onnela, Jukka-Pekka; Johnson, Neil F

    2007-01-01

    Evolving out-of-equilibrium networks have been under intense scrutiny recently. In many real-world settings the number of links added per new node is not constant but depends on the time at which the node is introduced in the system. This simple idea gives rise to the concept of accelerating networks, for which we review an existing definition and-after finding it somewhat constrictive-offer a new definition. The new definition provided here views network acceleration as a time dependent property of a given system as opposed to being a property of the specific algorithm applied to grow the network. The definition also covers both unweighted and weighted networks. As time-stamped network data becomes increasingly available, the proposed measures may be easily applied to such empirical datasets. As a simple case study we apply the concepts to study the evolution of three different instances of Wikipedia, namely, those in English, German, and Japanese, and find that the networks undergo different acceleration regimes in their evolution

  12. Particle acceleration in binaries

    Directory of Open Access Journals (Sweden)

    Sinitsyna V.G.

    2017-01-01

    Full Text Available Cygnus X-3 massive binary system is one of the powerful sources of radio and X-ray emission consisting of an accreting compact object, probably a black hole, with a Wolf-Rayet star companion. Based on the detections of ultra high energy gamma-rays by Kiel and Havera Park, Cygnus X-3 has been proposed to be one of the most powerful sources of charged cosmic ray particles in the Galaxy. The results of long-term observations of the Cyg X-3 binary at energies 800 GeV–85 TeV detected by SHALON in 1995 are presented with images, integral spectra and spectral energy distribution. The identification of source with Cygnus X-3 detected by SHALON was secured by the detection of its 4.8 hour orbital period in TeV gamma-rays. During the whole observation period of Cyg X-3 with SHALON significant flux increases were detected at energies above 0.8 TeV. These TeV flux increases are correlated with flaring activity at a lower energy range of X-ray and/or at observations of Fermi LAT as well as with radio emission from the relativistic jets of Cygnus X-3. The variability of very high-energy gamma-radiation and correlation of radiation activity in the wide energy range can provide essential information on particle mechanism production up to very high energies. Whereas, modulation of very high energy emission connected to the orbital motion of the binary system, provides an understanding of the emission processes, nature and location of particle acceleration.

  13. The FERMI @ Elettra Technical Optimization Study: General Layoutand Parameters and Physics Studies of Longitudinal Space Charge, theSpreader, the Injector, and Preliminary FEL Performance

    Energy Technology Data Exchange (ETDEWEB)

    Byrd, John; Corlett, John; Doolittle, Larry; Fawley, William; Lidia, Steven; Penn, Gregory; Ratti, Alex; Staples, John; Wilcox,Russell; Wurtele, Jonathan; Zholents, Alexander

    2005-09-01

    The FERMI {at} Elettra facility will make use of the existing GeV linac at Sincrotrone Elettra, which will become available for dedicated FEL applications following the completion of construction of a new injector booster complex for the storage ring. With a new rf photocathode injector, and some additional accelerating sections, this linac will be capable of providing high brightness bunches at 1.2 GeV and up to 50 Hz repetition rates.

  14. The FERMI (at) Elettra Technical Optimization Study: General Layout and Parameters and Physics Studies of Longitudinal Space Charge, the Spreader, the Injector, and Preliminary FEL Performance

    International Nuclear Information System (INIS)

    Byrd, John; Corlett, John; Doolittle, Larry; Fawley, William; Lidia, Steven; Penn, Gregory; Ratti, Alex; Staples, John; Wilcox, Russell; Wurtele, Jonathan; Zholents, Alexander

    2005-01-01

    The FERMI (at) Elettra facility will make use of the existing GeV linac at Sincrotrone Elettra, which will become available for dedicated FEL applications following the completion of construction of a new injector booster complex for the storage ring. With a new rf photocathode injector, and some additional accelerating sections, this linac will be capable of providing high brightness bunches at 1.2 GeV and up to 50 Hz repetition rates

  15. Particle Acceleration, Magnetic Field Generation and Emission from Relativistic Jets

    Science.gov (United States)

    Nishikawa, K.-I.; Hardee, P.; Hededal, C.; Mizuno, Yosuke; Fishman, G. Jerry; Hartmann, D. H.

    2006-01-01

    Nonthermal radiation observed from astrophysical systems containing relativistic jets and shocks, e.g., active galactic nuclei (AGNs), gamma-ray bursts (GRBs), supernova remnants, and Galactic microquasar systems usually have power-law emission spectra. Fermi acceleration is the mechanism usually assumed for the acceleration of particles in astrophysical environments. Recent PIC simulations using injected relativistic electron-ion (electro-positron) jets show that particle acceleration occurs within the downstream jet, rather than by the scattering of particles back and forth across the shock as in Fermi acceleration. Shock acceleration' is a ubiquitous phenomenon in astrophysical plasmas. Plasma waves and their associated instabilities (e.g., the Buneman instability, other two-streaming instability, and the Weibel instability) created in the shocks are responsible for particle (electron, positron, and ion) acceleration. The simulation results show that the Weibel instability is responsible for generating and amplifying highly nonuniform, small-scale magnetic fields. These magnetic fields contribute to the electron's transverse deflection behind the jet head. The "jitter" radiation from deflected electrons has different spectral properties than synchrotron radiation which is calculated in a uniform magnetic field. This jitter radiation may be important to understanding the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets, and supernova remnants. We will review recent PIC simulations of relativistic jets and try to make a connection with observations.

  16. High-Precision Half-Life Measurements for the Superallowed Fermi β+ Emitters 14O and 18Ne

    Science.gov (United States)

    Laffoley, A. T.; Andreoiu, C.; Austin, R. A. E.; Ball, G. C.; Bender, P. C.; Bidaman, H.; Bildstein, V.; Blank, B.; Bouzomita, H.; Cross, D. S.; Deng, G.; Diaz Varela, A.; Dunlop, M. R.; Dunlop, R.; Finlay, P.; Garnsworthy, A. B.; Garrett, P.; Giovinazzo, J.; Grinyer, G. F.; Grinyer, J.; Hadinia, B.; Jamieson, D. S.; Jigmeddorj, B.; Ketelhut, S.; Kisliuk, D.; Leach, K. G.; Leslie, J. R.; MacLean, A.; Miller, D.; Mills, B.; Moukaddam, M.; Radich, A. J.; Rajabali, M. M.; Rand, E. T.; Svensson, C. E.; Tardiff, E.; Thomas, J. C.; Turko, J.; Voss, P.; Unsworth, C.

    High-precision half-life measurements, at the level of ±0.04%, for the superallowed Fermi emitters 14O and 18Ne have been performed at TRIUMF's Isotope Separator and Accelerator facility. Using 3 independent detector systems, a gas-proportional counter, a fast plastic scintillator, and a high-purity germanium array, a series of direct β and γ counting measurements were performed for each of the isotopes. In the case of 14O, these measurements were made to help resolve an existing discrepancy between detection methods, whereas for 18Ne the half-life precision has been improved in anticipation of forthcoming high-precision branching ratio measurements.

  17. FERMI LARGE AREA TELESCOPE DETECTION OF THE YOUNG SUPERNOVA REMNANT TYCHO

    International Nuclear Information System (INIS)

    Giordano, F.; Naumann-Godo, M.; Ballet, J.; Bechtol, K.; Funk, S.; Lande, J.; Tanaka, T.; Uchiyama, Y.; Mazziotta, M. N.; Rainò, S.; Tibolla, O.

    2012-01-01

    After almost three years of data taking in sky-survey mode, the Fermi Large Area Telescope has detected γ-ray emission toward Tycho's supernova remnant (SNR). The Tycho SNR is among the youngest remnants in the Galaxy, originating from a Type Ia Supernova in AD 1572. The γ-ray integral flux from 400 MeV up to 100 GeV has been measured to be (3.5 ± 1.1 stat ± 0.7 syst )× 10 –9 cm –2 s –1 with a photon index of 2.3 ± 0.2 stat ± 0.1 syst . A simple model consistent with TeV, X-ray, and radio data is sufficient to explain the observed emission as originating from π 0 decays as a result of cosmic-ray acceleration and interaction with the ambient medium.

  18. Heavy-ion peripheral collisions in the Fermi energy domain: fragmentation processes or dissipative collisions

    International Nuclear Information System (INIS)

    Borderie, B.; Rivet, M.F.; Tassan-Got, L.

    1990-01-01

    For several years a new field in nuclear physics has been opened by the opportunity to accelerate heavy ions through an energy domain including the Fermi energy of nucleons. This new domain has to be seen as a link between dissipative processes observed at low energies, dominated by mean field considerations, and high energy collisions for which nucleon-nucleon collisions play an important role. This paper reviews our present knowledge on peripheral collisions. A reminder of contiguous energy domains is done as well as their extension in the new field. Specific calculations are also presented. Finally a wide comparison between experiments and calculations is performed. A fast dissipative stage proves to be responsible for the dominant mechanisms involved, at least when the incident energy is lower than 50 MeV/nucleon

  19. Advanced concepts for acceleration

    International Nuclear Information System (INIS)

    Keefe, D.

    1986-07-01

    Selected examples of advanced accelerator concepts are reviewed. Such plasma accelerators as plasma beat wave accelerator, plasma wake field accelerator, and plasma grating accelerator are discussed particularly as examples of concepts for accelerating relativistic electrons or positrons. Also covered are the pulsed electron-beam, pulsed laser accelerator, inverse Cherenkov accelerator, inverse free-electron laser, switched radial-line accelerators, and two-beam accelerator. Advanced concepts for ion acceleration discussed include the electron ring accelerator, excitation of waves on intense electron beams, and two-wave combinations

  20. Monte Carlo study of neutrino acceleration in supernova shocks

    International Nuclear Information System (INIS)

    Kazanas, Demosthenes; Ellison, D.C.; National Aeronautics and Space Administration, Greenbelt, MD

    1981-01-01

    The first order Fermi acceleration mechanism of cosmic rays in shocks may be at work for neutrinos in supernova shocks when the latter are at densities rho>10 13 g cm -3 at which the core material is opaque to neutrinos. A Monte Carlo approach to study this effect is employed and the emerging neutrino power law spectra are presented. The increased energy acquired by the neutrinos may facilitate their detection in supernova explosions and provide information about the physics of collapse

  1. Effective spectral index properties for Fermi blazars

    Science.gov (United States)

    Yang, JiangHe; Fan, JunHui; Liu, Yi; Zhang, YueLian; Tuo, ManXian; Nie, JianJun; Yuan, YuHai

    2018-05-01

    Blazars are a special subclass of active galactic nuclei with extreme observation properties. This subclass can be divided into two further subclasses of flat spectrum radio quasars (FSRQs) and BL Lacertae objects (BL Lacs) according to their emission line features. To compare the spectral properties of FSRQs and BL Lacs, the 1.4 GHz radio, optical R-band, 1 keV X-ray, and 1 GeV γ-ray flux densities for 1108 Fermi blazars are calculated to discuss the properties of the six effective spectral indices of radio to optical ( α RO), radio to X-ray ( α RX), radio to γ ray ( α Rγ), optical to X-ray ( α OX), optical to γ ray ( α Oγ), and X-ray to γ ray ( α Xγ). The main results are as follows: For the averaged effective spectral indices, \\overline {{α _{OX}}} > \\overline {{α _{Oγ }}} > \\overline {{α _{Xγ }}} > \\overline {{α _{Rγ }}} > \\overline {{α _{RX}}} > \\overline {{α _{RO}}} for samples of whole blazars and BL Lacs; \\overline {{α _{Xγ }}} ≈ \\overline {{α _{Rγ }}} ≈ \\overline {{α _{RX}}} for FSRQs and low-frequency-peaked BL Lacs (LBLs); and \\overline {{α _{OX}}} ≈ \\overline {{α _{Oγ }}} ≈ \\overline {{α _{Xγ }}} for high-synchrotron-frequency-peaked BL Lacs (HBLs). The distributions of the effective spectral indices involving optical emission ( α RO, α OX, and α Oγ) for LBLs are different from those for FSRQs, but if the effective spectral index does not involve optical emission ( α RX, α Rγ, and α Xγ), the distributions for LBLs and FSRQs almost come from the same parent population. X-ray emissions from blazars include both synchrotron and inverse Compton (IC) components; the IC component for FSRQs and LBLs accounts for a larger proportion than that for HBLs; and the radiation mechanism for LBLs is similar to that for FSRQs, but the radiation mechanism for HBLs is different from that for both FSRQs and LBLs in X-ray bands. The tendency of α Rγ decreasing from LBLs to HBLs suggests that the synchrotron self

  2. The Enrico Fermi Atomic Power Plant; La centrais nucleaire Enrico Fermi; Atomnaya ehlektrostantsiya im Ehnriko Fermi.; La central nucleoelectrica Enrico Fermi

    Energy Technology Data Exchange (ETDEWEB)

    Hartwell, R. W. [Power Reactor Development Company, Detroit, MI (United States)

    1963-10-15

    Construction of the Enrico Fermi Atomic Power Plant, which utilizes a 100 MW(e) fast breeder reactor, was essentially completed in December 1961. During the past eighteen-month period, systems and components have been extensively tested. This pre-operational test programme has proved most valuable in verifying the design and in indicating needed modifications. All the problems encountered have proved manageable. The more important modifications are summarized. Graphite shielding. In December 1960, the primary system was filled with sodium, and extensive testing began. When the primary shield tank was reopened after a 1000{sup o}F primary system test, it was found that much of the graphite block shielding which had been installed around the reactor had deteriorated. These hightemperature blocks which were impregnated with boron had increased in volume and lost strength. Extensive analysis indicated that the graphite binder had failed. It was decided to replace all of the graphite, to use boron carbide as the boronating agent, to install the block with mechanical fasteners, and to keep moisture to a minimum. Modifications within the reactor vessel. Repairs and design modifications were made to correct the cause of sub-assembly sticking, the damage which resulted, and to prevent further malfunctions of the offset handling mechanism. In order to make repairs and alterations, the offset handling mechanism was removed, the reactor vessel was drained of sodium, and trained personnel wearing specially designed protective suits entered the reactor vessel. Entrance to the work area was through a special air lock since an argon atmosphere was maintained inside the vessel. Steam generator modifications. During hydrostatic testing of the No. 2 steam generator, several leaking tubes were discovered. Tube failure was traced to stress corrosion cracking. The No. 2 bundle was retubed, all units were stress relieved, and a hydrogen detector system was installed. In December 1962, a

  3. Quasiparticles and Fermi liquid behaviour in an organic metal

    Science.gov (United States)

    Kiss, T.; Chainani, A.; Yamamoto, H.M.; Miyazaki, T.; Akimoto, T.; Shimojima, T.; Ishizaka, K.; Watanabe, S.; Chen, C.-T.; Fukaya, A.; Kato, R.; Shin, S.

    2012-01-01

    Many organic metals display exotic properties such as superconductivity, spin-charge separation and so on and have been described as quasi-one-dimensional Luttinger liquids. However, a genuine Fermi liquid behaviour with quasiparticles and Fermi surfaces have not been reported to date for any organic metal. Here, we report the experimental Fermi surface and band structure of an organic metal (BEDT-TTF)3Br(pBIB) obtained using angle-resolved photoelectron spectroscopy, and show its consistency with first-principles band structure calculations. Our results reveal a quasiparticle renormalization at low energy scales (effective mass m*=1.9 me) and ω2 dependence of the imaginary part of the self energy, limited by a kink at ~50 meV arising from coupling to molecular vibrations. The study unambiguously proves that (BEDT-TTF)3Br(pBIB) is a quasi-2D organic Fermi liquid with a Fermi surface consistent with Shubnikov-de Haas results. PMID:23011143

  4. Discrete nature of thermodynamics in confined ideal Fermi gases

    International Nuclear Information System (INIS)

    Aydin, Alhun; Sisman, Altug

    2014-01-01

    Intrinsic discrete nature in thermodynamic properties of Fermi gases appears under strongly confined and degenerate conditions. For a rectangular confinement domain, thermodynamic properties of an ideal Fermi gas are expressed in their exact summation forms. For 1D, 2D and 3D nano domains, variations of both number of particles and internal energy per particle with chemical potential are examined. It is shown that their relation with chemical potential exhibits a discrete nature which allows them to take only some definite values. Furthermore, quasi-irregular oscillatory-like sharp peaks are observed in heat capacity. New nano devices can be developed based on these behaviors. - Highlights: • “Discrete behaviors” appear in thermodynamic properties of ideal Fermi gases at nano scale. • Variations of particle number and internal energy with chemical potential have stepwise behavior. • There are oscillations and peaks in the variation of heat capacity with domain size and particle number. • Fermi line and Fermi surface at nano scale are not continuous but “discrete”. • Heat capacity oscillations can be used for excess thermal energy storage at nano scale

  5. Tuning the Fano factor of graphene via Fermi velocity modulation

    Science.gov (United States)

    Lima, Jonas R. F.; Barbosa, Anderson L. R.; Bezerra, C. G.; Pereira, Luiz Felipe C.

    2018-03-01

    In this work we investigate the influence of a Fermi velocity modulation on the Fano factor of periodic and quasi-periodic graphene superlattices. We consider the continuum model and use the transfer matrix method to solve the Dirac-like equation for graphene where the electrostatic potential, energy gap and Fermi velocity are piecewise constant functions of the position x. We found that in the presence of an energy gap, it is possible to tune the energy of the Fano factor peak and consequently the location of the Dirac point, by a modulation in the Fermi velocity. Hence, the peak of the Fano factor can be used experimentally to identify the Dirac point. We show that for higher values of the Fermi velocity the Fano factor goes below 1/3 at the Dirac point. Furthermore, we show that in periodic superlattices the location of Fano factor peaks is symmetric when the Fermi velocity vA and vB is exchanged, however by introducing quasi-periodicity the symmetry is lost. The Fano factor usually holds a universal value for a specific transport regime, which reveals that the possibility of controlling it in graphene is a notable result.

  6. High-energy transients with Fermi/GBM

    Energy Technology Data Exchange (ETDEWEB)

    Gruber, David

    2012-10-09

    . Finally, I present the results of the search for untriggered GRBs in GBM data. This project focuses on GRBs which triggered Swift but not GBM although the GRBs came from positions above the horizon, with a favorable orientation to at least one GBM detector. The properties of these GRBs are then compared to the full sample of GBM GRBs published in the GBM spectral catalogue. Although designed mainly for GRB studies, GBM observes solar flares as well. In Chapter 3, I made use of the high temporal quality of GBM data to perform a detailed timing analysis of four solar flares. Contrary to recent claims in the literature, where quasiperiodic pulsations (QPPs) have been allegedly identified in the {gamma}-ray data of solar flares, I did not find any statistical significant signatures of such QPPs. When red-noise, an intrinsic source component, is accounted for, most of the claimed QPPs fall below the threshold of a significant detection. Moreover, I developed a new background estimation method for solar flares, called SOBER{sup 2} (SOlar Background Employing Relative Rates). This method uses the count rate of the complementary and shaded BGO detector as an a priori information to determine the background fluctuations for the Sun-facing BGO detector. Such a method is especially useful and beneficial for solar flares because they are usually of very long duration and the standard GBM background subtraction fails in such cases. Finally, in Chapter 4, I present the log-parabolic model which I used to fit the spectra of SGR bursts. Even though the spectra of the latter are usually and preferentially fit by a sum of two blackbodies in the literature, I show that the log-parabolic model fits the data as least as well as the double blackbody function. Additionally, the log-parabolic model is based on a strong underlying physical mechanism, i.e. second order Fermi acceleration, which gives it even more credibility.

  7. A Tale of cosmic rays narrated in γ rays by Fermi

    International Nuclear Information System (INIS)

    Tibaldo, Luigi

    2014-01-01

    Because cosmic rays are charged particles scrambled by magnetic fields, combining direct measurements with other observations is crucial to understanding their origin and propagation. As energetic particles traverse matter and electromagnetic fields, they leave marks in the form of neutral interaction products. Among those, γ rays trace interactions of nuclei that inelastically collide with interstellar gas, as well as of leptons that undergo Bremsstrahlung and inverse-Compton scattering. Data collected by the Fermi large area telescope (LAT) are therefore telling the story of cosmic rays along their journey from sources through their home galaxies. Supernova remnants emerge as a notable γ -ray source population, and older remnants interacting with interstellar matter finally show strong evidence of the presence of accelerated nuclei. Yet the maximum energy attained by shock accelerators is poorly constrained by observations. Cygnus X, a massive star-forming region established by the LAT as housing cosmic-ray sources, provides a test case to study the impact of wind-driven turbulence on the early propagation. Interstellar emission resulting from the large-scale propagation of cosmic rays in the Milky Way is revealed in unprecedented detail that challenges some of the simple assumptions used for the modeling. Moreover, the cosmic-ray induced γ -ray luminosities of galaxies-scale quasi-linearly with their massive-star formation rates: the overall normalization of that relation below the calorimetric limit suggests that for most systems, a substantial fraction of energy in cosmic rays escapes into the intergalactic medium. The nuclear production models and the distribution of target gas and radiation fields, not determined precisely enough yet, are key to exploiting the full potential of γ - ray data. Nevertheless, data being collected by Fermi and complementary multiwavelength/multi messenger observations are bringing ever closer to solving the cosmic-ray mystery

  8. A Tale of cosmic rays narrated in γ rays by Fermi

    Energy Technology Data Exchange (ETDEWEB)

    Tibaldo, Luigi, E-mail: ltibaldo@slac.stanford.edu [Kavli Institute for Particle Astrophysics and Cosmology, SLAC National Accelerator Laboratory, Menlo Park (United States)

    2014-07-01

    Because cosmic rays are charged particles scrambled by magnetic fields, combining direct measurements with other observations is crucial to understanding their origin and propagation. As energetic particles traverse matter and electromagnetic fields, they leave marks in the form of neutral interaction products. Among those, γ rays trace interactions of nuclei that inelastically collide with interstellar gas, as well as of leptons that undergo Bremsstrahlung and inverse-Compton scattering. Data collected by the Fermi large area telescope (LAT) are therefore telling the story of cosmic rays along their journey from sources through their home galaxies. Supernova remnants emerge as a notable γ -ray source population, and older remnants interacting with interstellar matter finally show strong evidence of the presence of accelerated nuclei. Yet the maximum energy attained by shock accelerators is poorly constrained by observations. Cygnus X, a massive star-forming region established by the LAT as housing cosmic-ray sources, provides a test case to study the impact of wind-driven turbulence on the early propagation. Interstellar emission resulting from the large-scale propagation of cosmic rays in the Milky Way is revealed in unprecedented detail that challenges some of the simple assumptions used for the modeling. Moreover, the cosmic-ray induced γ -ray luminosities of galaxies-scale quasi-linearly with their massive-star formation rates: the overall normalization of that relation below the calorimetric limit suggests that for most systems, a substantial fraction of energy in cosmic rays escapes into the intergalactic medium. The nuclear production models and the distribution of target gas and radiation fields, not determined precisely enough yet, are key to exploiting the full potential of γ - ray data. Nevertheless, data being collected by Fermi and complementary multiwavelength/multi messenger observations are bringing ever closer to solving the cosmic-ray mystery

  9. Accelerators and the Accelerator Community

    Energy Technology Data Exchange (ETDEWEB)

    Malamud, Ernest; Sessler, Andrew

    2008-06-01

    In this paper, standing back--looking from afar--and adopting a historical perspective, the field of accelerator science is examined. How it grew, what are the forces that made it what it is, where it is now, and what it is likely to be in the future are the subjects explored. Clearly, a great deal of personal opinion is invoked in this process.

  10. Accelerators and the Accelerator Community

    International Nuclear Information System (INIS)

    Malamud, Ernest; Sessler, Andrew

    2008-01-01

    In this paper, standing back--looking from afar--and adopting a historical perspective, the field of accelerator science is examined. How it grew, what are the forces that made it what it is, where it is now, and what it is likely to be in the future are the subjects explored. Clearly, a great deal of personal opinion is invoked in this process

  11. Ring accelerators

    International Nuclear Information System (INIS)

    Gisler, G.; Faehl, R.

    1983-01-01

    We present two-dimensional simulations in (r-z) and r-theta) cylinderical geometries of imploding-liner-driven accelerators of rings of charged particles. We address issues of azimuthal and longitudinal stability of the rings. We discuss self-trapping designs in which beam injection and extraction is aided by means of external cusp fields. Our simulations are done with the 2-1/2-D particle-in-cell plasma simulation code CLINER, which combines collisionless, electromagnetic PIC capabilities with a quasi-MHD finite element package

  12. accelerating cavity

    CERN Multimedia

    On the inside of the cavity there is a layer of niobium. Operating at 4.2 degrees above absolute zero, the niobium is superconducting and carries an accelerating field of 6 million volts per metre with negligible losses. Each cavity has a surface of 6 m2. The niobium layer is only 1.2 microns thick, ten times thinner than a hair. Such a large area had never been coated to such a high accuracy. A speck of dust could ruin the performance of the whole cavity so the work had to be done in an extremely clean environment.

  13. Constrain the SED Type of Unidentified Fermi Objects

    Directory of Open Access Journals (Sweden)

    An-Li Tsai

    2013-09-01

    Full Text Available 2FGL J1823.8+4312 and 2FGL J1304.1-2415 are two unidentified Fermi objects which are associated with cluster of galaxies. In order to exam the possibility of cluster of galaxies as gamma-ray emitters, we search for counterpart of these two unidentified Fermi objects in other wavebands. However, we find other candidate to be more likely the counterpart of the unidentified Fermi object for both sources. We compare their light curves and SEDs in order to identify their source types. However, data at millimeter and sub-millimeter wavebands, which is important for us to constrain the SED at synchrotron peak, is lacking of measurement. Therefore, we proposed to SMA observation for these two sources. We have got data and are doing further analysis.

  14. The great silence science and philosophy of Fermi's paradox

    CERN Document Server

    Cirkovic, Milan M

    2018-01-01

    The Great Silence explores the multifaceted problem named after the great Italian physicist Enrico Fermi and his legendary 1950 lunchtime question "Where is everybody?" In many respects, Fermi's paradox is the richest and the most challenging problem for the entire field of astrobiology and the Search for ExtraTerrestrial Intelligence (SETI) studies. This book shows how Fermi's paradox is intricately connected with many fields of learning, technology, arts, and even everyday life. It aims to establish the strongest possible version of the problem, to dispel many related confusions, obfuscations, and prejudices, as well as to offer a novel point of entry to the many solutions proposed in existing literature. Cirkovic argues that any evolutionary worldview cannot avoid resolving the Great Silence problem in one guise or another.

  15. Von Weizsaecker and exchange corrections in the Thomas Fermi theory

    International Nuclear Information System (INIS)

    Benguria, R.D.

    1979-01-01

    Two corrections to the Thomas-Fermi theory of atoms are studied. First the correction for exchange, that is the effect of the Pauli principle in the interaction energy, is considered. The defining variational problem is non-convex and standard technique to prove existence of a minimizing solution do not apply. Existence and uniqueness of solutions are established by convexifying or relaxing the energy functional. Properties of the minimizing solution are studied. A second correction due to von Weizsaecker is also discussed. Finally the dual principle to the Thomas-Fermi variational problem is studied (only in the neutral case). A dual principle is suggested for the ionic case. Also, a review of recent rigorous results concerning Thomas-Fermi theory is presented

  16. String effects on Fermi-Dirac correlation measurements

    International Nuclear Information System (INIS)

    Duran Delgado, R.M.; Gustafson, G.; Loennblad, L.

    2007-01-01

    We investigate some recent measurements of Fermi-Dirac correlations by the LEP collaborations indicating surprisingly small source radii for the production of baryons in e + e - annihilation at the Z 0 peak. In hadronization models there is besides the Fermi-Dirac correlation effect also a strong dynamical (anti-) correlation. We demonstrate that the extraction of the pure FD effect is highly dependent on a realistic Monte Carlo event generator, both for separation of those dynamical correlations that are not related to Fermi-Dirac statistics, and for corrections of the data and background subtractions. Although the model can be tuned to well reproduce single particle distributions, there are large model uncertainties when it comes to correlations between identical baryons. We therefore, unfortunately, have to conclude that it is at present not possible to draw any firm conclusion about the source radii relevant for baryon production at LEP. (orig.)

  17. FERMI(at)Elettra FEL Design Technical Optimization Final Report

    International Nuclear Information System (INIS)

    Fawley, William; Penn, Gregory; Allaria, Enrico; De Ninno, Giovanni; Graves, William

    2006-01-01

    This is the final report of the FEL Design Group for the Technical Optimization Study for the FERMI(at)ELETTRA project. The FERMI(at)ELETTRA project is based on the principle of harmonic upshifting of an initial ''seed'' signal in a single pass, FEL amplifier employing multiple undulators. There are a number of FEL physics principles which underlie this approach to obtaining short wavelength output: (1) the energy modulation of the electron beam via the resonant interaction with an external laser seed (2) the use of a chromatic dispersive section to then develop a strong density modulation with large harmonic overtones (3) the production of coherent radiation by the microbunched beam in a downstream radiator. Within the context of the FERMI project, we discuss each of these elements in turn

  18. Particle acceleration in the interplanetary medium

    International Nuclear Information System (INIS)

    Engelmann, J.J.

    1987-07-01

    Variations in solar wind properties are dominated by a number of high speed streams. By interacting with the quiet wind, the fast streams give rise in the first case to a travelling shock wave, in the second case to a pair of forward and backward shock waves, by which the interaction region, corotating with the sun, is bounded. Two acceleration mechanisms are invoked to account for the energetic ion flux increases: 1) The first order Fermi process, whereby particles increase their energy by compression between converging magnetic scattering centers, located upstream and downstream of the shock. 2) The shock drift mechanism. The composition and the spectrum of the accelerated ions suggest that they probably originate from the suprathermal tail of the solar wind distribution [fr

  19. Oscillating Casimir force between two slabs in a Fermi sea

    DEFF Research Database (Denmark)

    Li-Wei, Chen; Guo-Zhen, Su; Jin-Can, Chen

    2012-01-01

    that the Casimir force decreases monotonically with the increase of the separation L between two slabs in an electromagnetic field and a massive Bose gas, the Casimir force in a Fermi gas oscillates as a function of L. The Casimir force can be either attractive or repulsive, depending sensitively on the magnitude...... of L. In addition, it is found that the amplitude of the Casimir force in a Fermi gas decreases with the increase of the temperature, which also is contrary to the case in a Bose gas, since the bosonic Casimir force increases linearly with the increase of the temperature in the region T

  20. Full scope upgrade project for the Fermi 2 simulator

    International Nuclear Information System (INIS)

    Bollacasa, D.; Gonsalves, J.B.; Newcomb, P.C.

    1994-01-01

    The Detroit Edison company (DECO) concentrated the Simulation Division of Asea Brown Boveri (ABB) to perform a full scope upgrade of the Fermi 2 simulator. The Fermi 2 plant is a BWR 6 generation Nuclear Steam Supply System (NSSS). The project included the complete replacement of the existing simulation model sofware with ABB's high fidelity BWR models, addition of an advanced instructor station facility and new simulation computers. Also provided on the project were ABB's advanced simulation environment (CETRAN), a comprehensive configuration management system based on a modern relational database system and a new computer interface to the input/output system. (8 refs., 2 figs.)

  1. The radio-γ-ray connection in Fermi blazars

    Science.gov (United States)

    Ghirlanda, G.; Ghisellini, G.; Tavecchio, F.; Foschini, L.; Bonnoli, G.

    2011-05-01

    We study the correlation between the γ-ray flux (Fγ), averaged over the first 11 months of the Fermi survey and integrated above 100 MeV, and the radio flux density (Fr at 20 GHz) of Fermi sources associated with a radio counterpart in the 20-GHz Australia Telescope Compact Array (AT20G) survey. Considering the blazars detected in both bands, the correlation is highly significant and has the form Fγ∝F0.85±0.04r, similar to BL Lacertae objects and flat-spectrum radio quasars. However, only a small fraction (˜1/15) of the AT20G radio sources with flat radio spectra are detected by Fermi. To understand if this correlation is real, we examine the selection effects introduced by the flux limits of both the radio and the γ-ray surveys, and the importance of variability of the γ-ray flux. After accounting for these effects, we find that the radio-γ-ray flux correlation is real, but its slope is steeper than the observed one, that is, Fγ∝Fδr with δ in the range 1.25-1.5. The observed Fγ-Fr correlation and the fraction of radio sources detected by Fermi are reproduced assuming a long-term γ-ray flux variability, following a lognormal probability distribution with standard deviation σ≥ 0.5 (corresponding to Fγ varying by at least a factor of 3). Such a variability is compatible, even if not necessarily equal, with what is observed when comparing, for the sources in common, the EGRET and the Fermi γ-ray fluxes (even if the Fermi fluxes are averaged over ˜1 yr). Another indication of variability is the non-detection of 12 out of 66 EGRET blazars by Fermi, despite its higher sensitivity. We also study the strong linear correlation between the γ-ray and the radio luminosity of the 144 AT20G-Fermi associations with known redshift and show, through partial correlation analysis, that it is statistically robust. Two possible implications of these correlations are discussed: the contribution of blazars to the extragalactic γ-ray background and the prediction

  2. Pairing and condensation in a resonant Bose-Fermi mixture

    International Nuclear Information System (INIS)

    Fratini, Elisa; Pieri, Pierbiagio

    2010-01-01

    We study by diagrammatic means a Bose-Fermi mixture, with boson-fermion coupling tuned by a Fano-Feshbach resonance. For increasing coupling, the growing boson-fermion pairing correlations progressively reduce the boson condensation temperature and make it eventually vanish at a critical coupling. Such quantum critical point depends very weakly on the population imbalance and, for vanishing boson densities, coincides with that found for the polaron-molecule transition in a strongly imbalanced Fermi gas, thus bridging two quite distinct physical systems.

  3. Hydrodynamics in a Degenerate, Strongly Attractive Fermi Gas

    Science.gov (United States)

    Thomas, John E.; Kinast, Joseph; Hemmer, Staci; Turlapov, Andrey; O'Hara, Ken; Gehm, Mike; Granade, Stephen

    2004-01-01

    In summary, we use all-optical methods with evaporative cooling near a Feshbach resonance to produce a strongly interacting degenerate Fermi gas. We observe hydrodynamic behavior in the expansion dynamics. At low temperatures, collisions may not explain the expansion dynamics. We observe hydrodynamics in the trapped gas. Our observations include collisionally-damped excitation spectra at high temperature which were not discussed above. In addition, we observe weakly damped breathing modes at low temperature. The observed temperature dependence of the damping time and hydrodynamic frequency are not consistent with collisional dynamics nor with collisionless mean field interactions. These observations constitute the first evidence for superfluid hydrodynamics in a Fermi gas.

  4. Enhanced diphoton rates at Fermi and the LHC

    International Nuclear Information System (INIS)

    Schmidt-Hoberg, Kai; Staub, Florian

    2012-11-01

    We show that within MSSM singlet extensions the experimental hints beyond the standard model from the Fermi LAT telescope as well as from the LHC can be explained simultaneously while being consistent with all experimental constraints. In particular we present an example point which features a ∝130 GeV lightest neutralino with an annihilation cross section into photons consistent with the indication from the Fermi satellite with simultaneously the right relic abundance, a continuum photon spectrum consistent with observation, direct detection cross section below the experimental limits, electroweak observables consistent with experiment and a 125 GeV light Higgs boson with a slightly enhanced h→γγ rate.

  5. Quantum hydrodynamics and nonlinear differential equations for degenerate Fermi gas

    International Nuclear Information System (INIS)

    Bettelheim, Eldad; Abanov, Alexander G; Wiegmann, Paul B

    2008-01-01

    We present new nonlinear differential equations for spacetime correlation functions of Fermi gas in one spatial dimension. The correlation functions we consider describe non-stationary processes out of equilibrium. The equations we obtain are integrable equations. They generalize known nonlinear differential equations for correlation functions at equilibrium [1-4] and provide vital tools for studying non-equilibrium dynamics of electronic systems. The method we developed is based only on Wick's theorem and the hydrodynamic description of the Fermi gas. Differential equations appear directly in bilinear form. (fast track communication)

  6. ROLE OF NUCLEONIC FERMI SURFACE DEPLETION IN NEUTRON STAR COOLING

    Energy Technology Data Exchange (ETDEWEB)

    Dong, J. M.; Zuo, W. [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Lombardo, U. [Universita di Catania and Laboratori Nazionali del Sud (INFN), Catania I-95123 (Italy); Zhang, H. F. [School of Nuclear Science and Technology, Lanzhou University, Lanzhou 730000 (China)

    2016-01-20

    The Fermi surface depletion of beta-stable nuclear matter is calculated to study its effects on several physical properties that determine the neutron star (NS) thermal evolution. The neutron and proton Z factors measuring the corresponding Fermi surface depletions are calculated within the Brueckner–Hartree–Fock approach, employing the AV18 two-body force supplemented by a microscopic three-body force. Neutrino emissivity, heat capacity, and in particular neutron {sup 3}PF{sub 2} superfluidity, turn out to be reduced, especially at high baryonic density, to such an extent that the cooling rates of young NSs are significantly slowed.

  7. An Integrable Approximation for the Fermi Pasta Ulam Lattice

    Science.gov (United States)

    Rink, Bob

    This contribution presents a review of results obtained from computations of approximate equations of motion for the Fermi-Pasta-Ulam lattice. These approximate equations are obtained as a finite-dimensional Birkhoff normal form. It turns out that in many cases, the Birkhoff normal form is suitable for application of the KAM theorem. In particular, this proves Nishida's 1971 conjecture stating that almost all low-energetic motions of the anharmonic Fermi-Pasta-Ulam lattice with fixed endpoints are quasi-periodic. The proof is based on the formal Birkhoff normal form computations of Nishida, the KAM theorem and discrete symmetry considerations.

  8. Itinerant Ferromagnetism in a Polarized Two-Component Fermi Gas

    DEFF Research Database (Denmark)

    Massignan, Pietro; Yu, Zhenhua; Bruun, Georg

    2013-01-01

    We analyze when a repulsively interacting two-component Fermi gas becomes thermodynamically unstable against phase separation. We focus on the strongly polarized limit, where the free energy of the homogeneous mixture can be calculated accurately in terms of well-defined quasiparticles, the repul......We analyze when a repulsively interacting two-component Fermi gas becomes thermodynamically unstable against phase separation. We focus on the strongly polarized limit, where the free energy of the homogeneous mixture can be calculated accurately in terms of well-defined quasiparticles...

  9. Exotic Paired States with Anisotropic Spin-Dependent Fermi Surfaces

    International Nuclear Information System (INIS)

    Feiguin, Adrian E.; Fisher, Matthew P. A.

    2009-01-01

    We propose a model for realizing exotic paired states in cold Fermi gases by using a spin-dependent optical lattice to engineer mismatched Fermi surfaces for each hyperfine species. The BCS phase diagram shows a stable paired superfluid state with coexisting pockets of momentum space with gapless unpaired carriers, similar to the Sarma state in polarized mixtures, but in our case the system is unpolarized. We propose the possible existence of an exotic 'Cooper-pair Bose-metal' phase, which has a gap for single fermion excitations but gapless and uncondensed 'Cooper-pair' excitations residing on a 'Bose surface' in momentum space.

  10. Stabilization of Ag nanostructures by tuning their Fermi levels

    Science.gov (United States)

    Tani, Tadaaki; Kan, Ryota; Yamano, Yuka; Uchida, Takayuki

    2018-05-01

    The oxidation of Ag nanostructures has been studied as a key step for their degradation under the guiding principle in the previous paper that they are stable when their Fermi level is lower than those of their surroundings. The drop of the Fermi level of a thin Ag layer was caused by the formation of self-assembled monolayers (SAMs) of certain organic compounds including those of photographic interest and a monolayer of AgI, and attributed to the formation of dielectric layers, whose positive charges were closer to the Ag layer than negative charges. A consideration is given on further examinations needed to realize the above guiding principle in individual devices.

  11. Deconstructing continuous flash suppression.

    Science.gov (United States)

    Yang, Eunice; Blake, Randolph

    2012-03-08

    In this paper, we asked to what extent the depth of interocular suppression engendered by continuous flash suppression (CFS) varies depending on spatiotemporal properties of the suppressed stimulus and CFS suppressor. An answer to this question could have implications for interpreting the results in which CFS influences the processing of different categories of stimuli to different extents. In a series of experiments, we measured the selectivity and depth of suppression (i.e., elevation in contrast detection thresholds) as a function of the visual features of the stimulus being suppressed and the stimulus evoking suppression, namely, the popular "Mondrian" CFS stimulus (N. Tsuchiya & C. Koch, 2005). First, we found that CFS differentially suppresses the spatial components of the suppressed stimulus: Observers' sensitivity for stimuli of relatively low spatial frequency or cardinally oriented features was more strongly impaired in comparison to high spatial frequency or obliquely oriented stimuli. Second, we discovered that this feature-selective bias primarily arises from the spatiotemporal structure of the CFS stimulus, particularly within information residing in the low spatial frequency range and within the smooth rather than abrupt luminance changes over time. These results imply that this CFS stimulus operates by selectively attenuating certain classes of low-level signals while leaving others to be potentially encoded during suppression. These findings underscore the importance of considering the contribution of low-level features in stimulus-driven effects that are reported under CFS.

  12. Quantum-mechanical suppression of bremsstrahlung

    Energy Technology Data Exchange (ETDEWEB)

    Becker-Szendy, R.; Keller, L.; Niemi, G.; Perl, M.; Rochester, L. [Stanford Univ., CA (United States); Anthony, P. [Stanford Univ., CA (United States)]|[Lawrence Livermore National Lab., CA (United States); Bosted, P. [American Univ., Washington, DC (United States); Cavalli-Sforza, M.; Kelley, L.; Klein, S. [Univ. of California, Santa Cruz, CA (United States)] [and others

    1994-12-01

    The authors have studied quantum-mechanical suppression of bremsstrahlung of low-energy 1-500 MeV photons from high-energy 25 GeV electrons. They have measured the LPM effect, where multiple scattering of the radiating electron destroys coherence required for the emission of low-energy photons, and the dielectric effect, where the emitted photon traveling in the radiator medium interferes with itself. For the experiment, the collaboration developed a novel method of extracting a parasitic low-intensity high-energy electron beam into the fixed target area during normal SLC operation of the accelerator. The results agree quantitatively with Migdal`s calculation of the LPM effect. Surface effects, for which there is no satisfactory theoretical prediction, are visible at low photon energies. For very thin targets, the suppression disappears, as expected. Preliminary results on dielectric suppression of bremsstrahlung are in qualitative agreement with the expectation.

  13. Reconstruction de la surface de Fermi dans l'etat normal d'un supraconducteur a haute Tc: Une etude du transport electrique en champ magnetique intense

    Science.gov (United States)

    Le Boeuf, David

    Des mesures de resistance longitudinale et de resistance de Hall en champ magnetique intense transverse (perpendiculaire aux plans CuO2) ont ete effectuees au sein de monocristaux de YBa2Cu3Oy (YBCO) demacles, ordonnes et de grande purete, afin d'etudier l'etat fondamental des supraconducteurs a haute Tc dans le regime sous-dope. Cette etude a ete realisee en fonction du dopage et de l'orientation du courant d'excitation J par rapport a l'axe orthorhombique b de la structure cristalline. Les mesures en champ magnetique intense revelent par suppression de la supraconductivite des oscillations magnetiques des resistances longitudinale et de Hall dans YBa2Cu 3O6.51 et YBa2Cu4O8. La conformite du comportement de ces oscillations quantiques au formalisme de Lifshitz-Kosevich, apporte la preuve de l'existence d'une surface de Fermi fermee a caractere quasi-2D, abritant des quasiparticules coherentes respectant la statistique de Fermi-Dirac, dans la phase pseudogap d'YBCO. La faible frequence des oscillations quantiques, combinee avec l'etude de la partie monotone de la resistance de Hall en fonction de la temperature indique que la surface de Fermi d'YBCO sous-dope comprend une petite poche de Fermi occupee par des porteurs de charge negative. Cette particularite de la surface de Fermi dans le regime sous-dope incompatible avec les calculs de structure de bande est en fort contraste avec la structure electronique presente dans le regime surdope. Cette observation implique ainsi l'existence d'un point critique quantique dans le diagramme de phase d'YBCO, au voisinage duquel la surface de Fermi doit subir une reconstruction induite par l'etablissement d'une brisure de la symetrie de translation du reseau cristallin sous-jacent. Enfin, l'etude en fonction du dopage de la resistance de Hall et de la resistance longitudinale en champ magnetique intense suggere qu'un ordre du type onde de densite (DW) est responsable de la reconstruction de la surface de Fermi. L'analogie de

  14. Search for a neutrino emission from the Fermi Bubbles with the ANTARES telescope

    CERN Multimedia

    BIAGI, S

    2012-01-01

    The first search for neutrinos from the Fermi Bubbles is presented using data collected by the ANTARES telescope. No evidence of a neutrino signal from the Fermi Bubbles region was found, hence upper limits were calculated for different energy cutoffs.

  15. Effect of Cleaving Temperature on the Surface and Bulk Fermi Surface of Sr2RuO4 Investigated by High Resolution Angle-Resolved Photoemission

    International Nuclear Information System (INIS)

    Liu Shan-Yu; Zhang Wen-Tao; Weng Hong-Ming; Zhao Lin; Liu Hai-Yun; Jia Xiao-Wen; Liu Guo-Dong; Dong Xiao-Li; Zhang Jun; Dai Xi; Fang Zhong; Zhou Xing-Jiang; Mao Zhi-Qiang; Chen Chuang-Tian; Xu Zu-Yan

    2012-01-01

    High resolution angle-resolved photoemission measurements are carried out to systematically investigate the effect of cleaving temperature on the electronic structures and Fermi surfaces of Sr 2 RuO 4 . Unlike previous reports, which found that a high cleaving temperature can suppress the surface Fermi surface, we find that the surface Fermi surface remains obvious and strong in Sr 2 RuO 4 cleaved at high temperature, even at room temperature. This indicates that cleaving temperature is not a key effective factor in suppressing surface bands. On the other hand, the bulk bands can be enhanced in an aged surface of Sr 2 RuO 4 that has been cleaved and held for a long time. We have also carried out laser ARPES measurements on Sr 2 RuO 4 by using a vacuum ultra-violet laser (photon energy at 6.994 eV) and found an obvious enhancement of bulk bands even for samples cleaved at low temperature. This information is important for realizing an effective approach to manipulating and detecting the surface and bulk electronic structure of Sr 2 RuO 4 . In particular, the enhancement of bulk sensitivity, along with the super-high instrumental resolution of VUV laser ARPES, will be advantageous in investigating fine electronic structure and superconducting properties of Sr 2 RuO 4 in the future. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  16. Progress toward NLC / GLC prototype accelerator structures

    CERN Document Server

    Wang, J W; Arkan, T; Baboi, N; Boffo, C; Bowden, G B; Burke, D L; Carter, H; Chan, J; Cornuelle, J; Döbert, Steffen; Dolgashev, Valery A; Finley, D; Gonin, I; Higashi, Y; Higo, T; Jones, R M; Khabiboulline, T; Kume, T; Lewandowski, J; Li, Z; Miller, R H; Mishra, S; Morozumi, Y; Nantista, C; Pearson, C; Romanov, G; Ruth, Ronald D; Solyak, N; Tantawi, S; Toge, N; Ueno, K; Wilson, P B; Xiao, L

    2004-01-01

    The accelerator structure groups for NLC (Next Linear Collider) and GLC (Global Linear Colliders) have successfully collaborated on the research and development of a major series of advanced accelerator structures based on room-temperature technology at X-band frequency. The progress in design, simulation, microwave measurement and high gradient tests are summarized in this paper. The recent effort in design and fabrication of the accelerator structure prototype for the main linac is presented in detail including HOM (High Order Mode) suppression and couplers, fundamental mode couplers, optimized accelerator cavities as well as plans for future structures. We emphasize techniques to reduce the field on the surface of the copper structures (in order to achieve high accelerating gradients), limit the dipole wakefields (to relax alignment tolerance and prevent a beam break up instability) and improve shunt impedance (to reduce the RF power required).

  17. Application of the Thomas-Fermi statistical model to the thermodynamics of high density matter

    International Nuclear Information System (INIS)

    Martin, R.

    1977-01-01

    The Thomas-Fermi statistical model, from the N-body point of view is used in order to have systematic corrections to the T-Fermi's equation. Approximate calculus methods are found from analytic study of the T-Fermi's equation for non zero temperature. T-Fermi's equation is solved with the code ''Golem''written in Fortran V (Univac). It also provides the thermodynamical quantities and a new method to calculate several isothermal tables. (author) [es

  18. Application of the Thomas-Fermi statistical model to the thermodynamics of high density matter

    International Nuclear Information System (INIS)

    Martin, R.

    1977-01-01

    The Thomas-Fermi statistical model, from the N-body point of view is used in order to have systematic corrections to the T-Fermis equation. Approximate calculus methods are found from analytic study of the T-Fermis equation for non zero temperature. T-Fermis equation is solved with the code GOLEM written in FORTRAN V (UNIVAC). It also provides the thermodynamical quantities and a new method to calculate several isothermal tables. (Author) 24 refs

  19. Chemical potential and internal energy of the noninteracting Fermi ...

    Indian Academy of Sciences (India)

    entropy by T, dV is the change in volume by p and µ is the chemical potential. When S .... thin films are actually not 2D objects, but fractals with Hausdorff dimensionalities between 2D ..... sharpness of the edge of the Fermi surface is lost. In the ...

  20. The First Fermi-LAT Gamma-Ray Burst Catalog

    NARCIS (Netherlands)

    Ackermann, M.; et al., [Unknown; van der Horst, A.J.

    2013-01-01

    In three years of observations since the beginning of nominal science operations in 2008 August, the Large Area Telescope (LAT) on board the Fermi Gamma-Ray Space Telescope has observed high-energy (gsim 20 MeV) γ-ray emission from 35 gamma-ray bursts (GRBs). Among these, 28 GRBs have been detected

  1. All-Sky Monitoring of Variable Sources with Fermi GBM

    Science.gov (United States)

    Wilson-Hodge, Colleen A.; Cherry, Michael L.; Case, Gary L.; Camero-Arranz, Ascension; Chaplin, Vandiver; Connaughton, Valerie; Finger, Mark H.; Jenke, Pater; Rodi, James C.; Baumgartner, Wayne H.; hide

    2011-01-01

    This slide presentation reviews the monitoring of variable sources with the Fermi Gamma Ray Burst Monitor (GBM). It reviews the use of the Earth Occultation technique, the observations of the Crab Nebula with the GBM, and the comparison with other satellite's observations. The instruments on board the four satellites indicate a decline in the Crab from 2008-2010.

  2. Transference of Fermi Contour Anisotropy to Composite Fermions.

    Science.gov (United States)

    Jo, Insun; Rosales, K A Villegas; Mueed, M A; Pfeiffer, L N; West, K W; Baldwin, K W; Winkler, R; Padmanabhan, Medini; Shayegan, M

    2017-07-07

    There has been a surge of recent interest in the role of anisotropy in interaction-induced phenomena in two-dimensional (2D) charged carrier systems. A fundamental question is how an anisotropy in the energy-band structure of the carriers at zero magnetic field affects the properties of the interacting particles at high fields, in particular of the composite fermions (CFs) and the fractional quantum Hall states (FQHSs). We demonstrate here tunable anisotropy for holes and hole-flux CFs confined to GaAs quantum wells, via applying in situ in-plane strain and measuring their Fermi wave vector anisotropy through commensurability oscillations. For strains on the order of 10^{-4} we observe significant deformations of the shapes of the Fermi contours for both holes and CFs. The measured Fermi contour anisotropy for CFs at high magnetic field (α_{CF}) is less than the anisotropy of their low-field hole (fermion) counterparts (α_{F}), and closely follows the relation α_{CF}=sqrt[α_{F}]. The energy gap measured for the ν=2/3 FQHS, on the other hand, is nearly unaffected by the Fermi contour anisotropy up to α_{F}∼3.3, the highest anisotropy achieved in our experiments.

  3. Noninteracting Fermi gas in a square-well potential.

    Science.gov (United States)

    Nash, C. E.

    1971-01-01

    The problem of a noninteracting Fermi gas in a finite square-well potential is solved analytically in the limit that the well becomes infinitely wide. The errors of previous authors using this model as a first approximation to the problem of a simple metal with surfaces are pointed out.

  4. Cold pasta phase in the extended Thomas–Fermi approximation

    International Nuclear Information System (INIS)

    Avancini, S.S.; Bertolino, B.P.

    2015-01-01

    In this paper, we aim to obtain more accurate values for the transition density to the homogenous phase in the nuclear pasta that occurs in the inner crust of neutron stars. To that end, we use the nonlinear Walecka model at zero temperature and an approach based on the extended Thomas–Fermi (ETF) approximation. (author)

  5. Stochasticity thresholds in the Fermi-Pasta-Ulam model

    International Nuclear Information System (INIS)

    Callegari, B.; Galgani, L.; Milan Univ.

    1979-01-01

    The authors consider the celebrated model of Fermi, Pasta and Ulam and give a numerical estimate for its thresholds of stochasticity, thus determining a critical energy as a function of the frequency of the corresponding oscillators. The results turn out to be qualitatively similar to those already obtained for a chain of particles with nearest-neighbour Lennard-Jones interaction potential. (author)

  6. Unidentified EGRET sources and their possible Fermi counterparts

    International Nuclear Information System (INIS)

    Lyapin, A R; Arkhangelskaja, I V; Larin, D S

    2017-01-01

    Unidentified EGRET sources from 3EG catalog have been analyzed. Preliminary data analysis has shown at least 23 of these sources coincide with those in 3FGL Fermi catalogue within 1, 2 and 3 sigma error intervals of the coordinates and fluxes. Their properties are discussed in the presented work. Even 3-sigma difference allows supposing sources similarity because of more than 3-sigma distinctions in values of fluxes between identified EGRET sources and their Fermi counterparts. For instance, the coincidence between 3EG J1255-0549 and 3FGL J1256.1-0547 was reported in Fermi catalogues 1FGL, 2FGL, 3FGL. However, these sources fluxes (in units of 10 −8 photons × cm −2 × s −1 ) in the energy band E > 100 MeV were 179.7 ± 6.7 (3EG), 44.711 ± 0.724 (3FGL), 53.611 ± 0.997 (2FGL) and 67.939 ± 1.861 (1FGL). Such effect was observed for sufficient portion of identified EGRET sources. It could cause by troubles of particles identification by Fermi/LAT trigger system. Very often charged particles recognized as gamma-quanta because of wrong backsplash analysis. Nevertheless, gammas counts as charged particles due analogous reason and rejected during ground data processing. For example, it appears as geomagnetic modulation presence on gamma-quanta count rate latitudinal profiles in energy band E > 20 MeV. (paper)

  7. A new look at Thomas–Fermi theory

    DEFF Research Database (Denmark)

    Solovej, Jan Philip

    2016-01-01

    In this short note, we argue that Thomas–Fermi theory, the simplest of all density functional theories, although failing to explain features such as molecular binding or stability of negative ions, is surprisingly accurate in estimating sizes of atoms. We give both numerical, experimental and rig...

  8. Surface effects on the propagation of sound in Fermi liquids

    International Nuclear Information System (INIS)

    Nagai, K.; Woelfle, P.

    1981-01-01

    The propagation of sound in a resonator is discussed in both the normal and superfluid Fermi liquids. A set of model hydrodynamic equations is developed for describing the transition from the hydrodynamic regime to the collisionless regime. Surface effects are incorporated by using a slip boundary condition. The resonance condition for the sound propagation in a cylindrical resonator is derived

  9. Stochasticity thresholds in the Fermi-Pasta-Ulam model

    Energy Technology Data Exchange (ETDEWEB)

    Callegari, B [Ferrara Univ. (Italy). Ist. di Matematica; Carotta, M C; Ferrario, C [Ferrara Univ. (Italy). Ist. di Fisica; Lo Vecchio, G [Ferrara Univ. (Italy). Ist. di Fisica; Gruppo Nazionale di Struttura della Materia, Ferrara (Italy)); Galgani, L [Milan Univ. (Italy). Ist. di Fisica; Milan Univ. (Italy). Ist. di Matematica)

    1979-12-11

    The authors consider the celebrated model of Fermi, Pasta and Ulam and give a numerical estimate for its thresholds of stochasticity, thus determining a critical energy as a function of the frequency of the corresponding oscillators. The results turn out to be qualitatively similar to those already obtained for a chain of particles with nearest-neighbour Lennard-Jones interaction potential.

  10. Magnetic breakdown in an array of overlapping Fermi surfaces

    International Nuclear Information System (INIS)

    Kadigrobov, A.M.; Radić, D.; Bjeliš, A.

    2015-01-01

    We develop a theoretical framework for a magnetic breakdown in an array of circular two-dimensional bands with a finite overlap of neighboring Fermi surfaces due to the presence of a presumably weak periodic potential, and apply the obtained results to the electron bands in carbon honeycomb structures of doped graphene and intercalated graphite compounds. In contrast to the standard treatment, inaugurated more than fifty years ago by Slutskin and Kadigrobov, with electron semiclassical trajectories encircling significantly overlapping Fermi surfaces, we examine a configuration in which bands are related in a way that the Fermi surfaces only slightly overlap, forming internal band pockets with areas of the size comparable to the area of the quantum magnetic flux for a given external magnetic field. Such band configuration has to be treated quantum mechanically. The calculation leads to the results for magnetic breakdown coefficients comprising an additional large factor with respect to the standard results, proportional to the ratio of the Fermi energy and the cyclotron energy. Also, these coefficients show oscillating dependence on energy, as well as on the wave number of periodic potential. Both mentioned elements enable the adjustment of the preferred wave vector of possible magnetic breakdown induced density wave instability at the highest possible critical temperature

  11. Resonance superfluidity in a quantum degenerate Fermi gas

    NARCIS (Netherlands)

    Kokkelmans, S.J.J.M.F.; Holland, M.; Walser, R.; Chiofalo, M.L.; Chu, S.; Vuletic, V.; Kerman, A.J.; Chin, C.

    2002-01-01

    We consider the superfluid phase transition that arises when a Feshbach resonance pairing occurs in a dilute Fermi gas. This is related to the phenomenon of superconductivity described by the seminal Bardeen-Cooper-Schrieffer (BCS) theory. In superconductivity, the phase transition is caused by a

  12. Backward scattering in the one-dimensional Fermi gas

    International Nuclear Information System (INIS)

    Apostol, M.

    1980-05-01

    The Ward identity is derived for non-relativistic fermions with two-body spin-independent interaction. Using this identity for the one-dimensional Fermi gas with backward scattering the equations of the perturbation theory are solved for the effective interaction and the collective excitations of the particle density fluctuations are obtained. (author)

  13. Cold pasta phase in the extended Thomas-Fermi approximation

    Science.gov (United States)

    Avancini, S. S.; Bertolino, B. P.

    2015-10-01

    In this paper, we aim to obtain more accurate values for the transition density to the homogenous phase in the nuclear pasta that occurs in the inner crust of neutron stars. To that end, we use the nonlinear Walecka model at zero temperature and an approach based on the extended Thomas-Fermi (ETF) approximation.

  14. Rotational dependence of Fermi-type resonance interactions in molecules

    Science.gov (United States)

    Mikhailov, Vladimir M.; Smirnov, M. A.

    1997-03-01

    In Pasadena, (Milliken Lab., USA, 1930) F. Rossetti has observed in Raman spectrum of carbon-dioxide molecule the full symmetric vibration of carbon dioxide appeared as the group of four near lying lines instead of the waited single line. The true interpretation of this enigmatic effect (in that time) was given by E. Fermi -- accidental degeneration of the first excited state of the full symmetric vibration in carbon dioxide. It was the first example of the event observed later in various organic molecules. This event was named as resonance Fermi. The rotational dependence of Fermi type resonance interactions in quasirigid molecules in dominant approximation can be selected in an expansion of the effective vibration-rotation Hamiltonian Hvib- roteff by the operator H(g)(Fermi) equals H30 plus (Sigma) nH3n(g). Let us consider in detail the problem of the construction of the effective vibration-rotational Hamiltonian HVR yields Heff from the point of view of various ordering schemes (grouping) of the vibrational-rotational interactions with sequential analysis of the choice of the convenient grouping adequate to the spectroscopic problem.

  15. Where Was Everybody? Olaf Stapledon and the Fermi Paradox

    Science.gov (United States)

    Baxter, S.

    In 1948 Olaf Stapledon gave an address to the BIS in which he summarised his vision of mankind's cosmic future: `One can imagine some sort of cosmical community of worlds ...' One might ask, however, since the universe is vastly older than mankind, why races on other worlds have not already built such a community. This is a `Fermi Paradox' question. The Paradox is based on the observation that there has been time for extraterrestrial intelligence to arise and colonise the Galaxy many times over, yet we see no sign of such endeavours. In this paper Stapledon's novels are retrospectively analysed from the point of view of the Fermi Paradox. In Last and First Men (1930) humanity is forever isolated because life and mind are rare in the Galaxy, and interstellar distances are too large ever to be traversed. These are classic candidate Fermi `solutions'. The `solution' implicit in Star Maker (1937) might be criticised in that it posits that humanity lives at a special epoch, with the cosmically transforming development of interstellar travel occurring a `mere' ten billion years after mankind, in a universe supposedly ~200bn years old. Stapledon died in 1950, the year the Paradox was formulated, and was probably unaware of the Paradox. However to apply retrospectively Fermi thinking to Stapledon's cosmologies is to gain a new insight into the author's philosophy.

  16. Three scientists to receive presidential Enrico Fermi award

    CERN Multimedia

    2003-01-01

    "Secretary of Energy Spencer Abraham today named John Bahcall, Raymond Davis, Jr. and Seymour Sack as winners of the Enrico Fermi Award. ... Drs. Bahcall and Davis will receive the award for their research in neutrino physics. Dr. Sack will receive the award for his contributions to national security" (1 page).

  17. The early period of the universal Fermi interaction

    International Nuclear Information System (INIS)

    Tiomno, J.

    1984-01-01

    A critical analysis of the contributions which lead, in the early period, to the discovery of the universality of Fermi-type weak interactions is made. In particular the current references to this universality as 'Puppi's triangle' are shown to be incorrect. (Author) [pt

  18. Domain-averaged Fermi-hole Analysis for Solids

    Czech Academy of Sciences Publication Activity Database

    Baranov, A.; Ponec, Robert; Kohout, M.

    2012-01-01

    Roč. 137, č. 21 (2012), s. 214109 ISSN 0021-9606 R&D Projects: GA ČR GA203/09/0118 Institutional support: RVO:67985858 Keywords : bonding in solids * domain averaged fermi hole * natural orbitals Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.164, year: 2012

  19. Multi-Band Spectral Properties of Fermi Blazars Benzhong Dai ...

    Indian Academy of Sciences (India)

    ... FSRQs, 41 AGNs of other types and 72 AGNs of unknown type (Abdo et al. 2010a). This large sample enable us to investigate the spectral shapes of blazars from optical to X-ray to γ-ray in more detail than has been done before. For this purpose, we collected data for all Fermi blazars having available spectral information.

  20. Dressed molecules in resonantly interacting ultracold atomic Fermi gases

    NARCIS (Netherlands)

    Falco, G.M.; Stoof, H.T.C.

    2007-01-01

    We present a detailed analysis of the two-channel atom-molecule effective Hamiltonian for an ultracold two-component homogeneous Fermi gas interacting near a Feshbach resonance. We particularly focus on the two-body and many-body properties of the dressed molecules in such a gas. An exact result

  1. Potential motion for Thomas-Fermi non-topological solitons

    International Nuclear Information System (INIS)

    Bahcall, S.

    1992-04-01

    In the Thomas-Fermi approximation to theories of coupled fermions and scalars, the equations for spherically-symmetric non-topological solitons have the form of potential motion. This gives a straightforward method for proving the existence of non-topological solitons in a given theory and for finding the constant-density, saturating solutions

  2. On the semiclassical description of nuclear Fermi liquid drops

    International Nuclear Information System (INIS)

    Schuck, P.

    1983-11-01

    In this series of lectures we aimed at presenting a self-contained semiclassical theory entirely based on the extended Thomas-Fermi or Wigner-Kirkwood h expansion in phase space. We saw that not only the Wigner transform of the single particle density matrix can be understood and very accurately represented in this way but that also generalisations to correlation functions are straightforward. First, we demonstrated a generalisation to superfluid nuclei and to superfluid nuclei in slow rotation. The latter involves already the (static) particle-hole correlation function and we saw how e.g. the reduction of the moment of inertia by roughly a factor of two could be explained very easily in an analytic way. We very clearly pointed out the necessity to treat particles (holes) individually in Thomas Fermi approximation. A further very promising result is that the linear response function for transferred momenta q>0.6 fm -1 can be very accurately represented in our p-h-Thomas Fermi approach. In the last paragraph we give somewhat speculative arguments that say the 2 + states of quasi macroscopic Fermi Liquid Drops could be well calculated in expanding the time dependent density matrix on a set of coherent states and a simple example for nearly harmonic potentials is given

  3. Constraining decaying dark matter with Fermi LAT gamma-rays

    International Nuclear Information System (INIS)

    Zhang, Le; Sigl, Günter; Weniger, Christoph; Maccione, Luca; Redondo, Javier

    2010-01-01

    High energy electrons and positrons from decaying dark matter can produce a significant flux of gamma rays by inverse Compton off low energy photons in the interstellar radiation field. This possibility is inevitably related with the dark matter interpretation of the observed PAMELA and FERMI excesses. The aim of this paper is providing a simple and universal method to constrain dark matter models which produce electrons and positrons in their decay by using the Fermi LAT gamma-ray observations in the energy range between 0.5 GeV and 300 GeV. We provide a set of universal response functions that, once convolved with a specific dark matter model produce the desired constraints. Our response functions contain all the astrophysical inputs such as the electron propagation in the galaxy, the dark matter profile, the gamma-ray fluxes of known origin, and the Fermi LAT data. We study the uncertainties in the determination of the response functions and apply them to place constraints on some specific dark matter decay models that can well fit the positron and electron fluxes observed by PAMELA and Fermi LAT. To this end we also take into account prompt radiation from the dark matter decay. We find that with the available data decaying dark matter cannot be excluded as source of the PAMELA positron excess

  4. A new straight accelerator tube with U diaphragm

    International Nuclear Information System (INIS)

    Liu Jinhong; Lai Weiquan; Deng Yushen; Zhang Jidong

    1994-01-01

    After calculating the potential distribution and the particle trajectories in electrostatic accelerator tubes, a new straight tube with U diaphragm to suppress secondary particles is proposed. It's properties are demonstrated by the high voltage tests and the γ-rays measurements in the accelerator

  5. Computational Approach in Determination of 233U and 233Th Fermi Energy

    International Nuclear Information System (INIS)

    Kurniadi, R.; Perkasa, Y. S.; Waris, A.

    2010-01-01

    There are several methods to get Fermi energy such as hermit polynomial expansion and Wigner-Kirkwood expansion, these are analytical method. In this paper will be discussed numerical approach of calculating Fermi energy of 233 Th and 233 U nuclei. Our work demonstrates the simple technique of determining Fermi energy.

  6. A search for neutrino emission from the Fermi bubbles with the ANTARES telescope

    NARCIS (Netherlands)

    Adrian-Martinez, S.; Albert, A.; Al Samarai, I.; Andre, M.; Anton, G.; Anvar, S.; Ardid, M.; Astraatmadja, T.; Aubert, J.J.; Baret, B.; Barrios-Marti, J.; Basa, S.; Bertin, V.; Biagi, S.; Bigongiari, C.; Bogazzi, C.; Bouhou, B.; Bouwhuis, M.; Brunner, J.; Busto, J.; Capone, A.; Caramete, L.; Carloganu, C.; Carr, J.; Cecchini, S.; Charif, Z.; Charvis, P.; Chiarusi, T.; Circella, M.; Classen, F.; Coniglione, R.; Core, L.; Costantini, H.; Coyle, P.; Creusot, A.; Curtil, C.; De Bonis, G.; Dekeyser, I.; Deschamps, A.; Donzaud, C.; Dornic, D.; Dorosti, Q.; Drouhin, D.; Dumas, A.; Eberl, T.; Emanuele, U.; Enzenhofer, A.; Ernenwein, J.P.; Escoffier, S.; Fehn, K.; Fermani, P.; Flaminio, V.; Folger, F.; Fritsch, U.; Fusco, L.; Galata, S.; Gay, P.; Geisselsoder, S.; Geyer, K.; Giacomelli, G.; Giordano, V.; Gleixner, A.; Gomez-Gonzalez, J.P.; Graf, K.; Guillard, G.; van Haren, H.; Heijboer, A.; Hello, Y.; Hernandez-Rey, J.; Herold, B.; Hossl, J.; Hugon, C.; James, C.; de Jong, M.; Kadler, M.; Kalekin, O.; Kappes, A.; Katz, U.; Kooijman, P.; Kouchner, A.; Kreykenbohm, I.; Kulikovskiy, V.; Lahmann, R.; Lambard, E.; Lambard, G.; Larosa, G.; Lattuada, D.; Lefevre, D.; Leonora, E.; Lo Presti, D.; Loehner, H.; Loucatos, S.; Louis, F.; Mangano, S.; Marcelin, M.; Margiotta, A.; Martinez-Mora, J.; Martini, S.; Michael, T.; Montaruli, T.; Morganti, M.; Muller, C.; Neff, M.; Nezri, E.; Palioselitis, D.; Pavalas, G.E.; Perrina, C.; Popa, V.; Pradier, T.; Racca, C.; Riccobene, G.; Richter, R.; Riviere, C.; Robert, A.; Roensch, K.; Rostovtsev, A.; Samtleben, D.; Sanguineti, M.; Sapienza, P.; Schmid, J.; Schnabel, J.; Schulte, S.; Schussler, F.; Seitz, T.; Shanidze, R.; Sieger, C.; Simeone, F.; Spies, A.; Spurio, M.; Steijger, J.; Stolarczyk, T.; Sanchez-Losa, A.; Taiuti, M.; Tamburini, C.; Tayalati, Y.; Trovato, A.; Vallage, B.; Vallee, C.; Van Elewyck, V.; Vecchi, M.; Vernin, P.; Visser, E.; Wagner, S.; Wilms, J.; de Wolf, E.; Yatkin, K.; Yepes, H.; Zornoza, J.; Zuniga, J.; the ANTARES Collaboration

    2014-01-01

    Analysis of the Fermi-LAT data has revealed two extended structures above and below the Galactic Centre emitting gamma rays with a hard spectrum, the so-called Fermi bubbles. Hadronic models attempting to explain the origin of the Fermi bubbles predict the emission of high-energy neutrinos and gamma

  7. Fermi bubbles inflated by winds launched from the hot accretion flow in Sgr A*

    International Nuclear Information System (INIS)

    Mou, Guobin; Yuan, Feng; Bu, Defu; Sun, Mouyuan; Su, Meng

    2014-01-01

    A pair of giant gamma-ray Bubbles has been revealed by Fermi-LAT. In this paper we investigate their formation mechanism. Observations have indicated that the activity of the supermassive black hole located at the Galactic center, Sgr A*, was much stronger than at the present time. Specifically, one possibility is that while Sgr A* was also in the hot accretion regime, the accretion rate should be 10 3 -10 4 times higher during the past ∼10 7 yr. On the other hand, recent magnetohydrodynamic numerical simulations of hot accretion flows have unambiguously shown the existence and obtained the properties of strong winds. Based on this knowledge, by performing three-dimensional hydrodynamical simulations, we show in this paper that the Fermi Bubbles could be inflated by winds launched from the 'past' hot accretion flow in Sgr A*. In our model, the active phase of Sgr A* is required to last for about 10 million years and it was quenched no more than 0.2 million years ago. The central molecular zone (CMZ) is included and it collimates the wind orientation toward the Galactic poles. Viscosity suppresses the Rayleigh-Taylor and Kelvin-Helmholtz instabilities and results in the smoothness of the Bubbles edge. The main observational features of the Bubbles can be well explained. Specifically, the ROSAT X-ray features are interpreted by the shocked interstellar medium and the interaction region between the wind and CMZ gas. The thermal pressure and temperature obtained in our model are consistent with recent Suzaku observations.

  8. Effects of impurity and Bose-Fermi interactions on the transition temperature of a dilute dipolar Bose-Einstein condensation in trapped Bose-Fermi mixtures

    Science.gov (United States)

    Yavari, H.; Mokhtari, M.

    2014-03-01

    The effects of impurity and Bose-Fermi interactions on the transition temperature of a dipolar Bose-Einstein condensation in trapped Bose-Fermi mixture, by using the two-fluid model, are investigated. The shift of the transition temperature consists of four contributions due to contact, Bose-Fermi, dipole-dipole, and impurity interactions. We will show that in the presence of an anisotropic trap, the Bose-Fermi correction to the shift of transition temperature due to the excitation spectra of the thermal part is independent of anisotropy factor. Applying our results to trapped Bose-Fermi mixtures shows that, by knowing the impurity effect, the shift of the transition temperature due to Bose-Fermi interaction could be measured for isotropic trap (dipole-dipole contributions is zero) and Feshbach resonance technique (contact potential contribution is negligible).

  9. Suppression of Magnetoresistance in Thin WTe2 Flakes by Surface Oxidation.

    Science.gov (United States)

    Woods, John M; Shen, Jie; Kumaravadivel, Piranavan; Pang, Yuan; Xie, Yujun; Pan, Grace A; Li, Min; Altman, Eric I; Lu, Li; Cha, Judy J

    2017-07-12

    Recent renewed interest in layered transition metal dichalcogenides stems from the exotic electronic phases predicted and observed in the single- and few-layer limit. Realizing these electronic phases requires preserving the desired transport properties down to a monolayer, which is challenging. Surface oxides are known to impart Fermi level pinning or degrade the mobility on a number of different systems, including transition metal dichalcogenides and black phosphorus. Semimetallic WTe 2 exhibits large magnetoresistance due to electron-hole compensation; thus, Fermi level pinning in thin WTe 2 flakes could break the electron-hole balance and suppress the large magnetoresistance. We show that WTe 2 develops an ∼2 nm thick amorphous surface oxide, which shifts the Fermi level by ∼300 meV at the WTe 2 surface. We also observe a dramatic suppression of the magnetoresistance for thin flakes. However, due to the semimetallic nature of WTe 2 , the effects of Fermi level pinning are well screened and are not the dominant cause for the suppression of magnetoresistance, supported by fitting a two-band model to the transport data, which showed the electron and hole carrier densities are balanced down to ∼13 nm. However, the fitting shows a significant decrease of the mobilities of both electrons and holes. We attribute this to the disorder introduced by the amorphous surface oxide layer. Thus, the decrease of mobility is the dominant factor in the suppression of magnetoresistance for thin WTe 2 flakes. Our study highlights the critical need to investigate often unanticipated and sometimes unavoidable extrinsic surface effects on the transport properties of layered dichalcogenides and other 2D materials.

  10. FERMI LARGE AREA TELESCOPE OBSERVATIONS OF THE CYGNUS LOOP SUPERNOVA REMNANT

    International Nuclear Information System (INIS)

    Katagiri, H.; Tibaldo, L.; Ballet, J.; Grenier, I. A.; Giordano, F.; Porter, T. A.; Uchiyama, Y.; Roth, M.; Tibolla, O.; Yamazaki, R.

    2011-01-01

    We present an analysis of the gamma-ray measurements by the Large Area Telescope onboard the Fermi Gamma-ray Space Telescope in the region of the supernova remnant (SNR) Cygnus Loop (G74.0–8.5). We detect significant gamma-ray emission associated with the SNR in the energy band 0.2-100 GeV. The gamma-ray spectrum shows a break in the range 2-3 GeV. The gamma-ray luminosity is ∼1 × 10 33 erg s –1 between 1 and 100 GeV, much lower than those of other GeV-emitting SNRs. The morphology is best represented by a ring shape, with inner/outer radii 0. 0 7 ± 0. 0 1 and 1. 0 6 ± 0. 0 1. Given the association among X-ray rims, Hα filaments, and gamma-ray emission, we argue that gamma rays originate in interactions between particles accelerated in the SNR and interstellar gas or radiation fields adjacent to the shock regions. The decay of neutral pions produced in nucleon-nucleon interactions between accelerated hadrons and interstellar gas provides a reasonable explanation for the gamma-ray spectrum.

  11. Fermi Large Area Telescope Observations of the Cygnus Loop Supernova Remnant

    Energy Technology Data Exchange (ETDEWEB)

    Katagiri, H.; /Ibaraki U., Mito; Tibaldo, L.; /INFN, Padua /Padua U. /Paris U., VI-VII; Ballet, J.; /Paris U., VI-VII; Giordano, F.; /Bari U. /Bari Polytechnic /INFN, Bari; Grenier, I.A.; /Paris U., VI-VII; Porter, T.A.; /Stanford U., HEPL /KIPAC, Menlo Park /SLAC; Roth, M.; /Washington U., Seattle; Tibolla, O.; /Wurzburg U.; Uchiyama, Y.; /Stanford U., HEPL /KIPAC, Menlo Park /SLAC; Yamazaki, R.; /Sagamihara, Aoyama Gakuin U.

    2011-11-08

    We present an analysis of the gamma-ray measurements by the Large Area Telescope (LAT) onboard the Fermi Gamma-ray Space Telescope in the region of the supernova remnant (SNR) Cygnus Loop (G74.0-8.5). We detect significant gamma-ray emission associated with the SNR in the energy band 0.2-100 GeV. The gamma-ray spectrum shows a break in the range 2-3 GeV. The gamma-ray luminosity is {approx} 1 x 10{sup 33} erg s{sup -1} between 1-100 GeV, much lower than those of other GeV-emitting SNRs. The morphology is best represented by a ring shape, with inner/outer radii 0{sup o}.7 {+-} 0{sup o}.1 and 1{sup o}.6 {+-} 0{sup o}.1. Given the association among X-ray rims, H{alpha} filaments and gamma-ray emission, we argue that gamma rays originate in interactions between particles accelerated in the SNR and interstellar gas or radiation fields adjacent to the shock regions. The decay of neutral pions produced in nucleon-nucleon interactions between accelerated hadrons and interstellar gas provides a reasonable explanation for the gamma-ray spectrum.

  12. Fermi Large Area Telescope Observations of the Cygnus Loop Supernova Remnant

    International Nuclear Information System (INIS)

    Katagiri, H.; Tibaldo, L.; Ballet, J.; Giordano, F.; Grenier, I.A.; Porter, T.A.; Roth, M.; Tibolla, O.; Uchiyama, Y.; Yamazaki, R.

    2011-01-01

    We present an analysis of the gamma-ray measurements by the Large Area Telescope (LAT) onboard the Fermi Gamma-ray Space Telescope in the region of the supernova remnant (SNR) Cygnus Loop (G74.0-8.5). We detect significant gamma-ray emission associated with the SNR in the energy band 0.2-100 GeV. The gamma-ray spectrum shows a break in the range 2-3 GeV. The gamma-ray luminosity is ∼ 1 x 10 33 erg s -1 between 1-100 GeV, much lower than those of other GeV-emitting SNRs. The morphology is best represented by a ring shape, with inner/outer radii 0 o .7 ± 0 o .1 and 1 o .6 ± 0 o .1. Given the association among X-ray rims, Hα filaments and gamma-ray emission, we argue that gamma rays originate in interactions between particles accelerated in the SNR and interstellar gas or radiation fields adjacent to the shock regions. The decay of neutral pions produced in nucleon-nucleon interactions between accelerated hadrons and interstellar gas provides a reasonable explanation for the gamma-ray spectrum.

  13. Stability of accelerated metal shells

    International Nuclear Information System (INIS)

    Tahsiri, H.

    1976-01-01

    A systematic treatment has been developed for the Rayleigh-Taylor instability of an accelerated liner. It is applicable to one-dimensional models either compressible or incompressible. With this model several points have been clarified. For an incompressible liner model, the Rayleigh-Taylor instability will have about five e-folding periods and the usual growth rate is independent of the current distribution or current rise time. Adequate stability will therefore depend on the magnitude of the initial perturbations or the precision of the initial liner and the thickness over which the shell is accelerated. However, for a compressible model, theory predicts that the current rise time is important and the Rayleigh-Taylor instability is suppressed if the current rise time is less than the shock transit time

  14. Sector ring accelerator ''RESATRON''

    International Nuclear Information System (INIS)

    Schwabe, E.

    1980-01-01

    Project of sector ring accelerator RESATRON is described. The curiosity of this accelerator is the second cycle of acceleration of the beam after stripping it on the foil. In such an accelerator heavy ions with a different ratio Z to A can be accelerated. (S.B.)

  15. AFTERGLOW OBSERVATIONS OF FERMI LARGE AREA TELESCOPE GAMMA-RAY BURSTS AND THE EMERGING CLASS OF HYPER-ENERGETIC EVENTS

    International Nuclear Information System (INIS)

    Cenko, S. B.; Butler, N. R.; Cobb, B. E.; Cucchiara, A.; Bloom, J. S.; Perley, D. A.; Filippenko, A. V.; Frail, D. A.; Harrison, F. A.; Haislip, J. B.; Reichart, D. E.; Ivarsen, K. M.; LaCluyze, A. P.; Berger, E.; Chandra, P.; Fox, D. B.; Prochaska, J. X.; Glazebrook, K.; Kasliwal, M. M.; Kulkarni, S. R.

    2011-01-01

    We present broadband (radio, optical, and X-ray) light curves and spectra of the afterglows of four long-duration gamma-ray bursts (GRBs; GRBs 090323, 090328, 090902B, and 090926A) detected by the Gamma-Ray Burst Monitor and Large Area Telescope (LAT) instruments on the Fermi satellite. With its wide spectral bandpass, extending to GeV energies, Fermi is sensitive to GRBs with very large isotropic energy releases (10 54 erg). Although rare, these events are particularly important for testing GRB central-engine models. When combined with spectroscopic redshifts, our afterglow data for these four events are able to constrain jet collimation angles, the density structure of the circumburst medium, and both the true radiated energy release and the kinetic energy of the outflows. In agreement with our earlier work, we find that the relativistic energy budget of at least one of these events (GRB 090926A) exceeds the canonical value of 10 51 erg by an order of magnitude. Such energies pose a severe challenge for models in which the GRB is powered by a magnetar or a neutrino-driven collapsar, but remain compatible with theoretical expectations for magnetohydrodynamical collapsar models (e.g., the Blandford-Znajek mechanism). Our jet opening angles (θ) are similar to those found for pre-Fermi GRBs, but the large initial Lorentz factors (Γ 0 ) inferred from the detection of GeV photons imply θΓ 0 ∼ 70-90, values which are above those predicted in magnetohydrodynamic models of jet acceleration. Finally, we find that these Fermi-LAT events preferentially occur in a low-density circumburst environment, and we speculate that this might result from the lower mass-loss rates of their lower-metallicity progenitor stars. Future studies of Fermi-LAT afterglows at radio wavelengths with the order-of-magnitude improvement in sensitivity offered by the Extended Very Large Array should definitively establish the relativistic energy budgets of these events.

  16. Quantum nonlocal theory of topological Fermi arc plasmons in Weyl semimetals

    Science.gov (United States)

    Andolina, Gian Marcello; Pellegrino, Francesco M. D.; Koppens, Frank H. L.; Polini, Marco

    2018-03-01

    The surface of a Weyl semimetal (WSM) displays Fermi arcs, i.e., disjoint segments of a two-dimensional Fermi contour. We present a quantum-mechanical nonlocal theory of chiral Fermi arc plasmons in WSMs with broken time-reversal symmetry. These are collective excitations constructed from topological Fermi arc and bulk electron states and arising from electron-electron interactions, which are treated in the realm of the random phase approximation. Our theory includes quantum effects associated with the penetration of the Fermi arc surface states into the bulk and dissipation, which is intrinsically nonlocal in nature and arises from decay processes mainly involving bulk electron-hole pair excitations.

  17. The universal sound velocity formula for the strongly interacting unitary Fermi gas

    International Nuclear Information System (INIS)

    Liu Ke; Chen Ji-Sheng

    2011-01-01

    Due to the scale invariance, the thermodynamic laws of strongly interacting limit unitary Fermi gas can be similar to those of non-interacting ideal gas. For example, the virial theorem between pressure and energy density of the ideal gas P = 2E/3V is still satisfied by the unitary Fermi gas. This paper analyses the sound velocity of unitary Fermi gases with the quasi-linear approximation. For comparison, the sound velocities for the ideal Boltzmann, Bose and Fermi gas are also given. Quite interestingly, the sound velocity formula for the ideal non-interacting gas is found to be satisfied by the unitary Fermi gas in different temperature regions. (general)

  18. Gamma-Ray Emission in Dissipative Pulsar Magnetospheres: from Theory to Fermi Observations

    Science.gov (United States)

    Kalapotharakos, Konstantinos; Harding, Alice K.; Kazanas, Demosthenes

    2014-01-01

    We compute the patterns of gamma-ray emission due to curvature radiation in dissipative pulsar magnetospheres. Our ultimate goal is to construct macrophysical models that are able to reproduce the observed gamma-ray light curve phenomenology recently published in the Second Fermi Pulsar Catalog. We apply specific forms of Ohm's law on the open field lines using a broad range for the macroscopic conductivity values that result in solutions ranging, from near-vacuum to near-force-free. Using these solutions, we generate model gamma-ray light curves by calculating realistic trajectories and Lorentz factors of radiating particles under the influence of both the accelerating electric fields and curvature radiation reaction. We further constrain our models using the observed dependence of the phase lags between the radio and gamma-ray emission on the gamma-ray peak separation. We perform a statistical comparison of our model radio-lag versus peak-separation diagram and the one obtained for the Fermi standard pulsars. We find that for models of uniform conductivity over the entire open magnetic field line region, agreement with observations favors higher values of this parameter. We find, however, significant improvement in fitting the data with models that employ a hybrid form of conductivity, specifically, infinite conductivity interior to the light cylinder and high but finite conductivity on the outside. In these models the gamma-ray emission is produced in regions near the equatorial current sheet but modulated by the local physical properties. These models have radio lags near the observed values and statistically best reproduce the observed light curve phenomenology. Additionally, they also produce GeV photon cut-off energies.

  19. Multiperiodic accelerator structures for linear particle accelerators

    International Nuclear Information System (INIS)

    Tran, D.T.

    1975-01-01

    High efficiency linear accelerator structures, comprised of a succession of cylindrical resonant cavities for acceleration, are described. Coupling annular cavities are located at the periphery, each being coupled to two adjacent cylindrical cavities. (auth)

  20. Sodium fire suppression

    Energy Technology Data Exchange (ETDEWEB)

    Malet, J C [DSN/SESTR, Centre de Cadarache, Saint-Paul-lez-Durance (France)

    1979-03-01

    Ignition and combustion studies have provided valuable data and guidelines for sodium fire suppression research. The primary necessity is to isolate the oxidant from the fuel, rather than to attempt to cool the sodium below its ignition temperature. Work along these lines has led to the development of smothering tank systems and a dry extinguishing powder. Based on the results obtained, the implementation of these techniques is discussed with regard to sodium fire suppression in the Super-Phenix reactor. (author)

  1. Sodium fire suppression

    International Nuclear Information System (INIS)

    Malet, J.C.

    1979-01-01

    Ignition and combustion studies have provided valuable data and guidelines for sodium fire suppression research. The primary necessity is to isolate the oxidant from the fuel, rather than to attempt to cool the sodium below its ignition temperature. Work along these lines has led to the development of smothering tank systems and a dry extinguishing powder. Based on the results obtained, the implementation of these techniques is discussed with regard to sodium fire suppression in the Super-Phenix reactor. (author)

  2. Accelerators of atomic particles

    International Nuclear Information System (INIS)

    Sarancev, V.

    1975-01-01

    A brief survey is presented of accelerators and methods of accelerating elementary particles. The principle of collective accelerating of elementary particles is clarified and the problems are discussed of its realization. (B.S.)

  3. Dirac vacuum: Acceleration and external-field effects

    International Nuclear Information System (INIS)

    Jauregui, R.; Torres, M.; Hacyan, S.

    1991-01-01

    The quantization of the massive spin-1/2 field in Rindler coordinates is considered, including the effects of a background magnetic field. We calculate the expectation values of conserved quantities such as the stress-energy tensor, current density, and spin distribution, as detected by an accelerated observer. The ratio of the energy and particle densities is given by a Fermi-Dirac distribution, but the spectrum of these quantities takes in general a complicated form that cannot be simply interpreted as a thermal spectrum. For the free-particle case the spectrum of the energy-stress tensor has a Fermi-Dirac form only in the massless limit. In the presence of the magnetic field the Dirac vacuum is magnetized and exhibits plasmalike properties

  4. Dark matter annihilations search in dwarf spheroidal galaxies with fermi

    International Nuclear Information System (INIS)

    Farnier, C.; Nuss, E.; Cohen-Tanugi, J.

    2011-01-01

    Launched in June 2008, the Fermi Gamma-ray Telescope includes a pair conversion detector designed for the 20 MeV to ∼300GeV gamma-ray sky study, the Large Area Telescope (LAT). Operating in all-sky survey mode, its excellent sensitivity and angular resolution will allow either to discover or constrain a signal coming through the annihilation of dark matter particles. Predicted by cold dark matter scenarios as the largest clumps, dwarf spheroidal galaxies are amongst the most attractive targets for indirect search of dark matter by gamma-ray experiments. We present here an overview of the Fermi LAT Dark Matter and New Physics Working Group efforts in the searches of gamma-ray fluxes coming from WIMP pair annihilations in dwarf spheroidal galaxies.

  5. GRB Duration Distribution Considering the Position of the Fermi

    Directory of Open Access Journals (Sweden)

    D. Szécsi

    2012-01-01

    Full Text Available The Fermi satellite has a particular motion during its flight which enables it to catch the gamma-ray bursts mostly well. The side-effect of this favourable feature is that the lightcurves of the GBM detectors are stressed by rapidly and extremely varying background. Before this data is processed, it needs to be separated from the background. The commonly used methods [3,7] were useless for most cases of Fermi, so we developed a new technique based on the motion and orientation of the satellite. The background-free lightcurve can be used to perform statistical surveys, hence we showed the efficiency of our background-filtering method presenting a statistical analysis known from the literature.

  6. Magnetar Observations in the Swift-Fermi/GBM Era

    Science.gov (United States)

    Kouveliotou, Chryssa

    2010-01-01

    NASA's Fermi Observatory was launched June 11, 2008; the Fermi Gamma Ray Burst Monitor (GBM) began normal operations on July 14, about a month after launch, when the trigger algorithms were enabled. Since then, and against all odds, GBM recorded over 600 bursts from 4 SGRs. Of these four sources, only one was an old magnetar: SGR J1806+20. SGR J0501+4516, was discovered with Swift and extensively monitored with GBM. A source originally classified as AXP 1E1547.0-5408 exhibited SGR-like bursting behavior and we reclassified it as SGR J1550-5418. Finally, GBM discovered SGR J0418+5729 on 2009 June. Finally, on March 2010, a third new magnetar was discovered with Swift, SGR J1833-0832. I report below on the current status of the field and on several results combining multi-satellite and ground-based data

  7. Instanton effects in ABJM theory from Fermi gas approach

    Energy Technology Data Exchange (ETDEWEB)

    Hatsuda, Yasuyuki [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany). Gruppe Theorie; Tokyo Institute of Technology (Japan). Dept. of Physics; Moriyama, Sanefumi [Nagoya Univ. (Japan). Kobayashi Maskawa Inst.; Nagoya Univ. (Japan). Graduate School of Mathematics; Okuyama, Kazumi [Shinshu Univ., Matsumoto, Nagano (Japan). Dept. of Physics

    2012-11-19

    We study the instanton effects of the ABJM partition function using the Fermi gas formalism. We compute the exact values of the partition function at the Chern-Simons levels k=1, 2, 3, 4, 6 up to N=44, 20, 18, 16, 14 respectively, and extract non-perturbative corrections from these exact results. Fitting the resulting non-perturbative corrections by their expected forms from the Fermi gas, we determine unknown parameters in them. After separating the oscillating behavior of the grand potential, which originates in the periodicity of the grand partition function, and the worldsheet instanton contribution, which is computed from the topological string theory, we succeed in proposing an analytical expression for the leading D2-instanton correction. Just as the perturbative result, the instanton corrections to the partition function are expressed in terms of the Airy function.

  8. Localized-to-extended-states transition below the Fermi level

    Science.gov (United States)

    Tito, M. A.; Pusep, Yu. A.

    2018-05-01

    Time-resolved photoluminescence is employed to examine a transition from localized to extended electron states below the Fermi level in multiple narrow quantum well GaAs/AlGaAs heterostructures, where disorder was generated by interface roughness. Such a transition resembles the metal-insulator transition profoundly investigated by electric transport measurements. An important distinction distinguishes the localized-to-extended-states transition studied here: it takes place below the Fermi level in an electron system with a constant concentration, which implies unchanging Coulomb correlations. Moreover, for such a localized-to-extended-states transition the temperature is shown to be irrelevant. In the insulating regime the magnetic field was found to cause an additional momentum relaxation which considerably enhanced the recombination rate. Thus, we propose a method to explore the evolution of the localized electron states in a system with a fixed disorder and Coulomb interaction.

  9. Weyl states and Fermi arcs in parabolic bands

    Science.gov (United States)

    Doria, Mauro M.; Perali, Andrea

    2017-07-01

    Weyl fermions are shown to exist inside a parabolic band in a single electronic layer, where the kinetic energy of carriers is given by the non-relativistic Schroedinger equation. There are Fermi arcs as a direct consequence of the folding of a ring-shaped Fermi surface inside the first Brillouin zone. Our results stem from the decomposition of the kinetic energy into the sum of the square of the Weyl state, the coupling to the local magnetic field and the Rashba interaction. The Weyl fermions break the space and time reflection symmetries present in the kinetic energy, thus allowing for the onset of a weak three-dimensional magnetic field around the layer. This field brings topological stability to the current-carrying states through a Chern number. In the special limit for which the Weyl state becomes gapless, this magnetic interaction is shown to be purely attractive, thus suggesting the onset of a superconducting condensate of zero helicity states.

  10. THE FIVE YEAR FERMI/GBM MAGNETAR BURST CATALOG

    Energy Technology Data Exchange (ETDEWEB)

    Collazzi, A. C. [SciTec, Inc., 100 Wall Street, Princeton, NJ 08540 (United States); Kouveliotou, C.; Horst, A. J. van der; Younes, G. A. [Department of Physics, The George Washington University, 725 21st Street NW, Washington, DC 20052 (United States); Kaneko, Y.; Göğüş, E. [Sabancı University, Orhanlı-Tuzla, İstanbul 34956 (Turkey); Lin, L. [François Arago Centre, APC, 10 rue Alice Domon et Léonie Duquet, F-75205 Paris (France); Granot, J. [Department of Natural Sciences, The Open University of Israel, 1 University Road, P.O. Box 808, Raanana 43537 (Israel); Finger, M. H. [Universities Space Research Association, NSSTC, 320 Sparkman Drive, Huntsville, AL 35805 (United States); Chaplin, V. L. [School of Medicine, Vanderbilt University, 1161 21st Avenue S, Nashville, TN 37232 (United States); Huppenkothen, D. [Center for Data Science, New York University, 726 Broadway, 7th Floor, New York, NY 10003 (United States); Watts, A. L. [Anton Pannekoek Institute, University of Amsterdam, Postbus 94249, 1090 GE Amsterdam (Netherlands); Kienlin, A. von [Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse 1, D-85748 Garching (Germany); Baring, M. G. [Department of Physics and Astronomy, Rice University, MS-108, P.O. Box 1892, Houston, TX 77251 (United States); Gruber, D. [Planetarium Südtirol, Gummer 5, I-39053 Karneid (Italy); Bhat, P. N. [CSPAR, University of Alabama in Huntsville, 320 Sparkman Drive, Huntsville, AL 35899 (United States); Gibby, M. H., E-mail: acollazzi@scitec.com [Jacobs Technology, Inc., Huntsville, AL (United States); and others

    2015-05-15

    Since launch in 2008, the Fermi Gamma-ray Burst Monitor (GBM) has detected many hundreds of bursts from magnetar sources. While the vast majority of these bursts have been attributed to several known magnetars, there is also a small sample of magnetar-like bursts of unknown origin. Here, we present the Fermi/GBM magnetar catalog, providing the results of the temporal and spectral analyses of 440 magnetar bursts with high temporal and spectral resolution. This catalog covers the first five years of GBM magnetar observations, from 2008 July to 2013 June. We provide durations, spectral parameters for various models, fluences, and peak fluxes for all the bursts, as well as a detailed temporal analysis for SGR J1550–5418 bursts. Finally, we suggest that some of the bursts of unknown origin are associated with the newly discovered magnetar 3XMM J185246.6+0033.7.

  11. Metastability in spin polarised Fermi gases and quasiparticle decays

    DEFF Research Database (Denmark)

    Sadeghzadeh, Kayvan; Bruun, Georg; Lobo, Carlos

    2011-01-01

    We investigate the metastability associated with the first order transition from normal to superfluid phases in the phase diagram of two-component polarised Fermi gases.We begin by detailing the dominant decay processes of single quasiparticles.Having determined the momentum thresholds of each...... the interaction strength at which a polarised phase of molecules becomes the groundstate, to the one at which the single quasiparticle groundstate changes character from polaronic to molecular. Our argument in terms of a Fermi sea of polarons naturally suggests their use as an experimental probe. We propose...... experiments to observe the threshold of the predicted region of metastability, the interaction strength at which the quasiparticle groundstate changes character, and the decay rate of polarons....

  12. Enhanced diphoton rates at Fermi and the LHC

    Energy Technology Data Exchange (ETDEWEB)

    Schmidt-Hoberg, Kai [European Organization for Nuclear Research (CERN), Geneva (Switzerland); Staub, Florian [Bonn Univ. (Germany). Bethe Center for Theoretical Physics und Physikalisches Inst.; Winkler, Martin Wolfgang [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)

    2012-11-15

    We show that within MSSM singlet extensions the experimental hints beyond the standard model from the Fermi LAT telescope as well as from the LHC can be explained simultaneously while being consistent with all experimental constraints. In particular we present an example point which features a {proportional_to}130 GeV lightest neutralino with an annihilation cross section into photons consistent with the indication from the Fermi satellite with simultaneously the right relic abundance, a continuum photon spectrum consistent with observation, direct detection cross section below the experimental limits, electroweak observables consistent with experiment and a 125 GeV light Higgs boson with a slightly enhanced h{yields}{gamma}{gamma} rate.

  13. Plasma dispersion function for a Fermi-Dirac distribution

    International Nuclear Information System (INIS)

    Melrose, D. B.; Mushtaq, A.

    2010-01-01

    A plasma dispersion function (PDF) is defined for a nonrelativistic Fermi-Dirac distribution and its properties are explored. The degree of degeneracy is described by a parameter ξ=e μ e /T e , for electrons, with μ e /T e large and negative in the nondegenerate limit, and large and positive in the completely degenerate limit. The PDF is denoted Z(y,ξ), where the variable y=ω/√(2)kV e , is the argument of the conventional PDF, Z(y)=Z(y,0), for a Maxwellian distribution. In the completely degenerate limit, Z(y,ξ) approaches a logarithmic function that depends on the Fermi temperature and is independent of T e . Analytic approximations to Z(y,ξ) are derived in terms of polylogarithmic functions for y 2 >>1 and for y 2 <<1.

  14. Small metal particles and the ideal Fermi gas

    International Nuclear Information System (INIS)

    Barma, Mustanpir

    1991-01-01

    Kubo's theoretical model of a small metal particle consists of a number of noninteraction electrons (an ideal Fermi gas) confined to a finite volume. By 'small' it meant that the size of the particle is intermediate between that of a few atoms cluster and the bulk solid, the radius of the particle being 5 to 50 Angstroms. The model is discussed and size dependence of various energy scales is studied. For a fermi gas confined in a sphere or a cube, two size-dependent energy scales are important. The inner scale δ is the mean spacing between successive energy levels. It governs the very low temperature behaviour. The outer scale Δ is associated with the shell structure when δ ≤T<Δ, thermodynamic properties show an oscillatory fluctuations around a smooth background as the size or energy is varied. (M.G.B.) 23 refs

  15. Optimized digital feature extraction in the FERMI microsystem

    International Nuclear Information System (INIS)

    Alexanian, H.; Appelquist, G.; Bailly, P.

    1995-01-01

    We describe the digital filter section of the FERMI readout microsystem. The filter section, consisting of two separate filter blocks, extracts the pulse amplitude and time information for the first-level trigger process and performs a highly accurate energy measurement for higher-level triggering and data readout purposes. An FIR-order statistic hybrid filter structure is used to improve the amplitude extraction performance. Using a training procedure the filters are optimized to produce a precise and accurate output in the presence of electronics and pile-up noise, sample timing jitter and the superposition of high-energy pulses. As the FERMI system resides inside the detector where accessibility is limited, the filter implementations are presented together with fault tolerance considerations. The filter section is modelled with the VHDL hardware descriptive language and the subsystems are further optimized to minimize the system latency and circuit area. ((orig.))

  16. Poisson-Fermi Formulation of Nonlocal Electrostatics in Electrolyte Solutions

    Directory of Open Access Journals (Sweden)

    Liu Jinn-Liang

    2017-10-01

    Full Text Available We present a nonlocal electrostatic formulation of nonuniform ions and water molecules with interstitial voids that uses a Fermi-like distribution to account for steric and correlation efects in electrolyte solutions. The formulation is based on the volume exclusion of hard spheres leading to a steric potential and Maxwell’s displacement field with Yukawa-type interactions resulting in a nonlocal electric potential. The classical Poisson-Boltzmann model fails to describe steric and correlation effects important in a variety of chemical and biological systems, especially in high field or large concentration conditions found in and near binding sites, ion channels, and electrodes. Steric effects and correlations are apparent when we compare nonlocal Poisson-Fermi results to Poisson-Boltzmann calculations in electric double layer and to experimental measurements on the selectivity of potassium channels for K+ over Na+.

  17. Degenerate Fermi gas in a combined harmonic-lattice potential

    International Nuclear Information System (INIS)

    Blakie, P. B.; Bezett, A.; Buonsante, P.

    2007-01-01

    In this paper we derive an analytic approximation to the density of states for atoms in a combined optical lattice and harmonic trap potential as used in current experiments with quantum degenerate gases. We compare this analytic density of states to numerical solutions and demonstrate its validity regime. Our work explicitly considers the role of higher bands and when they are important in quantitative analysis of this system. Applying our density of states to a degenerate Fermi gas, we consider how adiabatic loading from a harmonic trap into the combined harmonic-lattice potential affects the degeneracy temperature. Our results suggest that occupation of excited bands during loading should lead to more favorable conditions for realizing degenerate Fermi gases in optical lattices

  18. Fulde–Ferrell superfluids in spinless ultracold Fermi gases

    Science.gov (United States)

    Zheng, Zhen-Fei; Guo, Guang-Can; Zheng, Zhen; Zou, Xu-Bo

    2018-06-01

    The Fulde–Ferrell (FF) superfluid phase, in which fermions form finite momentum Cooper pairings, is well studied in spin-singlet superfluids in past decades. Different from previous works that engineer the FF state in spinful cold atoms, we show that the FF state can emerge in spinless Fermi gases confined in optical lattice associated with nearest-neighbor interactions. The mechanism of the spinless FF state relies on the split Fermi surfaces by tuning the chemistry potential, which naturally gives rise to finite momentum Cooper pairings. The phase transition is accompanied by changed Chern numbers, in which, different from the conventional picture, the band gap does not close. By beyond-mean-field calculations, we find the finite momentum pairing is more robust, yielding the system promising for maintaining the FF state at finite temperature. Finally we present the possible realization and detection scheme of the spinless FF state.

  19. Suppressed Charmed B Decay

    Energy Technology Data Exchange (ETDEWEB)

    Snoek, Hella Leonie [Vrije Univ., Amsterdam (Netherlands)

    2009-06-02

    This thesis describes the measurement of the branching fractions of the suppressed charmed B0 → D*- a0+ decays and the non-resonant B0 → D*- ηπ+ decays in approximately 230 million Υ(4S) → B$\\bar{B}$ events. The data have been collected with the BABAR detector at the PEP-II B factory at the Stanford Linear Accelerator Center in California. Theoretical predictions of the branching fraction of the B0 → D*- a{sub 0}+ decays show large QCD model dependent uncertainties. Non-factorizing terms, in the naive factorization model, that can be calculated by QCD factorizing models have a large impact on the branching fraction of these decay modes. The predictions of the branching fractions are of the order of 10-6. The measurement of the branching fraction gives more insight into the theoretical models. In general a better understanding of QCD models will be necessary to conduct weak interaction physics at the next level. The presence of CP violation in electroweak interactions allows the differentiation between matter and antimatter in the laws of physics. In the Standard Model, CP violation is incorporated in the CKM matrix that describes the weak interaction between quarks. Relations amongst the CKM matrix elements are used to present the two relevant parameters as the apex of a triangle (Unitarity Triangle) in a complex plane. The over-constraining of the CKM triangle by experimental measurements is an important test of the Standard Model. At this moment no stringent direct measurements of the CKM angle γ, one of the interior angles of the Unitarity Triangle, are available. The measurement of the angle γ can be performed using the decays of neutral B mesons. The B0 → D*- a0+ decay is sensitive to the angle γ and, in comparison to the current decays that are being employed, could significantly

  20. THE FERMI BUBBLES AS A SCALED-UP VERSION OF SUPERNOVA REMNANTS

    International Nuclear Information System (INIS)

    Fujita, Yutaka; Ohira, Yutaka; Yamazaki, Ryo

    2013-01-01

    In this study, we treat Fermi bubbles as a scaled-up version of supernova remnants (SNRs). The bubbles are created through activities of the super-massive black hole (SMBH) or starbursts at the Galactic center (GC). Cosmic-rays (CRs) are accelerated at the forward shocks of the bubbles like SNRs, which means that we cannot decide whether the bubbles were created by the SMBH or starbursts from the radiation from the CRs. We follow the evolution of CR distribution by solving a diffusion-advection equation, considering the reduction of the diffusion coefficient by CR streaming. In this model, gamma rays are created through hadronic interaction between CR protons and the gas in the Galactic halo. In the GeV band, we can well reproduce the observed flat distribution of gamma-ray surface brightness because some amount of gas is left behind the shock. The edge of the bubbles is fairly sharp owing to the high gas density behind the shock and the reduction of the diffusion coefficient there. The latter also contributes the hard gamma-ray spectrum of the bubbles. We find that the CR acceleration at the shock began when the bubbles were small, and the time scale of the energy injection at the GC was much smaller than the age of the bubbles. We predict that if CRs are accelerated to the TeV regime, the apparent bubble size should be larger in the TeV band, which could be used to discriminate our hadronic model from other leptonic models. We also present neutrino fluxes

  1. AESS: Accelerated Exact Stochastic Simulation

    Science.gov (United States)

    Jenkins, David D.; Peterson, Gregory D.

    2011-12-01

    The Stochastic Simulation Algorithm (SSA) developed by Gillespie provides a powerful mechanism for exploring the behavior of chemical systems with small species populations or with important noise contributions. Gene circuit simulations for systems biology commonly employ the SSA method, as do ecological applications. This algorithm tends to be computationally expensive, so researchers seek an efficient implementation of SSA. In this program package, the Accelerated Exact Stochastic Simulation Algorithm (AESS) contains optimized implementations of Gillespie's SSA that improve the performance of individual simulation runs or ensembles of simulations used for sweeping parameters or to provide statistically significant results. Program summaryProgram title: AESS Catalogue identifier: AEJW_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEJW_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: University of Tennessee copyright agreement No. of lines in distributed program, including test data, etc.: 10 861 No. of bytes in distributed program, including test data, etc.: 394 631 Distribution format: tar.gz Programming language: C for processors, CUDA for NVIDIA GPUs Computer: Developed and tested on various x86 computers and NVIDIA C1060 Tesla and GTX 480 Fermi GPUs. The system targets x86 workstations, optionally with multicore processors or NVIDIA GPUs as accelerators. Operating system: Tested under Ubuntu Linux OS and CentOS 5.5 Linux OS Classification: 3, 16.12 Nature of problem: Simulation of chemical systems, particularly with low species populations, can be accurately performed using Gillespie's method of stochastic simulation. Numerous variations on the original stochastic simulation algorithm have been developed, including approaches that produce results with statistics that exactly match the chemical master equation (CME) as well as other approaches that approximate the CME. Solution

  2. Thermodynamics of partially confined Fermi gases at low temperature

    International Nuclear Information System (INIS)

    Toms, David J

    2004-01-01

    We examine the behaviour of non-interacting Fermi gases at low temperature. If there is a confining potential present the thermodynamic behaviour is altered from the familiar results for the unconfined gas. The role of de Haas-van Alphen type oscillations that are a consequence of the confining potential is considered. Attention is concentrated on the behaviour of the chemical potential and the specific heat. Results are compared and contrasted with those for an unconfined and a totally confined gas

  3. Particles with small violations of Fermi or Bose statistics

    International Nuclear Information System (INIS)

    Greenberg, O.W.

    1991-01-01

    I discuss the statistics of ''quons'' (pronounced to rhyme with muons), particles whose annihilation and creation operators obey the q-deformed commutation relation (the quon algebra or q-mutator) which interpolates between fermions and bosons. Topics discussed include representations of the quon algebra, proof of the TCP theorem, violation of the usual locality properties, and experimental constraints on violations of the Pauli exclusion principle (i.e., Fermi statistics) and of Bose statistics

  4. Search for Gravitational Wave Counterparts with Fermi GBM

    Science.gov (United States)

    Hui, C. M.

    2017-01-01

    The progenitor of short gamma-ray bursts (GRBs) is believed to be the merger of two compact objects. This type of events will also produce gravitational waves. Since the gravitational waves discovery by LIGO, the search for a joint detection with an electromagnetic counterpart has been ongoing. Fermi GBM detects approximately 40 short GRBs per year, and we have been expanding our search looking for faint events in the GBM data that did not trigger onboard.

  5. Fermi GBM Observations of Terrestrial Gamma-Ray Flashes

    Science.gov (United States)

    Wilson-Hodge, Colleen A.; Briggs, M. S.; Connaughton, V.; Fishman, G. J.; Bhat, P. N.; Paciesas, W. S.; Preece, R.; Kippen, R. M.; vonKienlin, A.; Dwyer, J. R.; hide

    2010-01-01

    This slide presentation explores the relationship between Terrestrial Gamma-Ray Flashes (TGF) and lightning. Using data from the World-Wide Lightning Location Network (WWLLN), and the gamma ray observations from Fermi's Gamma-ray Burst Monitor (GBM), the study reviews any causal relationship between TGFs and lightning. The conclusion of the study is that the TGF and lightning are simultaneous with out a causal relationship.

  6. Diagnosing alternative conceptions of Fermi energy among undergraduate students

    International Nuclear Information System (INIS)

    Sharma, Sapna; Ahluwalia, Pardeep Kumar

    2012-01-01

    Physics education researchers have scientifically established the fact that the understanding of new concepts and interpretation of incoming information are strongly influenced by the preexisting knowledge and beliefs of students, called epistemological beliefs. This can lead to a gap between what students actually learn and what the teacher expects them to learn. In a classroom, as a teacher, it is desirable that one tries to bridge this gap at least on the key concepts of a particular field which is being taught. One such key concept which crops up in statistical physics/solid-state physics courses, and around which the behaviour of materials is described, is Fermi energy (ε F ). In this paper, we present the results which emerged about misconceptions on Fermi energy in the process of administering a diagnostic tool called the Statistical Physics Concept Survey developed by the authors. It deals with eight themes of basic importance in learning undergraduate solid-state physics and statistical physics. The question items of the tool were put through well-established sequential processes: definition of themes, Delphi study, interview with students, drafting questions, administration, validity and reliability of the tool. The tool was administered to a group of undergraduate students and postgraduate students, in a pre-test and post-test design. In this paper, we have taken one of the themes i.e. Fermi energy of the diagnostic tool for our analysis and discussion. Students’ responses and reasoning comments given during interview were analysed. This analysis helped us to identify prevailing misconceptions/learning gaps among students on this topic. How spreadsheets can be effectively used to remove the identified misconceptions and help appreciate the finer nuances while visualizing the behaviour of the system around Fermi energy, normally sidestepped both by the teachers and learners, is also presented in this paper. (paper)

  7. Surface properties of semi-infinite Fermi systems

    International Nuclear Information System (INIS)

    Campi, X.; Stringari, S.

    1979-10-01

    A functional relation between the kinetic energy density and the total density is used to analyse the surface properties of semi-infinite Fermi systems. One find an explicit expression for the surface thickness in which the role of the infinite matter compressibility, binding energy and non-locality effects is clearly shown. The method, which holds both for nuclear and electronic systems (liquid metals), yields a very simple relation between the surface thickness and the surface energy

  8. Diboson Signals via Fermi Scale Spin-One States

    DEFF Research Database (Denmark)

    Franzosi, Diogo Buarque; Frandsen, Mads T.; Sannino, Francesco

    2015-01-01

    ATLAS and CMS observe deviations from the expected background in diboson invariant mass searches of new resonances around 2 TeV. We provide a general analysis of the results in terms of spin-one resonances and find that Fermi scale composite dynamics can be the culprit. The analysis and methodolo...... can be employed for future searches at run two of the Large Hadron Collider....

  9. Microscopic Fermi liquid approach to disordered narrow band systems

    International Nuclear Information System (INIS)

    Kolley, E.; Kolley, W.

    1977-01-01

    A Fermi liquid approach to tightly bound electrons in disordered systems is proposed to evaluate two-particle correlation functions L at T=0 deg K. Starting with a random Hubbard model and using a local ladder approximation in the particle-particle channel the irreducible particle-hole vertex is derived, being the kernel of the Bethe-Salpeter equation for L. CPA vertex corrections to the electrical conductivity and, for the ordered case, the correlation-enhanced paramagnetic susceptibility are calculated

  10. Direction Dependent Background Fitting for the Fermi GBM Data

    OpenAIRE

    Szécsi, Dorottya; Bagoly, Zsolt; Kóbori, József; Horváth, István; Balázs, Lajos G.

    2013-01-01

    We present a method for determining the background of Fermi GBM GRBs using the satellite positional information and a physical model. Since the polynomial fitting method typically used for GRBs is generally only indicative of the background over relatively short timescales, this method is particularly useful in the cases of long GRBs or those which have Autonomous Repoint Request (ARR) and a background with much variability on short timescales. We give a Direction Dependent Background Fitting...

  11. Fermi-Dirac statistics plus liquid description of quark partons

    International Nuclear Information System (INIS)

    Buccella, F.; Migliore, G.; Tibullo, V.

    1995-01-01

    A previous approach with Fermi-Dirac distributions for fermion partons is here improved to comply with the expected low x behaviour of structure functions. We are so able to get a fair description of the unpolarized and polarized structure functions of the nucleons as well as of neutrino data. We cannot reach definite conclusions, but confirm our suspicion of a relationship between the defects in Gottfried and spin sum rules. (orig.)

  12. Information entropy and Thomas-Fermi screening functions

    International Nuclear Information System (INIS)

    Donnamaria, M.C.; Meson, A.M.; Proto, A.N.

    1989-11-01

    In this work we apply the information entropy concept to analyze different trial electron densities in momentum and coordinate spaces, into the Thomas-Fermi density functional formalism. Furthermore, we try to assess how well-known physical properties of neutral atoms are reproduced and hence evaluate the quality of the screening functions in the light of their predictive capacity. (author). 32 refs, 4 figs, 3 tabs

  13. Traffic modifications on Routes Rutherford, Democrite and Fermi

    CERN Multimedia

    2015-01-01

    The GS Department would like to inform you that until the end of December, the construction of Building 245 will result in the following traffic modifications: Traffic on Route Rutherford will be partially restricted in front of the construction site, Traffic on Route Democrite will be one-way towards Route Rutherford. Also, please note that due to construction work in front of Building 377, Route Fermi will be closed from Wednesday, 10 June until Friday, 7 August. Thank you for your understanding.

  14. Coexistence of pairing gaps in three-component Fermi gases

    International Nuclear Information System (INIS)

    Nummi, O H T; Kinnunen, J J; Toermae, P

    2011-01-01

    We study a three-component superfluid Fermi gas in a spherically symmetric harmonic trap using the Bogoliubov-deGennes method. We predict a coexistence phase in which two pairing field order parameters are simultaneously non-zero, in stark contrast to studies performed for trapped gases using local density approximation. We also discuss the role of atom number conservation in the context of a homogeneous system.

  15. The Thomas-Fermi model: momentum expectation values

    International Nuclear Information System (INIS)

    Dmitrieva, I.K.; Plindov, G.I.

    1983-01-01

    Within the Thomas-Fermi model including the exchange interaction and contributions of strongly bound electrons, analytical expressions are obtained for all momentum expectation values and for some of the expectation values of powers of the electron density for an atom with an arbitrary degree of ionization. It is shown that a correct treatment of strongly bound electrons gives a quantitative estimate of and within 3 - 1 expansion coefficients for and are given as an explicit function of the electron number

  16. Fermi surface in V3Si from positron annihilation

    International Nuclear Information System (INIS)

    Peter, M.; Manuel, A.A.; Jarlborg, T.

    1982-01-01

    The recent work of the Geneva Group on the electronic structure of V 3 Si is briefly reviewed. Accurate self-consistent LMTO calculation leads to a Fermi surface and momentum distribution which is confirmed by high resolution 2-D angular correlation of positron annihilation radiation (2D-ACPAR). The bandstructure data are combined with phonon data from Junod's specific heat measurements to calculate parameters relevant to superconductivity. (orig.)

  17. Bose and Fermi walk configurations on planar graphs

    International Nuclear Information System (INIS)

    Arrowsmith, D K; Bhatti, F M; Essam, J W

    2012-01-01

    The number, f C n (H), of n-walk configurations of type C is investigated on certain two-rooted directed planar graphs H which will be always realized as plane graphs in R 2 . C may be Bose or Fermi as defined by Inui and Katori. Both types of configuration are collections of non-crossing walks which follow the directed paths between the roots of the plane graph H. In the case of configurations of Fermi type each walk may be included only once. The number f Bose n (H) is shown to be a polynomial in n of degree n max − 1 where n max is the maximum number of walks in a Fermi configuration. The coefficient of the highest power of n in this polynomial is simply related to the number of maximal Fermi walk configurations. It is also shown that n max = c(H) + 1 where c(H) is the number of finite faces on H. Extension of these results to multi-rooted graphs is also discussed. When H is the union of paths between two sites of the directed square lattice subject to various boundary conditions Kreweras showed that the number of Bose configurations is equal to the number of n-element multi-chains on segments of Young’s lattice. He expressed this number as a determinant the elements of which are polynomials in n. We evaluate this determinant by the method of LU decomposition in the case of ‘watermelon’ configurations above a wall. In this case the polynomial is a product of linear factors but on introducing a second wall the polynomial does not completely factorize but has a factor which is the number of watermelon configurations on the largest rectangular subgraph. The number of two-rooted ‘star’ configurations is found to be the product of the numbers of watermelon configurations on the three rectangular subgraphs into which it may be partitioned. (paper)

  18. High Energy Astrophysics with the Fermi Large Area Telescope

    Science.gov (United States)

    Hays, Elizabeth

    2009-01-01

    This slide presentation reviews some of the findings of the Large Area Telescope (LAT) aboard the Fermi Observatory. It includes information about the LAT, and the Gamma-Ray Burst Monitor (GBM), detection of the quiet sun and the moon in gamma rays, Pulsars observed by the observatory, Globular Star Clusters, Active Galactic Nucleus, and Gamma-Ray Bursts, with specific information about GRB 080916C.

  19. Thomas-Fermi theory for atomic nuclei revisited

    International Nuclear Information System (INIS)

    Centelles, M.; Schuck, P.; Vinas, X.

    2007-01-01

    The recently developed semiclassical variational Wigner-Kirkwood (VWK) approach is applied to finite nuclei using external potentials and self-consistent mean fields derived from Skyrme interactions and from relativistic mean field theory. VWK consists of the Thomas-Fermi part plus a pure, perturbative h 2 correction. In external potentials, VWK passes through the average of the quantal values of the accumulated level density and total energy as a function of the Fermi energy. However, there is a problem of overbinding when the energy per particle is displayed as a function of the particle number. The situation is analyzed comparing spherical and deformed harmonic oscillator potentials. In the self-consistent case, we show for Skyrme forces that VWK binding energies are very close to those obtained from extended Thomas-Fermi functionals of h 4 order, pointing to the rapid convergence of the VWK theory. This satisfying result, however, does not cure the overbinding problem, i.e., the semiclassical energies show more binding than they should. This feature is more pronounced in the case of Skyrme forces than with the relativistic mean field approach. However, even in the latter case the shell correction energy for e.g., 208 Pb turns out to be only ∼-6 MeV what is about a factor two or three off the generally accepted value. As an ad hoc remedy, increasing the kinetic energy by 2.5%, leads to shell correction energies well acceptable throughout the periodic table. The general importance of the present studies for other finite Fermi systems, self-bound or in external potentials, is pointed out

  20. Fermi-LAT: 4+ Years Out and Just Getting Started!

    CERN Multimedia

    CERN. Geneva

    2012-01-01

    The Fermi mission was launched into low Earth orbit in June, 2008. Now in its 5th year of data taking, the primary instrument, the Large Area Telescope (LAT), is now beginning to have a sufficient exposure to probe such fundamental issues as signals from Dark Matter. The achievements of the mission so far will be reviewed and a look towards what the next years could reveal will be presented.

  1. A Mobile Data Application for the Fermi Mission

    Science.gov (United States)

    Stephens, Thomas E.; Science Support Center, Fermi

    2014-01-01

    With the ever increasing use of smartphones and tablets among scientists and the world at large, it becomes increasingly important for projects and missions to have mobile friendly access to their data. This access could come in the form of mobile friendly websites and/or native mobile applications that allow the users to explore or access the data. The Fermi Gamma-ray Space Telescope mission has begun work along the latter path. In this poster I present the current version of the Fermi Data Portal, a native mobile application for both Android and iOS devices that allows access to various high level public data products from the Fermi Science Support Center (FSSC), the Gamma-ray Coordinate Network (GCN), and other sources. While network access is required to download data, most of the data served by the app are stored locally and are available even when a network connection is not available. This poster discusses the application's features as well as the development experience and lessons learned so far along the way.

  2. The First FERMI-LAT Gamma-Ray Burst Catalog

    Science.gov (United States)

    Ackermann, M.; Ajello, M.; Asano, K.; Axelsson, M.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; hide

    2013-01-01

    In three years of observations since the beginning of nominal science operations in 2008 August, the Large Area Telescope (LAT) on board the Fermi Gamma-Ray Space Telescope has observed high-energy great than (20 MeV) gamma-ray emission from 35 gamma-ray bursts (GRBs). Among these, 28 GRBs have been detected above 100 MeV and 7 GRBs above approximately 20 MeV. The first Fermi-LAT catalog of GRBs is a compilation of these detections and provides a systematic study of high-energy emission from GRBs for the first time. To generate the catalog, we examined 733 GRBs detected by the Gamma-Ray Burst Monitor (GBM) on Fermi and processed each of them using the same analysis sequence. Details of the methodology followed by the LAT collaboration for the GRB analysis are provided. We summarize the temporal and spectral properties of the LAT-detected GRBs. We also discuss characteristics of LAT-detected emission such as its delayed onset and longer duration compared with emission detected by the GBM, its power-law temporal decay at late times, and the fact that it is dominated by a power-law spectral component that appears in addition to the usual Band model.

  3. Dark Matter Searches with the Fermi Large Area Telescope

    International Nuclear Information System (INIS)

    Meurer, Christine

    2008-01-01

    The Fermi Gamma-Ray Space Telescope, successfully launched on June 11th, 2008, is the next generation satellite experiment for high-energy gamma-ray astronomy. The main instrument, the Fermi Large Area Telescope (LAT), with a wide field of view (>2 sr), a large effective area (>8000 cm 2 at 1 GeV), sub-arcminute source localization, a large energy range (20 MeV-300 GeV) and a good energy resolution (close to 8% at 1 GeV), has excellent potential to either discover or to constrain a Dark Matter signal. The Fermi LAT team pursues complementary searches for signatures of particle Dark Matter in different search regions such as the galactic center, galactic satellites and subhalos, the milky way halo, extragalactic regions as well as the search for spectral lines. In these proceedings we examine the potential of the LAT to detect gamma-rays coming from Weakly Interacting Massive Particle annihilations in these regions with special focus on the galactic center region.

  4. Some notes on time dependent Thomas Fermi approximation

    International Nuclear Information System (INIS)

    Holzwarth, G.

    1979-01-01

    The successful use of effective density-dependent potentials in static Hartree-Fock calculations for nuclear ground-state properties has led to the question whether it is possible to obtain significant further simplification by approximating also the kinetic energy part of the ground state energy by a functional of the local density alone. The great advantage of such an approach is that its complexity is independent of particle number; the size of the system enters only through parameters, Z and N. The simple 'extended Thomas Fermi' functionals are based on the assumption of a spherically symmetric local Fermi surface throughout the nucleus and they represent the 'liquid drop' part of the static total energy. Given this static formalism which is solved directly for the local density without considering individual particles one might ask for a possible dynamical extension in the same sense as TDHF is a dynamical extension of the static HF approach. The aim of such a Time Dependent Thomas Fermi (TDTF) approximation would be to determine directly the time-dependent local single-particle density from given initial conditions and the single-particle current density without following each particle on its individual orbit

  5. THE FIRST FERMI-LAT GAMMA-RAY BURST CATALOG

    Energy Technology Data Exchange (ETDEWEB)

    Ackermann, M. [Deutsches Elektronen Synchrotron DESY, D-15738 Zeuthen (Germany); Ajello, M. [Space Sciences Laboratory, 7 Gauss Way, University of California, Berkeley, CA 94720-7450 (United States); Asano, K. [Interactive Research Center of Science, Tokyo Institute of Technology, Meguro City, Tokyo 152-8551 (Japan); Axelsson, M. [Department of Astronomy, Stockholm University, SE-106 91 Stockholm (Sweden); Baldini, L. [Università di Pisa and Istituto Nazionale di Fisica Nucleare, Sezione di Pisa I-56127 Pisa (Italy); Ballet, J. [Laboratoire AIM, CEA-IRFU/CNRS/Université Paris Diderot, Service d' Astrophysique, CEA Saclay, 91191 Gif sur Yvette (France); Barbiellini, G. [Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, I-34127 Trieste (Italy); Bastieri, D. [Istituto Nazionale di Fisica Nucleare, Sezione di Padova, I-35131 Padova (Italy); Bechtol, K.; Bloom, E. D. [W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States); Bellazzini, R.; Bregeon, J. [Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, I-56127 Pisa (Italy); Bhat, P. N. [Center for Space Plasma and Aeronomic Research (CSPAR), University of Alabama in Huntsville, Huntsville, AL 35899 (United States); Bissaldi, E. [Institut für Astro- und Teilchenphysik and Institut für Theoretische Physik, Leopold-Franzens-Universität Innsbruck, A-6020 Innsbruck (Austria); Bonamente, E. [Istituto Nazionale di Fisica Nucleare, Sezione di Perugia, I-06123 Perugia (Italy); Bonnell, J.; Brandt, T. J. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Bouvier, A., E-mail: nicola.omodei@stanford.edu, E-mail: giacomov@slac.stanford.edu [Santa Cruz Institute for Particle Physics, Department of Physics and Department of Astronomy and Astrophysics, University of California at Santa Cruz, Santa Cruz, CA 95064 (United States); and others

    2013-11-01

    In three years of observations since the beginning of nominal science operations in 2008 August, the Large Area Telescope (LAT) on board the Fermi Gamma-Ray Space Telescope has observed high-energy (∼> 20 MeV) γ-ray emission from 35 gamma-ray bursts (GRBs). Among these, 28 GRBs have been detected above 100 MeV and 7 GRBs above ∼20 MeV. The first Fermi-LAT catalog of GRBs is a compilation of these detections and provides a systematic study of high-energy emission from GRBs for the first time. To generate the catalog, we examined 733 GRBs detected by the Gamma-Ray Burst Monitor (GBM) on Fermi and processed each of them using the same analysis sequence. Details of the methodology followed by the LAT collaboration for the GRB analysis are provided. We summarize the temporal and spectral properties of the LAT-detected GRBs. We also discuss characteristics of LAT-detected emission such as its delayed onset and longer duration compared with emission detected by the GBM, its power-law temporal decay at late times, and the fact that it is dominated by a power-law spectral component that appears in addition to the usual Band model.

  6. RADIO-WEAK BL LAC OBJECTS IN THE FERMI ERA

    Energy Technology Data Exchange (ETDEWEB)

    Massaro, F.; Marchesini, E. J. [Dipartimento di Fisica, Università degli Studi di Torino (UniTO), via Pietro Giuria 1, I-10125 Torino (Italy); D’Abrusco, R.; Smith, Howard A. [Smithsonian Astrophysical Observatory, 60 Garden Street, 02138 Cambridge, MA (United States); Masetti, N. [INAF—Istituto di Astrofisica Spaziale e Fisica Cosmica di Bologna, via Gobetti 101, I-40129, Bologna (Italy); Andruchow, I. [Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata, Paseo del Bosque, B1900FWA, La Plata (Argentina)

    2017-01-10

    The existence of “radio-weak BL Lac objects” (RWBLs) has been an open question, and has remained unsolved since the discovery that quasars could be radio-quiet or radio-loud. Recently, several groups identified RWBL candidates, mostly found while searching for low-energy counterparts of the unidentified or unassociated gamma-ray sources listed in the Fermi catalogs. Confirming RWBLs is a challenging task since they could be confused with white dwarfs (WDs) or weak emission line quasars (WELQs) when there are not sufficient data to precisely draw their broadband spectral energy distribution, and their classification is mainly based on a featureless optical spectra. Motivated by the recent discovery that Fermi BL Lacs appear to have very peculiar mid-IR emission, we show that it is possible to distinguish between WDs, WELQs, and BL Lacs using the [3.4]–[4.6]–[12] μ m color–color plot built using the WISE magnitudes when the optical spectrum is available. On the basis of this analysis, we identify WISE J064459.38+603131 and WISE J141046.00+740511.2 as the first two genuine RWBLs, both potentially associated with Fermi sources. Finally, to strengthen our identification of these objects as true RWBLs, we present multifrequency observations for these two candidates to show that their spectral behavior is indeed consistent with that of the BL Lac population.

  7. SU (2) lattice gauge theory simulations on Fermi GPUs

    International Nuclear Information System (INIS)

    Cardoso, Nuno; Bicudo, Pedro

    2011-01-01

    In this work we explore the performance of CUDA in quenched lattice SU (2) simulations. CUDA, NVIDIA Compute Unified Device Architecture, is a hardware and software architecture developed by NVIDIA for computing on the GPU. We present an analysis and performance comparison between the GPU and CPU in single and double precision. Analyses with multiple GPUs and two different architectures (G200 and Fermi architectures) are also presented. In order to obtain a high performance, the code must be optimized for the GPU architecture, i.e., an implementation that exploits the memory hierarchy of the CUDA programming model. We produce codes for the Monte Carlo generation of SU (2) lattice gauge configurations, for the mean plaquette, for the Polyakov Loop at finite T and for the Wilson loop. We also present results for the potential using many configurations (50,000) without smearing and almost 2000 configurations with APE smearing. With two Fermi GPUs we have achieved an excellent performance of 200x the speed over one CPU, in single precision, around 110 Gflops/s. We also find that, using the Fermi architecture, double precision computations for the static quark-antiquark potential are not much slower (less than 2x slower) than single precision computations.

  8. RADIO-WEAK BL LAC OBJECTS IN THE FERMI ERA

    International Nuclear Information System (INIS)

    Massaro, F.; Marchesini, E. J.; D’Abrusco, R.; Smith, Howard A.; Masetti, N.; Andruchow, I.

    2017-01-01

    The existence of “radio-weak BL Lac objects” (RWBLs) has been an open question, and has remained unsolved since the discovery that quasars could be radio-quiet or radio-loud. Recently, several groups identified RWBL candidates, mostly found while searching for low-energy counterparts of the unidentified or unassociated gamma-ray sources listed in the Fermi catalogs. Confirming RWBLs is a challenging task since they could be confused with white dwarfs (WDs) or weak emission line quasars (WELQs) when there are not sufficient data to precisely draw their broadband spectral energy distribution, and their classification is mainly based on a featureless optical spectra. Motivated by the recent discovery that Fermi BL Lacs appear to have very peculiar mid-IR emission, we show that it is possible to distinguish between WDs, WELQs, and BL Lacs using the [3.4]–[4.6]–[12] μ m color–color plot built using the WISE magnitudes when the optical spectrum is available. On the basis of this analysis, we identify WISE J064459.38+603131 and WISE J141046.00+740511.2 as the first two genuine RWBLs, both potentially associated with Fermi sources. Finally, to strengthen our identification of these objects as true RWBLs, we present multifrequency observations for these two candidates to show that their spectral behavior is indeed consistent with that of the BL Lac population.

  9. Constraining decaying dark matter with FERMI-LAT gamma rays

    International Nuclear Information System (INIS)

    Maccione, L.

    2011-01-01

    High energy electron sand positrons from decaying dark matter can produce a significant flux of gamma rays by inverse Compton of low energy photons in the interstellar radiation field. This possibility is inevitably related with the dark matter interpretation of the observed PAMELA and FERMI excesses. We will describe a simple and universal method to constrain dark matter models which produce electrons and positrons in their decay by using the FERMI-LAT gamma-ray observations in the energy range between 0.5 GeV and 300 GeV, by exploiting universal response functions that, once convolved with a specific dark matter model, produce the desired constraint. The response functions contain all the astrophysical inputs. Here is discussed the uncertainties in the determination of the response functions and apply them to place constraints on some specific dark matter decay models that can well fit the positron and electron fluxes observed by PAMELA and FERMI LAT, also taking into account prompt radiation from the dark matter decay. With the available data decaying dark matter can not be excluded as source of the PAMELA positron excess.

  10. THE FIRST FERMI-LAT GAMMA-RAY BURST CATALOG

    International Nuclear Information System (INIS)

    Ackermann, M.; Ajello, M.; Asano, K.; Axelsson, M.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bloom, E. D.; Bellazzini, R.; Bregeon, J.; Bhat, P. N.; Bissaldi, E.; Bonamente, E.; Bonnell, J.; Brandt, T. J.; Bouvier, A.

    2013-01-01

    In three years of observations since the beginning of nominal science operations in 2008 August, the Large Area Telescope (LAT) on board the Fermi Gamma-Ray Space Telescope has observed high-energy (∼> 20 MeV) γ-ray emission from 35 gamma-ray bursts (GRBs). Among these, 28 GRBs have been detected above 100 MeV and 7 GRBs above ∼20 MeV. The first Fermi-LAT catalog of GRBs is a compilation of these detections and provides a systematic study of high-energy emission from GRBs for the first time. To generate the catalog, we examined 733 GRBs detected by the Gamma-Ray Burst Monitor (GBM) on Fermi and processed each of them using the same analysis sequence. Details of the methodology followed by the LAT collaboration for the GRB analysis are provided. We summarize the temporal and spectral properties of the LAT-detected GRBs. We also discuss characteristics of LAT-detected emission such as its delayed onset and longer duration compared with emission detected by the GBM, its power-law temporal decay at late times, and the fact that it is dominated by a power-law spectral component that appears in addition to the usual Band model

  11. Heavy-ion accelerator mass spectrometry with a 'small' accelerator

    International Nuclear Information System (INIS)

    Steier, P.; Golser, R.; Priller, A.; Vockenhuber, C.; Irlweck, K.; Kutschera, W.; Lichtenstein, V.

    2001-01-01

    Full text: VERA, the Vienna environmental research accelerator, is based on a 3-MV pelletron tandem accelerator and is designed to allow the transport of ions of all elements, from the lightest to the heaviest. The VERA heavy ion program tries to establish measurement methods which work for the long-lived radionuclides where suppression of isobars is not required. Among these are 129 I, 210 Pb, 236 U and all heavier ions where no stable isobars exist. To suppress neighboring masses, the resolution of VERA was increased, both by improving the ion optics of existing elements and by installing a new electrostatic separator after the analyzing magnet. Interfering ions which pass all beam filters are identified with a high-resolution time-of-flight system, using a 0.5 μg/cm 2 DLC (diamond-like carbon) foil in the start detector, which substantially reduces beam straggling. Compared to heavy ion AMS at large tandem accelerators (TV ≥ 8 MV) and for cases where stable isobar interference is absent, it is possible to offset the disadvantage of lower ion energy. Moreover, the more compact facilities like VERA achieve higher stability and reliability and provide advanced computer control. This promises even higher precision and sensitivity for a larger number of samples, which is a prerequisite for research on natural-occurring heavy radioisotopes at environmental levels. First results on the measurement of 210 Pb (half-life 22 a) and 236 U (23 Ma) encourages us to push towards even heavier radionuclides (e.g. 224 Pu, 81 Ma). (author)

  12. Non-Fermi liquid scaling in UPdxCu5-x(x = 1,1.5)

    International Nuclear Information System (INIS)

    Aronson, M.C.; Osborn, R.; Lynn, J.W.; Chau, R.; Seaman, C.L.; Maple, M.B.

    1994-08-01

    The family of uranium based intermetallics UPd x Cu 5-x offers an ideal isostructural system to study the interplay of the impurity Kondo effect with the stability of long range magnetic order in a Kondo lattice. The parent compound UCu 5 is a prototypical Kondo impurity system at high temperatures, with Kondo temperature T K ∼ 5--10 meV. As the temperature is lowered, intersite interactions drive a transition to long-range antiferromagnetic order of the incompletely compensated uranium moments at 15 K. As Pd is substituted on the Cu sites, the antiferromagnetism is suppressed, with the ordering temperature driven to zero slightly below the composition UPdCu 4 . Unusual temperature and magnetic field scaling is observed in the magnetization, specific heat, and electrical resistivity of both UPdCu 4 and UPd 1.5 Cu 3.5 , inconsistent with the Fermi liquid description appropriate for many Kondo lattice systems, and in particular the parent compound UCu 5 . The authors report here the first direct measurements of the fundamental magnetic response for both compounds, providing a clear demonstration of non-Fermi liquid frequency and temperature scaling

  13. Extremely correlated Fermi liquid theory of the t-J model in 2 dimensions: low energy properties

    Science.gov (United States)

    Shastry, B. Sriram; Mai, Peizhi

    2018-01-01

    Low energy properties of the metallic state of the two-dimensional t-J model are presented for second neighbor hopping with hole-doping (t\\prime ≤slant 0) and electron-doping (t\\prime > 0), with various superexchange energy J. We use a closed set of equations for the Greens functions obtained from the extremely correlated Fermi liquid theory. These equations reproduce the known low energies features of the large U Hubbard model in infinite dimensions. The density and temperature dependent quasiparticle weight, decay rate and the peak spectral heights over the Brillouin zone are calculated. We also calculate the resistivity, Hall conductivity, Hall number and cotangent Hall angle. The spectral features display high thermal sensitivity at modest T for density n≳ 0.8, implying a suppression of the effective Fermi-liquid temperature by two orders of magnitude relative to the bare bandwidth. The cotangent Hall angle exhibits a T 2 behavior at low T, followed by an interesting kink at higher T. The Hall number exhibits strong renormalization due to correlations. Flipping the sign of t\\prime changes the curvature of the resistivity versus T curves between convex and concave. Our results provide a natural route for understanding the observed difference in the temperature dependent resistivity of strongly correlated electron-doped and hole-doped matter.

  14. Online monitoring of absorbed dose in undulator magnets with RADFET dosimeters at FERMI@Elettra

    International Nuclear Information System (INIS)

    Fröhlich, L.; Casarin, K.; Quai, E.; Holmes-Siedle, A.; Severgnini, M.; Vidimari, R.

    2013-01-01

    The FERMI@Elettra free-electron laser, based on a 1.3 GeV electron linac, requires the monitoring of radiation doses up to a few kGy for the protection of sensitive equipment such as permanent magnet undulators. A new dosimetry system DOSFET-L01, employing an array of RADFETs spread throughout the accelerator, was developed. So far, the system has performed flawlessly for almost two years, taking one dose reading per minute around the clock. The REM RFT-300 sensors were set in zero-bias mode, i.e. with all electrodes grounded during exposure. This choice of mode allows the measurement of a high range of integrated doses – up to a few kGy. The paper describes the new read-out system and its application, calibration measurements in cobalt-60 and 6 MeV bremsstrahlung radiation sources giving rise to a novel response function, and new data on “fade” under the zero-bias mode of use for over 300 days at room temperature. Regular readings from 28 RADFETs placed within seven undulators over the first 20 months of operation of the accelerator demonstrate how the system tracks and locates periods of high and low dose rate and thereby contributes to the protection from beam loss. The readings from the RADFET system are found to be in good agreement with Gafchromic EBT2 film dosimeters. Based on the results reported, the choice of bias mode may be revised so as to reduce fade and improve the accuracy conferred by a positive-bias mode. -- Highlights: ► We developed a system for online dosimetry with RADFET sensors under zero bias. ► The system is calibrated for doses up to 10 kGy with REM RFT-300 sensors. ► We collected data on fade for over 300 days from irradiation. ► We present undulator dose measurements for 20 months of operation of FERMI@Elettra. ► Dose measurements are in good agreement with chemical film dosimeters

  15. Anomalous transport phenomena in Fermi liquids with strong magnetic fluctuations

    International Nuclear Information System (INIS)

    Kontani, Hiroshi

    2008-01-01

    In this paper, we present recent developments in the theory of transport phenomena based on the Fermi liquid theory. In conventional metals, various transport coefficients are scaled according to the quasiparticles relaxation time, τ, which implies that the relaxation time approximation (RTA) holds well. However, such a simple scaling does not hold in many strongly correlated electron systems. The most famous example would be high-T c superconductors (HTSCs), where almost all the transport coefficients exhibit a significant deviation from the RTA results. This issue has been one of the most significant unresolved problems in HTSCs for a long time. Similar anomalous transport phenomena have been observed in metals near their antiferromagnetic (AF) quantum critical point (QCP). The main goal of this study is to demonstrate whether the anomalous transport phenomena in HTSC is evidence of a non-Fermi liquid ground state, or just RTA violation in strongly correlated Fermi liquids. Another goal is to establish a unified theory of anomalous transport phenomena in metals with strong magnetic fluctuations. For these purposes, we develop a method for calculating various transport coefficients beyond the RTA by employing field theoretical techniques. In a Fermi liquid, an excited quasiparticle induces other excited quasiparticles by collision, and current due to these excitations is called a current vertex correction (CVC). Landau noticed the existence of CVC first, which is indispensable for calculating transport coefficients in accord with the conservation laws. Here, we develop a transport theory involving resistivity and the Hall coefficient on the basis of the microscopic Fermi liquid theory, by considering the CVC. In nearly AF Fermi liquids, we find that the strong backward scattering due to AF fluctuations induces the CVC with prominent momentum dependence. This feature of the CVC can account for the significant enhancement in the Hall coefficient, magnetoresistance

  16. Accelerators of future generation

    International Nuclear Information System (INIS)

    Kolomenskij, A.A.

    1983-01-01

    A brief review of the prospects of development of various of types accelerator over next 10 to 15 years is given. The following directions are considered: superhign energy proton accelerators and storage rings, electron-positron colliding beams, heavy ion accelerators, medium energy, high-current proton accelerators superhigh power particle beams (electrons light- and heavy ions) for inertial fusion

  17. Future accelerator technology

    International Nuclear Information System (INIS)

    Sessler, A.M.

    1986-05-01

    A general discussion is presented of the acceleration of particles. Upon this foundation is built a categorization scheme into which all accelerators can be placed. Special attention is devoted to accelerators which employ a wake-field mechanism and a restricting theorem is examined. It is shown how the theorem may be circumvented. Comments are made on various acceleration schemes

  18. Pressure suppression device

    International Nuclear Information System (INIS)

    Mizumachi, Wataru; Fukuda, Akira; Kitaguchi, Hidemi; Shimizu, Toshiaki.

    1976-01-01

    Object: To relieve and absorb impact wave vibrations caused by steam and non-condensed gases releasing into the pressure suppression chamber at the time of an accident. Structure: The reactor container is filled with inert gases. A safety valve attached main steam pipe is provided to permit the excessive steam to escape, the valve being communicated with the pressure suppression chamber through an exhaust pipe. In the pressure suppression chamber, a doughnut-like cylindrical outer wall is filled at its bottom with pool water to condense the high temperature vapor released through the exhaust pipe. A head portion of a vent tube which leads the exhaust pipe is positioned at the top, and a down comer and an exhaust vent tube are locked by means of steady rests. At the bottom is mounted a pressure adsorber device which adsorbs a pressure from the pool water. (Kamimura, M.)

  19. Thyroxin hormone suppression treatment

    International Nuclear Information System (INIS)

    Samuel, A.M.

    1999-01-01

    One of the important modalities of treatment of thyroid cancer (TC) after surgery is the administration of thyroxin as an adjuvant treatment. The analysis supports the theory that thyroid suppression plays an important role in patient management. 300 μg of thyroxin, as this is an adequate dose for suppression is given. Ideally the dose should be tailored by testing s-TSH levels. However, since a large number of the patients come from out station cities and villages this is impractical. We therefore depend on clinical criteria of hyperthyroid symptoms and adjust the dose. Very few patients need such adjustment

  20. The fabrication of millimeter-wavelength accelerating structures

    International Nuclear Information System (INIS)

    Chou, P.J.; Bowden, G.B.; Copeland, M.R.

    1996-11-01

    There is a growing interest in the development of high gradient (≥ 1 GeV/m) accelerating structures. The need for high gradient acceleration based on current microwave technology requires the structures to be operated in the millimeter wavelength. Fabrication of accelerating structures at millimeter scale with sub-micron tolerances poses great challenges. The accelerating structures impose strict requirements on surface smoothness and finish to suppress field emission and multipactor effects. Various fabrication techniques based on conventional machining and micromachining have been evaluated and tested. These will be discussed and measurement results presented

  1. Progress Toward NLC/GLC Prototype Accelerator Structures

    International Nuclear Information System (INIS)

    Wang, J

    2004-01-01

    The accelerator structure groups for NLC (Next Linear Collider) and GLC (Global Linear Colliders) have successfully collaborated on the research and development of a major series of advanced accelerator structures based on room-temperature technology at X-band frequency. The progress in design, simulation, microwave measurement and high gradient tests are summarized in this paper. The recent effort in design and fabrication of the accelerator structure prototype for the main linac is presented in detail including HOM (High Order Mode) suppression and design of HOM couplers and fundamental mode couplers, optimized accelerator cavities as well as plans for future structures

  2. Fermi surface deformation in a simple iron-based superconductor, FeSe

    Science.gov (United States)

    Coldea, Amalia; Watson, Matthew; Kim, Timur; Haghighirad, Amir; McCollam, Alix; Hoesch, Moritz; Schofield, Andrew

    2015-03-01

    One of the outstanding problems in the field superconductivity is the identification of the normal state out of which superconductivity emerges. FeSe is one of the simplest and most intriguing iron-based superconductors, since in its bulk form it undergoes a structural transition before it becomes superconducting, whereas its single-layer form is believed to be a high-temperature superconductor. The nature of the structural transition, occurring in the absence of static magnetism, is rather unusual and how the electronic structure is stabilized by breaking of the rotational symmetry is the key to understand the superconductivity in bulk FeSe. Here we report angle-resolved photoemission spectroscopy measurements on FeSe that gives direct access to the band structure and orbital-dependent effects. We complement our studies on bulk FeSe with low-temperature angular-dependent quantum oscillation measurements using applied magnetic fields that are sufficiently strong to suppress superconductivity and reach the normal state. These studies reveal a strong deformation of Fermi surface through the structural transition driven by electronic correlations and orbital-dependent effects. . This work was supported by EPSRC, UK (EP/I004475/1), Diamond Light Source, UK and HFML, Nijmegen.

  3. Controlled Population of Floquet-Bloch States via Coupling to Bose and Fermi Baths

    Directory of Open Access Journals (Sweden)

    Karthik I. Seetharam

    2015-12-01

    Full Text Available External driving is emerging as a promising tool for exploring new phases in quantum systems. The intrinsically nonequilibrium states that result, however, are challenging to describe and control. We study the steady states of a periodically driven one-dimensional electronic system, including the effects of radiative recombination, electron-phonon interactions, and the coupling to an external fermionic reservoir. Using a kinetic equation for the populations of the Floquet eigenstates, we show that the steady-state distribution can be controlled using the momentum and energy relaxation pathways provided by the coupling to phonon and Fermi reservoirs. In order to utilize the latter, we propose to couple the system and reservoir via an energy filter which suppresses photon-assisted tunneling. Importantly, coupling to these reservoirs yields a steady state resembling a band insulator in the Floquet basis. The system exhibits incompressible behavior, while hosting a small density of excitations. We discuss transport signatures and describe the regimes where insulating behavior is obtained. Our results give promise for realizing Floquet topological insulators.

  4. Anisotropy of the Seebeck Coefficient in the Cuprate Superconductor YBa_{2}Cu_{3}O_{y}: Fermi-Surface Reconstruction by Bidirectional Charge Order

    Directory of Open Access Journals (Sweden)

    O. Cyr-Choinière

    2017-09-01

    Full Text Available The Seebeck coefficient S of the cuprate YBa_{2}Cu_{3}O_{y} is measured in magnetic fields large enough to suppress superconductivity, at hole dopings p=0.11 and p=0.12, for heat currents along the a and b directions of the orthorhombic crystal structure. For both directions, S/T decreases and becomes negative at low temperature, a signature that the Fermi surface undergoes a reconstruction due to broken translational symmetry. Above a clear threshold field, a strong new feature appears in S_{b}, for conduction along the b axis only. We attribute this feature to the onset of 3D-coherent unidirectional charge-density-wave modulations seen by x-ray diffraction, also along the b axis only. Because these modulations have a sharp onset temperature well below the temperature where S/T starts to drop towards negative values, we infer that they are not the cause of Fermi-surface reconstruction. Instead, the reconstruction must be caused by the quasi-2D bidirectional modulations that develop at significantly higher temperature. The unidirectional order only confers an additional anisotropy to the already reconstructed Fermi surface, also manifest as an in-plane anisotropy of the resistivity.

  5. Pressure suppressing device

    International Nuclear Information System (INIS)

    Naito, Makoto.

    1980-01-01

    Purpose: To prevent the pressure in the reactor container from excessively increasing even when vapor leaks from the dry well to a space of the suppression chamber, without passing though the suppression pool at the time of loss of coolant accident. Constitution: When vapor of a high temperature and a high pressure at the time of loss of coolant accident flows from the dry well to the suppression chamber without passing through suppression pool water, vapor dose not condense with pool water, and therefore the pressure within the chamber abnormally increases. For this reason, this abnormal pressure is detected by a pressure detector thereby to start the operations of a blower and a pump. By starting the blower, the pressure in the dry well becomes lower than the pressure in the chamber, and vapor entirely passes through the pool water and entirely condenses with the pool water. By starting the pump, the pool water is sprayed over the space of the chamber, and vapor in the space is condensed. (Yoshino, Y.)

  6. Analysis of secondary particle behavior in multiaperture, multigrid accelerator for the ITER neutral beam injector.

    Science.gov (United States)

    Mizuno, T; Taniguchi, M; Kashiwagi, M; Umeda, N; Tobari, H; Watanabe, K; Dairaku, M; Sakamoto, K; Inoue, T

    2010-02-01

    Heat load on acceleration grids by secondary particles such as electrons, neutrals, and positive ions, is a key issue for long pulse acceleration of negative ion beams. Complicated behaviors of the secondary particles in multiaperture, multigrid (MAMuG) accelerator have been analyzed using electrostatic accelerator Monte Carlo code. The analytical result is compared to experimental one obtained in a long pulse operation of a MeV accelerator, of which second acceleration grid (A2G) was removed for simplification of structure. The analytical results show that relatively high heat load on the third acceleration grid (A3G) since stripped electrons were deposited mainly on A3G. This heat load on the A3G can be suppressed by installing the A2G. Thus, capability of MAMuG accelerator is demonstrated for suppression of heat load due to secondary particles by the intermediate grids.

  7. The beginning of gamma-ray astronomy with Fermi

    International Nuclear Information System (INIS)

    Paneque, D.

    2008-01-01

    The Fermi observatory is designed to perform gamma-ray astronomy in the energy range 20 MeV to 300 GeV, with supporting measurements for gamma-ray bursts from 10 keV to 30 MeV. Fermi was successfully launched on June 11 (2008) from the Kennedy Space Center at Cape Canaveral. The main instrument of Fermi is the Large Area Telescope (LAT), which provides break-through high-energy measurements using techniques typically used in particle detectors for collider experiments. The LAT consists of 16 identical towers in a four-by-four grid, each one containing a pair conversion tracker and a hodoscopic crystal calorimeter, all covered by a segmented plastic scintillator anti-coincidence shield. The LAT is currently monitoring the GeV gamma-ray sky with rather uniform exposure (covering 20% of the sky at any instant and the entire sky on a timescale of a few hours) and a sensitivity ∼ 30 times better than its predecessor, EGRET. The large performance improvement of LAT opens a new and important window on a wide variety of high-energy astrophysical phenomena, as well as potential to discover/study non-conventional physics. In the talk I will report the instrument performance, the mission status and science opportunities and will present some results derived from the first months of operation, which includes astronomical telegrams on AGN flares, 2 GCN circulars on LAT-detected GRBs and the monitoring of some selected sources (22 blazars and 1 high mass X-ray Binary). (author)

  8. CLUSTERING OF γ-RAY-SELECTED 2LAC FERMI BLAZARS

    Energy Technology Data Exchange (ETDEWEB)

    Allevato, V.; Finoguenov, A. [Department of Physics, University of Helsinki, Gustaf Hällströmin katu 2a, FI-00014 Helsinki (Finland); Cappelluti, N. [University of Maryland, Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250 (United States)

    2014-12-20

    We present the first measurement of the projected correlation function of 485 γ-ray-selected blazars, divided into 175 BL Lacertae (BL Lacs) and 310 flat-spectrum radio quasars (FSRQs) detected in the 2 year all-sky survey by the Fermi-Large Area Telescope. We find that Fermi BL Lacs and FSRQs reside in massive dark matter halos (DMHs) with log M{sub h} = 13.35{sub −0.14}{sup +0.20} and log M{sub h} = 13.40{sub −0.19}{sup +0.15} h {sup –1} M {sub ☉}, respectively, at low (z ∼ 0.4) and high (z ∼ 1.2) redshift. In terms of clustering properties, these results suggest that BL Lacs and FSRQs are similar objects residing in the same dense environment typical of galaxy groups, despite their different spectral energy distributions, power, and accretion rates. We find no difference in the typical bias and hosting halo mass between Fermi blazars and radio-loud active galactic nuclei (AGNs), supporting the unification scheme simply equating radio-loud objects with misaligned blazar counterparts. This similarity in terms of the typical environment they preferentially live in, suggests that blazars tend to occupy the center of DMHs, as already pointed out for radio-loud AGNs. This implies, in light of several projects looking for the γ-ray emission from DM annihilation in galaxy clusters, a strong contamination from blazars to the expected signal from DM annihilation.

  9. The spectrum and morphology of the Fermi bubbles

    Energy Technology Data Exchange (ETDEWEB)

    Ackermann, M.; Buehler, R. [Deutsches Elektronen Synchrotron DESY, D-15738 Zeuthen (Germany); Albert, A.; Blandford, R. D.; Bloom, E. D.; Bottacini, E.; Caliandro, G. A.; Cameron, R. A. [W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States); Atwood, W. B. [Santa Cruz Institute for Particle Physics, Department of Physics and Department of Astronomy and Astrophysics, University of California at Santa Cruz, Santa Cruz, CA 95064 (United States); Baldini, L.; Bellazzini, R. [Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, I-56127 Pisa (Italy); Ballet, J. [Laboratoire AIM, CEA-IRFU/CNRS/Université Paris Diderot, Service d' Astrophysique, CEA Saclay, F-91191 Gif sur Yvette (France); Barbiellini, G. [Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, I-34127 Trieste (Italy); Bastieri, D.; Buson, S. [Istituto Nazionale di Fisica Nucleare, Sezione di Padova, I-35131 Padova (Italy); Bissaldi, E. [Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, and Università di Trieste, I-34127 Trieste (Italy); Brandt, T. J. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Bregeon, J. [Laboratoire Univers et Particules de Montpellier, Université Montpellier 2, CNRS/IN2P3, Montpellier (France); Bruel, P. [Laboratoire Leprince-Ringuet, École polytechnique, CNRS/IN2P3, Palaiseau (France); Caragiulo, M., E-mail: afrancko@slac.stanford.edu, E-mail: malyshev@stanford.edu, E-mail: vahep@stanford.edu [Istituto Nazionale di Fisica Nucleare, Sezione di Bari, I-70126 Bari (Italy); and others

    2014-09-20

    The Fermi bubbles are two large structures in the gamma-ray sky extending to 55° above and below the Galactic center. We analyze 50 months of Fermi Large Area Telescope data between 100 MeV and 500 GeV above 10° in Galactic latitude to derive the spectrum and morphology of the Fermi bubbles. We thoroughly explore the systematic uncertainties that arise when modeling the Galactic diffuse emission through two separate approaches. The gamma-ray spectrum is well described by either a log parabola or a power law with an exponential cutoff. We exclude a simple power law with more than 7σ significance. The power law with an exponential cutoff has an index of 1.9 ± 0.2 and a cutoff energy of 110 ± 50 GeV. We find that the gamma-ray luminosity of the bubbles is 4.4{sub −0.9}{sup +2.4}×10{sup 37} erg s{sup –1}. We confirm a significant enhancement of gamma-ray emission in the southeastern part of the bubbles, but we do not find significant evidence for a jet. No significant variation of the spectrum across the bubbles is detected. The width of the boundary of the bubbles is estimated to be 3.4{sub −2.6}{sup +3.7} deg. Both inverse Compton (IC) models and hadronic models including IC emission from secondary leptons fit the gamma-ray data well. In the IC scenario, synchrotron emission from the same population of electrons can also explain the WMAP and Planck microwave haze with a magnetic field between 5 and 20 μG.

  10. Fermi-Dirac correlation and Q-νKν(Q) distribution

    International Nuclear Information System (INIS)

    Dai Qirun; Li Jimei; Ma Zhanqing; Zhao Shusong

    1996-01-01

    The Fermi-Dirac correlation of identical protons is studied. Based on the non-perturbative theory of quantum fields, we put forward a kind of source distribution--the Q -ν K ν (Q) distribution. The Fermi-Dirac correlation of (p +- -p +- )-pairs is calculated from this distribution. The fitted curves agree with experimental data. The Q -ν K ν (Q) distribution has more advantages than the Gauss Source distribution. The radii of the source emitting hadrons and the anomalous dimensions of the Fermi field are calculated from the Fermi-Dirac correlation of identical protons

  11. FERMI-LAT AND WMAP OBSERVATIONS OF THE PUPPIS A SUPERNOVA REMNANT

    Energy Technology Data Exchange (ETDEWEB)

    Hewitt, J. W. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Grondin, M.-H. [Max-Planck-Institut fuer Kernphysik, D-69029 Heidelberg (Germany); Lemoine-Goumard, M.; Reposeur, T. [Centre d' Etudes Nucleaires de Bordeaux-Gradignan, Universite Bordeaux 1, CNRS/IN2p3, F-33175 Gradignan (France); Ballet, J. [Laboratoire AIM, CEA-IRFU/CNRS/Universite Paris Diderot, Service d' Astrophysique, CEA Saclay, F-91191 Gif sur Yvette (France); Tanaka, T., E-mail: john.w.hewitt@nasa.gov, E-mail: marie-helene.grondin@mpi-hd.mpg.de, E-mail: lemoine@cenbg.in2p3.fr [W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States)

    2012-11-10

    We report the detection of GeV {gamma}-ray emission from the supernova remnant (SNR) Puppis A with the Fermi Gamma-Ray Space Telescope. Puppis A is among the faintest SNRs yet detected at GeV energies, with a luminosity of only 2.7 Multiplication-Sign 10{sup 34} (D/2.2 kpc){sup 2} erg s{sup -1} between 1 and 100 GeV. The {gamma}-ray emission from the remnant is spatially extended, with a morphology matching that of the radio and X-ray emission, and is well described by a simple power law with an index of 2.1. We attempt to model the broadband spectral energy distribution (SED), from radio to {gamma}-rays, using standard nonthermal emission mechanisms. To constrain the relativistic electron population we use 7 years of Wilkinson Microwave Anisotropy Probe data to extend the radio spectrum up to 93 GHz. Both leptonic- and hadronic-dominated models can reproduce the nonthermal SED, requiring a total content of cosmic-ray electrons and protons accelerated in Puppis A of at least W {sub CR} Almost-Equal-To (1-5) Multiplication-Sign 10{sup 49} erg.

  12. High-precision half-life measurements for the superallowed Fermi β+ emitter 14O

    Science.gov (United States)

    Laffoley, A. T.; Svensson, C. E.; Andreoiu, C.; Austin, R. A. E.; Ball, G. C.; Blank, B.; Bouzomita, H.; Cross, D. S.; Diaz Varela, A.; Dunlop, R.; Finlay, P.; Garnsworthy, A. B.; Garrett, P. E.; Giovinazzo, J.; Grinyer, G. F.; Hackman, G.; Hadinia, B.; Jamieson, D. S.; Ketelhut, S.; Leach, K. G.; Leslie, J. R.; Tardiff, E.; Thomas, J. C.; Unsworth, C.

    2013-07-01

    The half-life of the superallowed Fermi β+ emitter 14O has been determined via simultaneous direct β and γ counting experiments at TRIUMF's Isotope Separator and Accelerator (ISAC) facility. A γ-ray counting measurement was performed by detecting the 2312.6-keV γ rays emitted from an excited state of the daughter 14N following the implantation of samples at the center of the 8π γ-ray spectrometer, a spherical array of 20 high-purity germanium (HPGe) detectors. A simultaneous β counting experiment was performed using a fast plastic scintillator positioned behind the implantation site with a solid angle coverage of ˜20%. The results, T1/2(β)=70.610±0.030s and T1/2(γ)=70.632±0.094s, form a consistent set and, together with eight previous measurements, establish a new average for the 14O half-life of T1/2=70.619±0.011s with a reduced χ2 of 0.99.

  13. Green Bank Telescope Detection of HI Clouds in the Fermi Bubble Wind

    Science.gov (United States)

    Lockman, Felix; Di Teodoro, Enrico M.; McClure-Griffiths, Naomi M.

    2018-01-01

    We used the Robert C. Byrd Green Bank Telescope to map HI 21cm emission in two large regions around the Galactic Center in a search for HI clouds that might be entrained in the nuclear wind that created the Fermi bubbles. In a ~160 square degree region at |b|>4 deg. and |long|<10 deg we detect 106 HI clouds that have large non-circular velocities consistent with their acceleration by the nuclear wind. Rapidly moving clouds are found as far as 1.5 kpc from the center; there are no detectable asymmetries in the cloud populations above and below the Galactic Center. The cloud kinematics is modeled as a population with an outflow velocity of 330 km/s that fills a cone with an opening angle ~140 degrees. The total mass in the clouds is ~10^6 solar masses and we estimate cloud lifetimes to be between 2 and 8 Myr, implying a cold gas mass-loss rate of about 0.1 solar masses per year into the nuclear wind.The Green Bank Telescope is a facility of the National Science Foundation, operated under a cooperative agreement by Associated Universities, Inc.

  14. Search for neutrinos from TANAMI observed AGN using Fermi lightcurves wit ANTARES

    International Nuclear Information System (INIS)

    Fehn, Kerstin

    2015-01-01

    Active galactic nuclei (AGN) are promising candidates for hadronic acceleration. The combination of radio, gamma ray and neutrino data should give information on their properties, especially concerning the sources of the high-energetic cosmic rays. Assuming a temporal correlation of gamma and neutrino emission in AGN the background of neutrino telescopes can be reduced using gamma ray lightcurves. Thereby the sensitivity for discovering cosmic neutrino sources is enhanced. In the present work a stacked search for a group of AGN with the ANTARES neutrino telescope in the Mediterranean is presented. The selection of AGN is based on the source sample of TANAMI, a multiwavelength observation program (radio to gamma rays) of extragalactic jets southerly of -30 declination. In the analysis lightcurves of the gamma satellite Fermi are used. In an unbinned maximum likelihood approach the test statistic in the background only case and in the signal and background case is determined. For the investigated 10% of data of ANTARES within the measurement time between 01.09.2008 and 30.07.2012 no significant excess is observed. So on the total flux of the AGN of the stacked search an upper limit can be set.

  15. Metal enrichment in the Fermi bubbles as a probe of their origin

    Science.gov (United States)

    Inoue, Yoshiyuki; Nakashima, Shinya; Tahara, Masaya; Kataoka, Jun; Totani, Tomonori; Fujita, Yutaka; Sofue, Yoshiaki

    2015-06-01

    The Fermi bubbles are gigantic gamma-ray structures in our Galaxy. The physical origin of the bubbles is still under debate. The leading scenarios can be divided into two categories. One is nuclear star-forming activity similar to extragalactic starburst galaxies and the other is past active galactic nucleus (AGN)-like activity of the Galactic center supermassive black hole. In this letter, we propose that metal abundance measurements will provide an important clue to probe their origin. Based on a simple spherically symmetric bubble model, we find that the generated metallicity and abundance patterns of the bubbles' gas strongly depend on assumed star formation or AGN activities. Star formation scenarios predict higher metallicities and abundance ratios of [O/Fe] and [Ne/Fe] than AGN scenarios do because of supernovae ejecta. Furthermore, the resultant abundance depends on the gamma-ray emission process because different mass injection histories are required for the different gamma-ray emission processes due to the acceleration and cooling time scales of non-thermal particles. Future X-ray missions such as ASTRO-H and Athena will give a clue to probe the origin of the bubbles through abundance measurements with their high energy resolution instruments.

  16. FERMI @ Elettra A Seeded Harmonic Cascade FEL for EUV and Soft X-Rays

    CERN Document Server

    Bocchetta, C J; Craievich, P; D'Auria, G; Danailov, M B; De Ninno, G; Di Mitri, S; Diviacco, B; Ferianis, M; Gomezel, A; Iazzourene, F; Karantzoulis, E; Penco, G; Trovò, M

    2005-01-01

    We describe the machine layout and major performance parameters for the FERMI FEL project funded for construction at Sincrotrone Trieste, Italy. The project will be the first user facility based on seeded harmonic cascade FELs, providing controlled, high peak-power pulses. With a high-brightness rf photocathode gun, and using the existing 1.2 GeV S-band linac, the facility will provide tunable output over a range from ~100 nm to ~10 nm, with pulse duration from 40 fs to ~ 1ps, and with fully variable output polarization. Initially, two FEL cascades are planned; a single-stage harmonic generation to operate > 40 nm, and a two-stage cascade operating from ~40 nm to ~10 nm or shorter wavelength. The output is spatially and temporally coherent, with peak power in the GW range. Lasers provide modulation to the electron beam, as well as driving the photocathode and other systems, and the facility will integrate laser systems with the accelerator infrastructure, including a state-of-the-art optical timing sys...

  17. Fermi Large Area Telescope Observations of the Supernova Remnant G8.7-0.1

    International Nuclear Information System (INIS)

    2012-01-01

    We present a detailed analysis of the GeV gamma-ray emission toward the supernova remnant (SNR) G8.7-0.1 with the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope. An investigation of the relationship between G8.7-0.1 and the TeV unidentified source HESS J1804-216 provides us with an important clue on diffusion process of cosmic rays if particle acceleration operates in the SNR. The GeV gamma-ray emission is extended with most of the emission in positional coincidence with the SNR G8.7-0.1 and a lesser part located outside the western boundary of G8.7-0.1. The region of the gamma-ray emission overlaps spatially connected molecular clouds, implying a physical connection for the gamma-ray structure. The total gamma-ray spectrum measured with LAT from 200 MeV-100 GeV can be described by a broken power-law function with a break of 2.4 ± 0.6 (stat) ± 1.2 (sys) GeV, and photon indices of 2.10 ± 0.06 (stat) ± 0.10 (sys) below the break and 2.70 ± 0.12 (stat) ± 0.14 (sys) above the break. Given the spatial association among the gamma rays, the radio emission of G8.7-0.1, and the molecular clouds, the decay of p0s produced by particles accelerated in the SNR and hitting the molecular clouds naturally explains the GeV gamma-ray spectrum. We also find that the GeV morphology is not well represented by the TeV emission from HESS J1804-216 and that the spectrum in the GeV band is not consistent with the extrapolation of the TeV gamma-ray spectrum. The spectral index of the TeV emission is consistent with the particle spectral index predicted by a theory that assumes energy-dependent diffusion of particles accelerated in an SNR. We discuss the possibility that the TeV spectrum originates from the interaction of particles accelerated in G8.7-0.1 with molecular clouds, and we constrain the diffusion coefficient of the particles.

  18. Fermi Large Area Telescope Observations of the Supernova Remnant G8.7-0.1

    Energy Technology Data Exchange (ETDEWEB)

    Ajello, M.; Allafort, A.; /Stanford U., HEPL /KIPAC, Menlo Park /SLAC; Baldini, L.; /INFN, Pisa; Ballet, J.; /AIM, Saclay; Barbiellini, G.; /INFN, Trieste /Trieste U.; Bastieri, D.; /INFN, Padua /Padua U.; Bechtol, K.; /Stanford U., HEPL /KIPAC, Menlo Park /SLAC; Bellazzini, R.; /INFN, Pisa; Berenji, B.; Blandford, R.D.; Bloom, E.D.; /Stanford U., HEPL /KIPAC, Menlo Park /SLAC; Bonamente, E.; /INFN, Perugia /Perugia U.; Borgland, A.W.; /Stanford U., HEPL /KIPAC, Menlo Park /SLAC; Bregeon, J.; /INFN, Pisa; Brigida, M.; /Bari Polytechnic /INFN, Bari; Bruel, P.; /Ecole Polytechnique; Buehler, R.; /Stanford U., HEPL /KIPAC, Menlo Park /SLAC; Buson, S.; /INFN, Padua /Padua U.; Caliandro, G.A.; /CSIC, Catalunya; Cameron, R.A.; /Stanford U., HEPL /KIPAC, Menlo Park /SLAC; Caraveo, P.A.; /IASF, Milan /AIM, Saclay /INFN, Perugia /Perugia U. /Stanford U., HEPL /KIPAC, Menlo Park /SLAC /Unlisted, US /Naval Research Lab, Wash., D.C. /Perugia U. /ASDC, Frascati /Stanford U., HEPL /KIPAC, Menlo Park /SLAC /Montpellier U. /ASDC, Frascati /Udine U. /INFN, Trieste /Bari Polytechnic /INFN, Bari /Naval Research Lab, Wash., D.C. /Stanford U., HEPL /KIPAC, Menlo Park /SLAC /Bari Polytechnic /INFN, Bari /Ecole Polytechnique /NASA, Goddard /Stanford U., HEPL /KIPAC, Menlo Park /SLAC /Udine U. /INFN, Trieste /Trieste Observ. /Hiroshima U. /Nagoya U. /Bari Polytechnic /INFN, Bari /INFN, Bari /ASDC, Frascati /INFN, Perugia /Perugia U. /Bari Polytechnic /INFN, Bari /ASDC, Frascati /Bari Polytechnic /INFN, Bari /Bologna Observ. /Stanford U., HEPL /KIPAC, Menlo Park /SLAC /Naval Research Lab, Wash., D.C. /Alabama U., Huntsville /CSIC, Catalunya /Hiroshima U. /NASA, Goddard /Hiroshima U.; /more authors..

    2012-09-14

    We present a detailed analysis of the GeV gamma-ray emission toward the supernova remnant (SNR) G8.7-0.1 with the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope. An investigation of the relationship between G8.7-0.1 and the TeV unidentified source HESS J1804-216 provides us with an important clue on diffusion process of cosmic rays if particle acceleration operates in the SNR. The GeV gamma-ray emission is extended with most of the emission in positional coincidence with the SNR G8.7-0.1 and a lesser part located outside the western boundary of G8.7-0.1. The region of the gamma-ray emission overlaps spatially connected molecular clouds, implying a physical connection for the gamma-ray structure. The total gamma-ray spectrum measured with LAT from 200 MeV-100 GeV can be described by a broken power-law function with a break of 2.4 {+-} 0.6 (stat) {+-} 1.2 (sys) GeV, and photon indices of 2.10 {+-} 0.06 (stat) {+-} 0.10 (sys) below the break and 2.70 {+-} 0.12 (stat) {+-} 0.14 (sys) above the break. Given the spatial association among the gamma rays, the radio emission of G8.7-0.1, and the molecular clouds, the decay of p0s produced by particles accelerated in the SNR and hitting the molecular clouds naturally explains the GeV gamma-ray spectrum. We also find that the GeV morphology is not well represented by the TeV emission from HESS J1804-216 and that the spectrum in the GeV band is not consistent with the extrapolation of the TeV gamma-ray spectrum. The spectral index of the TeV emission is consistent with the particle spectral index predicted by a theory that assumes energy-dependent diffusion of particles accelerated in an SNR. We discuss the possibility that the TeV spectrum originates from the interaction of particles accelerated in G8.7-0.1 with molecular clouds, and we constrain the diffusion coefficient of the particles.

  19. Topological charge and chiral anomalies in Fermi superfluids

    International Nuclear Information System (INIS)

    Stone, M.; Gaitan, F.

    1987-01-01

    We review some of the topological properties of Fermi superfluids, in particular the persistent currents in superfluid 3 He. We show that the topological charge formalism developed by Garg et al. is related to the chiral anomaly viewpoint of Volovik and co-workers through the Callan--Harvey effect. We stress that the question of the existence of a ''twist'' term in the current induced by a texture is a history-dependent phenomenon which depends on how the textures are envisaged as being created. copyright 1987 Academic Press, Inc

  20. Inhomogeneous atomic Bose-Fermi mixtures in cubic lattices

    International Nuclear Information System (INIS)

    Cramer, M.; Eisert, J.; Illuminati, F.

    2004-01-01

    We determine the ground state properties of inhomogeneous mixtures of bosons and fermions in cubic lattices and parabolic confining potentials. For finite hopping we determine the domain boundaries between Mott-insulator plateaux and hopping-dominated regions for lattices of arbitrary dimension within mean-field and perturbation theory. The results are compared with a new numerical method that is based on a Gutzwiller variational approach for the bosons and an exact treatment for the fermions. The findings can be applied as a guideline for future experiments with trapped atomic Bose-Fermi mixtures in optical lattices