1,721,006 research outputs found
Innovative X-γ ray sources based on laser-produced plasmas
No full textThe paper concerns with the dynamics and the emitted radiation of electrons undergoing betatron oscillations in laser-produced plasmas. The topic is relevant for a reliable interpretation of data will be obtained in forthcoming experiments in the LASER facility of the National Laboratories of Frascati (LNF) of the National Institute for Nuclear Physics (INFN). The blowout regime will be considered, which makes the electrons reaching very high energies by providing impressive accelerating gradients while keeping a low energy spread value. The accident that the betatron emission occurs meanwhile electrons gain energy is also considered here
High intensity laser-matter interaction and electron plasma acceleration
No full textThe basic principles of the electron acceleration in laser produced plasmas and the related secondary
sources of energetic radiation with a particular attention to betatron radiation are presented
Laser induced plasma channels and related X-γ ray sources
No full textDuring the propagation in the plasma, a super-intense and ultra-short laser pulse deeply changes its parameters due the onset of non-linear effects. These extreme conditions are suitable for the electron acceleration in high field gradient, opening the way for the realization of compact secondary sources of X-c rays. In particular the Betatron Radiation in the so called bubble regime and the all-optical Thomson Backscattering are presented as good candidate in this sense
Self-phase modulation effects as laser produced plasma diagnostics
No full textHigh intensity laser radiation propagating in a plasma suffers deep changes concerning both its spatial and spectral distribution. These changes can give information about the kind of the developed interaction. In particular the Self Phase Modulation (SPM) of the impinging laser radiation is currently used to evidence fast variation of the electron plasma density, produced for example by the target ionization or ponderomotive forces. The SPM effects dramatically increase as the laser pulse decreases and this is the reason for why they have to be specially considered in the experiments in which femtosecond laser pulses are used
Selection rules for the orbital angular momentum of optically-produced THz radiation
Full text linkIn this work we theoretically study the transduction ofthe Orbital Angular Momentum (OAM)lfor infraredpump lasers into the THz domain. In the case of opti-cal rectification, the transduction of OAM occurs onlythrough a spin-orbit interaction, with the selection ruleon the OAMl=0valid for any kind of polarizationof the pump, which means that there is no transfer ofOAM along the propagation axis. In the difference fre-quency generation the selection rule for the difference∆lbetween the OAM of the pump fields with linear orcircular polarization isl=∆l, whereaslranges from∆l−2to∆l+2in both the cases of radial and azimuthalpolarization. Moreover, for THz generation in the lat-ter case, high diffraction obtained with tightly focusedpumps yieldsltending to∆l±2, whileltends to zeroin the opposite case of large pump beam
Resonant interaction between laser and electrons undergoing betatron oscillations in the bubble regime
No full textThe betatron radiation in the bubble regime is studied in presence of resonant inter- action between the accelerated electrons and the driver laser pulse tail. The calculations refer to experimental parameters available at the laser FLAME facility of the National Laboratories of Frascati (LNF) and represent the radiation spectra and spatial distribu- tions which have to be expected in forthcoming experiments
Numerical and analytical models to study the laser-driven plasma perturbation in a dielectric gas-filled capillary waveguide
No full textAn alternative fast approach to study the propagation of an intense laser pulse through a dielectric capillary waveguide filled with plasma is presented. The numerical model com- putes the evolution of the capillary mode coupling coeffi- cients and from these the properties of the laser and plasma response are retrieved. Moreover, an analytical description of the process is presented and compared to the numerical model
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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