SwePub - sökning: WFRF:(Marklund Mattias 1970 )

Numrering	Referens	Omslagsbild	Hitta
1.	Dion, Claude, 1970-, et al. (författare) Anisotropic properties of spin avalanches in crystals of nanomagnets 2013 Ingår i: Physical Review B - Condensed Matter and Materials Physics. - : American Physical Society. - 2469-9950 .- 2469-9969 .- 1098-0121 .- 1550-235X. ; 87:1 Tidskriftsartikel (refereegranskat)abstract Anisotropy effects for spin avalanches in crystals of nanomagnets are studied theoretically with the external magnetic field applied at an arbitrary angle to the easy axis. Starting with the Hamiltonian for a single nanomagnet in the crystal, two essential quantities characterizing spin avalanches are calculated: the activation and Zeeman energies. The calculation is performed numerically for a wide range of angles and analytical formulas are derived within the limit of small angles. The anisotropic properties of a single nanomagnet lead to anisotropic behavior of the magnetic deflagration speed. Modifications of the magnetic deflagration speed are investigated for different angles between the external magnetic field and the easy axis of the crystals. Anisotropic properties of magnetic detonation are also studied, which concern, first of all, the temperature behind the leading shock and the characteristic time of spin switching in the detonation.
2.	Aboushelbaya, R., et al. (författare) Orbital Angular Momentum Coupling in Elastic Photon-Photon Scattering 2019 Ingår i: Physical Review Letters. - 0031-9007. ; 123:11 Tidskriftsartikel (refereegranskat)abstract In this Letter, we investigate the effect of orbital angular momentum (OAM) on elastic photon-photon scattering in a vacuum for the first time. We define exact solutions to the vacuum electromagnetic wave equation which carry OAM. Using those, the expected coupling between three initial waves is derived in the framework of an effective field theory based on the Euler-Heisenberg Lagrangian and shows that OAM adds a signature to the generated photons thereby greatly improving the signal-to-noise ratio. This forms the basis for a proposed high-power laser experiment utilizing quantum optics techniques to filter the generated photons based on their OAM state.
3.	Arrhenius, Gustaf, et al. (författare) Bevare oss för det brittiska utvärderingseländet 2012 Ingår i: Universitetsläraren. - 0282-4973. ; 2012:18 dec Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract SVENSKA universitetsledningar tenderar numera att prioritera lärosätets intäkter högre än allt annat, inklusive klassiska akademiska ideal som bildning och fri forskning. Därför fruktar vi att ett genomförande av Jan Björklunds planer kommer att leda till samma slags vansinne i Sverige som vi nu ser i Storbritannien.
4.	Aurand, B., et al. (författare) Manipulation of the spatial distribution of laser-accelerated proton beams by varying the laser intensity distribution 2016 Ingår i: Physics of Plasmas. - : AIP Publishing. - 1089-7674 .- 1070-664X. ; 23:2 Tidskriftsartikel (refereegranskat)abstract We report on a study of the spatial profile of proton beams produced through target normal sheath acceleration using flat target foils and changing the laser intensity distribution on the target front surface. This is done by either defocusing a single laser pulse or by using a split-pulse setup and irradiating the target with two identical laser pulses with variable spatial separation. The resulting proton beam profile and the energy spectrum are recorded as functions of the focal spot size of the single laser pulse and of the separation between the two pulses. A shaping of the resulting proton beam profile, related to both an increase in flux of low-energy protons in the target normal direction and a decrease in their divergence, in one or two dimensions, is observed. The results are explained by simple modelling of rear surface sheath field expansion, ionization, and projection of the resulting proton beam.
5.	Baird, C. D., et al. (författare) Realising single-shot measurements of quantum radiation reaction in high-intensity lasers 2019 Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 21:5 Tidskriftsartikel (refereegranskat)abstract Modern laser technology is now sufficiently advanced that collisions between high-intensity laser pulses and laser-wakefield-accelerated (LWFA) electron beams can reach the strong-field regime, so that it is possible to measure the transition between the classical and quantum regimes of light-matter interactions. However, the energy spectrum of LWFA electron beams can fluctuate significantly from shot to shot, making it difficult to clearly discern quantum effects in radiation reaction (RR), for example. Here we show how this can be accomplished in only a single laser shot. A millimetre-scale pre-collision drift allows the electron beam to expand to a size larger than the laser focal spot and develop a correlation between transverse position and angular divergence. In contrast to previous studies, this means that a measurement of the beam's energy-divergence spectrum automatically distinguishes components of the beam that hit or miss the laser focal spot and therefore do and do not experience RR.
6.	Behm, K. T., et al. (författare) A spectrometer for ultrashort gamma-ray pulses with photon energies greater than 10 MeV 2018 Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 1089-7623 .- 0034-6748. ; 89:11 Tidskriftsartikel (refereegranskat)abstract © 2018 Author(s). We present a design for a pixelated scintillator based gamma-ray spectrometer for non-linear inverse Compton scattering experiments. By colliding a laser wakefield accelerated electron beam with a tightly focused, intense laser pulse, gamma-ray photons up to 100 MeV energies and with few femtosecond duration may be produced. To measure the energy spectrum and angular distribution, a 33 × 47 array of cesium-iodide crystals was oriented such that the 47 crystal length axis was parallel to the gamma-ray beam and the 33 crystal length axis was oriented in the vertical direction. Using an iterative deconvolution method similar to the YOGI code, modeling of the scintillator response using GEANT4 and fitting to a quantum Monte Carlo calculated photon spectrum, we are able to extract the gamma ray spectra generated by the inverse Compton interaction.
7.	Bhadoria, Shikha, 1991, et al. (författare) Energy enhancement of laser-driven ions by radiation reaction and Breit-Wheeler pair production in the ultra-relativistic transparency regime 2024 Ingår i: High Power Laser Science and Engineering. - 2052-3289. ; 12 Tidskriftsartikel (refereegranskat)abstract The impact of radiation reaction and Breit-Wheeler pair production on acceleration of fully ionized Carbon ions driven by an intense linearly-polarized laser pulse has been investigated in the ultrarelativistic transparency regime. Against initial expectations radiation reaction and pair production at ultra-high laser intensities is found to enhance the energy gained by the ions. The electrons lose most of their transverse momentum and the additionally produced pair plasma of Breit-Wheeler electrons and positrons co-stream in the forward direction as opposed to the existing electrons streaming at an angle above zero. We discuss how these observations could be explained by the changes in the phase velocity of the Buneman instability, that is known to aid ion acceleration in the Breakout-Afterburner regime, by tapping the free energy in the relative electron and ion streams. We present evidence that these non-classical effects can further improve the highest Carbon ion energies in this transparency regime.
8.	Bhadoria, Shikha, 1991, et al. (författare) Mapping the power-law decay of high-harmonic spectra from few-cycle laser-solid interactions 2022 Ingår i: Physics of Plasmas. - : AIP Publishing. - 1070-664X .- 1089-7674. ; 29 Tidskriftsartikel (refereegranskat)abstract Visible or near infrared light can be manipulated to produce bursts of coherent extreme ultraviolet or x rays via the relativistic high-order harmonic generation process when a laser irradiates a solid plasma target. The intensity of the spectral components of the reflected signal decays with the increase in harmonic order and the efficiency of this non-linear process largely hinges on how prompt this decay is. This is governed by the conditions of the laser-plasma interaction for which various models have been proposed. At relativistic intensities, a spectrum exhibiting a power-law decay with an exponent of 8/3 or 4/3 is often stated. Here, we analyze the dependence of this exponent on interaction parameters, including the angle of incidence, the carrier envelope phase, intensity of the laser, and the pre-plasma length, and discuss opportunities for optimization. Our simulations show that, rather than there being one universal exponent, the spectral decay is a continuous function of the laser-plasma interaction parameters.
9.	Blackburn, Tom, 1989, et al. (författare) Benchmarking semiclassical approaches to strong-field QED: Nonlinear Compton scattering in intense laser pulses 2018 Ingår i: Physics of Plasmas. - : AIP Publishing. - 1089-7674 .- 1070-664X. ; 25:8 Tidskriftsartikel (refereegranskat)abstract The recoil associated with photon emission is key to the dynamics of ultrarelativistic electrons in strong electromagnetic fields, as found in high-intensity laser-matter interactions and astrophysical environments such as neutron star magnetospheres. When the energy of the photon becomes comparable to that of the electron, it is necessary to use quantum electrodynamics (QED) to describe the dynamics accurately. However, computing the appropriate scattering matrix element from strong-field QED is not generally possible due to multiparticle effects and the complex structure of the electromagnetic fields. Therefore, these interactions are treated semiclassically, coupling probabilistic emission events to classical electrodynamics using rates calculated in the locally constant field approximation. Here, we provide comprehensive benchmarking of this approach against the exact QED calculation for nonlinear Compton scattering of electrons in an intense laser pulse. We find agreement at the percentage level between the photon spectra, as well as between the models' predictions of absorption from the background field, for normalized amplitudes a0> 5. We discuss possible routes towards improved numerical methods and the implications of our results for the study of QED cascades.
10.	Blackburn, Thomas, 1989, et al. (författare) Model-independent inference of laser intensity 2020 Ingår i: Physical Review Accelerators and Beams. - 2469-9888. ; 23:6 Tidskriftsartikel (refereegranskat)abstract An ultrarelativistic electron beam passing through an intense laser pulse emits radiation around its direction of propagation into a characteristic angular profile. Here, we show that measurement of the variances of this profile in the planes parallel and perpendicular to the laser polarization, and the mean initial and final energies of the electron beam, allows the intensity of the laser pulse to be inferred in a way that is independent of the model of the electron dynamics. The method presented applies whether radiation reaction is important or not, and whether it is classical or quantum in nature, with an accuracy of a few percent across 3 orders of magnitude in intensity. It is tolerant of electron beams with a broad energy spread and finite divergence. In laser-electron-beam collision experiments, where spatiotemporal fluctuations cause the alignment of the beams to vary from shot to shot, this permits inference of the laser intensity at the collision point, thereby facilitating comparisons between theoretical calculations and experimental data.
11.	Blackburn, Tom, 1989, et al. (författare) Nonlinear Breit-Wheeler pair creation with bremsstrahlung γ rays 2018 Ingår i: Plasma Physics and Controlled Fusion. - : IOP Publishing. - 1361-6587 .- 0741-3335. ; 60:5 Tidskriftsartikel (refereegranskat)abstract Electron-positron pairs are produced through the Breit-Wheeler process when energetic photons traverse electromagnetic fields of sufficient strength. Here we consider a possible experimental geometry for observation of pair creation in the highly nonlinear regime, in which bremsstrahlung of an ultrarelativistic electron beam in a high-Z target is used to produce γ rays that collide with a counter-propagating laser pulse. We show how the target thickness may be chosen to optimize the yield of Breit-Wheeler positrons, and verify our analytical predictions with simulations of the cascade in the material and in the laser pulse. The electron beam energy and laser intensity required are well within the capability of today's high-intensity laser facilities.
12.	Blackburn, Thomas, 1989, et al. (författare) Radiation beaming in the quantum regime 2020 Ingår i: Physical Review A. - 2469-9926. ; 101:1 Tidskriftsartikel (refereegranskat)abstract Classical theories of radiation reaction predict that the electron motion is confined to the plane defined by the electron's instantaneous momentum and the force exerted by the external electromagnetic field. However, in the quantum radiation reaction regime, where the recoil exerted by individual quanta becomes significant, the electron can scatter "out of plane," as the photon is emitted into a cone with finite opening angle. We show that Monte Carlo implementation of an angularly resolved emission rate leads to substantially improved agreement with exact QED calculations of nonlinear Compton scattering. Furthermore, we show that the transverse recoil caused by this finite beaming, while negligible in many high-intensity scenarios, can be identified in the increase in divergence, in the plane perpendicular to the laser polarization and wave vector, of a high-energy electron beam that interacts with a linearly polarized, ultraintense laser.
13.	Blackburn, Thomas, 1989, et al. (författare) Reaching supercritical field strengths with intense lasers 2019 Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 21:5 Tidskriftsartikel (refereegranskat)abstract It is conjectured that all perturbative approaches to quantum electrodynamics (QED) break down in the collision of a high-energy electron beam with an intense laser, when the laser fields are boosted to supercritical strengths far greater than the critical field of QED. As field strengths increase toward this regime, cascades of photon emission and electron-positron pair creation are expected, as well as the onset of substantial radiative corrections. Here we identify the important role played by the collision angle in mitigating energy losses to photon emission that would otherwise prevent the electrons reaching the supercritical regime. Weshow that a collision between an electron beam with energy in the tens of GeV and a laser pulse of intensity 10 W cm 24 2 - at oblique, or even normal, incidence is a viable platform for studying the breakdown of perturbative strong-field QED. Our results have implications for the design of near-term experiments as they predict that certain quantum effects are enhanced at oblique incidence. © 2019 The Author(s). Published by IOP Publishing Ltd on behalf of the Institute of Physics and Deutsche Physikalische Gesellschaft.
14.	Blackburn, Tom, 1989, et al. (författare) Relativistically intense XUV radiation from laser-illuminated near-critical plasmas 2018 Ingår i: Physical Review A. - 2469-9934 .- 2469-9926. ; 98:2 Tidskriftsartikel (refereegranskat)abstract Pulses of extreme ultraviolet (XUV) light, with wavelengths between 10 and 100nm, can be used to image and excite ultrafast phenomena such as the motion of atomic electrons. Here we show that the illumination of plasma with near-critical electron density may be used as a source of relativistically intense XUV radiation, providing the means for novel XUV-pump-XUV-probe experiments in the nonlinear regime. We describe how the optimal regime may be reached by tailoring the laser-target interaction parameters and by the presence of preplasma. Our results indicate that currently available laser facilities are capable of producing XUV pulses with duration ∼10fs, brilliance in excess of 1023photons/s/mm2/mrad2 (0.1% bandwidth), and intensity Iλ21019Wcm-2μm2.
15.	Blackburn, Tom, 1989, et al. (författare) Scaling laws for positron production in laser-electron-beam collisions 2017 Ingår i: Physical Review A. - 2469-9934 .- 2469-9926. ; 96:2, s. Article no 022128 - Tidskriftsartikel (refereegranskat)abstract Showers of gamma rays and positrons are produced when a high-energy electron beam collides with a superintense laser pulse. We present scaling laws for the electron-beam energy loss, the gamma-ray spectrum, and the positron yield and energy that are valid in the nonlinear, radiation-reaction-dominated regime. As an application we demonstrate that by employing the collision of a > GeV electron beam with a laser pulse of intensity > 5 x 10(21) Wcm(-2), today's high-intensity laser facilities are capable of producing O(10(4)) positrons per shot via light-by-light scattering.
16.	Blackburn, Thomas, 1989, et al. (författare) Self-absorption of synchrotron radiation in a laser-irradiated plasma 2021 Ingår i: Physics of Plasmas. - : AIP Publishing. - 1070-664X .- 1089-7674. ; 28:5 Tidskriftsartikel (refereegranskat)abstract Electrons at the surface of a plasma that is irradiated by a laser with intensity in excess of 1 0 23 W c m - 2 are accelerated so strongly that they emit bursts of synchrotron radiation. Although the combination of high photon and electron density and electromagnetic field strength at the plasma surface makes particle-particle interactions possible, these interactions are usually neglected in simulations of the high-intensity regime. Here we demonstrate an implementation of two such processes: photon absorption and stimulated emission. We show that, for plasmas that are opaque to the laser light, photon absorption would cause complete depletion of the multi-keV region of the synchrotron photon spectrum, unless compensated by stimulated emission. Our results motivate further study of the density dependence of quantum electrodynamics phenomena in strong electromagnetic fields.
17.	Brodin, Gert, 1963-, et al. (författare) Interaction between gravitational waves and plasma waves in the Vlasov description 2010 Ingår i: Journal of Plasma Physics. - : Cambridge University Press. - 0022-3778 .- 1469-7807. ; :76, s. 345-353 Tidskriftsartikel (refereegranskat)abstract The nonlinear interaction between electromagnetic, electrostatic and gravitational waves in a Vlasov plasma is reconsidered. By using a orthonormal tetrad description the three-wave coupling coefficients are computed. Comparing with previous results, it is found that the present theory leads to algebraic expression that are much reduced, as compared to those computed using a coordinate frame formalism. Furthermore, here we calculate the back reaction on the gravitational waves, and a simple energy conservation law is deduced in the limit of a cold plasma.
18.	Brodin, Gert, et al. (författare) On the possibility of metamaterial properties in spin plasmas 2008 Ingår i: New Journal of Physics. - Bristol, UK : Institute of Physics Pub.. - 1367-2630. ; 10:11, s. 115031- Tidskriftsartikel (refereegranskat)abstract The fluid theory of plasmas is extended to include the properties of electron spin. The linear theory of waves in a magnetized plasma is presented, and it is shown that the spin effects cause a change of the magnetic permeability. Furthermore, by changing the direction of the external magnetic field, the magnetic permeability may become negative. This leads to instabilities in the long wavelength regimes. If these can be controlled, however, the spin plasma becomes a metamaterial for a broad range of frequencies, i.e. above the ion cyclotron frequency but below the electron cyclotron frequency. The consequences of our results are discussed.
19.	Brodin, G., et al. (författare) Particle-in-cell simulations of electron spin effects in plasmas 2013 Ingår i: Journal of Plasma Physics. - : Cambridge University Press (CUP). - 0022-3778 .- 1469-7807. ; 79:4, s. 377-382 Tidskriftsartikel (refereegranskat)abstract We present a particle-in-cell code accounting for the magnetic dipole force and for the magnetization currents associated with the electron spin. The electrons are divided into spin-up and spin-down populations relative to the magnetic field, where the magnetic dipole force acts in opposite directions for the two species. To validate the code, we study wakefield generation by an electromagnetic pulse propagating parallel to an external magnetic field. The properties of the generated wakefield are shown to be in good agreement with previous theoretical results. Generalizations of the code to account for other quantum effects are discussed.
20.	Brodin, Gert, 1963-, et al. (författare) Quantum-electrodynamical photon splitting in magnetized Nonlinear pair plasmas 2007 Ingår i: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 98:12 Tidskriftsartikel (refereegranskat)abstract We present for the first time the nonlinear dynamics of quantum electrodynamic (QED) photon splitting in a strongly magnetized electron-positron (pair) plasma. By using a QED corrected Maxwell equation, we derive a set of equations that exhibit nonlinear couplings between electromagnetic (EM) waves due to nonlinear plasma currents and QED polarization and magnetization effects. Numerical analyses of our coupled nonlinear EM wave equations reveal the possibility of a more efficient decay channel, as well as new features of energy exchange among the three EM modes that are nonlinearly interacting in magnetized pair plasmas. Possible applications of our investigation to astrophysical settings, such as magnetars, are pointed out.
21.	Brodin, Gert, 1963-, et al. (författare) Spin and magnetization effects in plasmas 2011 Ingår i: Plasma Physics and Controlled Fusion. - : iop publishing. - 0741-3335 .- 1361-6587. ; 53:7, s. 074013- Tidskriftsartikel (refereegranskat)abstract Quantum effects in plasmas are of interest for a diverse set of systems, and have thus as a field been revived and attracted a lot of attention from a wide community over the past decade. In models of quantum plasmas, the effects studied mostly are due to the quantum particle dispersion and tunnelling. Such effects can be of importance in dense systems and on short length scales. There are also a number of effects related to spin and statistics. However, up to recently the magnetization effect in plasmas due to the intrinsic electron spin has been largely ignored. The magnetization dynamics of e.g. solids has many important applications, such as components for memory storage, but has also been discussed in more 'proper' plasma environments, such as fusion plasmas. Furthermore, also from a basic science point-of-view the effects of intrinsic spin and gyromagnetic effects are of considerable interest. Here we give a short review of a number of different models for treating magnetization effects in plasmas, with a focus on recent results. In particular, the transition between kinetic models and fluid models is discussed. We also give a number of examples of applications of such theories, as well as an outlook for possible future work.
22.	Brodin, Gert, 1963-, et al. (författare) Spin contribution to the ponderomotive force in a plasma 2010 Ingår i: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 105:10, s. 105004- Tidskriftsartikel (refereegranskat)abstract The concept of a ponderomotive force due to the intrinsic spin of electrons is developed. An expression containing both the classical as well as the spin-induced ponderomotive force is derived. The results are used to demonstrate that an electromagnetic pulse can induce a spin-polarized plasma. Furthermore, it is shown that, for certain parameters, the nonlinear backreaction on the electromagnetic pulse from the spin magnetization current can be larger than that from the classical free current. Suitable parameter values for a direct test of this effect are presented.
23.	Bulanov, S. S., et al. (författare) Depletion of intense fields 2017 Ingår i: AIP Conference Proceedings. - : Author(s). - 1551-7616 .- 0094-243X. - 9780735414808 ; 1812:1, s. Article no. UNSP 100006 - Konferensbidrag (refereegranskat)abstract The problem of backreaction of quantum processes on the properties of the background field still remains on the list of outstanding questions of high intensity particle physics. Usually, photon emission by an electron or positron, photon decay into electron-positron pairs in strong electromagnetic fields, or electron-positron pair production by such fields are described in the framework of the external field approximation. It is assumed that the external field has infinite energy and is not affected by these processes. However, the above-mentioned processes have a multi-photon nature, i.e., they occur with the absorption of a significant number of field photons. As a result, the interaction of an intense electromagnetic field with either a highly charged electron bunch or a fast growing population of electrons, positrons, and gamma photons (as in the case of an electromagnetic cascade) may lead to a depletion of the field energy, thus making the external field approximation invalid. Taking the multi-photon Compton process as an example, we estimate the threshold of depletion and find it to become significant at field strengths (a0∼103) and electron bunch charge of about tens of nC. © 2017 Author(s).
24.	Bychkov, Vitaly, 1968-, et al. (författare) Magnetohydrodynamic instability in plasmas with intrinsic magnetization 2010 Ingår i: Physics of Plasmas. - : AIP Publishing. - 1070-664X .- 1089-7674. ; 17:11, s. 112107-112112 Tidskriftsartikel (refereegranskat)abstract From a magnetofluid description with intrinsic magnetization, a new plasma instability is obtained. The plasma magnetization is produced by the collective electron spin. The instability develops in a nonuniform plasma when the electron concentration and temperature vary along an externally applied magnetic field. Alfvén waves play an important role in the instability. The instability properties are numerically investigated for a particular example of an ultrarelativistic degenerate plasma in exploding white dwarfs.
25.	Bychkov, Vitaly, 1968-, et al. (författare) Speedup of doping fronts in organic semiconductors through plasma instability 2011 Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 107:1, s. 016103-016107 Tidskriftsartikel (refereegranskat)abstract The dynamics of doping transformation fronts in organic semiconductor plasma is studied for application in light-emitting electrochemical cells. We show that new fundamental effects of the plasma dynamics can significantly improve the device performance. We obtain an electrodynamic instability, which distorts the doping fronts and increases the transformation rate considerably. We explain the physical mechanism of the instability, develop theory, provide experimental evidence, perform numerical simulations, and demonstrate how the instability strength may be amplified technologically. The electrodynamic plasma instability obtained also shows interesting similarity to the hydrodynamic Darrieus-Landau instability in combustion, laser ablation, and astrophysics.
26.	Bychkov, Vitaly, 1968-, et al. (författare) The Darrieus-Landau instability in fast deflagration and laser ablation 2008 Ingår i: Physics of Plasmas. - : AIP Publishing. - 1070-664X .- 1089-7674. ; 15:3, s. 032702- Tidskriftsartikel (refereegranskat)abstract The problem of the Darrieus-Landau instability at a discontinuous deflagration front in a compressible flow is solved. Numerous previous attempts to solve this problem suffered from the deficit of boundary conditions. Here, the required additional boundary condition is derived rigorously taking into account the internal structure of the front. The derived condition implies a constant mass flux at the front; it reduces to the classical Darrieus-Landau condition in the limit of an incompressible flow. It is demonstrated that in general the solution to the problem depends on the type of energy source in the flow. In the common case of a strongly localized source, compression effects make the Darrieus-Landau instability considerably weaker. Particularly, the instability growth rate is reduced for laser ablation in comparison to the classical incompressible case. The instability disappears completely in the Chapman-Jouguet regime of ultimately fast deflagration.
27.	Bychkov, Vitaly, 1968-, et al. (författare) The Rayleigh-Taylor instability and internal waves in quantum plasmas 2008 Ingår i: Physics Letters A. - Amsterdam : North-Holland. - 0375-9601 .- 1873-2429. ; 372:17, s. 3042-3045 Tidskriftsartikel (refereegranskat)abstract Influence of quantum effects on the internal waves and the Rayleigh-Taylor instability in plasma is investigated. It is shown that quantum pressure always stabilizes the RT instability. The problem is solved both in the limit of short-wavelength perturbations and exactly for density profiles with layers of exponential stratification. In the case of stable stratification, quantum pressure modifies the dispersion relation of the inertial waves. Because of the quantum effects, the internal waves may propagate in the transverse direction, which was impossible in the classical case. A specific form of pure quantum internal waves is obtained, which do not require any external gravitational field.
28.	Bychkov, Vitaly, 1968-, et al. (författare) The structure of weak shocks in quantum plasmas 2008 Ingår i: Physics of Plasmas. - New York : American Institute of Physics. - 1070-664X .- 1089-7674. ; 15:3, s. 032309-032322 Tidskriftsartikel (refereegranskat)abstract The structure of a weak shock in a quantum plasma is studied, taking into account both dissipation terms due to thermal conduction and dispersive quantum terms due to the Bohm potential. Unlike quantum systems without dissipations, even a small thermal conduction may lead to a stationary shock structure. In the limit of zero quantum effects, the monotonic Burgers solution for the weak shock is recovered. Still, even small quantum terms make the structure nonmonotonic with the shock driving a train of oscillations into the initial plasma. The oscillations propagate together with the shock. The oscillations become stronger as the role of Bohm potential increases in comparison with thermal conduction. The results could be of importance for laser-plasma interactions, such as inertial confinement fusion plasmas, and in astrophysical environments, as well as in condensed matter systems.
29.	Cole, J. M., et al. (författare) Experimental Evidence of Radiation Reaction in the Collision of a High-Intensity Laser Pulse with a Laser-Wakefield Accelerated Electron Beam 2018 Ingår i: Physical Review X. - 2160-3308. ; 8:1 Tidskriftsartikel (refereegranskat)abstract The dynamics of energetic particles in strong electromagnetic fields can be heavily influenced by the energy loss arising from the emission of radiation during acceleration, known as radiation reaction. When interacting with a high-energy electron beam, today's lasers are sufficiently intense to explore the transition between the classical and quantum radiation reaction regimes. We present evidence of radiation reaction in the collision of an ultrarelativistic electron beam generated by laser-wakefield acceleration (μ 500 MeV) with an intense laser pulse (a0 > 10). We measure an energy loss in the postcollision electron spectrum that is correlated with the detected signal of hard photons (γ rays), consistent with a quantum description of radiation reaction. The generated γ rays have the highest energies yet reported from an all-optical inverse Compton scattering scheme, with critical energy > 30 MeV.
30.	de Andres Gonzalez, Aitor, 1992-, et al. (författare) Vacuum laser acceleration of electrons injected from nanotips 2023 Ingår i: 2023 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2023. - : Institute of Electrical and Electronics Engineers (IEEE). - 9798350345995 - 9798350346008 Konferensbidrag (refereegranskat)abstract Vacuum laser acceleration (VLA) is a paradigm that utilizes the strong fields of focused laser light to accelerate electrons in vacuum. Despite its conceptual simplicity and a large existing collection of theoretical studies, realizing VLA in practice has proven remarkably challenging due to the difficulties associated with efficient injection: the electrons to be accelerated must be pre-energized and temporally compressed below an optical half-cycle before timely entering the rapidly oscillating fields of the laser. Therefore, only a handful of experiments have been published up to date, and a knowledge gap remains [1-3].
31.	Dinu, V., et al. (författare) Photon polarization in light-by-light scattering: Finite size effects 2014 Ingår i: Physical Review D - Particles, Fields, Gravitation and Cosmology. - 2470-0010 .- 2470-0029. ; 90:4 Tidskriftsartikel (refereegranskat)abstract We derive a simple expression for the photon helicity and polarization-flip probabilities in arbitrary background fields, in the low-energy regime. Taking the background to model a focused laser beam, we study the impact of pulse shape and collision geometry on the probabilities and on ellipticity signals of vacuum birefringence. We find that models which do not account for pulse duration can overestimate all signals in near head-on collisions by up to an order of magnitude. Taking pulse duration into account, the flip probability becomes relatively insensitive to both angular incidence and the fine details of the pulse structure.
32.	Dinu, Victor, et al. (författare) Quantum Radiation Reaction: From Interference to Incoherence 2016 Ingår i: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 116:4 Tidskriftsartikel (refereegranskat)abstract We investigate quantum radiation reaction in laser-electron interactions across different energy and intensity regimes. Using a fully quantum approach which also accounts exactly for the effect of the strong laser pulse on the electron motion, we identify in particular a regime in which radiation reaction is dominated by quantum interference. We find signatures of quantum radiation reaction in the electron spectra which have no classical analogue and which cannot be captured by the incoherent approximations typically used in the high-intensity regime. These signatures are measurable with presently available laser and accelerator technology.
33.	Dinu, V., et al. (författare) Vacuum refractive indices and helicity flip in strong-field QED 2014 Ingår i: Physical Review D - Particles, Fields, Gravitation and Cosmology. - 2470-0010 .- 2470-0029. ; 89:12 Tidskriftsartikel (refereegranskat)abstract Vacuum birefringence is governed by the amplitude for a photon to flip helicity or polarization state in an external field. Here, we calculate the flip and nonflip amplitudes in arbitrary plane wave backgrounds, along with the induced spacetime-dependent refractive indices of the vacuum. We compare the behavior of the amplitudes in the low energy and high energy regimes, and analyze the impact of pulse shape and energy. We also provide the first lightfront-QED derivation of the coefficients in the Heisenberg-Euler effective action.
34.	Eerola, Paula, et al. (författare) Accelerator-based infrastructures in the fields of particle and nuclear physics 2020 Rapport (övrigt vetenskapligt/konstnärligt)abstract The Council for Research Infrastructures (RFI) within the Swedish Research Council (Vetenskapsrådet) commits a significant part of its annual budget to accelerator-based infrastructures in particle and nuclear physics. The funding covers membership fees, running costs and investments. The Swedish activities in these fields are mainly focused on CERN (Geneva, Switzerland) and FAIR (Darmstadt, Germany). In 2019, RFI decided to commission an investigation and landscape analysis of the research infrastructures they fund in these fields. The report is meant to support the Council’s work in ensuring that these funds are strategically well-spent and of maximum benefit to the research community. A panel of seven experts from the Nordic countries have worked on the task with the aid of data from relevant documentation, hearings, interviews and questionnaires. The report contains several concrete recommendations given from the authors to RFI.
35.	Forsberg, Mats, 1978-, et al. (författare) Nonlinear interactions between gravitational radiation and modified Alfvén modes in astrophysical dusty plasmas 2006 Ingår i: Physical Review D. Particles and fields. - : American Physical Society. - 0556-2821 .- 1089-4918. ; 74, s. 064014-064014-5 Tidskriftsartikel (refereegranskat)abstract We present an investigation of nonlinear interactions between gravitational radiation and modified Alfvén modes in astrophysical dusty plasmas. Assuming that stationary charged dust grains form neutralizing background in an electron-ion-dust plasma, we obtain the three-wave coupling coefficients and calculate the growth rates for parametrically coupled gravitational radiation and modified Alfvén-Rao modes. The threshold value of the gravitational wave amplitude associated with convective stabilization is particularly small if the gravitational frequency is close to twice the modified Alfvén wave frequency. The implication of our results to astrophysical dusty plasmas is discussed.
36.	Gonoskov, Arkady, 1984, et al. (författare) Charged particle motion and radiation in strong electromagnetic fields 2022 Ingår i: Reviews of Modern Physics. - 0034-6861. ; 94:4 Forskningsöversikt (refereegranskat)abstract The dynamics of charged particles in electromagnetic fields is an essential component of understanding the most extreme environments in our Universe. In electromagnetic fields of sufficient magnitude, radiation emission dominates the particle motion and effects of quantum electrodynamics (QED) in strong fields are crucial, which triggers electron-positron pair cascades and counterintuitive particle-trapping phenomena. As a result of recent progress in laser technology, high-power lasers provide a platform to create and probe such fields in the laboratory. With new large-scale laser facilities on the horizon and the prospect of investigating these hitherto unexplored regimes, this review explores the basic physical processes of radiation reaction and QED in strong fields, how they are treated theoretically and in simulation, the new collective dynamics they unlock, recent experimental progress and plans, and possible applications for high -flux particle and radiation sources.
37.	Gonoskov, Arkady, 1984, et al. (författare) Extended particle-in-cell schemes for physics in ultrastrong laser fields : Review and developments 2015 Ingår i: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics. - 1539-3755 .- 1550-2376. ; 92:2 Tidskriftsartikel (refereegranskat)abstract We review common extensions of particle-in-cell (PIC) schemes which account for strong field phenomena in laser-plasma interactions. After describing the physical processes of interest and their numerical implementation, we provide solutions for several associated methodological and algorithmic problems. We propose a modified event generator that precisely models the entire spectrum of incoherent particle emission without any low-energy cutoff, and which imposes close to the weakest possible demands on the numerical time step. Based on this, we also develop an adaptive event generator that subdivides the time step for locally resolving QED events, allowing for efficient simulation of cascades. Further, we present a unified technical interface for including the processes of interest in different PIC implementations. Two PIC codes which support this interface, PICADOR and ELMIS, are also briefly reviewed.
38.	Gonoskov, Arkady, et al. (författare) Probing Nonperturbative QED with Optimally Focused Laser Pulses 2013 Ingår i: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 111:6 Tidskriftsartikel (refereegranskat)abstract We study nonperturbative pair production in intense, focused laser fields called e-dipole pulses. We address the conditions required, such as the quality of the vacuum, for reaching high intensities without initiating beam-depleting cascades, the number of pairs which can be created, and experimental detection of the created pairs. We find that e-dipole pulses offer an optimal method of investigating nonperturbative QED.
39.	Gonoskov, A., et al. (författare) Radiation-dominated particle and plasma dynamics 2018 Ingår i: Physics of Plasmas. - : AIP Publishing. - 1089-7674 .- 1070-664X. ; 25:9 Tidskriftsartikel (refereegranskat)abstract We consider charged particle motion in a strong electromagnetic field of an arbitrary configuration and find a universal behaviour: for sufficient field strengths, the radiation losses lead to a general tendency of the charge to move along the direction that locally yields zero acceleration orthogonal to the direction of motion. This corresponds to the suppression of radiation losses according to both classical and quantum considerations. We show that such a radiation-free direction (RFD) exists at each point of an arbitrary electromagnetic field, while the time-scale of approaching this direction decreases with the increase in field strength. In the case of a sufficiently strong electromagnetic field, at each point of space, the charges mainly move and form currents along the local RFD, while the deviation of their motion from RFD can be calculated to determine their incoherent emission. This forms a general description of particle, and therefore plasma, dynamics in strong electromagnetic fields, the latter being generated by state-of-the-art lasers or in astrophysical environments.
40.	Gonoskov, Arkady, 1984, et al. (författare) Ultrabright GeV Photon Source via Controlled Electromagnetic Cascades in Laser-Dipole Waves 2017 Ingår i: Physical Review X. - 2160-3308. ; 7:4 Tidskriftsartikel (refereegranskat)abstract Electromagnetic cascades have the potential to act as a high-energy photon source of unprecedented brightness. Such a source would offer new experimental possibilities in fundamental science, but in the cascade process radiation reaction and rapid electron-positron plasma production seemingly restrict the efficient production of photons to sub-GeV energies. Here, we show how to overcome these energetic restrictions and how to create a directed GeV photon source, with unique capabilities as compared to existing sources. Our new source concept is based on a controlled interplay between the cascade and anomalous radiative trapping. Using specially designed advanced numerical models supported with analytical estimates, we demonstrate that the concept becomes feasible at laser powers of around 7 PW, which is accessible at soon-to-be-available facilities. A higher peak power of 40 PW can provide 10(9) photons with GeV energies in a well-collimated 3-fs beam, achieving peak brilliance 9 x 10(24) ph s(-1) mrad(-2) mm(-2)/0.1%BW.
41.	Gonoskov, Ivan, et al. (författare) Single-step propagators for calculation of time evolution in quantum systems with arbitrary interactions 2016 Ingår i: Computer Physics Communications. - : Elsevier BV. - 0010-4655 .- 1879-2944. ; 202, s. 211-215 Tidskriftsartikel (refereegranskat)abstract We propose and develop a general method of numerical calculation of the wave function time evolution in a quantum system which is described by Hamiltonian of an arbitrary dimensionality and with arbitrary interactions. For this, we obtain a general n-order single-step propagator in closed-form, which could be used for the numerical solving of the problem with any prescribed accuracy. We demonstrate the applicability of the proposed approach by considering a quantum problem with non-separable time-dependent Hamiltonian: the propagation of an electron in focused electromagnetic field with vortex electric field component.
42.	Grönlund, Andreas, 1974-, et al. (författare) Evolution of rogue waves in interacting wave systems 2009 Ingår i: Europhysics letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 86:2, s. 24001- Tidskriftsartikel (refereegranskat)abstract Large-amplitude water waves on deep water have long been known in the seafaring community, and are the cause of great concern for, e.g., oil platform constructions. The concept of such freak waves is nowadays, thanks to satellite and radar measurements, well established within the scientific community. There are a number of important models and approaches for the theoretical description of such waves. By analyzing the scaling behavior of freak wave formation in a model of two interacting waves, described by two coupled non-linear Schrödinger equations, we show that there are two different dynamical scaling behaviors above and below a critical angle θc of the direction of the interacting waves, below which all wave systems evolve and display statistics similar to a wave system of non-interacting waves. The results equally apply to other systems described by the non-linear Schrödinger equations, and should be of interest when designing optical wave guides.
43.	Hansson, T., et al. (författare) Scalar Wigner theory for polarized light in nonlinear Kerr media 2013 Ingår i: Journal of the Optical Society of America B: Optical Physics. - : The Optical Society. - 1520-8540 .- 0740-3224. ; 30:6, s. 1765-1769 Tidskriftsartikel (refereegranskat)abstract A scalar Wigner distribution function for describing polarized light is proposed in analogy with the treatment of spin variables in quantum kinetic theory. The formalism is applied to the propagation of circularly polarized light in nonlinear Kerr media, and an extended phase-space evolution equation is derived along with invariant quantities. The formalism is additionally used to analyze the modulational instability
44.	Harvey, Christopher, 1982, et al. (författare) Focusing effects in laser-electron Thomson scattering 2016 Ingår i: Physical Review Special Topics - Accelerators and Beams. - 1098-4402. ; 19:9 Tidskriftsartikel (refereegranskat)abstract We study the effects of laser pulse focusing on the spectral properties of Thomson scattered radiation. Modeling the laser as a paraxial beam we find that, in all but the most extreme cases of focusing, the temporal envelope has a much bigger effect on the spectrum than the focusing itself. For the case of ultrashort pulses, where the paraxial model is no longer valid, we adopt a subcycle vector beam description of the field. It is found that the emission harmonics are blue shifted and broaden out in frequency space as the pulse becomes shorter. Additionally the carrier envelope phase becomes important, resulting in an angular asymmetry in the spectrum. We then use the same model to study the effects of focusing beyond the limit where the paraxial expansion is valid. It is found that fields focussed to subwavelength spot sizes produce spectra that are qualitatively similar to those from subcycle pulses due to the shortening of the pulse with focusing. Finally, we study high-intensity fields and find that, in general, the focusing makes negligible difference to the spectra in the regime of radiation reaction.
45.	Harvey, Christopher, 1982, et al. (författare) High-energy gamma-ray beams from nonlinear Thomson and Compton scattering in the ultra-intense regime 2015 Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. - 9781628416305 ; 9509, s. 950908- Konferensbidrag (refereegranskat)abstract We consider the Thomson and Compton scattering of high-energy electrons in an intense laser pulse. Our simulations show that energy losses due to radiation reaction cause the emitted radiation to be spread over a broader angular range than the case without these losses included. We explain this in terms of the effect of these energy losses on the particle dynamics. Finally, at ultra-high intensities, i.e. fields with a dimensionless parameter a(0)similar to 200, the energy of the emission spectrum is significantly reduced by radiation reaction and also the classical and QED results begin to differ. This is found to be due to the classical theory overestimating the energy loss of the electrons. Such findings are relevant to radiation source development involving the next generation of high-intensity laser facilities.
46.	Harvey, Christopher, 1982, et al. (författare) Narrowing of the emission angle in high-intensity Compton scattering 2016 Ingår i: Physical Review A - Atomic, Molecular, and Optical Physics. - : American Physical Society. - 2469-9926 .- 2469-9934 .- 1050-2947 .- 1094-1622. ; 93:2 Tidskriftsartikel (refereegranskat)abstract We consider the emission spectrum of high-energy electrons in an intense laser field. At high intensities (a_0 \sim 200) we find that the QED theory predicts a narrower angular spread of emissions than the classical theory. This is due to the classical theory overestimating the energy loss of the particles, resulting in them becoming more susceptible to reflection in the laser pulse.
47.	Harvey, Christopher, 1982, et al. (författare) Quantum Quenching of Radiation Losses in Short Laser Pulses 2017 Ingår i: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 118:10 Tidskriftsartikel (refereegranskat)abstract Accelerated charges radiate, and therefore must lose energy. The impact of this energy loss on particle motion, called radiation reaction, becomes significant in intense-laser matter interactions, where it can reduce collision energies, hinder particle acceleration schemes, and is seemingly unavoidable. Here we show that this common belief breaks down in short laser pulses, and that energy losses and radiation reaction can be controlled and effectively switched off by appropriate tuning of the pulse length. This "quenching" of emission is impossible in classical physics, but becomes possible in QED due to the discrete nature of quantum emissions.
48.	Holkundkar, Amol, et al. (författare) Proton acceleration by circularly polarized traveling electromagnetic wave 2012 Ingår i: Physical Review Special Topics - Accelerators and Beams. - 1098-4402. ; 15:9 Tidskriftsartikel (refereegranskat)abstract The acceleration of charged particles, producing collimated monoenergetic beams, over short distances holds the promise to offer new tools in medicine and diagnostics. Here, we consider a possible mechanism for accelerating protons to high energies by using a phase modulated circularly polarized electromagnetic wave propagating along a constant magnetic field. It is observed that a plane wave with dimensionless amplitude of 0.1 is capable to accelerate a 1 keV proton to 386 MeV under optimum conditions. Finally, we discuss possible limitations of the acceleration scheme.
49.	Holkundkar, A.R, et al. (författare) Thomson scattering in high-intensity chirped laser pulses 2015 Ingår i: Physics of Plasmas. - : AIP Publishing. - 1089-7674 .- 1070-664X. ; 22:10, s. 103103- Tidskriftsartikel (refereegranskat)abstract We consider the Thomson scattering of an electron in an ultra-intense laser pulse. It is well known that at high laser intensities, the frequency and brilliance of the emitted radiation will be greatly reduced due to the electron losing energy before it reaches the peak field. In this work, we investigate the use of a small frequency chirp in the laser pulse in order to mitigate this effect of radiation reaction. It is found that the introduction of a negative chirp means the electron enters a high frequency region of the field while it still has a large proportion of its original energy. This results in a significant enhancement of the frequency and intensity of the emitted radiation as compared to the case without chirping.
50.	Ilderton, Antony, 1978, et al. (författare) Prospects for studying vacuum polarisation using dipole and synchrotron radiation 2016 Ingår i: Journal of Plasma Physics. - 0022-3778 .- 1469-7807. ; 82:2, s. 655820201- Tidskriftsartikel (refereegranskat)abstract The measurement of vacuum polarisation effects, in particular vacuum birefringence, using combined optical and X-ray laser pulses are now actively pursued. Here we briefly examine the feasibility of two alternative set-ups. The first utilises an alternative target, namely a converging dipole pulse, and the second uses an alternative probe, namely the synchrotron-like emission from highly energetic particles, themselves interacting with a laser pulse. The latter set-up has been proposed for experiments at ELI-NP.

Skapa referenser, mejla, bekava och länka

Länka till träfflistan

Träfflista för sökning "WFRF:(Marklund Mattias 1970 ) "

Avgränsa träffmängd

År