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1
Nishida, Yasushi. « Electron linear accelerator based on cross field acceleration principle ». Laser and Particle Beams 7, no 3 (août 1989) : 561–79. http://dx.doi.org/10.1017/s0263034600007540.
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Powerful lasers have the potential to be used for power sources of the high energy particle accelerators. However, we have to convert the transverse wave into a longitudinal one which can trap the charged particles in the wave trough to accelerate them. In order to obtain a high field-gradient in an accelerator, several new concepts have been proposed. One of them is a beat wave accelerator (BWA) which uses a nonlinear optical mixing of two laser beams. Another concept is a Cross Field Acceleration (or a Vp × B acceleration) scheme, in which the trapped particles in the wave trough are accelerated along the wavefront and across the static magnetic field applied externally. An overview is presented including some new results.
2
Guidoni, S. E., J. T. Karpen et C. R. DeVore. « Spectral Power-law Formation by Sequential Particle Acceleration in Multiple Flare Magnetic Islands ». Astrophysical Journal 925, no 2 (1 février 2022) : 191. http://dx.doi.org/10.3847/1538-4357/ac39a5.
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Abstract We present a first-principles model of pitch-angle and energy distribution function evolution as particles are sequentially accelerated by multiple flare magnetic islands. Data from magnetohydrodynamic (MHD) simulations of an eruptive flare/coronal mass ejection provide ambient conditions for the evolving particle distributions. Magnetic islands, which are created by sporadic reconnection at the self-consistently formed flare current sheet, contract and accelerate the particles. The particle distributions are evolved using rules derived in our previous work. In this investigation, we assume that a prescribed fraction of particles sequentially “hops” to another accelerator and receives an additional boost in energy and anisotropy. This sequential process generates particle number spectra that obey an approximate power law at mid-range energies and presents low- and high-energy breaks. We analyze these spectral regions as functions of the model parameters. We also present a fully analytic method for forming and interpreting such spectra, independent of the sequential acceleration model. The method requires only a few constrained physical parameters, such as the percentage of particles transferred between accelerators, the energy gain in each accelerator, and the number of accelerators visited. Our investigation seeks to bridge the gap between MHD and kinetic regimes by combining global simulations and analytic kinetic theory. The model reproduces and explains key characteristics of observed flare hard X-ray spectra as well as the underlying properties of the accelerated particles. Our analytic model provides tools to interpret high-energy observations for missions and telescopes, such as RHESSI, FOXSI, NuSTAR, Solar Orbiter, EOVSA, and future high-energy missions.
3
Hogan, Mark J. « Electron and Positron Beam–Driven Plasma Acceleration ». Reviews of Accelerator Science and Technology 09 (janvier 2016) : 63–83. http://dx.doi.org/10.1142/s1793626816300036.
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Particle accelerators are the ultimate microscopes. They produce high energy beams of particles — or, in some cases, generate X-ray laser pulses — to probe the fundamental particles and forces that make up the universe and to explore the building blocks of life. But it takes huge accelerators, like the Large Hadron Collider or the two-mile-long SLAC linac, to generate beams with enough energy and resolving power. If we could achieve the same thing with accelerators just a few meters long, accelerators and particle colliders could be much smaller and cheaper. Since the first theoretical work in the early 1980s, an exciting series of experiments have aimed at accelerating electrons and positrons to high energies in a much shorter distance by having them “surf” on waves of hot, ionized gas like that found in fluorescent light tubes. Electron-beam-driven experiments have measured the integrated and dynamic aspects of plasma focusing, the bright flux of high energy betatron radiation photons, particle beam refraction at the plasma–neutral-gas interface, and the structure and amplitude of the accelerating wakefield. Gradients spanning kT/m to MT/m for focusing and 100[Formula: see text]MeV/m to 50[Formula: see text]GeV/m for acceleration have been excited in meter-long plasmas with densities of 10[Formula: see text]–10[Formula: see text][Formula: see text]cm[Formula: see text], respectively. Positron-beam-driven experiments have evidenced the more complex dynamic and integrated plasma focusing, 100[Formula: see text]MeV/m to 5[Formula: see text]GeV/m acceleration in linear and nonlinear plasma waves, and explored the dynamics of hollow channel plasma structures. Strongly beam-loaded plasma waves have accelerated beams of electrons and positrons with hundreds of pC of charge to over 5[Formula: see text]GeV in meter scale plasmas with high efficiency and narrow energy spread. These “plasma wakefield acceleration” experiments have been mounted by a diverse group of accelerator, laser and plasma researchers from national laboratories and universities around the world. This article reviews the basic principles of plasma wakefield acceleration with electron and positron beams, the current state of understanding, the push for first applications and the long range R&D roadmap toward a high energy collider.
4
Ogata, Atsushi, et Kazuhisa Nakajima. « Recent progress and perspectives of laser–plasma accelerators ». Laser and Particle Beams 16, no 2 (juin 1998) : 381–96. http://dx.doi.org/10.1017/s0263034600011654.
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Recent progress in laser-plasma accelerators has matured a concept of particle acceleration as a possible next-generation particle accelerator promising ultrahigh accelerating gradients in a compact size. Four major concepts of laser-plasma accelerators—the plasma beat wave accelerator, the laser wakefield accelerator, the self-modulated laser wakefield accelerator, and the plasma wakefield accelerator—are reviewed on accelerator physics issues and experiments demonstrating the basic mechanisms of their concepts. As a perspective to the future practical application, a design of 5-TeV linear colliders based on the laser wakefield accelerator is discussed.
5
Kalmykov, S., O. Polomarov, D. Korobkin, J. Otwinowski, J. Power et G. Shvets. « Novel techniques of laser acceleration : from structures to plasmas ». Philosophical Transactions of the Royal Society A : Mathematical, Physical and Engineering Sciences 364, no 1840 (24 janvier 2006) : 725–40. http://dx.doi.org/10.1098/rsta.2005.1734.
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Compact accelerators of the future will require enormous accelerating gradients that can only be generated using high power laser beams. Two novel techniques of laser particle acceleration are discussed. The first scheme is based on a solid-state accelerating structure powered by a short pulse CO 2 laser. The planar structure consists of two SiC films, separated by a vacuum gap, grown on Si wafers. Particle acceleration takes place inside the gap by a surface electromagnetic wave excited at the vacuum/SiC interface. Laser coupling is accomplished through the properly designed Si grating. This structure can be inexpensively manufactured using standard microfabrication techniques and can support accelerating fields well in excess of 1 GeV m −1 without breakdown. The second scheme utilizes a laser beatwave to excite a high-amplitude plasma wave, which accelerates relativistic particles. The novel aspect of this technique is that it takes advantage of the nonlinear bi-stability of the relativistic plasma wave to drive it close to the wavebreaking.
6
Fang, Jun, Qi Xia, Shiting Tian, Liancheng Zhou et Huan Yu. « Kinetic simulation of electron, proton and helium acceleration in a non-relativistic quasi-parallel shock ». Monthly Notices of the Royal Astronomical Society 512, no 4 (14 avril 2022) : 5418–22. http://dx.doi.org/10.1093/mnras/stac886.
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ABSTRACT In addition to accelerating electrons and protons, non-relativistic quasi-parallel shocks are expected to possess the ability to accelerate heavy ions. The shocks in supernova remnants are generally supposed to be accelerators of Galactic cosmic rays, which consist of many species of particles. We investigate the diffusive shock acceleration of electrons, protons and helium ions in a non-relativistic quasi-parallel shock through a 1D particle-in-cell simulation with a helium-to-proton number density ratio of 0.1, which is relevant for Galactic cosmic rays. The simulation indicates that waves can be excited by the flow of energetic protons and helium ions upstream of a non-relativistic quasi-parallel shock with a sonic Mach number of 14 and an Alfvén Mach number of 19.5 in the shock rest frame, and that the charged particles are scattered by the self-generated waves and accelerated gradually. Moreover, the spectra of the charged particles downstream of the shock are thermal with a non-thermal tail, and the acceleration is efficient, with about $7{{\ \rm per\ cent}}$ and $5.4{{\ \rm per\ cent}}$ of the bulk kinetic energy transferred into the non-thermal protons and helium ions, respectively, in the near downstream region by the end of the simulation.
7
Sow Mondal, Shanwlee, Aveek Sarkar, Bhargav Vaidya et Andrea Mignone. « Acceleration of Solar Energetic Particles by the Shock of Interplanetary Coronal Mass Ejection ». Astrophysical Journal 923, no 1 (1 décembre 2021) : 80. http://dx.doi.org/10.3847/1538-4357/ac2c7a.
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Abstract Interplanetary coronal mass ejection (ICME) shocks are known to accelerate particles and contribute significantly to solar energetic particle events. We have performed magnetohydrodynamic-particle in cell simulations of ICME shocks to understand the acceleration mechanism. These shocks vary in Alfvénic Mach numbers as well as in magnetic field orientations (parallel and quasi-perpendicular). We find that diffusive shock acceleration plays a significant role in accelerating particles in a parallel ICME shock. In contrast, shock drift acceleration (SDA) plays a pivotal role in a quasi-perpendicular shock. High-Mach shocks are seen to accelerate particles more efficiently. Our simulations suggest that background turbulence and local particle velocity distribution around the shock can indirectly hint at the acceleration mechanism. Our results also point toward a few possible in situ observations that could validate our understanding of the topic.
8
Kocharov, L. G., G. A. Kovaltsov, G. E. Kocharov, E. I. Chuikin, I. G. Usoskin, M. A. Shea, D. F. Smart et al. « Electromagnetic and corpuscular emission from the solar flare of 1991 June 15 : Continuous acceleraton of relativistic particles ». Solar Physics 150, no 1-2 (mars 1994) : 267–83. http://dx.doi.org/10.1007/bf00712889.
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D’Arcy, R., J. Chappell, J. Beinortaite, S. Diederichs, G. Boyle, B. Foster, M. J. Garland et al. « Recovery time of a plasma-wakefield accelerator ». Nature 603, no 7899 (2 mars 2022) : 58–62. http://dx.doi.org/10.1038/s41586-021-04348-8.
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AbstractThe interaction of intense particle bunches with plasma can give rise to plasma wakes1,2 capable of sustaining gigavolt-per-metre electric fields3,4, which are orders of magnitude higher than provided by state-of-the-art radio-frequency technology5. Plasma wakefields can, therefore, strongly accelerate charged particles and offer the opportunity to reach higher particle energies with smaller and hence more widely available accelerator facilities. However, the luminosity and brilliance demands of high-energy physics and photon science require particle bunches to be accelerated at repetition rates of thousands or even millions per second, which are orders of magnitude higher than demonstrated with plasma-wakefield technology6,7. Here we investigate the upper limit on repetition rates of beam-driven plasma accelerators by measuring the time it takes for the plasma to recover to its initial state after perturbation by a wakefield. The many-nanosecond-level recovery time measured establishes the in-principle attainability of megahertz rates of acceleration in plasmas. The experimental signatures of the perturbation are well described by simulations of a temporally evolving parabolic ion channel, transferring energy from the collapsing wake to the surrounding media. This result establishes that plasma-wakefield modules could be developed as feasible high-repetition-rate energy boosters at current and future particle-physics and photon-science facilities.
10
Papini, Giorgio. « Maximal acceleration and radiative processes ». Modern Physics Letters A 30, no 31 (14 septembre 2015) : 1550166. http://dx.doi.org/10.1142/s0217732315501667.
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We derive the radiation characteristics of an accelerated, charged particle in a model due to Caianiello in which the proper acceleration of a particle of mass [Formula: see text] has the upper limit [Formula: see text]. We find two power laws, one applicable to lower accelerations, the other more suitable for accelerations closer to [Formula: see text] and to the related physical singularity in the Ricci scalar. Geometrical constraints and power spectra are also discussed. By comparing the power laws due to the maximal acceleration (MA) with that for particles in gravitational fields, we find that the model of Caianiello allows, in principle, the use of charged particles as tools to distinguish inertial from gravitational fields locally.
11
Bingham, Robert. « Basic concepts in plasma accelerators ». Philosophical Transactions of the Royal Society A : Mathematical, Physical and Engineering Sciences 364, no 1840 (février 2006) : 559–75. http://dx.doi.org/10.1098/rsta.2005.1722.
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In this article, we present the underlying physics and the present status of high gradient and high-energy plasma accelerators. With the development of compact short pulse high-brightness lasers and electron and positron beams, new areas of studies for laser/particle beam–matter interactions is opening up. A number of methods are being pursued vigorously to achieve ultra-high-acceleration gradients. These include the plasma beat wave accelerator (PBWA) mechanism which uses conventional long pulse (∼100 ps) modest intensity lasers ( I ∼10 14 –10 16 W cm −2 ), the laser wakefield accelerator (LWFA) which uses the new breed of compact high-brightness lasers (<1 ps) and intensities >10 18 W cm −2 , self-modulated laser wakefield accelerator (SMLWFA) concept which combines elements of stimulated Raman forward scattering (SRFS) and electron acceleration by nonlinear plasma waves excited by relativistic electron and positron bunches the plasma wakefield accelerator. In the ultra-high intensity regime, laser/particle beam–plasma interactions are highly nonlinear and relativistic, leading to new phenomenon such as the plasma wakefield excitation for particle acceleration, relativistic self-focusing and guiding of laser beams, high-harmonic generation, acceleration of electrons, positrons, protons and photons. Fields greater than 1 GV cm −1 have been generated with monoenergetic particle beams accelerated to about 100 MeV in millimetre distances recorded. Plasma wakefields driven by both electron and positron beams at the Stanford linear accelerator centre (SLAC) facility have accelerated the tail of the beams.
12
Lin, R. P. « Particle Acceleration in Solar Flares and Coronal Mass Ejections ». Symposium - International Astronomical Union 195 (2000) : 15–25. http://dx.doi.org/10.1017/s0074180900162746.
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The Sun accelerates ions up to tens of GeV and electrons up to 100s of MeV in solar flares and coronal mass ejections. The energy in the accelerated tens-of-keV electrons and possibly ~1 MeV ions constitutes a significant fraction of the total energy released in a flare, implying that the particle acceleration and flare energy release mechanisms are intimately related. The total rate of energy release in transients from flares down to microflares/nanoflares may be significant for heating the active solar corona.Shock waves driven by fast CMEs appear to accelerate the high-energy particles in large solar energetic particle events detected at 1 AU. Smaller SEP events are dominated by ~1 to tens-of-keV electrons, with low fluxes of up to a few MeV/nucleon ions, typically enriched in 3He. The acceleration in gamma-ray flares appears to resemble that in these small electron-3He SEP events.
13
Dröge, Wolfgang. « Particle Acceleration by Waves and Fields ». Highlights of Astronomy 11, no 2 (1998) : 865–68. http://dx.doi.org/10.1017/s1539299600018967.
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The acceleration of electrons and charged nuclei to high energies is a phenomenon occuring at many sites throughout the universe, including the galaxy, pulsars, quasars, and around black holes. In the heliosphere, large solar flares and the often associated coronal mass ejections (CMEs) are the most energetic natural particle accelerators, occasionally accelerating protons to GeV and electrons to tens of MeV energies. The observation of these particles offers the unique opportunity to study fundamental processes in astrophysics. Particles that escape into interplanetary space can be observed in situ with particle detectors on spacecraft. In particular, particle spectra can be diagnostic of flare acceleration processes. On the other hand, energetic processes on the sun can be studied indirectly, via observations of the electromagnetic emissions (radio, X-ray, gamma-ray) produced by the particles in their interactions with the solar atmosphere. The purpose of this article is to give a brief overview on current models on particle acceleration and the present status of observations of solar energetic particles.
14
Cerutti, Benoît, et Gwenael Giacinti. « A global model of particle acceleration at pulsar wind termination shocks ». Astronomy & ; Astrophysics 642 (octobre 2020) : A123. http://dx.doi.org/10.1051/0004-6361/202038883.
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Context. Pulsar wind nebulae are efficient particle accelerators, and yet the processes at work remain elusive. Self-generated, microturbulence is too weak in relativistic magnetized shocks to accelerate particles over a wide energy range, suggesting that the global dynamics of the nebula may be involved in the acceleration process instead. Aims. In this work, we study the role played by the large-scale anisotropy of the transverse magnetic field profile on the shock dynamics. Methods. We performed large two-dimensional particle-in-cell simulations for a wide range of upstream plasma magnetizations, from weakly magnetized to strongly magnetized pulsar winds. Results. The magnetic field anisotropy leads to a dramatically different structure of the shock front and downstream flow. A large-scale velocity shear and current sheets form in the equatorial regions and at the poles, where they drive strong plasma turbulence via Kelvin-Helmholtz vortices and kinks. The mixing of current sheets in the downstream flow leads to efficient nonthermal particle acceleration. The power-law spectrum hardens with increasing magnetization, akin to those found in relativistic reconnection and kinetic turbulence studies. The high end of the spectrum is composed of particles surfing on the wake produced by elongated spearhead-shaped cavities forming at the shock front and piercing through the upstream flow. These particles are efficiently accelerated via the shear-flow acceleration mechanism near the Bohm limit. Conclusions. Magnetized relativistic shocks are very efficient particle accelerators. Capturing the global dynamics of the downstream flow is crucial to understanding them, and therefore local plane parallel studies may not be appropriate for pulsar wind nebulae and possibly other astrophysical relativistic magnetized shocks. A natural outcome of such shocks is a variable and Doppler-boosted synchrotron emission at the high end of the spectrum originating from the shock-front cavities, reminiscent of the mysterious Crab Nebula gamma-ray flares.
15
Sapra, Neil V., Ki Youl Yang, Dries Vercruysse, Kenneth J. Leedle, Dylan S. Black, R. Joel England, Logan Su et al. « On-chip integrated laser-driven particle accelerator ». Science 367, no 6473 (2 janvier 2020) : 79–83. http://dx.doi.org/10.1126/science.aay5734.
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Particle accelerators represent an indispensable tool in science and industry. However, the size and cost of conventional radio-frequency accelerators limit the utility and reach of this technology. Dielectric laser accelerators (DLAs) provide a compact and cost-effective solution to this problem by driving accelerator nanostructures with visible or near-infrared pulsed lasers, resulting in a 104 reduction of scale. Current implementations of DLAs rely on free-space lasers directly incident on the accelerating structures, limiting the scalability and integrability of this technology. We present an experimental demonstration of a waveguide-integrated DLA that was designed using a photonic inverse-design approach. By comparing the measured electron energy spectra with particle-tracking simulations, we infer a maximum energy gain of 0.915 kilo–electron volts over 30 micrometers, corresponding to an acceleration gradient of 30.5 mega–electron volts per meter. On-chip acceleration provides the possibility for a completely integrated mega–electron volt-scale DLA.
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Lazarian, A., G. Kowal, E. de Gouveia Dal Pino et E. Vishniac. « Particle acceleration in fast magnetic reconnection ». Proceedings of the International Astronomical Union 6, S274 (septembre 2010) : 62–71. http://dx.doi.org/10.1017/s1743921311006582.
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AbstractOur numerical simulations show that the reconnection of magnetic field becomes fast in the presence of weak turbulence in the way consistent with the Lazarian & Vishniac (1999) model of fast reconnection. This process in not only important for understanding of the origin and evolution of the large-scale magnetic field, but is seen as a possibly efficient particle accelerator producing cosmic rays through the first order Fermi process. In this work we study the properties of particle acceleration in the reconnection zones in our numerical simulations and show that the particles can be efficiently accelerated via the first order Fermi acceleration.
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Ren, Fu Shen, Ruo Xu Ma et Xiao Ze Cheng. « Simulation of Particle Impact Drilling Nozzles Based on FLUENT ». Advanced Materials Research 988 (juillet 2014) : 475–78. http://dx.doi.org/10.4028/www.scientific.net/amr.988.475.
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The purpose of particles impact drilling is to increase the rate of penetration when drilling extra-hard and strong-abrasive rocks, where supposed to be time-consuming and costly. Now the technology becomes the world’s most potential drilling technology for deep wells and ultra-deep well. The most important part of the drilling technology is the nozzle which accelerate the particles. The paper introduces the basic four types of the nozzles, and researches the acceleration effect of nozzles based on FLUENT. By concluding the simulation, put up a new structure of nozzle, and simulates the acceleration of the particle of different drilling fluid and particles inlet velocities, discusses how the length of accelerating cavity affect the acceleration.
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Куцаев, С. В., Н. В. Аврелин, А. Н. Аврелин, R. Agustsson, J. Edelen, A. Mypox et А. Ю. Смирнов. « Прототип протонного ондуляторного линейного ускорителя ». Письма в журнал технической физики 47, no 15 (2021) : 42. http://dx.doi.org/10.21883/pjtf.2021.15.51234.18777.
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One of the ways to realize undulator acceleration is to ensure particles motion in a magnetostatic undulator, where spatial oscillations of particles in the transverse direction are synchronized with temporal oscillations of transverse high-frequency field, which allows its energy transfer to the accelerated particles. The resonators, tcapable to provide a uniform transverse field, are structurally simpler than resonators with a periodically variable longitudinal field, which makes undulator accelerators an attractive alternative to coventional accelerators.Although the physics of such accelerators was previously descussed in the literature, the task of creating a physical prototype of undulator linac is still not realized. In this paper, we privde a practical description of the project of a proton undulator linear accelerator based on based on this principle, developed by RadiaBeam (USA).
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Zhang, Chuang, et Shouxian Fang. « Particle Accelerators in China ». Reviews of Accelerator Science and Technology 09 (janvier 2016) : 265–312. http://dx.doi.org/10.1142/s1793626816300127.
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As the special machines that can accelerate charged particle beams to high energy by using electromagnetic fields, particle accelerators have been widely applied in scientific research and various areas of society. The development of particle accelerators in China started in the early 1950s. After a brief review of the history of accelerators, this article describes in the following sections: particle colliders, heavy-ion accelerators, high-intensity proton accelerators, accelerator-based light sources, pulsed power accelerators, small scale accelerators, accelerators for applications, accelerator technology development and advanced accelerator concepts. The prospects of particle accelerators in China are also presented.
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BINGHAM, R., R. A. CAIRNS et J. T. MENDONÇA. « Particle acceleration in plasmas by perpendicularly propagating waves ». Journal of Plasma Physics 64, no 4 (octobre 2000) : 481–87. http://dx.doi.org/10.1017/s0022377800008722.
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The acceleration of particles to high energy by relativistic plasma waves has received a great deal of attention lately. Most of the particle-acceleration schemes using relativistic plasma waves rely either on intense terawatt or petawatt lasers or on electron beams as the driver of the acceleration wave. These laboratory experiments have attained accelerating fields as high as 1 GeV cm−1 with the electrons being accelerated to about 100 MeV in millimetre distances. In space and astrophysical plasmas, relativistic plasma waves can also be important for acceleration. A process that is common to both laboratory and space plasmas is the surfatron concept, which operates as a wave acceleration mechanism in a magnetized plasma. In this paper, we present test-particle results for the surfatron process.
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Lu, Yingchao, Fan Guo, Patrick Kilian, Hui Li, Chengkun Huang et Edison Liang. « Studying particle acceleration from driven magnetic reconnection at the termination shock of a relativistic striped wind using particle-in-cell simulations ». EPJ Web of Conferences 235 (2020) : 07003. http://dx.doi.org/10.1051/epjconf/202023507003.
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A rotating pulsar creates a surrounding pulsar wind nebula (PWN) by steadily releasing an energetic wind into the interior of the expanding shockwave of supernova remnant or interstellar medium. At the termination shock of a PWN, the Poynting-flux- dominated relativistic striped wind is compressed. Magnetic reconnection is driven by the compression and converts magnetic energy into particle kinetic energy and accelerating particles to high energies. We carrying out particle-in-cell (PIC) simulations to study the shock structure as well as the energy conversion and particle acceleration mechanism. By analyzing particle trajectories, we find that many particles are accelerated by Fermi-type mechanism. The maximum energy for electrons and positrons can reach hundreds of TeV.
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Ebisuzaki, T., et T. Tajima. « Wakefield acceleration towards ZeV from a black hole emanating astrophysical jets ». International Journal of Modern Physics A 34, no 34 (10 décembre 2019) : 1943018. http://dx.doi.org/10.1142/s0217751x19430188.
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We consider that electromagnetic pulses produced in the jets of this innermost part of the accretion disk accelerate charged particles (protons, ions, electrons) to very high energies via wakefield acceleration, including energies above 10[Formula: see text] eV for the case of protons and nucleus and 10[Formula: see text] eV for electrons by electromagnetic wave-particle interaction. Thereby, the wakefield acceleration mechanism supplements the pervasive Fermi’s stochastic acceleration mechanism (and overcomes its difficulties in the highest energy cosmic ray generation). The episodic eruptive accretion in the disk by the magneto-rotational instability gives rise to the strong Alfvenic pulses, which acts as the driver of the collective accelerating pondermotive force. This pondermotive force drives the wakes. The accelerated hadrons (protons and nuclei) are released to the intergalactic space to be ultra-high energy cosmic rays. The high-energy electrons, on the other hand, emit photons to produce various non-thermal emissions (radio, IR, visible, UV, and gamma-rays) of active galactic nuclei in an episodic manner, giving observational telltale signatures.
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Bingham, R. « Particle acceleration by electromagnetic waves ». Philosophical Transactions of the Royal Society A : Mathematical, Physical and Engineering Sciences 366, no 1871 (24 janvier 2008) : 1749–56. http://dx.doi.org/10.1098/rsta.2007.2183.
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We consider the symmetry in the interaction of photons and electrons, which has led to a common description of electron and photon accelerations; effects such as photon Landau damping arise naturally from such a treatment. Intense electromagnetic waves can act as a photon mirror to charged particles. The subsequent acceleration is equivalent to the photon pulse accelerating electrons. During the interaction or reflection process, the charged particle can emit bursts of radiation similar to the radiation emitted from the particles during wave breaking of plasma waves.
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Kawata, Shigeo, Masami Matsumoto et Yukio Masubuchi. « Numerical simulation for particle acceleration and trapping by an electromagnetic wave ». Laser and Particle Beams 7, no 2 (mai 1989) : 267–76. http://dx.doi.org/10.1017/s0263034600006030.
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The interaction between particles and an electromagnetic (EM) wave is investigated numerically in the system of particle Vp × B acceleration by the EM wave. Numerical simulations show that the particle acceleration mechanism works well in the case of the appropriate number density of the imposed particles. When the interaction between particles and the wave is too strong, a part of the trapped and accelerated particles is detrapped. A condition is also presented for the efficient particle acceleration and trapping by the EM wave.
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Caporaso, George J., Yu-Jiuan Chen et Stephen E. Sampayan. « The Dielectric Wall Accelerator ». Reviews of Accelerator Science and Technology 02, no 01 (janvier 2009) : 253–63. http://dx.doi.org/10.1142/s1793626809000235.
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Dielectric wall accelerators, a class of induction accelerators, employ a novel insulating beam tube to impress a longitudinal electric field on a bunch of charged particles. The surface flashover characteristics of this tube may permit the attainment of accelerating gradients on the order of 100 MV/m for accelerating pulses on the order of a nanosecond in duration. A virtual traveling wave of excitation along the tube is produced at any desired speed by controlling the timing of pulse-generating modules that supply a tangential electric field to the tube wall. Because of the ability to control the speed of this virtual wave, the accelerator is capable of handling any charge-to-mass-ratio particle; hence it can be used for electrons, protons and any ion. The accelerator architectures, key technologies and development challenges will be described.
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Coutrakon, George B. « Accelerators for Heavy-charged-particle Radiation Therapy ». Technology in Cancer Research & ; Treatment 6, no 4_suppl (août 2007) : 49–54. http://dx.doi.org/10.1177/15330346070060s408.
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This paper focuses on current and future designs of medical hadron accelerators for treating cancers and other diseases. Presently, five vendors and several national laboratories have produced heavy-particle medical accelerators for accelerating nuclei from hydrogen (protons) up through carbon and oxygen. Particle energies are varied to control the beam penetration depth in the patient. As of the end of 2006, four hospitals and one clinic in the United States offer proton treatments; there are five more such facilities in Japan. In most cases, these facilities use accelerators designed explicitly for cancer treatments. The accelerator types are a combination of synchrotrons, cyclotrons, and linear accelerators; some carry advanced features such as respiration gating, intensity modulation, and rapid energy changes, which contribute to better dose conformity on the tumor when using heavy charged particles. Recent interest in carbon nuclei for cancer treatment has led some vendors to offer carbon-ion and proton capability in their accelerator systems, so that either ion can be used. These features are now being incorporated for medical accelerators in new facilities.
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Zhang, Dong, Pavel Kroupa, Jan Pflamm-Altenburg et Manfred Schmid. « The Possible Emergence of an Attractive Inverse-Square Law from the Wave-Nature of Particles ». Advances in High Energy Physics 2022 (20 décembre 2022) : 1–15. http://dx.doi.org/10.1155/2022/2907762.
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A model of a particle in finite space is developed and the properties that the particle may possess under this model are studied. The possibility that particles attract each other due to their own wave nature is discussed. The assumption that the particles are spatially confined oscillations (SCO) in the medium is used. The relation between the SCO and the refractive index of the medium in the idealized universe is derived. Due to the plane wave constituents of SCOs, the presence of a refractive index field with a nonzero gradient causes the SCO to accelerate. The SCO locally changes the refractive index such that another SCO is accelerated towards it, and vice versa. It is concluded that the particles can attract each other due to their wave nature and an inverse-square-type acceleration emerges. The constant parameter in the inverse-square-type acceleration is used to compare with the gravitational constant G N , and the possibility of non inverse-square-type behavior is preliminary discussed.
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Kimura, Shigeo S., Kengo Tomida et Kohta Murase. « Acceleration and escape processes of high-energy particles in turbulence inside hot accretion flows ». Monthly Notices of the Royal Astronomical Society 485, no 1 (1 février 2019) : 163–78. http://dx.doi.org/10.1093/mnras/stz329.
Texte intégralRésumé :
Abstract We investigate acceleration and propagation processes of high-energy particles inside hot accretion flows. The magnetorotational instability (MRI) creates turbulence inside accretion flows, which triggers magnetic reconnection and may produce non-thermal particles. They can be further accelerated stochastically by the turbulence. To probe the properties of such relativistic particles, we perform magnetohydrodynamic simulations to obtain the turbulent fields generated by the MRI, and calculate orbits of the high-energy particles using snapshot data of the MRI turbulence. We find that the particle acceleration is described by a diffusion phenomenon in energy space with a diffusion coefficient of the hard-sphere type: Dε ∝ ε2, where ε is the particle energy. Eddies in the largest scale of the turbulence play a dominant role in the acceleration process. On the other hand, the stochastic behaviour in configuration space is not usual diffusion but superdiffusion: the radial displacement increases with time faster than that in the normal diffusion. Also, the magnetic field configuration in the hot accretion flow creates outward bulk motion of high-energy particles. This bulk motion is more effective than the diffusive motion for higher energy particles. Our results imply that typical active galactic nuclei that host hot accretion flows can accelerate CRs up to ε ∼ 0.1−10 PeV.
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Xia, Q., et V. Zharkova. « Particle acceleration in coalescent and squashed magnetic islands ». Astronomy & ; Astrophysics 635 (mars 2020) : A116. http://dx.doi.org/10.1051/0004-6361/201936420.
Texte intégralRésumé :
Aims. Particles are known to have efficient acceleration in reconnecting current sheets with multiple magnetic islands that are formed during a reconnection process. Using the test-particle approach, the recent investigation of particle dynamics in 3D magnetic islands, or current sheets with multiple X- and O-null points revealed that the particle energy gains are higher in squashed magnetic islands than in coalescent ones. However, this approach did not factor in the ambient plasma feedback to the presence of accelerated particles, which affects their distributions within the acceleration region. Methods. In the current paper, we use the particle-in-cell (PIC) approach to investigate further particle acceleration in 3D Harris-type reconnecting current sheets with coalescent (merging) and squashed (contracting) magnetic islands with different magnetic field topologies, ambient densities ranging between 108 − 1012 m−3, proton-to-electron mass ratios, and island aspect ratios. Results. In current sheets with single or multiple X-nullpoints, accelerated particles of opposite charges are separated and ejected into the opposite semiplanes from the current sheet midplane, generating a strong polarisation electric field across a current sheet. Particles of the same charge form two populations: transit and bounced particles, each with very different energy and asymmetric pitch-angle distributions, which can be distinguished from observations. In some cases, the difference in energy gains by transit and bounced particles leads to turbulence generated by Buneman instability. In magnetic island topology, the different reconnection electric fields in squashed and coalescent islands impose different particle drift motions. This makes particle acceleration more efficient in squashed magnetic islands than in coalescent ones. The spectral indices of electron energy spectra are ∼ − 4.2 for coalescent and ∼ − 4.0 for squashed islands, which are lower than reported from the test-particle approach. The particles accelerated in magnetic islands are found trapped in the midplane of squashed islands, and shifted as clouds towards the X-nullpoints in coalescent ones. Conclusions. In reconnecting current sheets with multiple X- and O-nullpoints, particles are found accelerated on a much shorter spatial scale and gaining higher energies than near a single X-nullpoint. The distinct density and pitch-angle distributions of particles with high and low energy detected with the PIC approach can help to distinguish the observational features of accelerated particles.
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Iwamoto, Masanori, Takanobu Amano, Yosuke Matsumoto, Shuichi Matsukiyo et Masahiro Hoshino. « Particle Acceleration by Pickup Process Upstream of Relativistic Shocks ». Astrophysical Journal 924, no 2 (1 janvier 2022) : 108. http://dx.doi.org/10.3847/1538-4357/ac38aa.
Texte intégralRésumé :
Abstract Particle acceleration at magnetized purely perpendicular relativistic shocks in electron–ion plasmas is studied by means of two-dimensional particle-in-cell simulations. Magnetized shocks with the upstream bulk Lorentz factor γ 1 ≫ 1 are known to emit intense electromagnetic waves from the shock front, which induce electrostatic plasma waves (wakefield) and transverse filamentary structures in the upstream region via stimulated/induced Raman scattering and filamentation instability, respectively. The wakefield and filaments inject a fraction of the incoming particles into a particle acceleration process, in which particles are once decoupled from the upstream bulk flow by the wakefield, and are picked up again by the flow. The picked-up particles are accelerated by the motional electric field. The maximum attainable Lorentz factor is estimated as γ max , e ∼ α γ 1 3 for electrons and γ max , i ∼ ( 1 + m e γ 1 / m i ) γ 1 2 for ions, where α ∼ 10 is determined from our simulation results. α can increase up to γ 1 for a weakly magnetized shock if γ 1 is sufficiently large. This result indicates that highly relativistic astrophysical shocks such as external shocks of gamma-ray bursts can be an efficient particle accelerator.
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Tanaka, Shuta J. « On the Radio Emitting Particles of the Crab Nebula : Stochastic Acceleration Model ». Proceedings of the International Astronomical Union 13, S337 (septembre 2017) : 259–62. http://dx.doi.org/10.1017/s1743921317008754.
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AbstractThe standard shock acceleration model of pulsar wind nebulae (PWNe) does not account for the hard spectrum in radio wavelengths. The origin of the radio-emitting particles is also important to determine the pair production efficiency in the pulsar magnetosphere. Here, we propose a possible resolution for the particle energy distribution in PWNe; the radio-emitting particles are not accelerated at the pulsar wind termination shock but are stochastically accelerated by turbulence inside PWNe. We upgrade our past one-zone spectral evolution model including the energy diffusion, i.e., the stochastic acceleration, and apply to the Crab Nebula. For a particle injection to the stochastic acceleration process, we consider the continuous injection from the supernova ejecta or the impulsive injection associated with supernova explosion. The observed broadband spectrum and the decay of the radio flux are reproduced by tuning the amount of the particle injected to the stochastic acceleration process. Our results imply that some unveiled mechanisms, such as back reaction to the turbulence, are required to make the energies of stochastically and shock accelerated particles comparable.
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Suzuki, Hiromasa, Aya Bamba, Ryo Yamazaki et Yutaka Ohira. « Observational Constraints on the Maximum Energies of Accelerated Particles in Supernova Remnants : Low Maximum Energies and a Large Variety ». Astrophysical Journal 924, no 2 (1 janvier 2022) : 45. http://dx.doi.org/10.3847/1538-4357/ac33b5.
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Abstract Supernova remnants (SNRs) are thought to be the most promising sources of Galactic cosmic rays. One of the principal questions is whether they are accelerating particles up to the maximum energy of Galactic cosmic rays (∼PeV). In this work, a systematic study of gamma-ray-emitting SNRs is conducted as an advanced study of Suzuki et al. Our purpose is to newly measure the evolution of maximum particle energies with increased statistics and better age estimates. We model their gamma-ray spectra to constrain the particle-acceleration parameters. Two candidates of the maximum energy of freshly accelerated particles, the gamma-ray cutoff and break energies, are found to be well below PeV. We also test a spectral model that includes both the freshly accelerated and escaping particles to estimate the maximum energies more reliably, but no tighter constraints are obtained with current statistics. The average time dependences of the cutoff energy (∝t −0.81±0.24) and break energy (∝t −0.77±0.23) cannot be explained with the simplest acceleration condition (Bohm limit) and require shock–ISM (interstellar medium) interaction. The average maximum energy during lifetime is found to be ≲20 TeV ( t M / 1 kyr ) − 0.8 with t M being the age at the maximum, which reaches PeV if t M ≲ 10 yr. The maximum energies during lifetime are suggested to have a variety of 1.1–1.8 dex from object to object. Although we cannot isolate the cause of this variety, this work provides an important clue to understanding the microphysics of particle acceleration in SNRs.
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Ebrahim, N. A., et S. R. Douglas. « Acceleration of particles by relativistic electron plasma waves driven by the optical mixing of laser light in a plasma ». Laser and Particle Beams 13, no 1 (mars 1995) : 147–71. http://dx.doi.org/10.1017/s0263034600008910.
Texte intégralRésumé :
Electron acceleration by relativistic electron plasma waves is studied by theory and particle simulations. The maximum acceleration that can be obtained from this process depends on many different factors. This paper presents a study of how these various factors impact on the acceleration mechanism. Although particular reference is made to the laser plasma beatwave concept, the study is equally relevant to the acceleration of particles in the plasma wakefield accelerator and the laser wakefield accelerator.
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Shilov, Vladimir Kuz'mich, Aleksandr Nikolaevich Filatov et Aleksandr Evgen'evich Novozhilov. « Focusing Properties of a Modified Retarding Structure for Linear Electron Accelerators ». International Journal of Electrical and Computer Engineering (IJECE) 7, no 2 (1 avril 2017) : 741. http://dx.doi.org/10.11591/ijece.v7i2.pp741-747.
Texte intégralRésumé :
When using accelerators in industry and medicine, important are the dimensions of the device used, especially the radial ones. In the linear electron accelerators based on a biperiodic retarding structure, which operates in the standing wave mode, there is a possibility to provide focusing of the accelerated particles with the help of high-frequency fields without the use of external focusing elements. In the accelerating cell, due to the presence of the far protruding drift sleeves, the electric field lines become strongly curved, which leads to the appearance in the regions adjacent to these sleeves of a substantial in magnitude radial component of the electric field. The particles entering the accelerating gap experience the action of a force directed toward the axis of the system, and at the exit, of a force directed away from the axis. Under certain conditions, alternation of the focusing and defocusing fields can lead to a general focusing effect. In the paper we study the focusing properties of a modified biperiodic structure with standing wave. The main attention is paid to the possibility of using the focusing properties of the electromagnetic accelerating field for guiding the electron beam through the aperture of the accelerating system, which will lead to a significant reduction in the accelerator sizes. The proposed method can be applied in the calculation and design of linear electron accelerators.
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Hidding, B., B. Foster, M. J. Hogan, P. Muggli et J. B. Rosenzweig. « Directions in plasma wakefield acceleration ». Philosophical Transactions of the Royal Society A : Mathematical, Physical and Engineering Sciences 377, no 2151 (24 juin 2019) : 20190215. http://dx.doi.org/10.1098/rsta.2019.0215.
Texte intégralRésumé :
This introductory article is a synopsis of the status and prospects of particle-beam-driven plasma wakefield acceleration (PWFA). Conceptual and experimental breakthroughs obtained over the last years have initiated a rapid growth of the research field, and increased maturity of underlying technology allows an increasing number of research groups to engage in experimental R&D. We briefly describe the fundamental mechanisms of PWFA, from which its chief attractions arise. Most importantly, this is the capability of extremely rapid acceleration of electrons and positrons at gradients many orders of magnitude larger than in conventional accelerators. This allows the size of accelerator units to be shrunk from the kilometre to metre scale, and possibly the quality of accelerated electron beam output to be improved by orders of magnitude. In turn, such compact and high-quality accelerators are potentially transformative for applications across natural, material and life sciences. This overview provides contextual background for the manuscripts of this issue, resulting from a Theo Murphy meeting held in the summer of 2018. This article is part of the Theo Murphy meeting issue ‘Directions in particle beam-driven plasma wakefield acceleration’.
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Torsti, J., E. Valtonen, L. Kocharov, M. Lumme, T. Eronen, M. Louhola, E. Riihonen et al. « Energetic particle investigation using the ERNE instrument ». Annales Geophysicae 14, no 5 (31 mai 1996) : 497–502. http://dx.doi.org/10.1007/s00585-996-0497-5.
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Abstract. During solar flares and coronal mass ejections, nuclei and electrons accelerated to high energies are injected into interplanetary space. These accelerated particles can be detected at the SOHO satellite by the ERNE instrument. From the data produced by the instrument, it is possible to identify the particles and to calculate their energy and direction of propagation. Depending on variable coronal/interplanetary conditions, different kinds of effects on the energetic particle transport can be predicted. The problems of interest include, for example, the effects of particle properties (mass, charge, energy, and propagation direction) on the particle transport, the particle energy changes in the transport process, and the effects the energetic particles have on the solar-wind plasma. The evolution of the distribution function of the energetic particles can be measured with ERNE to a better accuracy than ever before. This gives us the opportunity to contribute significantly to the modeling of interplanetary transport and acceleration. Once the acceleration/transport bias has been removed, the acceleration-site abundance of elements and their isotopes can be studied in detail and compared with spectroscopic observations.
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Liu, Meng, Jia-Xiang Gao, Wei-Min Wang et Yu-Tong Li. « Theoretical Study of the Efficient Ion Acceleration Driven by Petawatt-Class Lasers via Stable Radiation Pressure Acceleration ». Applied Sciences 12, no 6 (13 mars 2022) : 2924. http://dx.doi.org/10.3390/app12062924.
Texte intégralRésumé :
Laser-driven radiation pressure acceleration (RPA) is one of the most promising candidates to achieve quasi-monoenergetic ion beams. In particular, many petawatt systems are under construction or in the planning phase. Here, a stable radiation pressure acceleration (SRPA) scheme is investigated, in which a circularly-polarized (CP) laser pulse illuminates a CH2 thin foil followed by a large-scale near-critical-density (NCD) plasma. In the laser-foil interaction, a longitudinal charge-separated electric field is excited to accelerate ions together with the heating of electrons. The heating can be alleviated by the continuous replenishment of cold electrons of the NCD plasma as the laser pulse and the pre-accelerated ions enter into the NCD plasma. With the relativistically transparent propagation of the pulse in the NCD plasma, the accelerating field with large amplitude is persistent, and its propagating speed becomes relatively low, which further accelerates the pre-accelerated ions. Our particle-in-cell (PIC) simulation shows that the SRPA scheme works efficiently with the laser intensity ranging from 6.85×1021 W cm−2 to 4.38×1023 W cm−2, e.g., a well-collimated quasi-monoenergetic proton beam with peak energy ∼1.2 GeV can be generated by a 2.74 × 1022 W cm−2 pulse, and the energy conversion efficiency from the laser pulse to the proton beam is about 16%. The QED effects have slight influence on this SRPA scheme.
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Frogner, L., B. V. Gudiksen et H. Bakke. « Accelerated particle beams in a 3D simulation of the quiet Sun ». Astronomy & ; Astrophysics 643 (27 octobre 2020) : A27. http://dx.doi.org/10.1051/0004-6361/202038529.
Texte intégralRésumé :
Context. Observational and theoretical evidence suggest that beams of accelerated particles are produced in flaring events of all sizes in the solar atmosphere, from X-class flares to nanoflares. Current models of these types of particles in flaring loops assume an isolated 1D atmosphere. Aims. A more realistic environment for modelling accelerated particles can be provided by 3D radiative magnetohydrodynamics codes. Here, we present a simple model for particle acceleration and propagation in the context of a 3D simulation of the quiet solar atmosphere, spanning from the convection zone to the corona. We then examine the additional transport of energy introduced by the particle beams. Methods. The locations of particle acceleration associated with magnetic reconnection were identified by detecting changes in magnetic topology. At each location, the parameters of the accelerated particle distribution were estimated from local conditions. The particle distributions were then propagated along the magnetic field, and the energy deposition due to Coulomb collisions with the ambient plasma was computed. Results. We find that particle beams originate in extended acceleration regions that are distributed across the corona. Upon reaching the transition region, they converge and produce strands of intense heating that penetrate the chromosphere. Within these strands, beam heating consistently dominates conductive heating below the bottom of the transition region. This indicates that particle beams qualitatively alter the energy transport even outside of active regions.
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Kirk, J. G., P. Duffy et Lewis Ball. « Radio Emission From Snr 1987A ». International Astronomical Union Colloquium 142 (1994) : 807–11. http://dx.doi.org/10.1017/s025292110007812x.
Texte intégralRésumé :
AbstractDiffusive acceleration of electrons by the blast wave of SNR 1987A is shown to provide a reasonable fit to observations of the radio emission since it reappeared in 1990 July. As well as determining the diffusion coefficient in this model, the observations indicate that the compression ratio of the gas subshock embedded in the blast wave is ~2.7, much lower than the value of 4 expected of a strong shock front. We propose that protons accelerated by the shock front itself cause the weakening of the subshock by both heating and accelerating the upstream plasma, producing a structure with a precursor to the gas subshock. Preliminary calculations using a fluid model for the energetic particle population indicate that these effects can significantly weaken the subshock just a few years after the explosion, if the same rate of particle injection is assumed as in other models of the acceleration of cosmic rays.Subject headings: acceleration of particles — ISM: individual (SNR 1987 A) — radio continuum: ISM — shock waves
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Sagheer, Alaa, et Hala Hamdoun. « Dynamics of multi-qubit states in non-inertial frames for quantum communication applications ». Quantum Information and Computation 14, no 3&4 (mars 2014) : 255–64. http://dx.doi.org/10.26421/qic14.3-4-4.
Texte intégralRésumé :
In this paper, some properties of multi-qubit states traveling in non-inertial frames are investigated, where we assume that all particles are accelerated. These properties are including fidelities, capacities and entanglement of the accelerated channels for three different states, namely, Greeberger-Horne-Zeilinger (GHZ) state, GHZ-like state and W-state. It is shown here that all these properties are decreased as the accelerations of the moving particles are increased. The obtained results show that the GHZ-state is the most robust state comparing to the others, where the degradation rate is less than that for the other states particularly in the second Rindler region. Also, it is shown here that the entangled property doesn't change in the accelerated frames. Additionally, the paper shows that the degree of entanglement decreases as the accelerations of the particles increase in the first Rindler region. However in the second region, where all subsystems are disconnected at zero acceleration, entangled states are generated as the acceleration increases.
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Li, Yan, Lei Ni, Jing Ye, Zhixing Mei et Jun Lin. « Particle Accelerations in a 2.5-dimensional Reconnecting Current Sheet in Turbulence ». Astrophysical Journal 938, no 1 (1 octobre 2022) : 24. http://dx.doi.org/10.3847/1538-4357/ac8b6d.
Texte intégralRésumé :
Abstract Electric field induced in magnetic reconnection is an efficient mechanism for generating energetic particles, but the detailed role it plays is still an open question in solar flares. In this work, accelerations of particles in an evolving reconnecting current sheet are investigated via the test-particle approach, and the electromagnetic field is taken in a self-consistent fashion from a 2.5D numerical experiment for the magnetic reconnection process in the corona. The plasma instabilities like the tearing mode in the current sheet produce magnetic islands in the sheet, and island merging occurs as well. For the motion of the magnetic island, it yields the occurrence of the opposite electric field at both endpoints of the island; hence, tracking the accelerated particles around magnetic islands suggests that the parallel acceleration does not apparently impact the energy gain of particles, but the perpendicular acceleration does. Furthermore, our results indicate that the impact of the guide field on the trajectory of accelerated particles in a more realistic electromagnetic configuration works only on those particles that are energetic enough. The energy spectra of both species show a single power-law shape. The higher-energy component of the power-law spectrum results from the particles that are trapped in the current sheet, while the escaped and partly trapped particles contribute to the lower-energy component of the spectrum. The evolution of the spectrum shows a soft-hard-soft pattern that has been observed in flares.
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Barrios, Siria, Pedro Lance, Anabella A. Abate, German Prieto, Nicolás A. García, Cristian M. Piqueras, Daniel A. Vega, Angel Satti et Leopoldo R. Gómez. « Velocity distributions in a gas-gun microparticle accelerator ». Review of Scientific Instruments 93, no 10 (1 octobre 2022) : 105101. http://dx.doi.org/10.1063/5.0109794.
Texte intégralRésumé :
Here, we build and characterize a single-stage gas-gun microparticle accelerator, where a pressurized gas expands and launches particles on a target. The microparticles in the range of 60–250 μm are accelerated by the expansion of pressurized nitrogen. By using a high-speed camera, we study how the velocity distribution of accelerated particles is modified by particle size, pressure in the gas reservoir, valve’s opening time, and diaphragm’s thickness and composition. We employ this microparticle accelerator to study the impact of glass particles with diameters of (69 ± 6) μm accelerated at moderate velocities ∼ (10–25) m/s, using films of poly-dimethylsiloxane as targets.
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Ruderman, M. « Neutron Star Powered Accelerators ». Symposium - International Astronomical Union 195 (2000) : 463–71. http://dx.doi.org/10.1017/s0074180900163508.
Texte intégralRésumé :
Neutron stars can be the underlying source of energetic particle acceleration in several ways. The huge gravitational-collapse energy released in their birth, or the violent fusion at the end of the life of a neutron-star binary, is the energy source for an accelerator in the surrounding medium far from the star. This would be the case for: (a) cosmic rays from supernova explosions with neutron-star remnants; (b) energetic radiation from “plerions” around young neutron stars (e.g., the Crab Nebula, see Pacini 2000); and (c) “afterglow” and γ-rays of cosmic Gamma-Ray Burst (GRB) sources with possible neutron-star central engines. Particles can also be energetically accelerated if a neutron star's gravitational pull sustains an accretion disk fed by a companion. Examples are accretion-powered X-ray pulsars and low-mass X-ray binaries. A third family of “neutron-star powered” accelerators consists of those which do not depend on the surrounding environment. These are the accelerators which must exist in the magnetospheres of many solitary, spinning-down, magnetized neutron stars (“spinsters”) when they are observed as radio pulsars or γ-ray pulsars. (There are probably ~ 103 dead radio pulsars for each one in our Galaxy that is still active; the ratio for γ-ray pulsars may well exceed 105.)
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Gschwendtner, Edda, Konstantin Lotov, Patric Muggli, Matthew Wing, Riccardo Agnello, Claudia Christina Ahdida, Maria Carolina Amoedo Goncalves et al. « The AWAKE Run 2 Programme and Beyond ». Symmetry 14, no 8 (12 août 2022) : 1680. http://dx.doi.org/10.3390/sym14081680.
Texte intégralRésumé :
Plasma wakefield acceleration is a promising technology to reduce the size of particle accelerators. The use of high energy protons to drive wakefields in plasma has been demonstrated during Run 1 of the AWAKE programme at CERN. Protons of energy 400 GeV drove wakefields that accelerated electrons to 2 GeV in under 10 m of plasma. The AWAKE collaboration is now embarking on Run 2 with the main aims to demonstrate stable accelerating gradients of 0.5–1 GV/m, preserve emittance of the electron bunches during acceleration and develop plasma sources scalable to 100s of metres and beyond. By the end of Run 2, the AWAKE scheme should be able to provide electron beams for particle physics experiments and several possible experiments have already been evaluated. This article summarises the programme of AWAKE Run 2 and how it will be achieved as well as the possible application of the AWAKE scheme to novel particle physics experiments.
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TZOUFRAS, M., C. HUANG, J. H. COOLEY, F. S. TSUNG, J. VIEIRA et W. B. MORI. « Simulations of efficient laser wakefield accelerators from 1 to 100GeV ». Journal of Plasma Physics 78, no 4 (29 février 2012) : 401–12. http://dx.doi.org/10.1017/s0022377812000232.
Texte intégralRésumé :
AbstractOptimization of laser wakefield acceleration involves understanding and control of the laser evolution in tenuous plasmas, the response of the plasma medium, and its effect on the accelerating particles. We explore these phenomena in the weakly nonlinear regime, in which the laser power is similar to the critical power for self-focusing. Using Particle-In-Cell simulations with the code QuickPIC, we demonstrate that a laser pulse can remain focused in a plasma channel for hundreds of Rayleigh lengths and efficiently accelerate a high-quality electron beam to 100GeV (25GeV) in a single stage with average gradient 3.6GV/m (7.2GV/m).
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Maslov, Vasyl I., Denys S. Bondar et Ivan N. Onishchenko. « Investigation of the Way of Phase Synchronization of a Self-Injected Bunch and an Accelerating Wakefield in Solid-State Plasma ». Photonics 9, no 3 (11 mars 2022) : 174. http://dx.doi.org/10.3390/photonics9030174.
Texte intégralRésumé :
The electron acceleration, in a laser wakefield accelerator, controlled through plasma density inhomogeneity is studied on a basis of 2.5-dimensional particle-in-cell simulation. The acceleration requires a concordance of the density scale length and shift of the accelerated electron bunch relative to wake bubble during electron acceleration. This paper considers the excitation of a wakefield in plasma with a density equal to the density of free electrons in metals, solid-state plasma (the original idea of Prof. T. Tajima), in the context of studying the wakefield process. As is known in the wake process, as the wake bubble moves through the plasma, the self-injected electron bunch shifts along the wake bubble. Then, the self-injected bunch falls into the phase of deceleration of the wake wave. In this paper, support of the acceleration process by maintaining the position of the self-injected electron bunch using an inhomogeneous plasma is proposed. It is confirmed that the method of maintaining phase synchronization proposed in the article by using a nonuniform plasma leads to an increase in the accelerating gradient and energy of the accelerated electron bunch in comparison with the case of self-injection and acceleration in a homogeneous plasma.
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Costa, G., M. P. Anania, S. Arjmand, A. Biagioni, M. Del Franco, M. Del Giorno, M. Galletti et al. « Characterisation and optimisation of targets for plasma wakefield acceleration at SPARC_LAB ». Plasma Physics and Controlled Fusion 64, no 4 (3 mars 2022) : 044012. http://dx.doi.org/10.1088/1361-6587/ac5477.
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Abstract One of the most important features of plasma-based accelerators is their compactness because plasma modules can have dimensions of the order of mm cm − 1 , providing very high-accelerating fields up to hundreds of GV m − 1 . The main challenge regarding this type of acceleration lies in controlling and characterising the plasma itself, which then determines its synchronisation with the particle beam to be accelerated in an external injection stage in the laser wakefield acceleration (LWFA) scheme. This issue has a major influence on the quality of the accelerated bunches. In this work, a complete characterisation and optimisation of plasma targets available at the SPARC_LAB laboratories is presented. Two plasma-based devices are considered: supersonic nozzles for experiments adopting the self-injection scheme of laser wakefield acceleration and plasma capillary discharge for both particle and laser-driven experiments. In the second case, a wide range of plasma channels, gas injection geometries and discharge voltages were extensively investigated as well as studies of the plasma plumes exiting the channels, to control the plasma density ramps. Plasma density measurements were carried out for all the different designed plasma channels using interferometric methods in the case of gas jets, spectroscopic methods in the case of capillaries.
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shan, Fei, Pengpo Wang, Pei Zhang, Jiahao Shi, Dapeng Li, Xianfeng Hang et Yilei Wang. « Research on in the interaction between laser and electron-positron plasma in cone target ». Journal of Physics : Conference Series 2248, no 1 (1 avril 2022) : 012024. http://dx.doi.org/10.1088/1742-6596/2248/1/012024.
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Abstract Laser is used to accelerate the electron-positron plasma by ponderomotive force. Due to the electric field, electron and positron will have transverse diffusion in the acceleration. In this paper, a scheme is proposed to get high-energy particle beam by binding electron-positron plasma with hollow gold target. The transverse diffusion is restrained in the gold target. Particles can be continuously accelerated by ponderomotive force and the neutral particle beam is obtained in space. The tight focusing of laser makes the ponderomotive force stronger and stronger in the cone target. The energy gain obtained by the scheme is far beyond the limit of the ponderomotive force, which provides theoretical support for the practical application of electron-positron beam.
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Williams, R. L., C. E. Clayton, C. Joshi, T. Katsouleas et W. B. Mori. « Studies of relativistic wave–particle interactions in plasma-based collective accelerators ». Laser and Particle Beams 8, no 3 (septembre 1990) : 427–49. http://dx.doi.org/10.1017/s0263034600008673.
Texte intégralRésumé :
The interaction of externally injected charged particles (electrons) with plasma waves moving with a phase velocity that is very close to the speed of light is examined. Such plasma waves form the basis of at least three collective accelerator schemes: the plasma beat wave accelerator (PBWA), the plasma wake-field accelerator (PWFA), and the laser wake-field accelerator (LWFA). First, the electron trapping threshold, energy gain and acceleration length are examined using a 1-D model. This model elucidates how the final energies of the injected test electrons depend upon their injection and extraction phases and phase slippage. Phase energy diagrams are shown to be extremely useful in visualizing wave-particle interactions in 1-D. Second, we examine, using a two-dimensional model, the effects of radial electric fields on focusing or defocusing the injected particles depending upon their radial positions and phases in the relativistically moving potential well. Finally, we extend the model to 3-D so that the effect of injected particles' emittance on the acceleration process may be determined. This simple 3-D model will be extremely useful in predicting the electron energy spectra of several current experiments designed to demonstrate ultrahigh gradient acceleration of externally injected test particles by relativistic plasma waves.
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Anttila, A., L. G. Kocharov, J. Torsti et R. Vainio. « Long-duration high-energy proton events observed by GOES in October 1989 ». Annales Geophysicae 16, no 8 (31 août 1998) : 921–30. http://dx.doi.org/10.1007/s00585-998-0921-0.
Texte intégralRésumé :
Abstract. We consider the prolonged injection of the high-energy (>10 MeV) protons during the three successive events observed by GOES in October 1989. We apply a solar-rotation-stereoscopy approach to study the injection of the accelerated particles from the CME-driven interplanetary shock waves in order to find out how the effectiveness of the particle acceleration and/or escape depends on the angular distance from the shock axis. We use an empirical model for the proton injection at the shock and a standard model of the interplanetary transport. The model can reproduce rather well the observed intensity–time profiles of the October 1989 events. The deduced proton injection rate is highest at the nose of the shock; the injection spectrum is always harder near the Sun. The results seem to be consistent with the scheme that the CME-driven interplanetary shock waves accelerate a seed particle population of coronal origin.Key words. Interplanetary physics · Energetic particles · Solar physics · astrophysics and astronomy · Flares and mass ejections