2017.03.21-Paper Reading-NP-laser acceleration 1, Title: GeV electron beams from a centimetre-scale accelerator 2, Weblink: http://www.nature.com/nphys/journal/v2/n10/abs/nphys418.html 3, Abstract: Gigaelectronvolt (GeV) electron accelerators are essential to synchrotron radiationfacilities and free-electron lasers, and as modules for high-energy particlephysics. Radiofrequency-basedaccelerators are limited to relatively low accelerating fields (10−50 MVm−1), requiring tens to hundreds of metres to reach the multi-GeV beam energiesneeded to drive radiation sources, and many kilometres to generate particleenergies of interest to high-energy physics. Laser-wakefield accelerators produce electric fields of theorder 10–100 GVm−1 enabling compact devices . Previously, the requiredlaser intensity was not maintained over the distance needed to reach GeV energies,and hence acceleration was limited to the 100 MeV scale. Contrary topredictions that petawatt class lasers would be needed to reach GeV energies, here we demonstrate production of ahigh quality electron beam with 1 GeV energy by channelling a 40 TW peak-powerlaser pulse in a 3.3-cm-long gas-filled capillary discharge waveguide . 4, Contents: · 4.1, Schematicdiagram of the capillary-guided laser wakefield accelerator: The plasma channel was formed in a hydrogen-filled capillary discharge waveguide (see inset).Hydrogen gas was introduced into the capillary waveguide using two gas slots in the 225 μmcapillary and three in the 310 μm capillary . A discharge was struckbetween two electrodes located at each end of the waveguide, using ahigh voltage pulser. Thepulser used a 2.7 nF capacitor charged to 20 kV. The laser beam wasfocused onto the entrance of the capillary using an f/25 off-axis parabola(OAP). The e-beam was analysed using an integrating current transformer (ICT) and a 1.2 T broadband magneticspectrometer (energy range of 0.03–0.15 and 0.175–1.1 GeV in a single shot) . · 4.2,Experimental results; Single-shote-beam spectra of the capillary-guided accelerator. a,b, Examples of bunches at 0.50 (+0.02, −0.015) GeV (5.6% r.m.s. energyspread, 2.0 mrad divergence r.m.s ., ～ 50 pC charge ) (a) and 1.0 (+0.08, −0.05) GeV (2.5% r.m.s. energy spread, 1.6 mrad divergence r.m.s ., ～ 30 pC ) (b). The horizontal axis is thebeam energy and the vertical axis is the beam size in the undeflected(horizontal) plane . The colour scale denotes the bunch charge in pC GeV −1 sr −1 . The 0.5GeV (1.0 GeV) beam shown was obtained in the 225 (310) μm capillary with adensity of 3.5×10^18 (4.3×10^18) cm^−3 and input laser power of 12 TW (40 TW) .The black stripe denotes the energy range not measured by the spectrometer. Inb, a second beam at 0.8GeV is also visible . Note that the energy spread and divergence areobtained after including the imaging properties of the spectrometer. The energyspread at 1 GeV may actually be less as the energy resolution is limited to2.4% at 1 GeV and there is slight saturation of the image. c,d, Vertically integrated spectra for the 0.5 (c) and 1.0 GeV (d) beams . Notes: TheGeV e-beam was obtained in a 310-μm-diameter channel capillary for P = 40 TWand a density 4.3×10^18 cm^−3. f 5, Summary: The GeV-class electron beams from thesecentimetre-scale structures offer unique applications. The short wavelength of the plasma acceleratingstructure results in femtosecond duration bunches (10 kA peak current),well suited for driving pulsedradiation sources . These devices may allow compact femtosecondfree-electron lasers producing keV X-rays using existing centimetre-scaleperiod undulators and, in general, provide intrinsically synchronized sources of femtosecond pulses of electronsand radiation tunable from X ray to THz frequencies . Furthermore, it isanticipated that longer accelerating structures can be made by stagingcapillary discharge waveguides, thereby opening a path to compact acceleratorsbeyond the multi-GeV level for high-energy physics applications.
一篇写的非常详细的综述文章，值得认真读几遍！PDF下载地址：http://ddl.escience.cn/f/yHs0 详细介绍了从large-global-scale to small-local scale 过程中 MHD, Test particle, PIC方法各自的特点、优势及局限性，只可惜没涉及LBM。 Recent Advances in Understanding Particle Acceleration Process in Solar Flares Recent Advances in Understanding Particle Acceleration Processes in Solar Flares Valentina V. Zharkova , Karpar Arzner , Arnold O. Benz , Philippa Browning , Cyril Dauphin , A. Gordon Emslie , Lyndsay Fletcher , Eduard P. Kontar , Gottfried Mann , Marco Onofri , Vahe Petrosian , Rim Turkmani , Nicole Vilmer , Loukas Vlahos (Submitted on 11 Oct 2011 ( v1 ), last revised 23 Oct 2011 (this version, v3)) We review basic theoretical concepts in particle acceleration, with particular emphasis on processes likely to occur in regions of magnetic reconnection. Several new developments are discussed, including detailed studies of reconnection in three-dimensional magnetic field configurations (e.g., current sheets, collapsing traps, separatrix regions) and stochastic acceleration in a turbulent environment. Fluid, test-particle, and particle-in-cell approaches are used and results compared. While these studies show considerable promise in accounting for the various observational manifestations of solar flares, they are limited by a number of factors, mostly relating to available computational power. Not the least of these issues is the need to explicitly incorporate the electrodynamic feedback of the accelerated particles themselves on the environment in which they are accelerated. A brief prognosis for future advancement is offered. Comments: This is a chapter in a monograph on the physics of solar flares, inspired by RHESSI observations. The individual articles are to appear in Space Science Reviews (2011) Subjects: Solar and Stellar Astrophysics (astro-ph.SR) ; Plasma Physics (physics.plasm-ph); Space Physics (physics.space-ph) DOI: 10.1007/s11214-011-9803-y Cite as: arXiv:1110.2359 (or arXiv:1110.2359v3 for this version)
标签: Acceleration
