Owing to their ultra-high accelerating gradients,combined with injection inside micrometer-scale accelerating wakefield buckets,plasma-based accelerators hold great potential to drive a new generation of free-electron...Owing to their ultra-high accelerating gradients,combined with injection inside micrometer-scale accelerating wakefield buckets,plasma-based accelerators hold great potential to drive a new generation of free-electron lasers(FELs).Indeed,the first demonstration of plasma-driven FEL gain was reported recently,representing a major milestone for the field.Several groups around the world are pursuing these novel light sources,with methodology varying in the use of wakefield driver(laser-driven or beam-driven),plasma structure,phase-space manipulation,beamline design,and undulator technology,among others.This paper presents our best attempt to provide a comprehensive overview of the global community efforts towards plasma-based FEL research and development.展开更多
We measured the parameter reproducibility and radial electron density profile of capillary discharge waveguides with diameters of 650µm to 2 mm and lengths of 9 to 40 cm.To the best of the authors’knowledge,40 c...We measured the parameter reproducibility and radial electron density profile of capillary discharge waveguides with diameters of 650µm to 2 mm and lengths of 9 to 40 cm.To the best of the authors’knowledge,40 cm is the longest discharge capillary plasma waveguide to date.This length is important for≥10 GeV electron energy gain in a single laser-driven plasma wakefield acceleration stage.Evaluation of waveguide parameter variations showed that their focusing strength was stable and reproducible to<0.2%and their average on-axis plasma electron density to<1%.These variations explain only a small fraction of laser-driven plasma wakefield acceleration electron bunch variations observed in experiments to date.Measurements of laser pulse centroid oscillations revealed that the radial channel profile rises faster than parabolic and is in excellent agreement with magnetohydrodynamic simulation results.We show that the effects of non-parabolic contributions on Gaussian pulse propagation were negligible when the pulse was approximately matched to the channel.However,they affected pulse propagation for a non-matched configuration in which the waveguide was used as a plasma telescope to change the focused laser pulse spot size.展开更多
Laser plasma accelerators （LPAs） have made great progress, achieving electron beam with energy up to 1 GeV from a centimeter scale capillary plasma waveguide. Here, we report the measurement of optical transition ra...Laser plasma accelerators （LPAs） have made great progress, achieving electron beam with energy up to 1 GeV from a centimeter scale capillary plasma waveguide. Here, we report the measurement of optical transition radiation （OTR） from the capillary-based LPA electron beams. Transition radiation images, produced by electrons passing through two separate foils （located at 2.3 m and 3.8 m away from the exit of the LPA） were recorded with a high resolution imaging system, respectively. Two magnetic quadrupole lenses were placed right after the capillary to focus and collimate the electron beams. Significant localized spikes appeared in the OTR images when the electron beam was focused by the magnetic quadrupole lenses, indicating the coherence of the radiation and the existence of ultrashort longitudinal structures inside the electron beam.展开更多
文摘Owing to their ultra-high accelerating gradients,combined with injection inside micrometer-scale accelerating wakefield buckets,plasma-based accelerators hold great potential to drive a new generation of free-electron lasers(FELs).Indeed,the first demonstration of plasma-driven FEL gain was reported recently,representing a major milestone for the field.Several groups around the world are pursuing these novel light sources,with methodology varying in the use of wakefield driver(laser-driven or beam-driven),plasma structure,phase-space manipulation,beamline design,and undulator technology,among others.This paper presents our best attempt to provide a comprehensive overview of the global community efforts towards plasma-based FEL research and development.
基金the Director,Office of Science,Office of High Energy Physics,of the U.S.Department of Energy under Contract No.DE-AC02-05CH11231used the computational facilities at the National Energy Research Scientific Computing Center(NERSC)as well as the project High Field Initiative(No.CZ.02.1.01/0.0/0.0/15_003/0000449)from the European Regional Development Fund.
文摘We measured the parameter reproducibility and radial electron density profile of capillary discharge waveguides with diameters of 650µm to 2 mm and lengths of 9 to 40 cm.To the best of the authors’knowledge,40 cm is the longest discharge capillary plasma waveguide to date.This length is important for≥10 GeV electron energy gain in a single laser-driven plasma wakefield acceleration stage.Evaluation of waveguide parameter variations showed that their focusing strength was stable and reproducible to<0.2%and their average on-axis plasma electron density to<1%.These variations explain only a small fraction of laser-driven plasma wakefield acceleration electron bunch variations observed in experiments to date.Measurements of laser pulse centroid oscillations revealed that the radial channel profile rises faster than parabolic and is in excellent agreement with magnetohydrodynamic simulation results.We show that the effects of non-parabolic contributions on Gaussian pulse propagation were negligible when the pulse was approximately matched to the channel.However,they affected pulse propagation for a non-matched configuration in which the waveguide was used as a plasma telescope to change the focused laser pulse spot size.
文摘Laser plasma accelerators （LPAs） have made great progress, achieving electron beam with energy up to 1 GeV from a centimeter scale capillary plasma waveguide. Here, we report the measurement of optical transition radiation （OTR） from the capillary-based LPA electron beams. Transition radiation images, produced by electrons passing through two separate foils （located at 2.3 m and 3.8 m away from the exit of the LPA） were recorded with a high resolution imaging system, respectively. Two magnetic quadrupole lenses were placed right after the capillary to focus and collimate the electron beams. Significant localized spikes appeared in the OTR images when the electron beam was focused by the magnetic quadrupole lenses, indicating the coherence of the radiation and the existence of ultrashort longitudinal structures inside the electron beam.
