Fig. 1. Schematic of laser wakefield acceleration^[29]

Fig. 2. Electric field on electron inside bubble. (a) Longitudinal electric field; (b) transverse electric field

Fig. 3. Cascaded electron acceleration of laser wakefield^[40]. After being focused by off-axis parabolic mirror, single-shot electron beam spectra from drive laser with focal spot size of ~16 μm and peak intensity of 2.08‒2.27 when (a) laser focusing position z=0 and laser power on target is 53 TW, (b) z=0.6 mm and laser power on target is 58 TW, and (c) z=1.2 mm and laser power on target is 60 TW; cascaded electron acceleration spectra when second stage plasma is 1 mm long at target powers of (d) 48 TW and (e) 60 TW; electron beam energy spectra obtained by cascaded electron acceleration when second stage plasma length is 3 mm at laser powers on target of (f) 50 TW, (g) 48 TW, and (h) 45 TW

Fig. 4. Experiments for generation of ultralow energy-spread and high-quality electron beam based on laser-wakefield acceleration^[65]. (a) Schematic of experimental setup for high-quality laser wakefield electron acceleration; (b) shock wave distribution observed by shadow method; (c) retrieved plasma density profile (solid line) from interferogram along dashed line direction in Fig.4(b) and evolution of laser beam in vacuum (dashed line) and in plasma (shaded area)

Fig. 5. Experimental measurement results for ultralow energy-spread and high-quality electron beam source^[65]. (a) Energy spectra of 15 shots with energy spread of 2.4‰‒4.1‰ measured by experiment; (b) charge integral diagram of 13th shot electron beam with peak energy of 817 MeV and RMS energy spread of 3.3‰ in Fig.5(a), with electron beam charge of 10.6 pC in threefold relative energy spread range and RMS divergence angle of 0.25 mrad shown in shaded portion

Fig. 6. Particle-in-cell simulation results^[65]. (a) Evolution diagram of normalized vector potential, wakefield phase velocity, and plasma density, in which evolution of normalized vector potential can be roughly divided into oscillation stage (middle shadow region) and near-matching stage (right shadow region); (b) evolution of electron beam energy and absolute energy spread; (c) chirp degree fitted by electron beam and mean longitudinal field at its spatial location

Fig. 7. Snapshots of electron beam density distribution in roz plane, on-axis accelerating field lineouts (solid line), and phase space dynamics of electron beam at different distances. (a) Electron beam stays in a highly nonlinear wakefield just after injection; (b) sawtooth-like accelerating field with negative slope acceleration gradient is formed as laser defocuses; (c) beam-loading effect makes electrons maintain relatively small energy spread during final acceleration process; (d) electron beam approaches dephasing; (e)‒(h) corresponding phase space dynamics and locally amplified longitudinal wakefield for Fig.7(a)‒(d)

Fig. 8. Betatron oscillation and radiation of electron in bubble^[87]. (a) Betatron oscillation; (b) betatron radiation

Fig. 9. Schematic of electron beam and betatron radiation manipulated by tilted plasma refraction slab in laser wakefield^[22]

Fig. 10. Experiments of laser wakfield electron acceleration and enhanced betatron radiation^[22]. (a) Schematic of experimental setup; (b) density distribution of measured tilted plasma slab via optical interferometry and shadowgraphy

Fig. 11. Experimental measurement results^[22]. (a)‒(d) Single-shot electron energy spectra measured at different positions before and after introducing tilted plasma shock; (e) distribution of central position of electron beam spot before and after introducing tilted plasma shock ; (f) measured average charge of electron beam and peak energy and total photon yield of betatron radiant source when tilted plasma shock wave is at different positions

Fig. 12. Diagnosis of betatron radiation without tilted plasma slab. (a) Typical betatron radiation photon distribution recorded on X-ray charge coupled device (CCD); (b) measured spectra of betatron radiation based on single-photon-counting (SPC) mode and X-ray detection system (XRDS)

Fig. 13. Experimental results of enhanced betatron radiation. Spatial distributions of X-ray sources (a) without and (b) with refractor enhanced betatron radiation; (c) radiation spectra of tilted plasma slab at different locations; (d) retrieved spectra of enhanced betatron radiation (solid line)

Fig. 14. Particle-in-cell simulation results^[22]. (a) Plasma density distribution with tilted plasma slab; evolution of injected electron beam and wakefield structures (b) before and (c) after introducing tilted plasma slab with corresponding electron energy spectra after 9.2 ps laser propagation shown on right; (d) transverse size and transverse oscillation of electron beam and partial electron trajectory tracking without and with tilted plasma slab; (e) evolutions of peak energy and RMS energy spread of electron beams when tilted plasma slab is placed at different positions with simulation result without tilted plasma slab shown by black curve

Fig. 15. Experimental diagram of 4 MeV γ-ray generation based on all-optical inverse Compton scattering by two laser pulses^[99]

Fig. 16. Experimental principle of all-optical inverse Compton backscattering X-ray source based on plasma mirror^[23]

Fig. 17. Experimental setup for all-optical self-synchronizing Compton scattering^[24]

Fig. 18. Experimental results of all-optical inverse Compton scattering driven by laser wakefield electron acceleration^[24]. (a) Typical background subtracted Gaussian-profile γ-ray beam spot; (b) beam spot distribution after passing different attenuating plates; (c) background radiation when film is placed at z=10 mm; (d)‒(f) corresponding photon distribution on detected system; (g) horizontal and vertical intensity distributions of γ-ray source and background; (h) γ-ray source spectra produced by electron beams with different energies

Fig. 19. Tunable γ‑ray sources generated from all-optical inverse Compton scattering^[24]. (a) Measured γ‑ray peak energy versus electron beam peak energy with fitted curve shown by dashed line, and uncertainties of electron beam and γ-ray peak energies shown by horizontal and vertical error bars; (b) relationship between number of γ-ray photons and position of film with mean bremsstrahlung background of film at z=6 mm shown by solid line; (c) γ-ray beam spot patterns of nine-grid filter at z=0 mm and z=5 mm

Fig. 20. Schematics of synchrotron radiation generated by laser-wakefield accelerated electron beam passing through conventional undulators^[13,108]. (a) Synchrotron radiation; (b) self-amplified spontaneous emission (SASE)

Fig. 21. Experimental setup of soft X-ray radiation after laser-wakefield accelerated electron beam passing through undulator^[109]

Fig. 22. Schematic of compact free-electron-laser radiation device based on laser wakefield acceleration and relate data^[110]. (a) Undulator beamline; (b) typical spectrum of electron beam; measured transverse profiles of electron beam at (c) entrance and (d) exit of undulator

Fig. 23. Experimental results for free-electron-laser radiation based on laser wakefield acceleration^[110]. (a) Measured radiation energy with (triangle) and without (square) orbit kick method; (b)(c) corresponding radiation patterns; (d) measured radiation spectra of undulator with central wavelength of 27 nm and (e) corresponding electron-beam energy spectra; (f) radiation energy of 270 shots