Physics of Quasi-Monoenergetic Laser-Plasma Acceleration of Electrons in the Blowout Regime

Optically Controlled Laser-Plasma Electron Acceleration for Compact γ-Ray Sources

“…As the pulse propagates, this shift reaches a large fraction of ω 0 , while the negative group velocity dispersion (GVD) in the plasma delays these low-frequency components, etching away the pulse leading edge. In the frame of reference comoving with the bubble, these components start to accumulate around the point where electron density drops to zero 1 , building up an optical shock with a subcycle rising edge [16,[22][23][24][25]. If the bubble were nonevolving, the etching velocity would be its phase velocity, which defines the electron dephasing length, L d ¼ 2=3 ðÞ n c =n 0 ðÞ r m [18].…”

“…Yet this process, apart from limiting the energy gain, destroys e-beam most assuredly if acceleration extends through the pulse depletion. (A plethora of evidence exists to this effect, both in laboratory experiments and numerical simulations [16,19,[22][23][24][25][38][39][40][41][42].) To enable a new generation of compact particle and radiation sources [43,44], one has to bypass the limitations this of scaling by designing an optical driver resilient to self-phase-modulation and self-compression.…”

“…kA) e-beams [75]. To drive narrowband TS γ-ray sources, these beams have to meet some minimal requirements, such as a combination of Accelerator Physics -Radiation Safety and Applicationsa near-GeV energy with a percent-scale energy spread, a five-dimensional (5-D) brightness above 10 16 A/m 2 [76], and preferably absent low-energy background. These requirements, in combination with the kHz-scale repetition rate dictated by the applications, are clearly conflicting even for the most ambitious laser technology [77,78].…”

“…Driving the accelerating plasma structures with a radiation pressure of a femtosecond, multiterawatt (TW) laser pulse (hence the term "laser wakefield") provides abundant opportunities for all-optical control of both injection and acceleration processes [16,17]. Early demonstrations of QME laser-plasma acceleration [4][5][6] were a perfect example of this control.…”

“…The difference between attractive force due to the charge separation and the repulsive radial ponderomotive force controls the trajectories of electrons making up the bubble shell. The resulting soft channel, approximately replicating the threedimensional (3-D) shape of the pulse [19], evolves in a lock-step with the optical driver [15,16,[20][21][22][23][24][25]. In consequence, it traps initially quiescent background electrons, eliminating the need for an external photocathode [16,21,22].…”