Generation of Compressed GeV-Electron Bunch by Intense Short Pulse Laser

Summary form only given. A purpose of this study is the generation of a high energy density and short size electron bunch by a focused intense short pulse laser of a TEM(1,0)+TEM(0,1) mode in vacuum. In our previous research, we presented that the TEM(1,0)+TEM(0,1) mode laser has a potential well in transverse and suppresses a transverse electron divergence by the transverse ponderomotive force. Therefore a low emittance electron bunch is produced near the laser axis after the interaction between the laser and the electrons. In this paper, we clarify the detail of the acceleration mechanism of the electrons and also present the electron bunch compression effect in our acceleration mechanism. The acceleration of the electron bunch confined comes from not the longitudinal ponderomotive force but the longitudinal electric field. In the case of the focused TEM(1,0)+TEM(0,1) mode laser, the longitudinal electric field has the maximum at the central axis. Consequently the electrons confined are mainly accelerated and compressed by the longitudinal electric field in the longitudinal direction. In our 3-dimensional particle simulations, the electrons are accelerated to the order of 0.5 GeV, and the normalized rms emittance is about 10^-6 pimrad at the following parameter values: a₀ = 10 (here, a₀ is the dimensionless parameter of the laser intensity), the wavelength of lambda = 0.8 mum, the pulse length of 5lambda, the minimal spot size of 20lambda, and the initial energy of the electrons is 3.62 MeV. The electron bunch accelerated and confined is also compressed to the order of a few femtoseconds in the longitudinal direction. In this paper, we also found a scaling law for the maximum electron energy. Both the simulation and analytical estimation results show that the maximum electron energy is proportional to a₀ in a relativistic region