On the production of flat electron bunches for laser wakefield acceleration

Kando, Masaki; Fukuda, Yuji; Kotaki, Hideyuki; Koga, J. K.; Bulanov, S. V.; Tajima, Toshiki; Chao, A. W.*; Pitthan, R.*; Schuler, K.-P.*; Zhidkov, A. G.*; Nemoto, Koshichi*

We suggest a novel method for injection of electrons into the acceleration phase of particle accelerators, producing low emittance beams appropriate even for the demanding high energy Linear Collider specifications. We discuss the injection mechanism into the acceleration phase of the wake field in a plasma behind a high intensity laser pulse, which takes advantage of the laser polarization and focusing. As shown in three-dimensional particle-in-cell simulations of the interaction of an elongated in transverse direction laser pulse with an underdense plasma, the electrons, injected via the transverse wake wave breaking and accelerated by the wake wave, perform betatron oscillations with different amplitudes and frequencies along the two transverse coordinates. The polarization and focusing geometry lead to a way to produce relativistic electron bunches with asymmetric emittance (flat beam). An approach for generating flat laser accelerated ion beams is briefly discussed.