On the Production of Flat Electron Bunches for Laser Wake Field Acceleration

Abstract

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. In this paper we work out the injection into the acceleration phase of the wake field in a plasma behind a high intensity laser pulse, taking advantage of the laser polarization and focusing. With the aid of catastrophe theory we categorize the injection dynamics. The scheme uses the structurally stable regime of transverse wake wave breaking, when electron trajectory self-intersection leads to the formation of a flat electron bunch. As shown in threedimensional particle-in-cell simulations of the interaction of a laser pulse in a linefocus 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. † Also at A. M. Prokhorov

On production and asymmetric focusing of flat electron beams using rectangular capillary discharge plasmas

“…Linear electron-positron colliders need asymmetric emittances and polarized electrons, with the smaller vertical emittance required to be of the order of 0.01 mm mrad. The asymmetric emittance, i.e., flat beams (see [5] and references therein), are needed to reduce the beam-induced synchrotron radiation (beamstrahlung [6][7][8][9]) at the interaction point. Since one of the laser plasma accelerator advantages is the short, compared to conventional ones, acceleration length (the 4.25 GeV electron beams were produced using a 9 cm long capillary [3]), it is desirable important to keep the size of the transport and focusing sections of such accelerators of the same order.…”

“…Within the framework of the Laser Wake Field Accelerator concept [10], M. Kando et al [5] suggested a method for the electron injection via the transverse wake wave breaking [11], when the electron trajectory self-intersection leads to the formation of an electron bunch elongated in the transverse direction thus implying the flat electron beam generation.…”