Controlled electron injection into beam driven plasma wakefield accelerators employing a co-propagating laser pulse

Abstract

A novel technique for generating high current electron bunches in electron beam driven plasma wakefield accelerators (PWFAs) is suggested based on co-propagation of an electron beam and a laser pulse. It is observed that propagation of a laser pulse in front of an electron beam driver leads to bubble expansion and consequently electron injection into a PWFA. The acceleration structure is extensively studied in this scheme and the bubble evolution process is discussed. The difference in propagation velocity of the laser pulse and the beam driver in the plasma and variation of electron beam driver density in presence of the laser pulse cause the bubble radius grows. Using a laser pulse in a PWFA leads to the generation of an ultra short (10 fs) electron bunch with charge three times larger than the electron beam driver total charge. It is shown by altering the initial electron beam driver density and the laser pulse intensity, the external control of the amount of loaded charge is possible. The number of self-injected electrons is enhanced by increasing the laser pulse intensity and the density of the electron beam driver. The results represent that the accelerator operates in a highly loaded regime. Therefore, by raising the density of the electron beam driver and the laser pulse intensity, the final energy spread of the generated electron bunch increases. An interpretive approach to find the appropriate parameters for the laser pulse and the electron beam is proposed in this scheme.