Colliding pulse injection experiments in non-collinear geometry for controlled laser plasma wakefield acceleration of electrons

An optical injection scheme for a laser-plasma based accelerator which employs a non-collinear counterpropagating laser beam to push background electrons in the focusing and acceleration phase via ponderomotive beat with the trailing part of the wakefield driver pulse is discussed. Preliminary experiments were preformed using a drive beam of a₀ sime 2.6 and colliding beam of a₁ sime 0.8 both focused on the middle of a 200 mum slit jet backed with 20 bar, which provided sime 250 mum long gas plume. The enhancement in the total charge by the colliding pulse was observed with sharp dependence on the delay time of the colliding beam. Enhancement of the neutron yield was also measured, which suggests a generation of electrons above 10 MeV.