High-intensity laser-driven electron beam and radiation generation from an underdense plasma in an axial magnetic field*

The experiments to study electron beam and betatron radiation generation were performed using the T-cubed laser at the University of Michigan. 15 TW (6J, 400 fs) laser pulses were focused with an f/4 off-axis parabolic mirror to the intensity of 10¹⁹ W/cm² onto a supersonic He gas jet with plasma densities n_e<10²⁰ cm^-3. The experiments were performed with a static magnetic field B=0.5 T or with a pulsed solenoidal magnetic field B_max=20 T, both were applied in the axial (laser) direction. The characterization of the generated electron beam divergence, charge and spectrum were performed for experiments with and without an axial magnetic field. A comparison of the divergence of the produced betatron radiation and its source size for both cases and different plasma densities will be presented.