Transverse dynamics of a short, relativistic electron bunch in a plasma lens

Dynamic focusing of a 3.8 MeV, 25 ps long, full width at half-maximum (FWHM), electron bunch by an overdense (n,+nb, where np and nb are the plasma and bunch densities, respectively) plasma lens has been studied experimentally. The plasma focused the bunch from an initial transverse size of approximately 2.4 mm (PWHM) to about 0.5 mm, 21 cm downstream of the plasma. The sharp rise time (7 ps lo%-90%) of the electron bunch, excites a large-amplitude (<l MeV/m) plasma wave (plasma wake field). The peak focusing force of the lens is partly (60%) due to the beam-generated, azimuthal magnetic field and partly (40%) due to the radial component of the electrostatic w&e field. 0 199.5 American Institute of Physics.