Acceleration of Electrons in Modulated Plasma Channels with Radially Polarized Laser Pulses

Two highly versatile experimental techniques are demonstrated for making preformed plasma waveguides with periodic structure capable of supporting the propagation of ultra-intense femtosecond laser pulses. These waveguides were made in hydrogen, nitrogen and argon plasmas with a length of 15 mm and modulation period as short as 35 μm. Simulations show that these guides allow direct laser acceleration of electrons, achieving gradients of 80 MV/cm and 10 MV/cm for laser pulse powers of 1.9 TW and 30 GW, respectively. We also demonstrate a technique for making the required radially polarized pulses.