Optical guiding of a radially polarized laser beam for inverse Cherenkov acceleration in a plasma channel

In a conventional inverse Cherenkov accelerator (ICA), the background neutr al gas provides the necessary dispersion to maintain the synchronism betwee n the drive laser and the accelerated electrons. A laser-driven ICA is susc eptible to diffraction, and the acceleration length is limited to approxima tely a Rayleigh range (for a Gaussian beam), In this paper, an ICA configur ation is proposed that avoids the laser diffraction Limitation by employing a preformed plasma channel, It is shown that a radially polarized laser be am can be optically guided if the plasma density increases with radius-like r(2). Expressions for the guided axial and radial components of the laser field are derived, and a numerical example is discussed.