In this work we discuss the propagation of the wave radiation focused by the axicon, and analyze optical discharges created by laser Besselian beam in gases, fluids and on solid surfaces. We consider formation processes of discharges, properties and structures of the plasma channels. Also, we describe the methods of research of Besselian beams, breakdowns, discharges and plasmas created by the beams.
The optical discharge arisen under the action of the Bessel beam field Jn(r) of solid (n = 0) or tubular (n > 0) configuration turns into the plasma solid or tubular cylinder (waveguide), thereof Rayleigh length being large, Zr = πd2/λ >>> 1, at the diameter of the diffraction limit. While the heating pulse front is short, the breakdown wave propagates along the beam in a mode of running focus at a velocity exceeding the light speed. The channel plasma parameters at the initial stage depend on the Besselian beam intensity level and distribution. The radial expansion velocity of the plasma channel is approximately in general agreement with the theory of cylindrical strong explosion.
The channel axial symmetry provides important advantage over the plasma of spherical symmetry, for it implies effective application of magnetic field. Besselian beams can be formed by electromagnetic radiation of any frequency range, as well as by wave radiation of any other nature, e.g. acoustic.
The capability of the plasma parameter distribution and that of the channel structure to be varied are important for applications. Examples of beam and plasma channel applications are considered in the book.