Using external magnetic field inhomogeneities to guide microwaves in plasma waveguides

Summary form only given, as follows. A new idea for the guiding of electromagnetic radiation by a plasma is presented. The scheme uses the magnetic field dependence of the index of refraction of in a magnetized plasma. An external DC axial magnetic field that varies with transverse position induces a transverse variation of the index of refraction of an electromagnetic wave propagation in the axial direction. The concept is similar to laser guiding in a density channel, but differs in that the plasma is now homogeneous and gradients are obtained by variation of the external fields. Using standard theoretical techniques employed in laser-plasma interactions, an equation for the evolution of the transverse size of the wave can be obtained. The equation relates the gradient in the magnetic field with the size of the guided electromagnetic wave. Two-dimensional XOOPIC simulations compared with theory. A further extension of the concept envisions using the cyclotron resonance in the dispersion relation to generate a highly localized steep gradient in the index of refraction. The resonance region acts as barrier to the wave in this magnetic waveguide. The theory is tested in a XOOPIC run using a planar magnetic wiggler field. The field model has transverse and axial fields, satisfying Maxwell´s Equations, with exponential increases transversely and sinusoidal variation in the axial direction. Simulations clear demonstrate the validity of the concept.