Electromagnetic wave scattering by an array of tubes filled with plasma

Periodic arrays of discharge tubes placed directly against each other were used to produce a plasma layer scattering and absorbing electromagnetic waves. Reflection, transmission and absorption factors of normally incident waves were studied both theoretically and experimentally for these arrays in the frequency range 5 - 12 GHz. Two wave polarizations were under investigation; the electric field of the wave was either parallel (E wave) or perpendicular (H wave) to the tube axis. Glass tubes with inner diameters 1.3 - 1.4 cm were filled with an Ar - Hg mixture or Xe at a pressure of several Torr. The plasma density on the tube axis varied in the range - . The results of calculations fitted the experimental data well. Better reflection can be achieved for E waves when employing tubes with a lower permittivity. From the point of view of better absorption it is preferable to deal with the H wave, for which resonant absorption dominates. Only a weak dependence of reflection, transmission and absorption factors on the tube wall permittivity and electron collision frequency held in this case. Power consumptions required to sustain plasmas with equal density in the tubes filled with Xe appeared to be smaller than those for the Ar - Hg mixture by a factor of about three.