Investigation of Radio Frequency Penetration through Collisional Plasma using a Reverberation Chamber

Radio waves are known to be strongly attenuated and reflected by plasmas, especially for frequencies below the plasma frequency. One area of interest is the situation of spacecraft traveling at velocities exceeding the speed of sound resulting in heating of the surface and ionization of the ambient air coupled with ablation of the surface of the craft. This forms dense plasma resulting in a radiofrequency blackout due to shielding of the waves by plasma. In the past, several mechanisms have been devised to mitigate this plasma RF blackout. We have proposed an alternate concept of a near-field collisional window, a novel mitigation technique, to overcome some of the difficulties with the existing mitigation mechanisms. This concept utilizes the non-zero collisional frequency of dense plasma and near-field radiation from different types of antennas to increase transmission at frequencies below the plasma frequency. While we continue to model this concept analytically and using computer simulations, it is critical to devise a methodology to study this mechanism in the laboratory. Here we present an experimental scheme to emulate the concept of the near-field collisional window using discharge plasma placed inside a reverberation chamber.