RADIOFREQUENCY SHEATH MITIGATION BY INSULATING ANTENNA LIMITERS

Previous work, undertaken in the low heat flux environment of small ex periments, has shown that insulating limiters made out of boron nitrid e can enhance the performance of rf antennas by mitigating the rf volt ages available to drive plasma sheaths. In the present study, we devel op a quantitative model of rf sheath mitigation and apply it to determ ine the rf electrical specifications that a material should meet to be suitable as an insulating rf limiter. Additional properties of a suit able material are discussed and compared with the properties of common ly available materials and with newly developed ceramic matrix composi te materials. It is concluded that an rf limiter made from composite m aterials looks promising for use in sheath mitigation, especially for fast wave antennas. (C) 1997 Elsevier Science B.V.