高密度プラズマ下で大電力マイクロ波放射を行うアンテナ表面の放電現像

摘要

The space solar power system (SSPS) transfers enormous amounts of electrical energy through microwave or laser. SSPS must have very large and light-weight structures to collect the solar energy. The surface is covered with solar photovoltaic cells to collect and transform the incoming solar radiation into DC electricity. The transmission to ground would be performed with microwaves. Considered microwave frequency is 5.8 GHz. For conversion a large number of active elements together with carbon-fiber slotted wave guides or patch/microstrip antennas may be used. Flight demonstration onboard a small satellite in low Earth orbit (LEO) is now under consideration. When high-power microwaves are irradiated from an antenna in LEO plasma environment, there is a concern about multi-pactoring discharge caused by interaction between the plasma and the microwaves. There has been no experimental observation of such an interaction phenomenon. Verification experiments are essential for SSPS to become a reality. We have set-up an experimental system that can simulate the radiation of high power microwave in dense plasma in a vacuum chamber. A RF plasma source is installed to the chamber and can now produce the Argon plasma environment of density from 1011 to 1013m-3 with 4eV to 6eV temperature under a back pressure of 1.9x10-5Pa. A patch antenna with Teflon or Glass epoxy substrate has been installed inside the vacuum chamber. The antenna is connected to a magnetron that can produce 5.8GHz microwave up to 400W continuous power. I examine interaction between patch antenna surface and microwave in a vacuum chamber. I observe discharge on the patch antenna depending on the microwave strength and plasma environment. This thesis is made of five chapters. The first chapter introduces the general objective of study. The second chapter describes the experimental experimental setup and procedure. The third chapter reports the experimental results. The fourth chapter compares a hypothesis about the discharge inception mechanism against the experimental results. The fifth chapter concludes the paper with suggestions to the future works.