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In order to achieve steady state operation in experimental advanced superconducting tokamak (EAST), a 6 MW/4.6 GHz lower hybrid current drive system with twenty-four 250 kW/4.6 GHz high power klystron amplifiers (model VKC7849A) has been developed. A 4.6 GHz lower hybrid wave (LHW) power control system (4.6 GHz LPCS) with continuous wave mode has been set up, which was used to control the LHW power as needed. This paper introduces the architecture and software design of LPCS system, including microwave preamplifier subsystem, power measurement subsystem, power control computers, and so on. Proportional integral differential (PID) closed-loop control time is less than 100 μs due to the use of high-speed acquisition cards and user-programmable Field Programmable Gate Arrays. So far, high power CW operation and power control experiments with PID feedback mode by plasma parameters (beta, loop voltage, and so on) were performed in detail. Results show that 4.6 GHz LPCS is stable and reliable, suggesting that it meets the needs of EAST. [ABSTRACT FROM AUTHOR]

Several advantages are associated with an atmospheric microwave plasma torch, including low cost, easy processing, and high density of electrons and reactive species. This paper develops a compact microwave plasma torch (CMPT) operating at 2.45 GHz with an ultrabandwidth of 30 MHz. The structure and equivalent circuit of CMPT is established and analyzed based on theory of transmission line. The simulation results indicate that the resonant frequency will drift downward with the presence of plasma. In order to keep the better coupling between the microwave and plasma, a new design scheme of a fully automatic microwave plasma system is proposed. The effects of different microwave powers on the CMPT discharge are carried out on this system. Finally, in order to demonstrate the performance of the CMPT, an experiment to modify the surface of polymethyl methacrylate (PMMA) is conducted. It is found that the water contact angle is reduced from 85.4° to 32.3°, and the surface morphology characterized by atomic force microscope indicates significant improvement of the surface wettability of PMMA, which proves that the CMPT system is feasible and available. [ABSTRACT FROM AUTHOR]

The lower hybrid current drive (LHCD) is an effective approach for auxiliary heating and non-inductive current drive in the experimental advanced superconducting tokamak. The 6 MW/4.6 GHz LHCD system is being designed and installed with twenty-four 250 KW/4.6 GHz high power klystron amplifiers. The test bench operating at 250 KW/4.6 GHz in continuous wave mode has been set up, which can test and train microwave components for the 6 MW/4.6 GHz LHCD system. In this paper, the system architecture and software of the microwave test bench are presented. Moreover, the test results of these klystrons and microwave units are described here in detail. The long term operation of the test bench and improved performance of all microwave component samples indicated that the related technologies on test bench can be applied in the large scale LHCD systems. [ABSTRACT FROM AUTHOR]