RESUMO
Mastering nuclear fusion, which is an abundant, safe, and environmentally competitive energy, is a great challenge for humanity. Tokamak represents one of the most promising paths toward controlled fusion. Obtaining a high-performance, steady-state, and long-pulse plasma regime remains a critical issue. Recently, a big breakthrough in steady-state operation was made on the Experimental Advanced Superconducting Tokamak (EAST). A steady-state plasma with a world-record pulse length of 1056 s was obtained, where the density and the divertor peak heat flux were well controlled, with no core impurity accumulation, and a new high-confinement and self-organizing regime (Super I-mode = I-mode + e-ITB) was discovered and demonstrated. These achievements contribute to the integration of fusion plasma technology and physics, which is essential to operate next-step devices.
RESUMO
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.