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A new in-vessel water-cooled coil has been placed below the lower tungsten-covered divertor in EAST, aiming at moving the strike points in the divertor and spreading the heat flow on the targets. To achieve controlled movement of the strike points by the plasma control system (PCS) when applying the in-vessel coil, the plasma equilibrium configurations are predicted by the tokamak equilibrium (TEQ) code. The divertor coil current is involved in these calculations. The shape control parameters in the PCS are adjusted according to the predesigned equilibria from the TEQ code. The strike point movement over a wide range has been achieved in the experiment while keeping the main plasma stable. Thus, this method for divertor strike point movement with the assistance of the divertor coil is feasible. [ABSTRACT FROM AUTHOR]

Robust real-time control algorithms for tracking plasma kinetic parameters in advanced tokamak scenarios are developed based on linear state-space (LSS) dynamic models. The real-time control algorithms under study comprise the H ∞ robust control, the linear quadratic integral control and the internal model control. The plasma models used in this work are restricted to LSS models identified from dedicated simulation/experimental data, though the proposed control algorithms can conveniently be extrapolated to broadly incorporate linear models obtained from first-principles plasma theory. The control objective is to track plasma kinetic parameters of interest to desired operating points in advanced tokamak scenarios by actuating additional heating & current drive systems in real-time. Plasma kinetic parameters involve the poloidal pressure parameter β p , the internal inductance li , the average toroidal rotation angular speed Ω ϕ and the electron temperature on axis T e , 0 while the actuators are the ion cyclotron resonance heating and lower hybrid current drive systems. In order to achieve enhanced control performance, two control layers are designed. The outer layer, i.e. an internal model-based proportional-integral actuator controller, operating on a fast timescale ( ≪ the energy confinement time τ E ) aiming at tracking the commands requested by the inner kinetic controllers, while the inner layer, i.e. a kinetic controller chosen from various alternatives, running on a slow timescale ( ∼ τ E ) is dedicated to tailoring plasma kinetic parameters. Simulation results for the experimental advanced superconducting tokamak (EAST) tokamak are provided and compared to show the capabilities of each control approach. Dedicated kinetic control experiments conducted in an H-mode scenario on EAST are reported as well. The advantages and limits of these control algorithms are discussed and summarised. [ABSTRACT FROM AUTHOR]

A multi-function divertor feedback control system has been built on Experimental Advanced Superconducting Tokamak (EAST) to treat the divertor heat load issue. With the real-time data of the Langmuir probes and the impurity seeding, the divertor electron temperature (Te,div) is well controlled to achieve the partial detachment phase. The first trial of the CD4 seeding for the Te,div reduction has been achieved on EAST long-pulse discharge. In the seeding phase, the Te,div was maintained close to 5 eV, and the surface temperature of the target plate (Tsurface,div) had a reduction of about 150 °C. The plasma stored energy had a reduction in the control phase, so it is necessary to find a way to keep the good plasma confinement in the next step. The CD4 injection also mitigated the low hybrid wave coupling rate in some degree. The big volume of the CD4 injection lifted the Greenwald density fraction from ∼0.4 to ∼0.7, which made the SOL into high recycling state. Most of the injected carbon particles were in the high ionized state, and with the lower of the Te,div, the tungsten line emission was suppressed obviously. [ABSTRACT FROM AUTHOR]

Vertical displacement event (VDE) is one of the most important events related to disruptions. A real-time disruption prediction tool for VDE is presented in this article. Vertical growth rate is an essential parameter to describe vertical instability, which can be obtained based on the rigid plasma response model. A real-time vertical growth rate calculation system is built, which utilizes graphics process unit (GPU) parallel computation and reflective memory (RFM) boards communication with plasma control system (PCS). Based on real-time vertical growth rate calculation system, an alarm algorithm for detecting vertical instability is integrated into experimental advanced superconducting tokamak (EAST) PCS. It is designed to provide the capabilities of a switching control method and to trigger a warning signal in PCS when uncontrollable vertical instability is detected. Such a disruption prediction tool has been preliminarily applied in the 2019 EAST spring experiment. [ABSTRACT FROM AUTHOR]

For the purpose of keeping a plasma in steady state and avoiding instabilities, the experimental advanced superconducting tokamak (EAST) plasma control system (PCS) needs more diagnostic data produced by the EAST distributed subsystems to perform its complex control algorithms. To solve the transmission problem of all these data, a real-time communication system based on the messaging, real time, and grid real time operating system and reflective memory (RFM) network is designed. It is expected to enable the data acquisition (DAQ) systems of various EAST subsystems to be able to transfer the diagnostic data to the PCS in real time through the RFM network as the data are acquired. Then, the PCS can use these available data to carry out the necessary calculations according to the control algorithms and send the commands to the subsystems in every control cycle. To reach this goal, a small real-time communication system, adapted from the prototype of the EAST vacuum DAQ system (sampling rate of 10 KHz), was built for a performance test. In this test, the vacuum DAQ system transferred the acquired data to the PCS within the control cycle of $100~\mu \text{s}$ , which tentatively meets the abovementioned requirements. The test was performed for 1000 s to get a stable and reliable result, which is described in detail in this paper as well as plans for future work. [ABSTRACT FROM AUTHOR]

This paper briefly outlines the current status of CODAC system of the EAST tokamak. Integrated central system has been working for synchronizing all the subsystems and responsible for the integral safety protection by interlock. Data acquisition system has been established for the discharge with duration up to 100 seconds. Various data visualization tools such as EASTVIEWER to view the flux surfaces, RTSCOPE to view plasma boundary and CCD image in real-time, WEBSCOPE to view the diagnostic data via a web browser and EASTVOD to view and search plasma discharge image at different time, haven developed for EAST operation. Plasma control system is inherited from DIII-D, and has been matured to a stage to feedback control the EAST plasma shape, density and current in real time. [ABSTRACT FROM AUTHOR]

Recent commissioning of two major fully superconducting (SC)-shaped tokamaks, Experimental Advanced Superconducting Tokamak (EAST) and Korean Superconducting Tokamak Advanced Research (KSTAR), represents a significant advance in magnetic fusion research. The key to commissioning success in these complex and unique tokamaks was as follows: 1) use of a robust, flexible plasma control system (PCS) based on the validated DIII-D design; 2) use of the TokSys design and modeling environment, which is tightly coupled with the DIII-D PCS architecture for first-plasma scenario development and plasma diagnosis; and 3) collaborations with experienced internationally recognized teams of tokamak operations and control experts. We provide an overview of the generic modeling environment and plasma control tools developed and validated within the DIII-D experimental program and applied through an international collaborative program to successfully address the unique constraints associated with the startup of these next-generation tokamaks. The unique characteristics of each tokamak and the machine constraints that must be included in device modeling and simulation, such as SC coil current slew rate limits and the presence of nonlinear magnetic materials, are discussed, along with commissioning and initial operational results. Lessons learned from the startup experience in these devices are summarized, with special emphasis on ramifications for International Thermonuclear Experimental Reactor (ITER). [ABSTRACT FROM AUTHOR]

Abstract: The DIII-D digital plasma control system (PCS) has been adapted and used at a number of tokamaks around the world over the past several years. Implementations of the DIII-D PCS at KSTAR and EAST in particular have made use of, and improved upon, the methodology for off-normal event/fault detection and response that was originally incorporated into the DIII-D PCS. This work discusses the lessons learned implementing and installing codes for detecting and responding to off-normal events in both plasma discharges and tokamak systems. In particular, we discuss the implementation details for codes at DIII-D, EAST, and KSTAR, and discuss how those experiences are being incorporated into a proposed finite state machine architecture in support of ITER research at DIII-D. [ABSTRACT FROM AUTHOR]