Physical design of a new set of high poloidal mode number coils in the EAST tokamak

An external resonant magnetic perturbation (RMP) field, an effective method to mitigate or suppress the edge localized mode (ELM), has been planned to be applied on the ELM control issue in ITER. A new set of magnetic perturbation coils, named as high m coils, has been developed for the EAST tokamak. The magnetic perturbation field of the high m coils is localized in the midplane of the low field side (LFS), with a spectrum characteristic of high m and wide n, where m and n are the poloidal and toroidal mode numbers, respectively. The high m coils generates a strong localized perturbation field. Edge magnetic topology under the application of high m coils should have either a small or no stochastic region. With the combination of the high m coils and the current RMP coils, flexible working scenarios of the magnetic perturbation field are available, which is beneficial for ELM control exploration on EAST. Numerical simulations have been carried out to characterize the high m coil system, including the magnetic spectrum and magnetic topology, which shows a great flexibility of magnetic perturbation variation as a tool to investigate the interaction between ELM and external magnetic perturbation.

Analysis of nonlinear time-fractional Klein-Gordon equation with power law kernel

<abstract><p>We investigate the nonlinear Klein-Gordon equation with Caputo fractional derivative. The general series solution of the system is derived by using the composition of the double Laplace transform with the decomposition method. It is noted that the obtained solution converges to the exact solution of the model. The existence of the model in the presence of Caputo fractional derivative is performed. The validity and precision of the presented method are exhibited with particular examples with suitable subsidiary conditions, where good agreements are obtained. The error analysis and its corresponding surface plots are presented for each example. From the numerical solutions, we observe that the proposed system admits soliton solutions. It is noticed that the amplitude of the wave solution increases with deviations in time, that concludes the factor $ \omega $ considerably increases the amplitude and disrupts the dispersion/nonlinearity properties, as a result, may admit the excitation in the dynamical system. We have also depicted the physical behavior that states the advancement of localized mode excitations in the system.</p></abstract>

Preemptive RMP-driven ELM crash suppression automated by a real-time machine-learning classifier in KSTAR

Suppression or mitigation of edge-localized mode (ELM) crashes is necessary for ITER. The strategy to suppress all the ELM crashes by the resonant magnetic perturbation (RMP) should be applied as soon as the first low-to-high confinement (L-H) transition occurs. A control algorithm based on real-time machine learning (ML) enables such an approach: it classifies the H-mode transition and the ELMy phase in real-time and automatically applies the preemptive RMP. This paper reports the algorithm design, which is now implemented in the KSTAR plasma-control system, and the corresponding experimental demonstration of typical high-δ KSTAR H-mode plasmas. As a result, all initial ELM crashes are suppressed with an acceptable safety factor at the edge (q95) and with RMP field adjustment. Moreover, the ML-driven ELM-crash-suppression discharges remain stable without further degradation due to the regularization of the plasma pedestal.

Progress of HL-2A experiments and HL-2M program

Since the last IAEA Fusion Energy Conference in 2018, significant progress of the experimental program of HL-2A has been achieved on developing advanced plasma physics, edge localized mode (ELM) control physics and technology. Optimization of plasma confinement has been performed. In particular, high-N H-mode plasmas exhibiting an internal transport barrier have been obtained (normalized plasma pressure N reached up to 3). Injection of impurity improved the plasma confinement. ELM control using resonance magnetic perturbation (RMP) or impurity injection has been achieved in a wide parameter regime, including Types I and III. In addition, the impurity seeding with supersonic molecular beam injection (SMBI) or laser blow-off (LBO) techniques has been successfully applied to actively control the plasma confinement and instabilities, as well as the plasma disruption with the aid of disruption prediction. Disruption prediction algorithms based on deep learning are developed. A prediction accuracy of 96.8% can be reached by assembling convolutional neural network (CNN). Furthermore, transport resulted from a wide variety of phenomena such as energetic particles and magnetic islands have been investigated. In parallel with the HL-2A experiments, the HL-2M mega-ampere class tokamak was commissioned in 2020 with its first plasma. Key features and capabilities of HL-2M are briefly presented.

Derrida's typology: on the status of a deconstructive logic

This thesis begins with a simple question: what is the status of a theory of construction? Is such a theory itself constructed? What does this tell us about the post-structuralist or deconstructive reappropriation of research and theory? To address these questions, this thesis makes two moves. The first consists in identifying a general argumentative structure or logic of construction at work across several of Jacques Derrida's published works. The second move consists in thinking through how this logic reconfigures itself by affecting the status of theories or explanatory models. We will argue that a 'deconstructrive logic', if there is such a thing, cannot be final, fixed and atemporal. Departing from previous interpretations of Derrida's work, we will make the case that this is not simply a negative limitation: rather, it marks a commitment to a localized mode of philosophy, or thinking on the terms of a particular context.

Derrida's typology: on the status of a deconstructive logic

This thesis begins with a simple question: what is the status of a theory of construction? Is such a theory itself constructed? What does this tell us about the post-structuralist or deconstructive reappropriation of research and theory? To address these questions, this thesis makes two moves. The first consists in identifying a general argumentative structure or logic of construction at work across several of Jacques Derrida's published works. The second move consists in thinking through how this logic reconfigures itself by affecting the status of theories or explanatory models. We will argue that a 'deconstructrive logic', if there is such a thing, cannot be final, fixed and atemporal. Departing from previous interpretations of Derrida's work, we will make the case that this is not simply a negative limitation: rather, it marks a commitment to a localized mode of philosophy, or thinking on the terms of a particular context.