Study of Globus-M Tokamak Poloidal System and Plasma Position Control

A unique sequence of 120 almost identical plasmas in the Joint European Torus (JET) recently provided two orders of magnitude more statistically equivalent data than ever previously available. The purpose was to study movement of eroded plasma-facing material from JET's new Beryllium wall, but it has allowed the statistical detection of otherwise unobservable phenomenon. This includes a sequence of resonant-like waiting times between edge-localised plasma instabilities (ELMs), instabilities that must be mitigated or avoided in large magnetically confined plasmas such as those planned for ITER. Here, we investigate the cause of this phenomenon, using the unprecedented quantity of data to produce a detailed picture of the plasma's behaviour. After combining the data, oscillations are clearly observable in the plasma's vertical position, in edge losses of ions, and in Beryllium II (527 nm) light emissions. The oscillations are unexpected, are not obvious in data from a single pulse alone, and are all clearly correlated with each other. They are likely to be caused by a small vertical oscillation that the plasma control system is not reacting to prevent, but a more complex explanation is possible. The clearly observable but unexpected link between small changes in the plasma's position and changes to edge-plasma transport and stability suggest that these characteristics cannot always be studied in isolation. It also suggests new opportunities for ELM mitigation and control that may exist.

A key component of the DIII-D Advanced Tokamak and Radiative Divertor Programs is the development and implementation of methods to actively control a large number of plasma parameters. These parameters include plasma shape and position, total stored energy, density, RF loading resistance, radiated power and more detailed control of the current profile. To support this research goal, a flexible and easily expanded digital control system has been developed and implemented. We have made parallel progress in modeling of the plasma, poloidal coils, vacuum vessel, and power system dynamics and in ensuring the integrity of diagnostic and command circuits used in control. Recent activity has focused on exploiting the mature digital control platform through the implementation of simple feedback controls of more exotic plasma parameters such as enhanced divertor radiation, neutral pressure and Marfe creation and more sophisticated identification and digital feedback control algorithms for plasma shape, vertical position, and safety factor on axis (q/sub 0/). A summary of recent progress in each of these areas will be presented.

Model-based plasma vertical stabilization and position control at EAST

This paper describes the progress in analysis of the ITER plasma vertical stabilisation (VS) system since its design review in 2007–2008. Two indices characterising plasma VS were studied. These are (1) the maximum value of plasma vertical displacement due to free drift that can be stopped by the VS system and (2) the maximum root mean square value of low frequency noise in the dZ/dt measurement signal used in the VS feedback loop. The first VS index was calculated using the PET code for 15 MA plasmas with the nominal position and shape. The second VS index was studied with the DINA code in the most demanding simulations for plasma magnetic control of 15 MA scenarios with the fastest plasma current ramp-up and early X-point formation, the fastest plasma current ramp-down in a divertor configuration, and an H to L mode transition at the current flattop. The studies performed demonstrate that the VS in-vessel coils, adopted recently in the baseline design, significantly increase the range of plasma controllability in comparison with the stabilising systems VS1 and VS2, providing operating margins sufficient to achieve ITER's goals specified in the project requirements. Additionally two sets of the DINA code simulations were performed with the goal of assessment of the capability of the PF system with the VS in-vessel coils: (i) to control the position of runaway electrons generated during disruptions in 15 MA scenarios and (ii) to trigger ELMs in H-mode plasmas of 7.5 MA/2.65 T scenarios planned for the early phase of ITER operation. It was also shown that ferromagnetic structures of the vacuum vessel (ferromagnetic inserts) and test blanket modules insignificantly affect the plasma VS.

We consider synthesis and modeling of hierarchical robust magnetic control systems for plasma in tokamaks with adaptation of the magnetic axis' vertical position. The studies were done for ITER (Cadarache, France) and Globus-M (St. Petersburg, Russia) tokamaks. Our original synthesis method ensures an improvement in performance for the shape of the plasma by resolving the contradiction between position and plasma shape via adaptation in a hierarchical system. Numerical modeling of synthesized control systems on multivariable linear models of plasma and nonlinear plasma-physics code DINA that unites basic equations of plasma dynamics in a magnetic field has shown the efficiency of the proposed approach and a possibility to apply it in a physical experiment.

Real-time reflectometry – An ASDEX Upgrade DCS plugin App for plasma position and shape feedback control

Leadless pacemaker (LP) implantation at the apical septum has been linked to pacing-induced cardiomyopathy (PICM). This study aimed to examine the precise position for LP implantation in the RV septum using the three-dimensional rotational angiography (3D-RA) system. The accurate implantation sites were visualized through the fluoroscopic image, and the relationship to the measured QRS duration during pacing (p-QRS duration) was investigated to evaluate their potential association with cardiomyopathy. Fifty-four patients underwent LP implantation with 3D-RA guidance. Implantation sites were assessed using the horizontal axis from the apex to the center of the tricuspid valve and the vertical axis from the inferior border of the apex to the outflow tract transition. The p-QRS durations were measured intraoperatively using electrocardiograms. Echocardiography was performed 12months later to assess PCIM progression. All 54 LPs were successfully implanted in the septum. Mean horizontal and vertical positions within the RV were 69.7±10.5% and 66.5±13.1%, respectively. Mean p-QRS duration was 148±11ms. The horizontal position was correlated with QRS duration (R=0.59), while the vertical position showed no correlation (R=0.03). The native QRS (n-QRS) duration was also an independent predictor of prolonged p-QRS duration (p=0.018). No patients developed cardiomyopathy progression on follow-up, and no association with p-QRS duration was observed. In LP implantation, the horizontal position within the RV septum correlates more strongly with p-QRS duration than vertical position. Prolonged n-QRS duration also prolonged p-QRS duration; however, further research is needed to evaluate the relationship between the implanted position and the occurrence of PICM.

In tokamak and other fusion devices, magnetic control is the main tool that allows to regulate the plasma current, position and shape; it is in charge of actuating the desired plasma current waveform, steering the plasma position to a given set point and maintain the plasma shape close to a prescribed plasma equilibrium. This work describes the application of several physics concepts and computational tools in order to obtain a novel optimal controller for the plasma centroid position, which has been implemented and tested in the real-time plasma control system at the ISTTOK tokamak. A key point for the development of the new control system was the installation of a recently upgraded hardware, that numerically integrates in real-time the magnetic probes signals.

Investigation of characteristics of vertical plasma position relay control system in tokamak is performed by example of plasma movement model in the ITER1.3. Calculation procedure of actuator current and output voltage restrictions is proposed which is independent of an actuator type. Transitional regime control laws providing maximum speed of response at elimination of “large” disturbances in plasma column displacements are considered. The comparitive estimation of output plant signal pulsation value in steady-state stabilization regimes is carried out.

In tokamak, eddy currents are produced due to change in plasma positions during plasma instabilities that result into generation of electromagnetic forces on interaction with the induced currents. Measurement of this current is essential to design a mechanical structure that can withstand this force. Principle objective of this paper is the development of Rogowski coil sensor to measure eddy currents on a toroidal vessel. The paper presents an elaborative and practical construction technique of a Rogowski coil. The calibration method for the Rogowski coil is also presented. Rogowski coils as an eddy currents diagnostics are tested and experiments to measure induced currents on the toroidal vessel are performed using the coils. Experimental values of eddy currents are compared with the ANSYS simulation results.

It is pointed out that plasma position and shape control calls for fast algorithms for plasma boundary identification, i.e. methods capable of determining the shape in a time interval not longer than the sampling time of the controller. The authors present an online identification algorithm which realizes a trade-off between accurate plasma shape reconstruction and computational burden. The proposed identification has been tested with reference to some types of ITER (International Thermonuclear Experimental Reactor) plasmas.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

This paper proposes a method for standing up that utilizes a patient's own power to their fullest extent while allowing the person to stand up easily. Analyzing the skills of physiotherapists, we extracted two skills that we believe allowed them to assist patients in standing up by themselves: (1) promoting a forward-bending posture by making it easier to arch their backs and antevert the pelvis, and (2) providing balance so the patient does not fall down. In order to implement these skills, we propose (1) an inbuilt passive joint using a body holder to hold the patient's upper body which reinforces a natural forward-bending posture, and (2) a horizontal position and vertical force assist control system which guides position control in the horizontal direction and assists with exerting force through force control in the vertical direction. We conducted experiments using linear stage system to assist with standing-up motion and confirmed that it promoted a comfortable and natural forward-bending posture through the inbuilt passive joint. Moreover, we compared standing-up motion using a control system that controls both vertical and horizontal positions with the proposed method, which guides the horizontal direction while assisting with vertical force. We found that in the position control system, when the patient performs the standing-up motion, they stand up at a predetermined constant velocity regardless of the force applied to the robot. On the other hand, the proposed method varied velocity in response to the force the patient applied to the robot. In other words, when velocity increases, the robot's motion changes to apply more lifting force, and when velocity decreases, the robot's motion changes to apply less lifting force. In other words, we confirmed that the system uses the patient's remaining body power while assisting with standing-up motion.

Optimizing the mass transport phenomenon around micro-electrodes of an enzymatic biofuel cell inside a blood artery via finite element analysis method

This work evaluates the influence of the cellar conditions and bottle orientation, on the phenolic and volatile composition of a Vintage Port wine, sealed with natural cork stoppers, for 44 months post-bottling. The storage was performed in two different cellars, namely a cellar A with controlled temperature and humidity, and a cellar B, representing a traditional cellar, with uncontrolled temperature and humidity. The impact of bottle orientation was studied in cellar A, where the bottles were stored in horizontal and vertical positions. The phenolic and volatile composition of the bottled Vintage Port wine were analyzed after 6, 15 and 44 months. The results unveiled that the cellar conditions and bottle orientation had an impact in Port wine composition which was higher at 44 months post-bottling. The samples stored in the traditional cellar unveiled significantly higher yellow tones, lower tannin specific activity, and higher levels of furfural and 5-methylfurfural. Furthermore, the samples stored in the horizontal position revealed significant higher levels of total proanthocyanidins and higher tannin specific activity than the samples stored in the vertical position. Interestingly, for the first time to our knowledge, an ellagitannin-derived compound (Corklin) was detected in Vintage Port wines stored in the horizontal position, which results from the reaction of cork constituents with phenolic compounds present in wines.

Static analysis of wind turbine blades that convert kinetic energy using wind to electrical power has been analyzed using Ansys model. The geometry was imported in ANSYS workbench 2020R1, where the material was changed to Epoxy E-Glass Wet. The mesh independence that occurred at 800 and 600 element sizes and an element size of 800 was chosen for subsequent static analysis. The static analysis shows that the total deformation and von Mises stress of the wind turbine blade was improved at both the vertical position and the horizontal position by 40.0% and 38.61%, respectively. Besides, the static analysis showed an almost linear mode shape increased from mode lines. Nevertheless, Campbell's diagram showed that resonance vibration occurred at an amplitude of 5.5x106Pa with a corresponding frequency of 5Hz, which gave a rotational speed of 262.4x106 rpm. This shows that the impulse force is better applied in wind turbine blade transient analysis at a lower von Mises stress to attain a quicker damping response steady-state, which favors wind turbine blade analysis. Overall, the wind turbine blade is better designed at a vertical position to allow better deformation stress at a static position. Conversely, the von Mises stress showed 44.64% and 38.61% at horizontal and vertical positions. This also agrees with static total deformation, since stress is better managed at a lower percentage range.