When it comes to magnetic confinement nuclear fusion, high-quality magnetic fields are crucial for sustaining high-heat plasmas and managing plasma density, fast particles, and turbulence. Transport and turbulence are particularly important factors in this process. Traditional designs of stellarator machines, like those seen in the HSX and W7-X experiments, typically optimize magnetic fields...
The design of optimized, commercially-attractive reactors requires careful understanding of the core plasma physics and the development of accurate predictive frameworks. Historically, first-principles gyrokinetic turbulence simulations were too expensive to be used in predictive workflows, as they often required hundreds or thousands of evaluations to reach multi-channel steady-state or...
Magnetic nuclear fusion reactors such as tokamaks and stellarators rely on superconducting coils (also called magnets) to confine and shape the plasma in which the fusion reactions occur. Stellarators are fusion devices based on three-dimensional plasma shapes which enable steady state and more stable operations compared with tokamaks. Nevertheless, the complex stellarator plasma shape demands...
Due to a number of factors, long pulse experiments conducted under Negative ion source based Netutral Beam Injection (NNBI) are not always stable. The occurrence of breakdown can lead to damage of the ion source device. Currently, low-speed data acquisition (DAQ) systems operating in NNBI have low sampling rates, which make it difficult to accurately characterize the changes of each key...
For machine control and safety as well as physics studies, present and future fusion devices have to analyse a huge amount of measurements coming from many redundant and complementary diagnostics. Integrated Data Analysis (IDA) in the framework of Bayesian probability theory provides a concept to analyse a coherent combination of measured data from heterogeneous diagnostics including their...
At ASDEX Upgrade (AUG) Integrated Data Analysis (IDA) is used to infer kinetic plasma profiles like electron density by a joint analysis of several heterogeneous diagnostics. A reliable forward model for each diagnostic is essential for the probabilistic approach, linking parameter space to data space, and prediction measurements accurately. The IDA approach enables the identification of...
An accurate estimation of impurity concentrations in fusion devices is crucial for understanding impurity transport and controlling impurities. However, this is challenging due to the involvement of multiple diagnostics and their various sources of uncertainties. In this work, we utilize integrated data analysis (IDA) based on Bayesian probabilistic theory to jointly estimate impurity...
The characterization of magnetic-confined-fusion plasmas requires a comprehensive set of diagnostic systems measuring a wide range of parameters. New machines, such as the ST40 high-field spherical tokamak [1], typically start with a small subset and gradually increase the diagnostic suite to include more complex and comprehensive systems. To make the most of each plasma operation phase,...
EXL-50 is a solenoid-free spherical torus that uses electron cyclotron wave (ECW) as the primary heating source. The typical range for plasma density is between 1~10*1018 m-3and the ECW generates superthermal electrons that can be accelerated to high energies by multiple resonance layers in the torus. These high-energy electrons have low collisionality in the low-density...
Design is an iterative, creative process. In the context of plasma scenarios in magnetic confinement devices, a pulse design represents the specification or plan for a future pulse. Generation of these plans requires an understanding of the scenario’s goals, any constraints that restrict the design space, and a list of assumptions that must be made in order to pose a well-formed problem....
Neutral beam injection is now focused on thousands of seconds for the long-pulse experiment. It is of great significance to establish a simple physical calculation model for evaluating the current parameters of the long-pulse Negative Ion based Neutral Beam Injection (NNBI) facility before the experiment for adjusting and setting the experimental parameters of long-pulse negative ion source...
MINT (Make Informative and Nice Trends) is an ITER graphical data visualization and exploration tool designed for plant engineers, operators, and physicists. Its requirements were gathered through interviews with various stakeholders, and its architecture was planned for a long-term project such as ITER. As such, a modular design and clear definition of generic interfaces (abstraction layer)...
Modern real-time plasma control systems will be modular and distributed. This provides several advantages: component isolation, component simplicity and robustness, scalability, and the possibility of utilizing heterogenous execution environments. In addition these systems are amenable to machine learned pipelines. However such systems incur the liabilities of system complexity and...
Interpreting diagnostic data as early as possible after a plasma pulse is an important capability of modern tokamaks [1, 2, 3]. This is particularly critical for ITER, since a quick feedback on the plasma performance (shape, confinement, power balance, impurities, ELMs, …) during the pulse is increases efficiency of operation and furthers the implementation of the scientific program that...
Most databases in fusion research are devoted to a single topic, such as energy confinement, H-modes, profiles or disruptions. In order to allow for a wide range of analysis, modelling and validation tasks, a broad-based multi-purpose database, JETPEAK, has been developed for JET. This database currently includes 23000 stationary state (∂/∂t≈0) manually selected samples, averaged time windows...
Due to the specificity of Neutral Beam Injection (NBI) system, the control of its actual physical system is achieved through the Integrated Control System (ICS). The NBI ICS is used to coordinate the operation of various subsystems of NBI while ensuring steady-state operation of entire system and the safety of experimenters. The early NBI ICS in our lab was designed based on a centralized...
Metallic Spherical Tokamak (MT-I) is modified form of the GLAST-II (GLAss Spherical Tokamak) operational in PTPRI at Pakistan. It has major radius 15 cm and minor radius 9 cm with aspect ratio 1.67. It is equipped with optical, electrical and magnetic diagnostics. Impurities present in the vacuum vessel disturb the performance of the device and hinder the achievement of the higher values of...
To be filled out in the upcoming days.
Event detection will play an increasingly important role for operating fusion devices in a safe and efficient way. In the plasma, various events require detection and identification, such as the onset of magnetohydrodynamic instabilities, appearance of disruption precursors, impurity events, confinement mode transitions, etc. However, in a future fusion power plant, a wide variety of events...
Inferring physics parameters from experimental data is a key analysis need for physicists. Often it is desired for this inference process to have grounding in detailed models contained in simulation. Simulation-based inference (SBI) are techniques which utilize simulations in the forward model, create approximate posteriors which are faithful to the simulation. Recently neural networks have...
The Integrated Data Analysis (IDA) approach employs a combination of various diagnostics within a Bayesian probability framework to determine electron density and temperature profiles of ASDEX Upgrade plasmas. These profiles frequently serve as a benchmark for validating transport simulations. However, as some areas of the plasma are not covered by the diagnostics or measurements may be...
Modelling the diagnostic signals for specific conditions of plasma operation is essential for an optimal and comprehensive analysis of the discharge behaviour and the preparation of the tools to design, optimize and validate scenarios on existing or future fusion devices.
This contribution gives a brief overview of the diagnostic models available in the Integrated Modelling and Analysis Suite...
A fundamental feature of reversed-field pinch fusion plasmas is helical self-organized states. In the past few decades, MHD theory and numerical simulations have played a key role in describing these states. An important parameter is the dimensionless Hartmann number [1], which is determined by the resistivity and the viscosity. It can be interpreted as the electromagnetic equivalent of the...
Even if the understanding of the tokamak configuration has progressed significantly in the last years, these devices are all plagued by the collapses of the plasma called disruptions. Moreover, devices with metallic plasma-facing components, similar to those foreseen in the next generation of reactors, are also vulnerable in this respect, particularly when operated at q95 around 3. In these...
Focusing the attention on disruption mitigation, the locked mode (LM) signal is typically used as single signal to recognise incoming disruptions. However, if the LM signal is not available in real-time (as it will happen in the first JT-60SA discharges) or the LM signal is not reliable enough, simple predictors have to use other signals. This work shows that a line integrated density (LID)...
Because of electromagnetic interference from the environment, vacuum chamber potential fluctuations or other various reasons, the plasma diagnostic signal waveform often jumps, bringing great trouble to the data analysis. There are already some methods to achieve jump detection, such as by detecting the ratio of change over RMS, or comparing short-time Fourier transform spectrogram. However,...
Recently in energetic-particle physics study, nonlinear mode-mode interaction has been noticed to play key roles in production of new modes. Bispectral analysis is the common way to identify the nonlinear interaction. However, a number of statistical ensembles are necessary for the bispectral analysis. In this presentation we propose to use Hilbert transform to detect the nonlinear mode-mode...
Fusion power plants will need to run in a reliable way, in order to maximize the power output and avoid delays due to unscheduled maintenance or damage to components. Predictive maintenance is an approach that can contribute to this requirement by periodic or continuous monitoring of the condition of equipment. The goal is to predict when the equipment will require maintenance and, ultimately,...
Superconducting magnets play a critical role in a superconducting-based nuclear fusion device. As the temperature of superconducting magnets increases with a change in current, it is important to predict their temperature to prevent excessive temperature rise of coils and operate them efficiently. We present Multi-Scale Recurrent Transformer(MSR-Transformer) system, a deep learning model for...
Extensive studies on regulations of the plasma profile by flucating modes may shed light on the plasma control techniques for ameliorating impurity content and plasma performance [1]. In this report, we present the data processing of radially distributed BES measurements related to the two-dimension mapping of the avalanche structure and its related impurity analysis in the HL-2A neutral beam...
Empirical scaling of the thermal energy confinement time $\tau_{E_{th}}$ in tokamak H-mode plasmas, determined from multi-machine databases, remains a convenient tool for studying the dependencies of $\tau_{E_{th}}$ and for predicting confinement based on experimental data. Based on regression analysis, the approach is essentially data-driven, but this does not prevent the incorporation of...
Tokamak operations and Fusion plasma research datasets are vast and complex, presenting various challenges in data analysis and interpretation.
The development of cutting-edge tools based on Artificial Intelligence (AI), and machine learning (ML) algorithms can significantly accelerate fusion plasma research outcomes and optimize the tokamak operations.
We discuss the potential...
While the Integrated Modelling & Analysis Suite (IMAS [1]) is being developed further, the number of simulations available in IMAS is increasing both at ITER and within the Members. As a result, tools are needed to manage, curate and expose the large IMAS simulation databases to the potential users. Ad-hoc solutions have been developed in some cases, such as the ITER scenario database (2500+...
The analysis of data from fusion devices is a common and important task in Fusion Data Research (FDR). One which poses several practical challenges to scientists.
First, experimental programs generate an enormous amount of data which is hosted by dedicated institutions. Accessing this raw data requires authorization and either a very fast direct connection or enormous local storage...
As a necessary auxiliary heating method, Neutral Beam Injection (NBI) heating technology has high heating efficiency and clear physical mechanism to meet various needs of fusion experiments, so it will definitely become an indispensable key technology in future fusion research. NBI requires parameter tuning and optimization before it can be formally put into operation, so its operational data...
Plasma edge codes like SOLPS-ITER [1] are currently the main tools for interpreting exhaust scenarios in existing experiments, and for designing next step fusion reactors like ITER and DEMO. These codes typically couple a multi-fluid model for the plasma with a kinetic model for the neutral particles. While the former is implemented in a (deterministic) Finite Volume setting, the latter is...
The suite of tools being developed to support the preparations for ITER operation, including data interpretation and analysis, and the refinement of the ITER Research Plan, are underpinned by a common data representation that forms the basis around which the Integrated Modelling & Analysis Suite (IMAS) is built and which strives to make fusion data more FAIR.
Adopting a common standard for...
This contribution presents the methodology used for implementing two intelligent data processing applications using real-time heterogeneous platforms.
• The first application involves discriminating between gamma and neutron pulses acquired using a scintillator through the use of deep learning techniques implemented with 1-D convolutional neural networks (CNNs) and high-sampling rate analog...
Wendelstein 7-X (W7-X) is the most advanced drift-optimized stellarator, designed to demonstrate the feasibility of the stellarator concept for a future fusion power plant with steady-state operation. Its primary goal is to prove quasi-steady-state operation with plasmas of up to 30 minutes in a reactor-relevant parameter regime. Achieving high-performance operation in W7-X and other fusion...
A series of methods, based on the time series analysis of the main plasma diagnostic signals, are used to determine when significant changes in the plasma dynamics of the tokamak configuration occur, indicating the onset of drifts towards a disruption. Dynamical indicators, such as embedding dimension, 0-1 chaos test, recurrence plots measures, but also informational criteria, such as...
In science an inverse problem can be defined in full generality as the task of calculating from a set of observations the factors that generated them. Such problems are called inverse because they are meant to derive the causes from their effects. They can therefore be considered the opposite of forward problems, whose objective is calculating the effects of causes. Many data-centric problems...
In tokamak plasmas, estimating the local impurity concentration can be subject to many uncertainties. In particular, it requires accurate knowledge of plasma temperature, magnetic equilibrium, impurity cooling factor and the spectral response of the diagnostics used. When all other plasma parameters are well-known, the impurity density profile can be reconstructed in the core with the help of...
On the Joint European Torus (JET) first and more recently on ASDEX-Upgrade (AUG), an Expectation Maximization algorithm has been implemented to derive the Maximum Likelihood (ML) between the line integrated measurements of the bolometers, and the reconstructed tomograms representing specific poloidal emissive distributions. On both devices, the Line of Sights (LOSs) coverage of the foil...
Accurate measurement and control of the radiation emitted by tokamak plasmas is crucial for the successful operation of fusion reactors. Many macroscopic plasma instabilities, which can rapidly yield to lost of plasma confinement, are related to radiation patterns differing in localisation, shape and intensity. Current tokamaks use bolometers to measure the plasma emission, but they only...
