The control policy produces a reference voltage command at each time step for the active control coils. We see that a similar level of performance can be achieved with a large reduction in the number of actors for a moderate cost in training time. DIII-D research towards resolving key issues for ITER and steady-state tokamaks. The control policy can learn to be robust against very non-linear hardware-specific phenomena. Yang, F. et al. 3a. Errors on scalar quantities, such as Ip or elongation, are computed from the error between the reference and the respective estimation from the equilibrium reconstruction over the time period of interest. Preprint at https://arxiv.org/abs/2006.00979 (2020). Hofmann, F. et al. Degrave, J., Felici, F., Buchli, J. et al. Sonnet: TensorFlow-based neural network library. Magnetic confinement fusion is an approach to generate thermonuclear fusion power that uses magnetic fields to confine fusion fuel in the form of a plasma. If material is not included in the articles Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. The control policies learn to stay within the specified limits, for example, on maximum coil current or the edge safety factor25. 4a), without being explicitly told to do so. Fusion 51, 083013 (2011). Bosch, H.-S. et al. Phys. the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in In order to minimize power losses in the coils, designs involving superconducting coils have begun to replace copper coils. A charged particle in a magnetic field experiences a Lorentz force that is proportional to the product of the particle's velocity and the magnetic field.. Although these controllers are usually effective, they require substantial engineering effort, design effort and expertise whenever the target plasma configuration is changed, together with complex, real-time calculations for equilibrium estimation. Control. The first real effort to build a control fusion reactor used the pinch effect in a toroidal container. Lastly, we demonstrate the power of our architecture to explore new plasma configurations. The poloidal field is generated by a toroidal electric current that is forced to flow within the conducting plasma. Its most recent schedule is for it to begin operation in 2025. Magnetic confinement is one of two major branches of fusion energy research, along with inertial confinement fusion. The controllers designed by our architecture are greatly structurally simplified compared with conventional designs, as depicted in Fig. 12, 384386 (2016). Therefore, in later shots, a reward was added to keep the current in both ohmic coils close together. Nucl. 25th IAEA Fusion Energy Conf. C.G., F.C., F.F., J.D. Ignition is the process . If the plasma pressure is greater in the core than at the edge, this pressure differential spontaneously drives a toroidal current in the plasma. Three such alternatives are the stellarator, reversed-field pinch (RFP), and compact torus concepts. Magnetic-confinement fusion. Plasma Phys. The images or other third party material in this article are included in the articles Creative Commons license, unless indicated otherwise in a credit line to the material. The results suggest that a hydrogen-boron fuel mix has the potential to be used in utility-scale fusion power. This asymmetry enables the critic to infer the underlying state from measurements, deal with complex state-transition dynamics over different timescales and assess the influence of system measurement and action delays. The control policies are learned through interaction with a tokamak simulator and are shown to be directly capable of tokamak magnetic control on hardware, successfully bridging the sim-to-real gap. Fusion 47, S128S202 (2007). Cassirer, A. et al. 74, 42174220 (1995). These bent the plasma into a new shape that was concave at all points, avoiding the problem Teller had pointed out. Relative entropy regularized policy iteration. The net effect is to transport energy from the hot core to the wall. The plasma in a tokamak fusion reactor would have a major diameter in the range of 10 metres (33 feet) and a minor diameter of roughly 2 to 3 metres. This highlights the advantage of a general, learning-based control architecture to adapt control for previously unknown configurations. Ferron, J. R. et al. Carpanese, F. Development of Free-boundary Equilibrium and Transport Solvers for Simulation and Real-time Interpretation of Tokamak Experiments. You are using a browser version with limited support for CSS. In contrast, an unstable plasma would likely depart from its equilibrium state and rapidly (perhaps in less than one-thousandth of a second) escape the confining magnetic field following any small perturbation. B. Diffusion driven plasma currents and bootstrap tokamak. This stochastic policy is represented by a diagonal Gaussian distribution over coil actions. A snowflake divertor: a possible solution to the power exhaust problem for tokamaks. As can be seen in, for example, Extended Data Fig. Therefore we created a deployment system that compiles our neural network into real-time-capable code that is guaranteed to run within this time window. The amount of variation is set within ranges identified from experimental data as shown in Extended Data Table 2. It is necessary that these particle trajectories do not intersect the bounding wall. Magnetic confinement fusion: a brief review Chuanjun Huang & Laifeng Li Frontiers in Energy 12 , 305-313 ( 2018) Cite this article 824 Accesses 4 Citations Metrics Abstract Fusion energy is considered to be the ultimate energy source, which does not contribute to climate change compared with conventional fossil fuel. MathSciNet Nucl. 1, is a research tokamak at the Swiss Plasma Center, with a major radius of 0.88m and vessel height and width of 1.50m and 0.512m, respectively. Simultaneously, the thermal energy of all the particles exerts an expansive pressure force on the plasma. 50, 473489 (2006). Google Scholar. a, Elongation of 1.9 with vertical instability growth rate of 1.4kHz. Technol. MPT/1-4 (IAEA, 2014). This results in a very high fuel pressure, which inevitably causes the fuel to disassemble. Fusion 54, 124009 (2012). Nature 588, 7782 (2020). Plasma Phys. Austin, M. E. et al. Inertial confinement uses laser beams or ion beams to squeeze and heat the hydrogen plasma. Nonetheless, great investment would be required to develop feedforward coil-current programming, implement real-time estimators, tune controller gains and successfully take control after plasma creation. Gerki and DeTommasi45 propose a model predictive control approach, demonstrating linear model predictive control for plasma position and shape control in simulation, including a feasibility estimate for hardware deployment. Additionally, the network needs to perform this inference to sufficient numerical accuracy on the control system, which uses a different processor architecture from the hardware used for training. Since then the majority of effort in magnetic confinement has been based on the tokamak principle. We feed the inputs to a stack of a linear layer with 256 outputs. The controllers are designed on the basis of linearized model dynamics, and gain scheduling is required to track time-varying control targets. Plasma Phys. http://github.com/deepmind/dm_env (2019). & Tang, W. Predicting disruptive instabilities in controlled fusion plasmas through deep learning. 1c) and a much larger recurrent neural network in the critic. High performance experiments in JT-60U reversed shear discharges. Phys. B. et al. A beam of high-energy neutral atoms is injected into the plasma along the toroidal direction. c, Our control policy is an MLP with three hidden layers that takes measurements and control targets and outputs voltage commands. Technol. In the tokamak a current is periodically driven through the plasma itself, creating a field "around" the torus that combines with the toroidal field to produce a winding field in some ways similar to that in a modern stellarator, at least in that nuclei move from the inside to the outside of the device as they flow around it. The ITER magnet systems: progress on construction. FIP/2-1 (IAEA, 2014). B. et al. Electron cyclotron resonance heating and neutral beam injection35 systems provide external heating and current drive, as used in the experiment in Fig. [4] Electromagnetic waves can be injected and steered to manipulate the paths of plasma particles and then to produce the large electrical currents necessary to produce the magnetic fields to confine the plasma. d, Snowflake configuration with a time-varying control of the bottom X-point, where the target X-points aremarked in blue. Lawson, J. D. Some Criteria for a Useful Thermonuclear Reactor (Atomic Energy Research Establishment, 1955). First, for each objective, the difference between the actual and target values is computed, and then transformed with a non-linear function to a quality measure between 0 and 1. These data are sent to the replay buffer, which feeds data to the learner to update the policy. A lower hybrid current drive system for ITER. Preprint at https://arxiv.org/abs/1910.07113 (2019). Magnetic confinement fusion - Wikipedia and O.S. Dumont, R. J. et al. After this, the output is fed through a three-layer MLP using exponential linear unit non-linearity and 256 latents each. This gives a deterministic policy to execute on the plant. The development of magnetic fusion energy (MFE) came in three distinct phases. In the third phase, the control policy is bundled with the associated experiment control targets into an executable using a compiler tailored towards real-time control at 10kHz that minimizes dependencies and eliminates unnecessary computations. It operated at Princeton from 1982 to 1997 and made many contributions to the study of nuclear fusion. Not long after the construction of the earliest figure-8 machines, it was noticed the same effect could be achieved in a completely circular arrangement by adding a second set of helically-wound magnets on either side. A new look at density limits in tokamaks. Our architecture, depicted in Fig. Buckingham, R. & Loving, A. Remote-handling challenges in fusion research and beyond. In the single-plasma experiments, we vary the plasma resistivity Rp, as well as the profile parameters p and qA. Injecting frozen pellets of deuterium into the fuel mixture can cause enough turbulence to disrupt the islands.[2]. The control of tokamak configuration variable plasmas. This (stepwise) reward is then normalized so that the maximum cumulative reward is 100 for 1s of control. Nucl. Zohm, H. for the ASDEX Upgrade Team and the EUROfusion MST1 Team Recent ASDEX Upgrade research in support of ITER and DEMO. Mirrors have seen little development since that time. The ions must be held together in close proximity at high temperature with a confinement time long enough to avoid cooling. [16][17][18] The experiments will test the optimized concept of Wendelstein 7-X as a stellarator fusion device for potential use in a power plant. Fusion 26, 209215 (1984). The US Navy has also claimed a "Plasma Compression Fusion Device" capable of TW power levels in a 2018 US patent filing: "It is a feature of the present invention to provide a plasma compression fusion device that can produce power in the gigawatt to terawatt range (and higher), with input power in the kilowatt to megawatt range." This steady progress has resulted in the construction of ITER, a fusion device with a planned fusion power output of 500MW in pulses of 400s. ITER should provide answers to remaining important questions on the integration of physics and technology, through a full-size demonstration of a tenfold power multiplication, and on nuclear safety aspects. In 1997, scientists at the Joint European Torus (JET) facilities in the UK produced 16 megawatts of fusion power. Inspired by ITER project. Feedforward beta control in the KSTAR tokamak by deep reinforcement learning. Correspondence to It then manipulated the far X-point to approach the limiting X-point, ending with a separation of 6.6cm. 3b, the plasma position and current were maintained accurately, with an Ip RMSE of 2.6kA and shape RMSE of 1.4cm. Magnetic control of tokamak plasmas through deep reinforcement learning, https://doi.org/10.1038/s41586-021-04301-9. Therefore, the policy network is built as follows. A main direction of research is to study the effects of shaping the distribution of the plasma into different configurations3,4,5 to optimize the stability, confinement and energy exhaust, and, in particular, to inform the first burning-plasma experiment, ITER. Further considerations are required for deployment. The time-varying flux induces a toroidal electric field that drives the plasma current. Akkaya, I. et al. Rev. ISSN 1476-4687 (online) All of these devices have faced considerable problems being scaled up and in their approach toward the Lawson criterion. 87, 395402 (2012). You are using a browser version with limited support for CSS. Software available from https://www.tensorflow.org/ 2015. Extension of the ECRH operational space with O2 and X3 heating schemes to control tungsten accumulation in ASDEX Upgrade. Magnetic and inertial confinement are addressed. In a fusion reactor that uses magnetic confinement, strong magnets are used to control the plasma. It is a magnetic confinement reactor using the toroidal geometry of the tokamak, a device first developed in the USSR. Get the most important science stories of the day, free in your inbox. The plasma boundary is defined by the last closed-flux surface (LCFS) in the domain. The table of time-varying control targets is also compiled into the binary for ease of deployment. In 2018 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS) 12411246 (IEEE, 2018). [26], Kronos Fusion Energy has announced the development of an aneutronic fusion energy generator for clean and limitless power in national defense. J. Ongena. Initial development of the DIIID snowflake divertor control. Fusion 55, 124012 (2013). J. Nucl. Control. Descriptions of the targets used are listed in Extended Data Table 4. Fusion 54, 073018 (2014). UK Magnetic Fusion Research Programme This research area covers the UK Atomic Energy Agency (UKAEA) UK Magnetic Fusion Research Programme. Kotschenreuther, M. et al. Article Nucl. The plasma current would likely be on the order of tens of millions of amperes, and the flex density of the toroidal magnetic field would measure several teslas. In addition to the fuel loss problems, it was also calculated that a power-producing machine based on this system would be enormous, the better part of a thousand feet long. Warmer, F. System code analysis of helias fusion reactor and economic comparison to tokamaks. Our learning framework has the potential to shape future fusion research and tokamak development.