Fusion Energy Development Research Articles

Obtaining frequency-time diagram from perturbation signal-time diagram

Abstract In the field of nuclear fusion energy development, magnetic confinement tokamak reactors, which use strong magnetic fields to confine high-temperature plasmas, are crucial for sustainable and clean fusion energy. Disruption caused by plasma instability can terminate the fusion reaction and even cause irreparable damage to the equipment. Therefore, a thorough understanding of the underlying physical mechanisms is essential for predicting and preventing plasma disruption. The recently proposed analytical theory of plasma disruption may predict and prevent plasma disruption, but its validation requires the frequency-time signals. The Heavy Ion Beam Probe (HIBP) can provide such signals, however, because its scarcity in the world, particularly in China, it is necessary to develop more suitable methods. Here we show a new approach that employs Fast Fourier Transform (FFT) on magnetic perturbation signals to obtain frequency-time diagrams. We successfully applied this algorithm to acquire the frequency-time diagram of the J-TEXT-1054560 discharge. This new method offers an effective tool for validating the plasma disruption theory, overcoming the limitations of traditional techniques and providing a crucial methodological basis for understanding and predicting plasma disruption. This new analytical approach will accelerate the advancement of fusion technology.

The Spherical Tokamak for Energy Production (STEP) in context: UK public sector approach to fusion energy.

The UK's fusion energy approach has developed over the past 5 years to include government policy initiatives and a range of public sector investments designed to be delivered in partnership with the private sector. These have aimed to create an environment that stimulates innovation and investment to deliver economic as well as scientific and environmental benefits throughout the lifetime of the public sector fusion energy programme. The Spherical Tokamak for Energy Production acts as a focus and anchor for both public and private sector efforts to develop fusion energy, developing the supply chain and potential for Intellectual Property development and export opportunities well ahead of the anticipated STEP completion date of 2040. This is maximized by the UK's approach to a holistic research and innovation programme backed up by a regulatory and skills programme. This article is part of the theme issue 'Delivering Fusion Energy - The Spherical Tokamak for Energy Production (STEP)'.

Needed computations and computational capabilities for stellarators

Stellarator plasmas are externally controlled to a degree unparalleled by any other fusion concept, magnetic or inertial. This control is largely through the magnetic fields produced by external coils. The development of fusion energy could be expedited by carrying out remarkably straight-forward computations to define strategies for exploiting this external control. In addition to these computations, which have a reliability limited only by competence, certain physics areas that affect the development of stellarator power plants should have a more intense study. The low cost and speed with which computations can be carried out relative to experiments have implications for the development of fusion. Computations should be used to develop a strategy that to the extent possible allows major issues to be circumvented. Required computations for this strategy are the subject of this paper.

Benefits of the Super-X divertor configuration for scenario integration on MAST Upgrade

The integration of good core and edge/pedestal confinement with strong dissipation of heat and particles in the divertors is a significant challenge for the development of fusion energy. Alternative divertor configurations offer potential advantages by broadening the operational space where a device can operate with detached divertors and acceptable power exhaust. First results from MAST Upgrade are presented from high confinement mode experiments with outer divertors in the Super-X divertor configuration, showing that the outer divertors naturally detach when the Super-X is formed with no discernible impact on the plasma core and pedestal. These initial findings confirm predicted benefits of the Super-X configuration in terms of facilitating scenario integration.

Experimental investigation on heat transfer characteristics of a novel hypervapotron channel for divertor target in nuclear fusion reactors

In the further development of nuclear fusion energy, managing the high heat flux on a divertor target remains a significant issue. To address this, the development of innovative cooling channels capable of efficiently managing high heat loads is essential. Among various cooling techniques, the hypervapotron (HV) method stands out for its exceptional heat transfer capabilities. This study undertakes an in-depth analysis of a novel HV cooling channel, evaluating its heat transfer performance via an electron beam high heat flux testing system. The focus was on subcooled flow boiling, observing that the novel HV channel displayed varied flow patterns with increasing heat flux. Additionally, a comparative investigation was conducted to assess the heat transfer efficiency of this novel HV channel against traditional ITER-like HV channel and smooth channel. The analysis incorporated various system parameters, such as mass flow rate and system pressure, to understand their effects on heat transfer. To effectively predict the heat transfer performance of the novel HV channel, efforts have been made to evaluate existing and develop new heat transfer correlations for the channel. Furthermore, Artificial Neural Networks (ANNs) have also been utilized as a crucial approach in this predictive endeavor. The outcomes of this study hold significant implications for understanding and optimizing the design of cooling channels for divertor target in nuclear fusion reactors.

The spherical tokamak path to fusion power: Opportunities and challenges for development via public–private partnerships

In this article, we aim to show that the spherical tokamak (ST) device with high temperature superconducting (HTS) magnets could offer the quickest and lowest risk path to develop commercial fusion energy, which may be significantly advanced by the use of private–public partnerships. Our starting point is based on what we have learned and will continue to learn from publicly funded research on STs. Keeping prototype ST devices and HTS magnets small has enabled rapid innovation toward a commercial goal. Our ST40 compact, high field ST has proven exceptional performance, with plasma ion temperatures over 100 × 106 °C (above 8 keV) and a record triple product for any private company (n T τE ∼ 1019 keV s/m3). Meanwhile, our robust, compact, quench-safe, HTS magnets can routinely achieve over 24 T. We now have results of great interest to fusion scientists, so as well as pursuing our commercial goals, we are contributing to scientific progress in fusion. Opportunities to participate in public–private partnerships are emerging with Tokamak Energy already selected for the U.S. Department of Energy milestone program and well-positioned to participate in the U.K. Government Spherical Tokamak for Energy Production program. Other countries are likely to adopt similar approaches as the need for rapid development of fusion energy becomes ever more apparent.

Nuclear fusion losing the race with global warming

According to plans for development of fusion energy, the first stage is construction of device tokamak ITER [1] with main task of establishing burning gas plasma with required stability and duration. This stage should be accomplished by 2035, starting in 2005. The next stage should be the construction of complex DEMO [2] with the task of producing all the equipment for energy production and finally producing large amounts of carbon free energy. We do not want to make predictions on the outcome of fusion program, wishing the final success to the thousands of scientists and engineers who are contributing to this heroic effort. However, there are reasons to think (Seife [18], Stork[7]) that the time is too short. Starting with a planned date of end of work with ITER by 2035, we estimate that one needs to add 25 years for development of DEMO. By 2060 it would be too late to initiate actions to stop global warming. In the present situation we propose the intervention use of nuclear fission energy. New nuclear fission energy of PWR type could be available not later than 2034, some 25 years before expected fusion energy device could start. Our proposal could be of dramatic importance depending on the evolution of global warming.

High-temperature interaction of water vapor with lithium ceramics Li2TiO3

Selection of materials for fusion reactors and, in particular, for blanket systems is one of the most important tasks that determine the development of fusion energy. Lithium ceramics Li2TiO3 is considered as prospective candidate for solid breeders of future fusion reactors' blankets. The paper presents the results of high-temperature tests of Li2TiO3 + 5 mol% TiO2 ceramics, performed under conditions of blowing with argon containing impurities of water vapor of different isotopic compositions (H2O, HDO, D2O) in the range of temperature from 100 °C to 1400 °C. The vapor–gas mixture for the experiment was prepared in a special mixing tank. The interaction of Li2TiO3 + 5 mol% TiO2 ceramics with chemically active gases and water vapors was investigated by thermogravimetry (TG), differential scanning calorimetry (DSC) and mass spectrometry (MS) methods. As a result of experiment, the dependences of the sample mass change during heating under single purge gas composition was obtained. Mass spectra that characterize the changes in the qualitative composition of the gas mixture in the reaction chamber with the investigated sample were recorded and subsequently analyzed. An isotope effect is observed during the experiment: the release of D2 gas begins significantly earlier than the release of HD gas. The observed effect appears only in the high-temperature region (above 1050 °C), which characterizes the investigated material as almost completely chemically neutral towards water vapor.

Thermal-assisted resistive sensor based on the PdCr alloy thin film for sensitive detection of hydrogen isotopes in helium atmosphere

The detection of hydrogen isotopes is not only the premise of ensuring safety of hydrogen energy, but also has very important application value and scientific significance in the field of fusion energy. Therefore, it is imperative to develop efficient and reliable hydrogen isotope sensors. Herein, a thermal-assisted resistive sensor is constructed based on the hydrogen isotope effect of PdCr alloy thin film for sensitive detection of hydrogen isotopes in helium atmosphere. The permeation of hydrogen isotopes in palladium lattice is facilitated through thermal effect to improve the dynamic response capability of sensor. The research results show that the response time of sensor to hydrogen and deuterium is reduced from 192 s to 113 s–17 s and 10 s respectively. However, the sensitivity deteriorated by about 40% at 110 °C compared with room temperature. Meanwhile, the PdCr alloy thin film resistive sensor represents a remarkable linear response in a range of 0.1%–4% hydrogen and deuterium, with correlation coefficients of 0.9971 and 0.9998 respectively. And the response difference of hydrogen and deuterium may be utilized to discriminate hydrogen isotopes. Furthermore, the sensor exhibits prominent selectivity, extraordinary working stability and a wide range of 100ppm-100%. Therefore, this work presents a feasible approach to design high-performance resistive hydrogen isotope sensors for the development of hydrogen energy and fusion energy.

Long plasma duration operation analyses with an international multi-machine (tokamaks and stellarators) database

Combined high-fusion performance and long-pulse operation is one of the key integration challenges for fusion energy development in magnetic devices. Addressing these challenges requires an integrated vision of physics and engineering aspects with the purpose of simultaneously increasing time duration and fusion performance. Significant progress has been made in tokamaks and stellarators, including very recent achievement in duration and/or performance. This progress is reviewed by analyzing the experimental data (109 plasma pulses with a total of 3200 data points, i.e. on average 29 data per pulse) provided by ten tokamaks (in alphabetical order: Axially Symmetric Divertor Experiment Upgrade, DIII-D, Experimental Advanced Superconducting Tokamak, Joint European Torus, JT-60 Upgrade, Korea Superconducting Tokamak Advanced Research, tokamak à configuration variable, Tokamak Fusion Test Reactor, Tore Supra, W Environment in Steady-State Tokamak) and two stellarators (Large Helical Device and Wendelstein 7-X) expanding the pioneering work of Kikuchi (Kikuchi M. and Azumi M. 2015 Frontiers in Fusion Research II: Introduction to Modern Tokamak Physics (Springer)). Data have been gathered up to January 2022 and coordination has been provided by the recently created International Energy Agency-International Atomic Energy Agency international Coordination on International Challenges on Long duration OPeration group. By exploiting the multi-machine international database, recent progress in terms of injected energies (e.g. 1730 MJ in L-mode, 425 MJ in H-mode), durations (1056 s in L-mode, 101 s in H-mode), injected powers, and sustained performance will be reviewed. Progress has been made to sustain long-pulse operation in tokamaks and stellarators with superconducting coils, actively cooled components, and/or with metallic walls. The graph of the fusion triple products as a function of duration shows a dramatic reduction of, at least two orders of magnitude when increasing the plasma duration from less than 1 s to 100 s. Indeed, long-pulse operation is usually reached in dominant electron-heating modes at reduced density (current drive optimization) but with low ion temperatures ranging from 1 to 3 keV for discharges above 100 s. Difficulties in extending the duration may arise from coupling high heating powers over long durations and the evolving plasma-wall interaction towards an unstable operational domain. Possible causes limiting the duration and critical issues to be addressed prior to ITER operation and DEMO design are reported and analyzed.

Progress, challenge, and perspective of the development of magnetic confinement fusion energy

Progress, challenge, and perspective of the development of magnetic confinement fusion energy

Back to the future: Revisiting the perspectives on nuclear fusion and juxtaposition to existing energy sources

This article reviews and launches perspectives on the progress of nuclear fusion research and development. To this end, the current state of nuclear fusion technology, the recent breakthroughs in nuclear fusion research occurred in the US, Japan, and China, the role of private companies and investments in nuclear fusion research and development are investigated for both advanced and emerging economies. The survey draws upon academic sources and media contributions from experts in the field of nuclear fusion. While nuclear fusion has reached the break-even point in the generation of nuclear fusion electricity, there are still serious challenges that will obviate the market alignment of nuclear fusion energy until the early 2030s – and more realistically the mid-2050s. Nonetheless, never in history, the level of public support and private engagement for nuclear fusion energy research and development has been as high as now. Furthermore, the study shows that there is a steadily increasing accumulation of scholarly knowledge on nuclear fusion and a broad consensus among the leading experts that nuclear fusion is the “holy grail” of the transition toward a post-resource, and hence, fully circular energy system.

The academic research ecosystem required to support the development of fusion energy

The advent of a fusion energy industry is being strongly supported by academics and universities, with the majority of fusion companies launching out of universities. Universities also play critical roles in technical innovation, workforce development, and independent arbiters of science and technology. The ability of the US academic landscape to support and grow the fusion energy sector is analyzed via a numerical distribution of full time faculty engaged in fusion and plasma. This data is compared to university support in two existing technology-driven industries: nuclear and aeronautics. This comparison clearly shows that the university system requires not only significant absolute growth but also a wider distribution of faculty at universities and across the required disciplines.

Steady-state burning plasma: a new stage in the development of magnetic confinement fusion energy.

Over the past 20 years, advances in tokamak physics and technology have prepared the field of magnetic confinement fusion research for the next step toward a steady-state burning plasma.

Plasma Confinement in the L-2M Stellarator at High Microwave Heating Powers

The results of experiments on high-temperature plasma confinement in a quasi-stationary fusion facility are presented. The results were obtained on the L-2M stellarator in which superposition of magnetic fields with three-dimensional spatial symmetry is created with the help of external windings. The plasma was created and heated using microwave pulses with a record specific power of 2 to 4 MW/m3. Under these conditions, spontaneous transition processes were observed in a plasma stable with respect to large-scale instabilities, leading to an abrupt increase in energy. High thermal loads on the wall of the vacuum chamber are observed in the area of the helical separatrix, which leads to an increase in the penetration of impurities into the plasma. Plasma energy and confinement time correspond to L-2M single-machine scaling at lower powers while at specific powers above 3 MW/m3, confinement time decreases due to the accumulation of impurities. The research results can be used to develop fusion energy facilities or to simulate astrophysical phenomena.

Kyoto Fusioneering’s Mission to Accelerate Fusion Energy: Technologies, Challenges and Role in Industrialisation

Making fusion power viable both technologically and commercially has been a challenge for decades due to the great complexity of the science and engineering challenges. In recent years, changes in both government policies and the emergence of private fusion companies have ushered a newfound push to accelerate fusion energy development. Kyoto Fusioneering (KF) is a privately funded fusion engineering start-up, founded to accelerate the development of high performance, commercially viable technologies that will be required for a fusion power plant, specifically those associated with heating and current drive systems, power generation, and the tritium fuel cycle. The company is focused on supporting the rapid expansion of the budding fusion industry. This paper provides a high-level description of some of the technical and industrial challenges it is tackling in developing a commercial fusion reactor, in particular in relation to: plasma heating with gyrotrons, tritium handling and breeding, energy conversion, and fusion materials. It provides an overview of KF's activities in finding solutions to challenges in each of these areas, including via its new testing facility now under construction, UNITY (Unique Integrated Testing Facility). KF’s core capabilities and areas of R&D focus are discussed, with reference to how they benefit the development of a new fusion industry as a whole and bring the technology closer to industrialisation, including via UNITY and through collaboration with external partners. The importance of industrialisation and subsequently commercialisation is also discussed, through KF’s assessment of the newly emerging fusion ecosystem, and where KF as a company sits within it.

Suspending failure: temporalities, ontologies, and gigantism in fusion energy development

AbstractTracing the history of terrestrial fusion energy to a giant multinational experimental fusion facility under construction reveals a series of consequential failures, re‐evaluations of once defunct designs, but also persistence. To account for how this vast enterprise, dogged by failure, endures, I suggest that different ontological narratives re‐orientate the enterprise both temporally and vis‐à‐vis different forms and valences of failure. Thus the rhetoric of mission‐driven project vies with that of open‐ended, present‐focused experiment: the former is positioned as the crucial solution to the threat of climate change; the latter ‘bakes in’ virtuous failure as integral to creative practice. Visionary promise moves to a focus on the meanwhile. Finally, the sheer unfurling size to which attention is constantly drawn offers a disorientating spectacle, denying perspective or closure and acting to suspend judgements of failure.

Effective current drive in the pedestal region of high-confinement tokamak plasma using electron cyclotron waves

Large-amplitude edge-localized modes (ELMs) are a major concern in the development of tokamak fusion energy. According to the peeling–ballooning theoretical model, effective current drive in the pedestal region of high-confinement (H-mode) tokamak plasmas can alter the current profile in this region and hence affect ELM instabilities. Using ray-tracing and Fokker–Planck quasilinear codes, effective and localized current drive by electron cyclotron (EC) waves in the H-mode pedestal region is studied in this paper. Numerical investigations are performed under present-day medium-sized tokamaks with an aspect ratio (A = R/a) covering a typical range of [2.7, 4.0]. Localized non-inductive current can be generated effectively by the Ohkawa mechanism of EC waves in the low-electron collisionality H-mode pedestal region. The Ohkawa mechanism-dominated current drive (OKCD) is much more effective than traditional electron cyclotron current drive (ECCD), which is the Fisch–Boozer mechanism-dominated one. Under 1–2 MW EC power, the current density of both co-OKCD and counter-OKCD has the same magnitude as edge bootstrap current density, which is calculated using the Sauter model. However, edge ECCD is much smaller than the bootstrap current. Consequently, the use of edge ECCD to control ELM failed in experiments, and only the EC heating can affect ELM behavior. Simulations on OKCD are performed in the H-mode pedestal region of realistic DIII-D tokamak plasma, and the results also support the above conclusions. The dependence of effective edge OKCD on the ratio of magnetic field and EC frequency is also found in tokamaks with a typical aspect ratio range. This work opens up a new possible field for active control of ELMs (triggering or suppressing an ELM) by edge current drive in present-day medium-sized tokamaks.

Nuclear Fusion Diffusion: Theory, Policy, Practice, and Politics Perspectives

Fusion energy has the potential to address long-term energy requirements and climate change. However, fusion energy is characterized by a “development divide” between the International Thermonuclear Experimental Reactor (ITER) consortium members and the non-ITER “Global South” states. It is beset with problems, which can be divided into geopolitical, geo-economic, geo-sociocultural, and geo-technological (GEO-PEST). Geopolitical problems include cooperation on fusion energy development between ITER members (of the Global North) and the Global South on fusion development. Geo-economic problems include the cost of funding ITER versus newly emerging private-sector fusion companies. Geo-sociocultural problems include the requirement to maintain the peacebuilding tradition of nuclear energy (embodied by the Cold War-era “Atoms for Peace” initiative), as well as public perceptions of radiation. Geo-technological problems include tokamak lock-in, fuel type, the viability of “compact reactors,” and disruptive technology events. In this article, we outline these problems and discuss how to address them in a timely fashion via an external independent review mechanism, modeled on the International Energy Agency's “Global Commission for Urgent Action on Energy Efficiency,” established in 2019 and due to deliver recommendations in 2020.

Start of experiments in the design configuration of the GOL-NB multiple-mirror trap

A multiple-mirror confinement is an alternative concept in fusion energy development that improves the particle and energy confinement times in open traps (linear magnetic systems). The paper discusses the development progress of the GOL-NB multiple-mirror experiment that was recently commissioned at BINP. The reference description of the GOL-NB hardware is presented. Properties of a low-temperature start plasma are discussed. The first results from test experiments with injection of one 25 keV neutral beam are shown. Methods of plasma stabilization in the non-min-B configuration are discussed. In general, the ongoing commissioning progress and results of the preliminary experiments are modestly optimistic for the expected device performance.