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Disruption mitigation | Final design review is a major step forward

The generations of physicists, engineers, technicians and other specialists who have worked in nuclear fusion share a common goal, dedication and responsibility: making nuclear fusion possible for the next generations. While grappling with unsolved issues can make a career in fusion feel a little bit like Ulysses' long and difficult journey in Homer's Odyssey, the large international team working on the disruption mitigation system for ITER has now completed a major milestone in its journey. During the final design review held in late March at ITER Headquarters under the chairmanship of George Sips (General Atomics, San Diego), no showstoppers were identified and the disruption mitigation system (DMS) for ITER has been greenlit to continue its path towards manufacturing, installation and operation. As part of the review, the teams working together on the design and physics of the disruption mitigation system and diagnostics port integration, along with many international collaborators, introduced to the review panel a subset of the system's complete technical documentation, amounting to over 30,000 pages of design descriptions, diagrams, engineering analyses, calculation reports, and prototype test reports. Over four days the full detailed design of the disruption mitigation system of ITER, comprising more than 100,000 components, was presented in person in the ITER Council Room and via video conference in 40 concise presentations by 33 presenters. More than 100 internal and external technical experts were invited to review the detailed design of this crucial ITER machine protection system. The disruption mitigation system will protect machine components against excessive heat loads and electromagnetic forces that result from plasma disruptions, which cause a sudden loss of stored thermal and magnetic energy. The disruption mitigation system will use shattered pellet injection to deliver massive amounts of protium and neon in the form of small ice fragments into the plasma to convert the energy into radiation. In 2017, a workshop with worldwide plasma disruption experts was held in the exact same room as the final design review. The verdict was clear: due to the complex nature of disruptions, significant gaps existed in the physics understanding which had to be addressed. One year later, in 2018, the ITER Science and Technology Advisory Committee concluded that plasma disruptions posed an existential threat to the ITER mission and that their mitigation was of the highest priority. The ITER Council instructed the ITER Organization to set up project teams to develop the required physics basis and to design an efficient disruption mitigation system for the project. To understand why the worldwide experts are worried about the fast accidental losses of plasma current and stored energy that occur during disruptions, one only has to keep in mind that the stored magnetic energy in ITER can reach about 1 GJ, and it would be released within a fraction of a second. This is equivalent to the kinetic energy of a 100-tonne railroad locomotive travelling at about 500 km/h as it impacts a massive wall. While most parts of the ITER machine like the vacuum vessel are designed to withstand any possible disruption event, it is still important to protect the components inside the machine from excessive electromagnetic loads. Although armoured with tungsten, which has the highest melting point of all known elements (3422 °C), the components facing the fusion plasma can be subject to melting from heat loads and the impact of so-called runaway electrons. If such damage were to occur, plasma operation would have to be halted for long periods of repair, moving ITER's goal of demonstrating the feasibility of fusion further into the future. To cope with these potentially damaging effects, an international scientific and engineering team has developed a sophisticated and robust mitigation method that can protect the ITER machine by reacting within milliseconds, similar to the way an airbag is deployed in a car. The ITER disruption mitigation system is based on shattered pellet injection. Wine-cork-sized hydrogen and neon pellets formed in what is called a cold cell assembly (see gallery below)—at the cryogenic temperature of -268 °C and in an ultra-high vacuum environment—are released by a specially developed electromagnetic valve opening within 1-2 milliseconds of the start of a disruption. The pellets are then accelerated to supersonic speeds (> 1800 km/h) and fly with an exceptionally accurate trajectory (with just 5 mm clearance between the pellet and the wall on either side) through a narrow flight channel over a distance of six metres. At the end of its path each pellet deliberately collides with an inclined surface and is shattered into thousands of small broken pellet fragments, which will enter the plasma and mitigate the disruption. By the time these pellet fragments arrived in the plasma, about 12 milliseconds will have passed since the system was activated which is about ten times shorter than a blink of an eye. For the last six years a large international effort—involving science and engineering teams under DMS Task Force Leader Michael Lehnen and Technology Group Leader Stefan Jachmich; the ITER disruption mitigation design team; disruption mitigation experiments and accompanying simulation efforts (read more here and here); and countless technical meetings (see reports here and here)—has built not only a solid knowledge basis in terms of physics and technology, but has led to the development of technologically advanced design solutions that work reliably in cramped space and in one of the most extreme environments on the planet. More hurdles remain ahead before the disruption mitigation system can demonstrate its capability to protect the ITER machine against the detrimental consequences of disruptions and ensure that ITER will reach its final goal. But judging from the challenges already overcome by the ITER and international teams we are confident that we will get there ... one step at a time.

Image of the week | Like grasping a bowl of cereal

Contrary to the vast majority of ITER machine components, the modules that form the central solenoid cannot be lifted by way of hooks and attachments. The 110-tonne cylindrical components provide no space for a robust structure for the bolting or welding of lift devices; instead, a central solenoid module needs to be handled like one would grasp a giant bowl of cereal, by exerting pressure from the outside. A bowl of cereal can be grasped and moved with two hands. A central solenoid module requires nine powerful wedge pads located at the bottom of a lifting fixture, each one exerting a radial force of 220 kN (equivalent to 22 tf (tonne-force)) on nine friction pads distributed around the cylinder. Designed and manufactured by US ITER, who procures the central solenoid, the system has once again proved its efficiency. On Thursday 11 April, the third module was successfully lifted and positioned with a slight radial offset on top of the existing two-module stack. The 325-millimetre offset provides room for equipment and connection work to be completed before the module gets positioned in its final location, aligned on the central solenoid axis.

Education | 13th ITER International School announced

The 13th ITER International School (IIS) will be held from 9 to 13 December in Nagoya hosted by National Institute for Fusion Science (NIFS), Japan. The subject of the 2024 school is 'Magnetic fusion diagnostics and data science,' with a scientific program coordinated by Profs. M. Yokoyama and K. Tanaka (National Institute for Fusion Science) and Drs. M. Kocan and S. McIntosh (ITER Organization). Diagnostics are key to the achievement of ITER fusion power demonstration goals and they require the application of a wide range of techniques. But diagnostics are not enough to ensure ITER's success; only through the advanced analysis of the data they provide will it be possible to guide the experiments towards their fusion power goals. It is timely to address these multidisciplinary areas during the 13th ITER International School. The ITER International School aims to prepare young scientists and engineers for working in the field of nuclear fusion and in research applications associated with the ITER Project. The adoption of a "school" format was a consequence of the need to prepare future scientists and engineers on a range of different subjects and to provide them with a wide overview of the interdisciplinary skills required by ITER. The first ITER School was organized in Aix-en-Provence, France, in July 2007 and focused on turbulent transport in fusion plasmas. Eleven successive schools have followed on a variety of subjects: magnetic confinement (Fukuoka, Japan, 2008); plasma-surface interactions (Aix-en-Provence, 2009); magneto-hydro-dynamics and plasma control (Austin, Texas, USA, 2010); energetic particles (Aix-en-Provence, 2011); radio-frequency heating (Ahmedabad, India, 2012); high-performance computing in fusion science (Aix-en-Provence, 2014); transport and pedestal physics in tokamaks (Hefei, China, 2016); physics of disruptions and control (Aix-en-Provence, 2017); the physics and technology of power flux handling (Daejeon, Korea, 2019); ITER plasma scenarios and control (San Diego, USA, 2022) and the impact and consequences of energetic particles on fusion plasmas (Aix-en-Provence, 2023). Browse through the presentations made at past schools here. Further information on the 2024 school is available https://iis2024.org/. Pre-registration begins in early May.

Open Doors Day | Having fun while discovering ITER

A public event on Saturday 13 April draws a big crowd. It was a beautiful, summer-like day on Saturday 13 April. Perfect for a journey into ITER. Nearly 800 members of the public, were welcomed on site by an all-volunteer roster of guides, timekeepers, hosts and hostesses, plasmagicians and specialists of all kinds. It's a regular occurance at ITER. Twice a year since 2011, in spring and autumn (with only one notable year excepted) the gates open to visitors of all ages who have been lucky enough to secure a spot. Curiousity in the region about ITER is understandably high—after all, the tallest buildings are visible to all who drive north to the French Alpes. Open Doors Days are one way to share ITER with the public; the ITER visits team also runs a program that welcomes individuals and small groups throughout the year. (Just over 25,000 people visited ITER in all last year; since 2007 the figure tops 200,000). For those who were not able to make it this time, another Open Doors Day event is planned in November 2024. See the gallery below for some of the scenes from the day. Or watch "Having fun while discovering ITER" on YouTube.

Fusion world | Increased awareness in a changing landscape

The world of fusion research is changing fast, and world leaders are taking notice. The large public projects that occupied centre stage for the past decades are now sharing it with an ever-growing number of private startups. The Fusion Industry Association reports that in about five years, private fusion entities have more than doubled in number to close to sixty overall, and total private investment in the fusion sector has surpassed USD 6 billion. Whereas public projects are largely oriented towards proving the scientific and industrial feasibility of fusion, private companies, by nature, are concerned with the economic viability of producing and eventually commercializing fusion energy. However, these two 'cultures' are not by any means opposed or contradictory—instead, they can form the basis of efficient synergies that will accelerate progress towards the common goal of harnessing fusion energy. World institutions and world leaders are increasingly aware of the multiplier effect that public-private collaboration could have. The International Atomic Energy Agency (IAEA) recently established the World Fusion Energy Group, an initiative to encourage cross-sector collaboration in the fusion industry. And in back-to-back announcements last week, world leaders from Japan, the United States and Europe also indicated their intention to promote the development of fusion through targeted support efforts including for public/private cooperation. On 10 April, Japanese Prime Minister Fumio Kishida and US President Joe Biden announced a joint partnership to accelerate the development and commercialization of nuclear fusion, including efforts to 'identify and support the development of resilient global supply chains that facilitate commercial fusion deployment, welcoming and considering discussions among fusion industry groups in the respective countries.' Andrew Holland, the head of the Fusion Industry Association praised the initiative, saying: 'Fusion is too important for needless competition: like-minded countries should work together towards the common goal.' And on 11 April during a visit to the Max Planck Institute for Plasma Physics in Garching, Germany, Ursula von der Leyen, president of the European Commission, insisted on the importance of promoting 'more public-private research partnerships' and encouraged industry to invest [...] even more in fusion technology.' Fostering ways to accelerate the development of public/private cooperation in fusion energy will also be the subject of two important workshops in the next weeks and months. The European Commission's Directorate-General for Energy is bringing together key fusion stakeholders in Strasbourg, France, on 23 April to discuss cooperation mechanisms between governments, laboratories and industry. And the ITER Organization—the global leader in multinational fusion collaboration—is hosting a key workshop in the context of this renewed landscape. On 27-29 May, ITER's Inaugural Private-Public Fusion Workshop will be attended by the representatives of approximately 50 fusion startups from around the world.

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FuseNet PhD Event

The annual PhD Event organized by the European Fusion Education Network, FuseNet, will take place this year at the University of Stuttgart, Germany, from 3 to 5 September.Meet and greet fellow fusion researchers from Europe and expand your network. The event will feature high-profile keynote speakers, a top-notch scientific program and the much anticipate PechaKucha contest, where students present their research in 20 slides, 20 seconds per slide. Registration is open through 15 June 2024. See more information at this address.

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Neutronics Workshop at ITER

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Nuclear Fusion / Washington And Tokyo Sign Agreement To Deepen Cooperation Towards Commercialisation

核融合の陣営強化

西物院一行访问核聚变中心交流近期工作进展

Europe delivers equipment for ITER's cold vacuum circuit

Adding to the energy mix: Fusion breakthroughs lead to new options

Japan and USA form strategic partnership for fusion

Von Der Leyen, Söder Speak at Max Planck Plasma Physics Institute

EU-Kommissionspräsidentin von der Leyen und Ministerpräsident Söder wollen Allianz für Kernfusion

EU Commission President von der Leyen and Minister President Söder want an alliance for nuclear fusion

US and Japan Partner to "Accelerate Fusion Energy Demonstration and Commercialization"

Erklärung von Präsidentin von der Leyen mit dem Bayerischen Ministerpräsidenten Söder beim Max-Planck-Institut für Plasmaphysik

Statement by President von der Leyen with Bavarian Minister-President Söder at the Max Planck Institute for Plasma Physics

Déclaration de la Présidente von der Leyen avec le Ministre-Président de Bavière Söder à l'Institut Max Planck de physique des plasmas

Von der Leyen, "Europa leader nella ricerca nella fusione nucleare"

PPPL's new tabletop stellarator uses off-the-shelf magnets

Joint Statement between DOE and the Japan Ministry of Education, Sports, Science and Technology Concerning a Strategic Partnership to Accelerate Fusion Energy Demonstration and Commercialization

[인터뷰]김웅채 핵융합연 연구부장 "한국의 인공태양 KSTAR, 1억도 플라즈마 300초 유지 목표로 도전"

핵융합 학습하는 인공지능, 인공지능으로 빨라지는 인공태양

DONES Programme collaboration takes shape

Deutsches Kernfusions-Start-up gewinnt weitere Investoren

UKAEA develops optical viewport technology for quantum applications

US and Japan announce joint partnership to accelerate nuclear fusion

Nuclear Fusion Is Not A Moonshot But An Attainable Goal