Device type | Stellarator |
---|---|
Location | Greifswald, Germany |
Affiliation | Max Planck Institute for Plasma Physics |
Technical specifications | |
Major radius | 5.5 m (18 ft) |
Minor radius | 0.53 m (1 ft 9 in) |
Plasma volume | 30 m3 |
Magnetic field | 3 T (30,000 G) |
Heating power | 14 MW |
Plasma temperature | (6–13)×107 K |
History | |
Year(s) of operation | 2015–present |
Preceded by | Wendelstein 7-AS |
Links | |
Website | https://www.ipp.mpg.de/w7x |
The Wendelstein 7-X (abbreviated W7-X) reactor is an experimental stellarator built in Greifswald, Germany, by the Max Planck Institute for Plasma Physics (IPP), and completed in October 2015. [1] [2] Its purpose is to advance stellarator technology: though this experimental reactor will not produce electricity, it is used to evaluate the main components of a future fusion power plant; it was developed based on the predecessor Wendelstein 7-AS experimental reactor.
As of 2023 [update] , the Wendelstein 7-X reactor is the world's largest stellarator device. [3] After two successful operation phases ending in October 2018, the reactor was taken offline for upgrades. [4] [5] The upgrade completed in 2022. New fusion experiments in February 2023 demonstrated longer confinement and increased power. [6] The goal of this phase is to gradually increase power and duration for up to 30 minutes of continuous plasma discharge, thus demonstrating an essential feature of a future fusion power plant: continuous operation. [7] [8]
The name of the project, referring to the mountain Wendelstein in Bavaria, was decided at the end of the 1950s, referencing the preceding project from Princeton University under the name Project Matterhorn. [9]
The research facility is an independent partner project of the Max-Planck Institute for Plasma Physics with the University of Greifswald.
The Wendelstein 7-X device is based on a five-field-period Helias configuration. It is mainly a toroid, consisting of 50 non-planar and 20 planar superconducting magnetic coils, 3.5 m high, which induce a magnetic field that prevents the plasma from colliding with the reactor walls. The 50 non-planar coils are used for adjusting the magnetic field. It aims for a plasma density of 3×1020 particles per cubic metre, and a plasma temperature of 60–130 megakelvins (MK). [1]
The W7-X is optimised along the quasi-isodynamic principle. [10]
The main components are the magnetic coils, cryostat, plasma vessel, divertor and heating systems. [11]
The coils (NbTi in aluminium [11] ) are arranged around a heat insulating cladding with a diameter of 16 metres, called the cryostat. A cooling device produces enough liquid helium to cool down the magnets and their enclosure (about 425 metric tons of "cold mass") to superconductivity temperature (4 K [12] ). The coils will carry 12.8 kA current and create a field of up to 3 teslas. [12]
The plasma vessel, built of 20 parts, is on the inside adjusted to the complex shape of the magnetic field. It has 254 ports (holes) for plasma heating and observation diagnostics. The whole plant is built of five nearly identical modules, which were assembled in the experiment hall. [11]
The heating system [13] includes high power gyrotrons for electron cyclotron resonance heating (ECRH), which will deliver up to 15 MW of heating to the plasma. [14] For operational phase 2 (OP-2), after completion of the full armor/water-cooling, up to 8 megawatts of neutral beam injection will also be available for 10 seconds. [15] An ion cyclotron resonance heating (ICRH) system will become available for physics operation in OP1.2. [16]
A system of sensors and probes based on a variety of complementary technologies will measure key properties of the plasma, including the profiles of the electron density and of the electron and ion temperature, as well as the profiles of important plasma impurities and of the radial electric field resulting from electron and ion particle transport. [17]
The German funding arrangement for the project was negotiated in 1994, establishing the Greifswald Branch Institute of the IPP in the north-eastern corner of the recently integrated East Germany. Its new building was completed in 2000. Construction of the stellarator was originally expected to reach completion in 2006. Assembly began in April 2005. Problems with the coils took about 3 years to fix. [11] The schedule slipped into late 2015. [11] [18] [19]
A three-laboratory American consortium (Princeton, Oak Ridge, and Los Alamos) became a partner in the project, paying €6.8 million of the eventual total cost of €1.06 billion. [20] In 2012, Princeton University and the Max Planck Society announced a new joint research center in plasma physics, [21] to include research on W7-X.
The end of the construction phase, which required more than 1 million assembly hours, [22] was officially marked by an inauguration ceremony on 20 May 2014. [23] After a period of vessel leak-checking, beginning in the summer of 2014, the cryostat was evacuated, and magnet testing was completed in July 2015. [12]
Operational phase 1 (OP1.1) began 10 December 2015. [24] On that day the reactor successfully produced helium plasma (with temperatures of about 1 MK) for about 0.1 s. For this initial test with about 1 mg of helium gas injected into the evacuated plasma vessel, microwave heating was applied for a short 1.3 MW pulse. [25]
The aim for the OP 1.1 was to conduct integrated testing of the most important systems as quickly as possible and to gain first experience with the physics of the machine. [24] [26]
More than 300 discharges with helium were done in December and January with gradually increasing temperatures finally reaching six million degrees Celsius, to clean the vacuum vessel walls and test the plasma diagnostic systems. Then, on 3 February 2016, production of the first hydrogen plasma initiated the science program. The highest temperature plasmas were produced by four-megawatt microwave heater pulses lasting one second; plasma electron temperatures reached 100 MK, while ion temperatures reached 10 MK. More than 2,000 pulses were conducted before shutdown. [27]
Five poloidal graphite limiters served as the main plasma-facing components during this first campaign (instead of the divertor modules). Experimental observations confirmed 3D modeling predictions that showed heat and particle flux deposition patterns on the limiters in clear correlation with the lengths of the open magnetic field lines in the plasma boundary. [28] [29]
Such tests were planned to continue for about a month, followed by a scheduled shut-down to open the vacuum vessel and line it with protective carbon tiles and install a "divertor" for removing impurities and heat from the plasma. The science program continued while gradually increasing discharge power and duration. [30] The special magnetic field topology was confirmed in 2016. [31] [32]
Operational phase 1 (OP1.1) concluded 10 March 2016 [24] [33] and an upgrade phase began.
Operational phase 1 continued (OP1.2) in 2017 [34] to test the (uncooled) divertor. [35] [24] [36]
In June 2018 a record ion temperature of about 40 million degrees, a density of 0.8 × 1020 particles/m3, and a confinement time of 0.2 second yielded a record fusion product of 6 × 1026 degree-seconds per cubic metre. [37]
During the last experiments of 2018, the density reached 2 × 1020 particles/m3 at a temperature of 20 million degrees. With good plasma values, long-lasting plasmas with long discharge times of 100 seconds were obtained. Energy content exceeded 1 megajoule. [38] [39] [40] [41]
In 2021 an analysis of X-ray imaging crystal spectrometer data collected in the 2018 experiment substantially reduced troubling neoclassical transport heat loss. Collisions between heated particles cause some to escape the magnetic field. This was due to magnetic field cage optimization that was essential in achieving the record results. [42] [43]
Date | Event |
---|---|
1980 | Planning initiated [44] [45] |
1994 | Project initiated |
2005 | Assembly began |
2014 | Inaugurated |
December 2015 | Begin operational phase OP1.1 |
2015 | Successful helium plasma test at 1 MK for ~0.1 s |
2016 | Hydrogen plasma at 80 MK for 0.25 s |
March 2016 | End OP1.1, begin upgrade phase [24] [46] |
June 2017 | Begin operational phase OP1.2 |
June 2018 | Fusion triple product of 6 × 1026 degree-second/m3 [47] |
November 2018 | End OP1.2, begin upgrade phase |
August 2022 [48] | Final assembly step with water-coolers finished |
February 2023 [6] | Start of OP2, demonstrated steady-state operation at higher power levels |
Financial support for the project is about 80% from Germany and about 20% from the European Union. 90% of German funding comes from the federal government and 10% from the state government of Mecklenburg-Vorpommern. The total investment for the stellarator itself over 1997–2014 amounted to €370 million, while the total cost for the IPP site in Greifswald including investment plus operating costs (personnel and material resources) amounted to €1.06 billion for that 18-year period. This exceeded the original budget estimate, mainly because the initial development phase was longer than expected, doubling the personnel costs. [49]
In July 2011, the President of the Max Planck Society, Peter Gruss, announced that the United States would contribute $7.5 million under the program "Innovative Approaches to Fusion" of the United States Department of Energy. [50]
A stellarator confines plasma using external magnets. Scientists aim to use stellarators to generate fusion power. It is one of many types of magnetic confinement fusion devices, most commonly tokamak. The name "stellarator" refers to stars because fusion mostly occurs in stars such as the Sun. It is one of the earliest human-designed fusion power devices.
Princeton Plasma Physics Laboratory (PPPL) is a United States Department of Energy national laboratory for plasma physics and nuclear fusion science. Its primary mission is research into and development of fusion as an energy source. It is known for the development of the stellarator and tokamak designs, along with numerous fundamental advances in plasma physics and the exploration of many other plasma confinement concepts.
Fusion power is a proposed form of power generation that would generate electricity by using heat from nuclear fusion reactions. In a fusion process, two lighter atomic nuclei combine to form a heavier nucleus, while releasing energy. Devices designed to harness this energy are known as fusion reactors. Research into fusion reactors began in the 1940s, but as of 2024, no device has reached net power, although net positive reactions have been achieved.
This timeline of nuclear fusion is an incomplete chronological summary of significant events in the study and use of nuclear fusion.
The Max Planck Institute for Plasma Physics is a physics institute investigating the physical foundations of a fusion power plant. The IPP is an institute of the Max Planck Society, part of the European Atomic Energy Community, and an associated member of the Helmholtz Association.
The Large Helical Device (LHD) is a fusion research device located in Toki, Gifu, Japan. It is operated by the National Institute for Fusion Science, and is the world's second-largest superconducting stellarator, after Wendelstein 7-X. The LHD employs a heliotron magnetic field originally developed in Japan.
Magnetic confinement fusion (MCF) is an approach to generate thermonuclear fusion power that uses magnetic fields to confine fusion fuel in the form of a plasma. Magnetic confinement is one of two major branches of controlled fusion research, along with inertial confinement fusion.
ASDEX Upgrade is a divertor tokamak at the Max-Planck-Institut für Plasmaphysik, Garching that went into operation in 1991. At present, it is Germany's second largest fusion experiment after stellarator Wendelstein 7-X.
The Helically Symmetric Experiment, is an experimental plasma confinement device at the University of Wisconsin–Madison, with design principles that are intended to be incorporated into a fusion reactor. The HSX is a modular coil stellarator which is a toroid-shaped pressure vessel with external electromagnets which generate a magnetic field for the purpose of containing a plasma. It began operation in 1999.
In nuclear fusion power research, the plasma-facing material (PFM) is any material used to construct the plasma-facing components (PFC), those components exposed to the plasma within which nuclear fusion occurs, and particularly the material used for the lining the first wall or divertor region of the reactor vessel.
In magnetic confinement fusion, a divertor is a magnetic field configuration which diverts the heat and particles escaped from the magnetically confined plasma to dedicated plasma-facing components, thus spatially separating the region plasma-surface interactions from the confined core. This requires establishing a separatrix-bounded magnetic configuration, typically achieved by creating poloidal field nulls (X-points) using external coils.
The Hybrid Illinois Device for Research and Applications (HIDRA) is a medium-sized toroidal magnetic fusion device housed in the Nuclear Radiation Laboratory and operated by the Center for Plasma-Material Interactions (CPMI) within the Department of Nuclear, Plasma and Radiological Engineering at the University of Illinois at Urbana–Champaign, United States. HIDRA had its first plasma at the end of April 2016 and started experimental campaigns by December of that year. HIDRA is the former WEGA classical stellarator that was operated at the Max Planck Institute for Plasma Physics in Greifswald Germany from 2001 to 2013.
TJ-II is a flexible Heliac installed at Spain's National Fusion Laboratory.
The Compact Toroidal Hybrid (CTH) is an experimental device at Auburn University that uses magnetic fields to confine high-temperature plasmas. CTH is a torsatron type of stellarator with an external, continuously wound helical coil that generates the bulk of the magnetic field for containing a plasma.
Jürgen Nührenberg is a German plasma physicist.
Friedrich E. Wagner is a German physicist and emeritus professor who specializes in plasma physics. He was known to have discovered the high-confinement mode of magnetic confinement in fusion plasmas while working at the ASDEX tokamak in 1982. For this discovery and his subsequent contributions to fusion research, was awarded the John Dawson Award in 1987, the Hannes Alfvén Prize in 2007 and the Stern–Gerlach Medal in 2009.
Wendelstein 7-AS was an experimental stellarator which was in operation from 1988 to 2002 by the Max Planck Institute for Plasma Physics (IPP) in Garching. It was the first of a new class of advanced stellarators with modular coils, designed with the goal of developing a nuclear fusion reactor to generate electricity.
Omnigeneity is a property of a magnetic field inside a magnetic confinement fusion reactor. Such a magnetic field is called omnigenous if the path a single particle takes does not drift radially inwards or outwards on average. A particle is then confined to stay on a flux surface. All tokamaks are exactly omnigenous by virtue of their axisymmetry, and conversely an unoptimized stellarator is generally not omnigenous.
Per Helander is a Swedish theoretical plasma physicist and a leading scientist in the world in stellarator physics. He is the head of Stellarator Theory Division at the Max Planck Institute for Plasma Physics.