Of Interest archive

For hydrogen atoms to fuse into helium, the heat of the ultrahot plasma in the tokamak must be maintained. But, like boiling water, plasma has blobs (or bubbles) that percolate within the plasma edge, reducing the performance of the plasma by taking away heat that sustains the fusion reactions.

Now, scientists at the Princeton Plasma Physics Laboratory (PPPL) in the US have completed new simulations that could provide insight into how blobs at the plasma edge behave. The simulations, produced by a code called XGC1 developed by a national team based at PPPL, performed kinetic simulations of two different regions of the plasma edge simultaneously. This ability produces a more fundamental and fuller picture of how heat moves from plasma to the walls, potentially causing damage.

Blobs play an important role in the outward movement of particles in plasma. Blobs cause approximately 50 percent of the particle loss at the plasma edge, and researchers have observed blobs in a wide range of plasma devices, including tokamaks, figure-eight-shaped fusion devices known as stellarators, and linear machines. "The big picture is that blobs can pull energy and particles out of the plasma, and you don't want that," said PPPL physicist Michael Churchill, lead author of a paper describing the results in the journal Plasma Physics and Controlled Fusion. Churchill said. "You want to keep things confined."

Read more on the PPPL website.

-- Physicist Michael Churchill

Researchers led by the Princeton Plasma Physics Laboratory (PPPL) have proposed an innovative design to improve the ability of future fusion power plants to generate safe, clean and abundant energy in a steady state, or constant, manner. The design uses loops of liquid lithium to clean and recycle the tritium, the radioactive hydrogen isotope that fuels fusion reactions, and to protect the divertor plates from intense exhaust heat from the tokamak that contains the reactions.

"There are many challenges to developing fusion energy and the handling of heat on divertor plates is among them," said PPPL physicist Masa Ono, lead author of a paper about the design published in the journal Nuclear Fusion. "We wanted to see how we can protect the divertor plates and keep the fusion chamber clean."

The system that Ono and colleagues designed calls for pumping liquid lithium in and out of a tokamak, a type of magnetic fusion device, to maintain steady state operation while cleaning out dust and other impurities from the plasma and safeguarding the divertor. The lithium, a silvery metal that readily combines with other elements, would serve a number of functions, including protecting the divertor plates, capturing tritium for recycling, and removing dust and other unwanted elements.

Continue reading on the PPPL website.

-- Physicist Masa Ono of the Princeton Plasma Physics Laboratory.

According to the United States Energy Information Administration, the amount of energy supplied by all fuel sources across the world is tremendous: 155,481 teraWatt-hours as of 2014, the latest year on record.

In order to meet this enormous energy demand in a given year, we need to burn 24 billions tonnes of coal, or 12 billion tonnes of oil, or a bit less of natural gas (10.4 billion tonnes).That's for fossil fuels.

If we were to use only conventional nuclear energy to power the world, we would need to consume approximately 7,000 tonnes of nuclear fuel (enriched uranium or mixed oxyde).

However with nuclear fusion, only 867 tonnes of hydrogen would suffice...

Forbes magazine has a detailed article on this topic here.

The WEST project is based on an upgrade of the Tore Supra tokamak, in operation since 1988 in France (CEA- IRFM).

With its new tungsten divertor WEST has become a test bed for ITER, capable of testing ITER high heat flux component technologies in relevant plasma conditions. 

Following the commissioning of its sub-systems, WEST has had a short shutdown period during which the ICRH antenna was installed and other machine optimization activities carried out. Plasma experiments should resume in October.

See the latest news in WEST's October newsletter.

The European Domestic Agency has successfully tested prototypes of a specific type of magnetic diagnostic sensor at the Belgian SCK-CEN and the Czech REZ laboratories.

The diagnostic sensor prototypes, based on Low-Temperature Co-fired Ceramic (LTCC) technology, responded well to neutron exposure. Data collected throughout the experimentation will help engineers optimize the sensors' final design.

The diagnostic LTCC sensors measure the magnetic field around the plasma core and yield vital information regarding its position and shape. Of the more than 1,500 magnetic field sensors of various different types required on ITER, the LTCC-based sensors will be most exposed to neutrons.

The prototypes were manufactured by EPFL (Switzerland), Via Electronic (Germany) and VTT (Finland).

Read the full story on the European Domestic Agency website.

It was against the backdrop of the magnificent National Museum of Natural History where "Let there be Light" celebrated its most recent success by opening the 2017 edition of the Pariscience Film Festival.

More than 200 guests, among them many film-producers and journalists, had gathered in the historic amphitheatre to watch the award-winning 90-minute documentary on fusion energy produced by Canadian director Mila Aung-Thwin and cinematographer Van Royko.

Only four days before, Mila Aung-Thwin had attended the Zurich Film Festival where the film screened twice. Now he was on stage in Paris, together with ITER Director-General Bernard Bigot and ITER scientist Mark Henderson, answering the questions from the audience. For most of the attendees, the film had been the first contact with the ITER Project and so the crowd was curious to learn more about the international quest for fusion energy.

The applause at the end paid tribute to an entertaining evening and—as many professional film producers attested—to an outstanding film.

A third batch of electrotechnical equipment has left the port of Saint Petersburg, Russia, for delivery to ITER. On board are 85 tonnes of aluminium DC busbars and system components, part of an overall procurement package that includes some 5 kilometres of busbars (500 tonnes) as well as fast discharge units and switching networks.

Busbars are the long metal components that will "snake" through the installation to feed the superconducting magnets with large amounts of current. The biggest are designed to carry close to 70 kiloamps of current to the 18 toroidal field coils of the machine; others will connect to the poloidal field coils, correction coils and the central solenoid.

The first two batches of equipment were delivered and 2015 and 2016, and more are expected. The main supplier of this equipment is the Efremov Institute (NIIEFA), St. Petersburg.

--Alex Petrov, ITER Russia

Rich Hawryluk—who was Deputy Director-General for the Administration Department at the ITER Organization from 2011 to 2013—has been appointed interim director of the Princeton Plasma Physics Laboratory (PPPL) while an international search for a permanent director moves forward. 

The leadership change comes as PPPL moves forward with the recovery phase of the NSTX-U spherical tokamak, which encountered a malfunction in one of its magnet coils in 2016. The lab is constructing prototype magnets in preparation for replacing the one that failed last year, as well as five others that were built under similar conditions. 

Hawryluk has a long association with the PPPL lab, having served as former head of the Tokamak Fusion Test Reactor (TFTR) in the 1990s, deputy director of the laboratory from 1997 to 2008, and head of the ITER and Tokamaks Department from 2009 to 2011 and 2013 to the present.

The KTM tokamak, based at the National Nuclear Center in Kurchatov, Kazakhstan, is a small and versatile machine that is capable of testing materials under high particle and heat flux.

The spotlight turned this summer to this recent member of the worldwide tokamak community, as Kazakhstan hosted the 2017 World's Fair. A Cooperation Agreement was also signed between Kazakhstan's National Nuclear Center and the ITER Organization in June 2017 that opens the door to scientific and engineering cooperation between the two institutions.

Kazakh Journalist Grigory Bedenko has visited the KTM Tokamak in Kurchatov, where commissioning operations are underway in preparation for the start of operations next year.

See his long photo reportage here.

ITER's vacuum vessel port plugs are critical components that seal the plasma chamber and allow experiments to take place in a high vacuum environment.

The Russian Domestic Agency—responsible for supplying four test stands for the vacuum, heat and functional testing of the port plugs before their installation on the machine—has contracted with the Russian firm Cryogenmash for the development of the technology.

The team at Cryogenmash is currently testing the sealing flanges that will secure the port plugs on the test stand and running tests on the gaskets to arrive at a final choice of technology and material. Vacuum and leak tests were run recently with results that surpassed expectations.

Watch a five-minute video of the work underway courtesy of ITER Russia.

The latest podcast from Decrypted by Bloomberg starts with the question: "How close are we to realizing the silver bullet for clean, cheap and abundant energy ... fusion?"

Featuring lengthy interviews at the US Department of Energy's largest science and energy laboratory, the Oak Ridge National Laboratory in Tennessee, journalists Jing Cao and Aki Ito delve into the way nuclear fusion fuels our Sun and stars and how scientists plan to make it commercially viable on Earth, despite a lack of funding ...

Follow the 25-minute podcast "The Nuclear Tech Breakthrough That Could Make Oil Obsolete" here. 

Physicist Fatima Ebrahimi from the Princeton Plasma Physics Laboratory (PPPL) has for the first time used advanced models to accurately simulate key characteristics of the cyclic behaviour of edge-localized modes (ELMs), a particular type of plasma instability.

The findings could help physicists more fully comprehend the behaviour of plasma, the hot, charged gas that fuels fusion reactions in doughnut-shaped fusion facilities called tokamaks, and more reliably produce plasmas for fusion reactions. The findings could also provide insight into solar flares, the eruptions of enormous masses of plasma from the surface of the sun into space.

ELMs occur around the outer edge of high-confinement, or H-mode, plasmas due to strong edge currents. Ebrahimi used a computer simulation code known as NIMROD to show how ELMs go through a repeated cycle in which they form, develop, and vanish.

The model demonstrates that ELMs can form when a steep gradient of current exists at the plasma edge. The gradient develops when the plasma moves suddenly up or down, creating a bump in the current and forming an edge current sheet. The instability then forms a current-carrying filament that moves around the tokamak, producing electrical fields that interfere with the currents that caused the ELMs to form. With the original currents disrupted, the ELM dies. "In a way," Ebrahimi said, "an ELM eliminates its own source — erases the bump on the edge current — by its own motion."

Ebrahimi's findings are consistent with observations of cyclic behaviour of ELMs in tokamaks around the world. These include Pegasus, a small spherical device at the University of Wisconsin; the Mega Ampere Spherical Tokamak (MAST) in the United Kingdom; and the National Spherical Torus Experiment (NSTX), the flagship facility at PPPL before its recent upgrade. The research could also improve understanding of solar eruptions, which are accompanied by filamentary structures similar to those produced by ELMs. Her next step will involve investigating the impact of differences in plasma pressure on the cyclic behaviour of ELMs.

Read the full article on the PPPL website.

The elements of the ITER divertor that will directly face the hot plasma must withstand a heat load that is estimated at ten times that of a spacecraft re-entering Earth's atmosphere.

Procuring parties Russia (divertor dome), Japan (divertor outer targets) and Europe (divertor inner targets) are all engaged in multiyear qualification programs that include prototype fabrication and high heat flux testing.

The European Domestic Agency made the choice of contracting with three separate manufacturers for the development of small-scale inner vertical target prototypes that are 1/19th of the actual scale needed for ITER. In the first stage of the pre-qualification program the prototypes were successfully tested in high heat flux conditions; the next step will now be to develop full-scale prototypes. This phase—which involves the three manufacturers plus a fourth, pre-qualified supplier—is expected to last approximately three years.

Read the full article on the European Domestic Agency website.

We have learned with profound sadness of the passing of Dr Yasuo Shimomura, who served as ITER Deputy Director from the beginning of the Engineering Design Activities (EDA) in 1992 until 2001. From 2001 until 2003 Dr Shimomura was ITER International Team Co-Leader, and from 2003 until 2005 he was ITER Interim Project Leader; during this last period he led the ITER team through the difficult transitional phase from the design activity to the start of construction in 2006.

A graduate of Osaka University, Dr Shimomura had a distinguished career in fusion research at the Japan Atomic Energy Research Institute, JAERI (now part of the National Institutes for Quantum and Radiological Science and Technology, QST). He was a leading figure in the construction and operation of the JFT-2a/DIVA tokamak, developing a reactor-relevant divertor concept that is currently being applied to ITER. He was also Leader of the JT-60 Experimental Planning and Analysis Group, and in 1986 was appointed as Head of the Large Tokamak Experiment Division at JAERI, with overall responsibility for the JT-60 tokamak. From 1988 he combined the leadership of the JT-60 device and its conversion to JT-60U with an appointment as Head of the Poloidal Field Design Group within the ITER Conceptual Design Activities (CDA). He was appointed ITER Deputy Director within the ITER EDA in July 1992, with responsibility for the design integration of the project. Dr Shimomura also held guest scientist positions at Princeton Plasma Physics Laboratory from 1976 to 1977 and at the Max-Planck-Institut für Plasmaphysik in Garching from 1981 to 1982.

Dr Shimomura will be remembered by his many friends and colleagues in the ITER community as a gifted physicist who contributed greatly to the project during an involvement spanning 20 years. He will be greatly missed by all who knew him and who benefitted from his leadership and guidance.

In ITER, six technological solutions for tritium breeding—in the form of test blanket modules plus associated ancillary systems—will be operated and tested for the first time. Their experimental validation will represent a major step for fusion development beyond ITER, when tritium fuel will necessarily have to be bred within the reactor.

In China, Europe, India, Japan and Korea these solutions are under development, with Russia and the United States contributing R&D and providing general support for the test blanket module program.

Europe is developing two types of test blanket modules, which consist of a steel box containing tritium breeders, neutron multiplier materials and heat extraction plates. Over the past two years, the European Domestic Agency and industrial partners have been manufacturing mockups of these boxes to test welding techniques. A preliminary welding procedure, employing a tungsten inert gas (TIG) welding robot to carry out the tasks within the limited space of the box, has been identified. The welding qualification cycle is expected to end within the next two years.

See the full article on the European Domestic Agency website.

Edmund Synakowski—the Associate Director of the US Department of Energy (DOE) Office of Fusion Energy Sciences and former ITER Council Vice-Chair—has been chosen as the University of Wyoming's vice president for research and economic development. Synakowski will also be a professor in the university's Department of Physics and Astronomy.

The role of the vice president for research and economic development is to support and facilitate the research efforts of University of Wyoming's faculty, staff and students; direct the university's research mission as a public research university; promote the university's research program with stakeholders; and direct technology transfer and commercialization efforts for the university's intellectual property.

Synakowski has held his current position, associate director of science in the Department of Energy, since 2009, administering a budget of about $400 million annually to develop nuclear fusion as an energy source. His agency supports research at more than 50 universities, eight national and two federal laboratories, and 15 industry groups.

He previously led the Fusion Energy Program at the Lawrence Livermore National Laboratory in California and held a number of roles at Princeton University's Plasma Physics Laboratory.

Read the full report on the University of Wyoming's website here.

At least 100 miniature cameras will be installed inside the ITER machine to act as the eyes for operators charged with machine maintenance.

Some of them will give a wide-angle view of the inside of the machine; others will be embedded on the robotic arms used for repairs. By receiving live image from the cameras, engineers hundreds of metres away will be able to operate maintenance and repair equipment with extreme accuracy.

The European Domestic Agency has been working with Oxford Technologies Limited (OTL) to develop and validate the different subsystems of the miniature cameras, which will have to operate within severe space constraints and often in an environment exposed to radiation. Subsystems developed by ISAE, France (image sensors); CEA, France (illumination system); and Jean Monnet University Saint Etienne, France (optic system) have been successfully tested over the past year at Belgium's SCK-CEN facility where they were exposed to different levels of gamma radiation.

The next step will be to develop a camera prototype.

Read the full story on the European Domestic Agency website.

To predict the impact of removing exhaust heat from the ITER Tokamak, researchers are calling on the Titan supercomputer at the Oak Ridge Leadership Computing Facility in the US.

Using the 27-petaflop behemoth, researchers based at Princeton Plasma Physics Laboratory (PPPL) are simulating the area where the plasma edge meets the divertor—the material structure engineered to remove exhaust heat from the vacuum vessel. Specifically, the team has evaluated the heat-flux width at the divertor, or the width of the material surface that might sustain the highest heat load.

Because the divertor directly faces the exhaust flow, it is bombarded with hot particles driven by electromagnetic fluctuations. In ITER, in order to withstand the highest surface heat load, the divertor will be made of the toughest element on Earth: tungsten.

"You don't want to start and stop ITER too often to replace this divertor material, so it has to be able to withstand the heat load," team leader C.S. Chang reports. "Ideally, we want the hot exhaust particles to hit the surface in a much wider area so that it's not damaged."

Based on simulations made possible by Titan's supercomputing capacity, Chang's team predicts that in ITER, due to the size of the plasma, edge plasma turbulence may spread heat across a larger area of the divertor surface and significantly increase the heat-flux width relative to current smaller-scale fusion devices.

Read the full report on research results at OLCF.

At the Swiss Plasma Center in Lausanne, Switzerland, the TCV tokamak was recently shut down for an upgrade of its Thomson scattering diagnostic. The operation was successful: shortly after commissioning the first measurements demonstrated greatly enhanced spatial and spectral resolution for the temperature and density profile measurements of TCV plasmas.

TCV is a variable configuration tokamak with highly specialized capabilities (plasma shaping, versatile electron cyclotron heating, measurement, control systems) for the exploration of the physics of magnetically confined plasmas.

See the full article on the EPFL/Swiss Plasma Center website.

Under contract with the European Domestic Agency, a team of experts has been working for more than a year to identify key technologies to perform the cutting and welding operations that will be required during the change-out of ITER divertor cassettes.

The technical constraints are enormous—the work (both cutting and welding) will have to be performed remotely, the operational space is severely limited, and no lubricant can be applied as ITER is a nuclear environment.

Experts from Assystem UK and the UKAEA robotics development laboratory RACE (for Remote Applications in Challenging Environments) have identified candidate techniques; now trials are underway and the search is on for the best tools to do the work remotely.

Read more on the European Domestic Agency website.