Of Interest archive

Researchers at the US Department of Energy's (DOE) Princeton Plasma Physics Laboratory (PPPL) have challenged the understanding of a key element in fusion plasmas. At issue has been an accurate prediction of the size of the "bootstrap current"—a self-generating electric current—and an understanding of what carries the current at the edge of plasmas in doughnut-shaped facilities called tokamaks. This bootstrap-generated current combines with the current in the core of the plasma to produce a magnetic field to hold the hot gas together during experiments, and can produce stability at the edge of the plasma.

The recent work, published in the April issue of the journal Physics of Plasmas, focuses on the region at the edge in which the temperature and density drop off sharply. In this steep gradient region—or pedestal—the bootstrap current is large, enhancing the confining magnetic field but also triggering instability in some conditions.

The bootstrap current appears in a plasma when the pressure is raised. [...] Physics understanding and accurate prediction of the size of the current at the edge of the plasma is essential for predicting its effect on instabilities that can diminish the performance of fusion reactors.

--Illustration: Simulation shows trapped electrons at left and passing electron at right that are carried in the bootstrap current of a tokamak. Credit: Kwan Liu-Ma, University of California, Davis.

Read the full article on the PPPL website.

Another shipment of in-kind components from India has arrived at the PRIMA neutral beam test facility in Padua, Italy. At PRIMA, ITER's most powerful heating system—neutral beam injection—will be tested in advance of operation. 

The SPIDER test bed is a 1:1-scale ion source that will be used to develop the technology for the production of negative ions. India already delivered the beam dump in late 2014; this time, 13 trucks carried the components of the 100 kV power supply.

Read more about the lastest shipment here.

A senior researcher at MIT's Plasma Science and Fusion Center (PSFC) in the US is using a gyrotron, a specialized radio-frequency (RF) wave generator developed for fusion research, to explore how millimetre RF waves can open holes through hard rock by melting or vaporizing it.

Penetrating deep into rock is necessary to access virtually limitless geothermal energy resources, to mine precious metals or explore new options for nuclear waste storage. But it is a difficult and expensive process, and today's mechanical drilling technology has limitations. Woskov believes that powerful millimetre-wave sources could increase deep hard rock penetration rates by more than ten times at lower cost over current mechanical drilling systems, while providing other practical benefits.

"There is plenty of heat beneath our feet," he says, "something like 20 billion times the energy the world uses in one year." But, Woskov notes, most studies of the accessibility of geothermal energy are based on current mechanical technology and its limitations. They do not consider that a breakthrough advance in drilling technology could make possible deeper, less expensive penetration, opening into what Woskov calls "an enormous reserve of energy, second only to fusion: base energy, available 24/7."

Current rotary technology is a mechanical grinding process, limited by rock hardness, deep pressures, and high temperatures.  Specially designed "drilling mud," pumped through the hollow drill pipe interior, is used to enable deep drilling and to remove the excess cuttings, returning them to the surface via the ring-shaped space between the drill pipe and borehole wall. The pressure of the mud also keeps the hole from collapsing, sealing and strengthening the hole in the process. But there is a limit to the pressures such a borehole can withstand, and typically holes cannot be drilled beyond 30,000 feet (9km).

Woskov asks, "What if you could drill beyond this limit? What if you could drill over ten kilometers into the earth's crust?" With his proposed gyrotron technology this is theoretically possible.

Continue reading on the PSFC website.

The ASDEX-Upgrade team at the Max Planck Institute for Plasma Physics (IPP) in Garching, Germany is experimenting with a new mode of tokamak operation.

In recent experimental results, an operational mode described as offering "stable plasma, high plasma pressure and good confinement properties in a parameter range in which future power plants are to be working" has been achieved almost without the transformer, or solenoid, that is typically used to induce the strong current in the plasma that contributes to creating the magnetic cage of tokamaks like ITER and ASDEX-Upgrade.

In its place, microwaves and particle beams injected close to the plasma core were used to prolong the plasma pulse.

This type of "advanced tokamak operation" was the object of investigation for IPP scientist Alexander Bock, who details the advantages that continuous operation would have over pulsed operation as part of his PhD thesis. Advantages included better control of the plasma current profile in the plasma, longer pulses, and decreased turbulence.

Read the IPP press release in English or in German.

EUROfusion, the coordinating body for fusion research activities in Europe, is seeking student writers to contribute to the summer issue of Fusion in Europe.

If you possess strong writing skills, are curious, and can explain complex science with compelling metaphors, please send in your writing samples to this address by 16 May 2016.

Find out more about the program here.

On April 6, 2016, the largest-scale nuclear industry exhibition in China opened its doors and the ITER Project was there.

For four days, the actors of the global nuclear industry gathered in the National Convention Center in Beijing for the 14th China International Nuclear Industry Exhibition. One of the themes of the conference was "Fusion & Plasma Technology Applications."

The Chinese Domestic Agency for ITER (ITER China) was invited to participate by one of the sponsors of the event, the Chinese Nuclear Society. At its 36 m² stand, complete with graphic display boards, model exhibits and promotional videos, the public was given a comprehensive introduction to the ITER Project, the status of domestic fusion research and development, and the specific contribution of China to ITER.

The Director-General of the ITER Organization, Bernard Bigot, and the head of the Korean Domestic Agency, Kijung Jung, both visited the ITER stand, as well as representatives from institutes, universities, and suppliers involved with fusion at home and abroad.

--By Raphael Rosen

Scientists at the US Department of Energy's Princeton Plasma Physics Laboratory (PPPL) have helped design and test a component that could improve the performance of doughnut-shaped fusion facilities known as tokamaks.

Called a "liquid lithium limiter," the device has circulated the protective liquid metal within the walls of China's Experimental Advanced Superconducting Tokamak (EAST) and kept the plasma from cooling down and halting fusion reactions. The journal Nuclear Fusion published results of the experiment in March 2016.

This system reduces the production of impurities that typically are created when the plasma reaches other components of the vessel. Moreover, plasmas tolerate higher amounts of lithium impurities, compared with the impurities from other materials, because the low atomic number of lithium produces very low amounts of plasma radiation that typically cools the plasma core.

Serving as the main point of contact with plasma enables the lithium to absorb the hot deuterium ions that drift from the centre of the plasma, and keeps them from striking the interior walls of the tokamak and cooling down. Limiting the amount of cool deuterium at the edge of the plasma reduces the difference in temperature between the hot plasma centre and the cooler edge, and reduces turbulence. As a side note, however, contact with the ions was found to slightly damage the thin stainless steel foil surface of the limiter device, prompting work on an improved design.

Read the full report on the PPPL website.

Photo of the white-hot limiter glowing in contact with the plasma during an EAST discharge.

WEST's international call for modelling and experimental proposals was successfully completed on 15 March 2016 with more than 150 proposals received from the ITER Organization, Europe, USA, China, Japan, India, Korea and Russia. The first WEST Experiment Planning Meeting will be held on 18-20 April 2016 at CEA Cadarache to discuss the prioritization of experimental and modelling proposals and to define a timeline for the 2016-2017 WEST experimental campaigns.

At the first edition of the Security Meetings exhibition in Cannes, France, on 22-24 March 2016, ITER Head of Security, Health & Safety Christophe Ramu was awarded the title of "Security Director of the Year."

A first of its kind, the exhibition brought together more than 120 participants from prestigious organizations such as CEA, Aéroport de Paris, Airbus, Air France, Banque de France, Bolloré, Bouygues, Capgemini, Cartier, City of Marseille, Engie, Gendarmerie Nationale, Hyatt, Intercontinental, Lafarge, Razel-bec, Saint-Gobain, Suez, Orange, DHL and Musée du Louvres.

During the event, four security awards were also attributed to reward outstanding initiatives in security approach.

In the category "Security Director of the Year," Christophe Ramu was recognized for his professionalism and innovation in the exercise of his profession. Christophe, who joined ITER in 2012 after serving for 20 years at Marseille's Marine Fire Battalion, is managing—among many other tasks—the evolution in the implementation of a pre-enrolment system for accessing the ITER site.

This system will enable on-site contracting companies, once they are accredited by the ITER Organization, to manage access requests for their own personnel. The system, which will be fully operational in the second half of 2016, will also improve the monitoring activity of personnel presence and localization on the ITER site.

Cooling 10,000 tons of superconducting magnets that will confine the energy-generating plasma is indispensable to the proper working of the ITER Tokamak. The cryogenic plant, whose design phase began in 2013, has now entered the fabrication phase at the Air Liquide factory near Grenoble, France.

This impressive centralized cryogenic refrigeration system will be composed of helium (He) and nitrogen (N2) refrigeration units and dedicated storage, operating in a closed loop. Helium, at a temperature of close to the absolute zero (-269°C, or 4.5K), will be used to cool magnets, vacuum pumps and certain diagnostic systems.

Nitrogen, whose temperature (-196°C, or 77K) is not quite as low, will contribute among other things to the cooling of the heat shield and to the pre-cooling of the helium refrigeration unit and the helium loops. The site's three helium units (LHe) will occupy 3,000 m2 of the 5,400 m2 set aside for the ITER cryogenic unit. LHe is composed of several compression stations and three large cold boxes, which weigh 135 tons each, measure 21 metres in length, and have a diameter of 4.2 metres.

On average, the helium refrigeration units will provide a global cooling capacity of 75kW to 4.5K, which translates into a maximum liquefaction rate of 12,300 liters/hour. They will be completed by two nitrogen units (LN2). The 11 helium and nitrogen gas storage units—with a total capacity of 3,700 m3 (of which 3,300 m3 for the helium)—will help to optimize the recovery of fluids in the various operational phases of the tokamak.

View the special issue on ITER in Cryoscope, a magazine from Air Liquide.

For Lego enthusiasts the ITER Tokamak is an endless source of inspiration.  In June 2012, Newsline reported on Japanese artist Sachiko Akinaga who had created an 8,000-piece tokamak assembly scene using standard Lego bricks.

Two years later an American videogame designer, Andrew Clark, tried to convince the Lego company to bring his model of the ITER Tokamak into commercial production; unfortunately, the proposal never gathered the 10,000 "votes of support" required to turn the project into an official set.

At the University of Kyoto in Japan, another Lego venture is taking shape. A group of students in fusion materials and reactor engineering (Konishi Laboratory, Dr Kasada's group) has built a highly realistic version of the ITER Tokamak with all major components in place—coils, ports, heating systems, and Test Blanket Modules are all identified by a different colour. The students even managed to insert a waveguide into the vacuum vessel wall...

An achievement in terms of both realism and poetry, the ITER-LEGO project will be used for the promotion of fusion energy in exhibitions and conferences.

Click here to view a video of the ITER-LEGO.

The European Domestic Agency has developed a new numerical model that represents ITER's 18 toroidal field magnets with remarkable detail. The model will be used to compute the magnetic fields produced by the coils and the resulting electromagnetic forces on the magnet system, which are the result of the interaction between electrical currents and the magnetic field.

"It's the first time we have a complete model of the entire ITER toroidal field system to such a level of detail," says Gabriele D'Amico, the technical support officer responsible for the development of the model. "The level of complexity of the tool is outstanding. For example there are more than 1,500 bolts connecting the different pieces of the toroidal field magnet system, and the model allows us to predict the behaviour of each one during operations."

The model, which took six months to develop, will allow the European Domestic Agency and the ITER Organization to simulate different scenarios using an approach that integrates the 18 coils and all major subsystems. Scientists will be able to study the occurrence of an electrical fault during operation, for example, or the impact of possible misalignment in the assembly of the coils on the behaviour of the whole system.

Read the full article on the European Domestic Agency website.

Progress on the MAST Upgrade project at the Culham Centre for Fusion Energy (CCFE) took another step forward from the "page" to completion, as the tokamak's bottom plate was lowered into place in the machine area last week.

Positioning of the 11-tonne bottom plate, which contains intricately-engineered magnetic coils assembled over many months, went smoothly. The team hopes to have the device ready for commissioning at the end of 2016.

See a video of the operation on the CCFE website.

European Domestic Agency contractors have made significant progress in the fabrication of the first toroidal field winding pack—the 110-ton inner core of ITER's D-shaped superconducting magnets known as toroidal field coils.

Following sophisticated, multi-stage winding operations, seven layers of coiled superconducting cable (double pancakes) have now been successfully stacked and electrically insulated. After vacuum-pressure insulation and testing, the winding pack will be inserted into a massive stainless steel case to form a final assembly that measures 9 x 17 metres and weighs 310 tons.

Eighteen D-shaped toroidal field coils—each made up of a winding pack and stainless steel coil case—will be responsible for magnetically confining the ITER plasma. Europe has the responsibility for half the coils plus one spare; Japan is producing another 9. The 19 stainless steel coil cases will be procured by Japan.

Beginning with the first manufacturing steps for the niobium-tin (Nb3Sn) superconducting wire in 2008, Europe estimates that over 600 people from at least 26 companies have contributed to this milestone.

Read the full report on the European Domestic Agency website.

--Europe's A. Bonito-Oliva, project manager for magnets, and R. Harrison, technical officer for magnets, stand in front of the first toroidal field coil winding pack at ASG Superconductors (La Spezia, Italy).

By John Greenwald

Big Bang neutrinos are believed to be everywhere in the universe but have never been seen. The expansion of the universe has stretched them and they are thought to be billions of times colder than neutrinos that stream from the sun. As the oldest known witnesses or "relics" of the early universe, they could shed new light on the birth of the cosmos if scientists could pin them down. That's a tall order since these ghostly particles can speed through planets as if they were empty space.

Now Princeton University physicist Chris Tully is readying a facility to detect these information-rich relics that appeared one second after the Big Bang, during the onset of the epoch that fused protons and neutrons to create all the light elements in the universe. Tully runs a prototype lab in the US Department of Energy's (DOE) Princeton Plasma Physics Laboratory (PPPL) that draws on the fact that neutrinos can be captured by tritium, a radioactive isotope of hydrogen, and provide a tiny boost of energy to the electrons emitted in tritium decay.

--Princeton physicist Chris Tully in the PTOLEMY laboratory. Behind him are powerful superconducting magnets on either side of the vacuum chamber. Photo Elle Starkman/PPPL

Read the whole article on the PPPL website.

The deadline is fast approaching to submit a proposal to the 2016 SOFT Innovation Prize, launched by the European Commission late last year for award at the 29th SOFT (Symposium on Fusion Technology) international conference in Prague in September.

Proposals are requested for physics or technology innovations related to magnetic confinement fusion research that have a potential for further exploitation.

Three prizes will be awarded: EUR 50,000 (1st prize), EUR 25,000 (2nd prize) and EUR 12,500 (3rd prize). The deadline for submission is 7 April 2016.

For more information on eligibility, exclusion and award criteria please see Europe's Horizon 2020 website.

ITER will use extensive cryogenic technology to create and maintain low-temperature conditions for the magnet, thermal shielding and vacuum pumping systems. The ITER cryoplant will be the largest concentrated cryogenic system in the world (one plant location) and second only to CERN in terms of total cooling power.

On the ITER platform, work is progressing on the foundations of the plant building while—following successive design phases—the procurement of cryoplant components is now underway by Europe (liquid nitrogen plant and auxiliary systems), the ITER Organization (helium plant) and India (cryolines and cryodistribution components).

In February, as part of Europe's procurement package, a 23-metre-long storage tank for liquid helium successfully passed leak detection tests. Responsible for keeping liquid helium at a steady -269 °C, the stainless-steel inner tank has multi-layer insulation to minimize thermal losses and will be assembled with exterior thermal shielding. The examination of 500 metres of linear welds was successfully performed by the manufacturer, opening the way to the delivery of the equipment at ITER before the end of the year.

The storage tank was manufactured by CryoAB (Sweden) as part of the contract signed between the European Domestic Agency and Air Liquide Global and EC Solutions and Fusion for Energy.

Read the original news item on the European Domestic Agency website.

-- Part of ITER's cryoplant, the 190 m³ stainless-steel tank will store liquid helium at -269 °C.

The path to creating sustainable fusion energy as a clean, abundant and affordable source of electric energy has been filled with "aha moments" that have led to a point in history when the ITER fusion experiment is poised to produce more fusion energy than it uses when it is completed in 15 to 20 years, said Ed Synakowski, associate director of Science for Fusion Energy Sciences at the US Department of Energy (DOE).

Synakowski spoke as part of the Ronald E. Hatcher "Science on Saturday" lecture series at the Princeton Plasma Physics Laboratory (PPPL).

Read the full report on the PPPL website.

-- Ed Synakowski is pictured at the Monaco-ITER International Fusion Energy Days (2013).

How to sustain and measure temperature in a fusion plasma? This challenging task requires different heating systems and diagnostic tools. Information on the spatial distribution of temperature is one of the key elements for improving and controlling plasma performance.

In a recently published Nature Physics article, Didier Mazon, Christel Fenzi and Roland Sabot, of CEA's Research Institute on Magnetic Fusion (IRFM) explore the fascinating realm of ultra-hot temperatures.

Illustration of a new X2D diagnostic: spectroscopy for ion temperature measurement in the WEST tokamak.

Click here to read the whole article in Nature Physics.