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  • richardmitnick 7:21 pm on October 16, 2018 Permalink | Reply
    Tags: , Fusion technology, , , MIT Plasma Science and Fusion Center, Nuno Loureiro, Physicist explores the behavior of the universe’s most abundant form of matter, Physics of plasmas, Plasma is a sort of fourth phase of matter, The solar wind is the best plasma turbulence laboratory we have, Turbulence-a major stumbling block so far to practical fusion power   

    From MIT News-“Nuno Loureiro: Probing the world of plasmas” 

    MIT News
    MIT Widget

    From MIT News

    October 15, 2018
    David L. Chandler

    1
    A major motivation for moving to MIT from his research position, Nuno Loureiro says, was working with students. Image: Jared Charney

    Physicist explores the behavior of the universe’s most abundant form of matter.

    Growing up in the small city of Viseu in central Portugal, Nuno Loureiro knew he wanted to be a scientist, even in the early years of primary school when “everyone else wanted to be a policeman or a fireman,” he recalls. He can’t quite place the origin of that interest in science: He was 17 the first time he met a scientist, he says with an amused look.

    By the time Loureiro finished high school, his interest in science had crystallized, and “I realized that physics was what I liked best,” he says. During his undergraduate studies at the IST Lisbon, he began to focus on fusion, which “seemed like a very appealing field,” where major developments were likely during his lifetime, he says.

    Fusion, and specifically the physics of plasmas, has remained his primary research focus ever since, through graduate school, postdoc stints, and now in his research and teaching at MIT. He explains that plasma research “lives in two different worlds.” On the one hand, it involves astrophysics, dealing with the processes that happen in and around stars; on the other, it’s part of the quest to generate electricity that’s clean and virtually inexhaustible, through fusion reactors.

    Plasma is a sort of fourth phase of matter, similar to a gas but with the atoms stripped apart into a kind of soup of electrons and ions. It forms about 99 percent of the visible matter in the universe, including stars and the wispy tendrils of material spread between them. Among the trickiest challenges to understanding the behavior of plasmas is their turbulence, which can dissipate away energy from a reactor, and which proceeds in very complex and hard-to-predict ways — a major stumbling block so far to practical fusion power.

    While everyone is familiar with turbulence in fluids, from breaking waves to cream stirred into coffee, plasma turbulence can be quite different, Loureiro explains, because plasmas are riddled with magnetic and electric fields that push and pull them in dynamic ways. “A very noteworthy example is the solar wind,” he says, referring to the ongoing but highly variable stream of particles ejected by the sun and sweeping past Earth, sometimes producing auroras and affecting the electronics of communications satellites. Predicting the dynamics of such flows is a major goal of plasma research.

    “The solar wind is the best plasma turbulence laboratory we have,” Loureiro says. “It’s increasingly well-diagnosed, because we have these satellites up there. So we can use it to benchmark our theoretical understanding.”

    Loureiro began concentrating on plasma physics in graduate school at Imperial College London and continued this work as a postdoc at the Princeton Plasma Physics Laboratory and later the Culham Centre for Fusion Energy, the U.K.’s national fusion lab. Then, after a few years as a principal researcher at the University of Portugal, he joined the MIT faculty at the Plasma Science and Fusion Center in 2016 and earned tenure in 2017. A major motivation for moving to MIT from his research position, he says, was working with students. “I like to teach,” he says. Another was the “peerless intellectual caliber of the Plasma Science and Fusion Center at MIT.”

    Loureiro, who holds a joint appointment in MIT’s Department of Physics, is an expert on a fundamental plasma process called magnetic reconnection. One example of this process occurs in the sun’s corona, a glowing irregular ring that surrounds the disk of the sun and becomes visible from Earth during solar eclipses. The corona is populated by vast loops of magnetic fields, which buoyantly rise from the solar interior and protrude through the solar surface. Sometimes these magnetic fields become unstable and explosively reconfigure, unleashing a burst of energy as a solar flare. “That’s magnetic reconnection in action,” he says.

    Over the last couple of years at MIT, Loureiro published a series of papers with physicist Stanislav Boldyrev at the University of Wisconsin, in which they proposed a new analytical model to reconcile critical disparities between models of plasma turbulence and models of magnetic reconnection. It’s too early to say if the new model is correct, he says, but “our work prompted a reanalysis of solar wind data and also new numerical simulations. The results from these look very encouraging.”

    Their new model, if proven, shows that magnetic reconnection must play a crucial role in the dynamics of plasma turbulence over a significant range of spatial scales – an insight that Loureiro and Boldyrev claim would have profound implications.

    Loureiro says that a deep, detailed understanding of turbulence and reconnection in plasmas is essential for solving a variety of thorny problems in physics, including the way the sun’s corona gets heated, the properties of accretion disks around black holes, nuclear fusion, and more. And so he plugs away, to continue trying to unravel the complexities of plasma behavior. “These problems present beautiful intellectual challenges,” he muses. “That, in itself, makes the challenge worthwhile. But let’s also keep in mind that the practical implications of understanding plasma behavior are enormous.”

    See the full article here .


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  • richardmitnick 9:33 am on October 10, 2018 Permalink | Reply
    Tags: , Fusion technology, , , ,   

    From MIT: “A new path to solving a longstanding fusion challenge” 

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    From MIT News

    October 9, 2018
    David L. Chandler

    1
    The ARC conceptual design for a compact, high magnetic field fusion power plant. The design now incorporates innovations from the newly published research to handle heat exhaust from the plasma. ARC rendering by Alexander Creely

    2
    The ARC conceptual design for a compact, high magnetic field fusion power plant. Numbered components are as follows: 1. plasma; 2. The newly designed divertor; 3. copper trim coils; 4. High-temperature superconductor (HTS) poloidal field coils, used to shape the plasma in the divertor; 5. FLiBe blanket, a liquid material that collects heat from emitted neutrons; 6. HTS toroidal field coils, which shape the main plasma torus; 7. HTS central solenoid; 8. vacuum vessel; 9. FLiBe tank; 10. joints in toroidal field coils, which can be opened to allow for access to the interior. ARC rendering by Alexander Creely

    Novel design could help shed excess heat in next-generation fusion power plants.

    A class exercise at MIT, aided by industry researchers, has led to an innovative solution to one of the longstanding challenges facing the development of practical fusion power plants: how to get rid of excess heat that would cause structural damage to the plant.

    The new solution was made possible by an innovative approach to compact fusion reactors, using high-temperature superconducting magnets. This method formed the basis for a massive new research program launched this year at MIT and the creation of an independent startup company to develop the concept. The new design, unlike that of typical fusion plants, would make it possible to open the device’s internal chamber and replace critical comonents; this capability is essential for the newly proposed heat-draining mechanism.

    The new approach is detailed in a paper in the journal Fusion Engineering and Design, authored by Adam Kuang, a graduate student from that class, along with 14 other MIT students, engineers from Mitsubishi Electric Research Laboratories and Commonwealth Fusion Systems, and Professor Dennis Whyte, director of MIT’s Plasma Science and Fusion Center, who taught the class.

    In essence, Whyte explains, the shedding of heat from inside a fusion plant can be compared to the exhaust system in a car. In the new design, the “exhaust pipe” is much longer and wider than is possible in any of today’s fusion designs, making it much more effective at shedding the unwanted heat. But the engineering needed to make that possible required a great deal of complex analysis and the evaluation of many dozens of possible design alternatives.

    Taming fusion plasma

    Fusion harnesses the reaction that powers the sun itself, holding the promise of eventually producing clean, abundant electricity using a fuel derived from seawater — deuterium, a heavy form of hydrogen, and lithium — so the fuel supply is essentially limitless. But decades of research toward such power-producing plants have still not led to a device that produces as much power as it consumes, much less one that actually produces a net energy output.

    Earlier this year, however, MIT’s proposal for a new kind of fusion plant — along with several other innovative designs being explored by others — finally made the goal of practical fusion power seem within reach.

    MIT SPARC fusion reactor tokamak

    But several design challenges remain to be solved, including an effective way of shedding the internal heat from the super-hot, electrically charged material, called plasma, confined inside the device.

    Most of the energy produced inside a fusion reactor is emitted in the form of neutrons, which heat a material surrounding the fusing plasma, called a blanket. In a power-producing plant, that heated blanket would in turn be used to drive a generating turbine. But about 20 percent of the energy is produced in the form of heat in the plasma itself, which somehow must be dissipated to prevent it from melting the materials that form the chamber.

    No material is strong enough to withstand the heat of the plasma inside a fusion device, which reaches temperatures of millions of degrees, so the plasma is held in place by powerful magnets that prevent it from ever coming into direct contact with the interior walls of the donut-shaped fusion chamber. In typical fusion designs, a separate set of magnets is used to create a sort of side chamber to drain off excess heat, but these so-called divertors are insufficient for the high heat in the new, compact plant.

    One of the desirable features of the ARC design is that it would produce power in a much smaller device than would be required from a conventional reactor of the same output. But that means more power confined in a smaller space, and thus more heat to get rid of.

    “If we didn’t do anything about the heat exhaust, the mechanism would tear itself apart,” says Kuang, who is the lead author of the paper, describing the challenge the team addressed — and ultimately solved.

    Inside job

    In conventional fusion reactor designs, the secondary magnetic coils that create the divertor lie outside the primary ones, because there is simply no way to put these coils inside the solid primary coils. That means the secondary coils need to be large and powerful, to make their fields penetrate the chamber, and as a result they are not very precise in how they control the plasma shape.

    But the new MIT-originated design, known as ARC (for advanced, robust, and compact) features magnets built in sections so they can be removed for service. This makes it possible to access the entire interior and place the secondary magnets inside the main coils instead of outside. With this new arrangement, “just by moving them closer [to the plasma] they can be significantly reduced in size,” says Kuang.

    In the one-semester graduate class 22.63 (Principles of Fusion Engineering), students were divided into teams to address different aspects of the heat rejection challenge. Each team began by doing a thorough literature search to see what concepts had already been tried, then they brainstormed to come up with multiple concepts and gradually eliminated those that didn’t pan out. Those that had promise were subjected to detailed calculations and simulations, based, in part, on data from decades of research on research fusion devices such as MIT’s Alcator C-Mod, which was retired two years ago. C-Mod scientist Brian LaBombard also shared insights on new kinds of divertors, and two engineers from Mitsubishi worked with the team as well. Several of the students continued working on the project after the class ended, ultimately leading to the solution described in this new paper. The simulations demonstrated the effectiveness of the new design they settled on.

    “It was really exciting, what we discovered,” Whyte says. The result is divertors that are longer and larger, and that keep the plasma more precisely controlled. As a result, they can handle the expected intense heat loads.

    “You want to make the ‘exhaust pipe’ as large as possible,” Whyte says, explaining that the placement of the secondary magnets inside the primary ones makes that possible. “It’s really a revolution for a power plant design,” he says. Not only do the high-temperature superconductors used in the ARC design’s magnets enable a compact, high-powered power plant, he says, “but they also provide a lot of options” for optimizing the design in different ways — including, it turns out, this new divertor design.

    Going forward, now that the basic concept has been developed, there is plenty of room for further development and optimization, including the exact shape and placement of these secondary magnets, the team says. The researchers are working on further developing the details of the design.

    “This is opening up new paths in thinking about divertors and heat management in a fusion device,” Whyte says.

    “All of the ARC work has been both eye-opening and stimulating of new ways of looking at tokamak fusion reactors,” says Bruce Lipschultz, a professor of physics at the University of York, in the U.K., who was not involved in this work. This latest paper, he says, “incorporates new ideas in the field with the many other significant improvements in the tokamak concept. … The ARC study of the extended leg divertor concept shows that the application to a reactor is not impossible, as others have contended.”

    Lipschultz adds that this is “very high-quality research that shows a way forward for the tokamak reactor and stimulates new research elsewhere.”

    The team included MIT graduate students Norman Cao, Alexander Creely, Cody Dennett, Jake Hecla, Brian LaBombard, Roy Tinguely, Elizabeth Tolman, H. Hoffman, Maximillian Major, Juan Ruiz Ruiz, Daniel Brunner, and Brian Sorbom, and Mitsubishi Electric Research Laboratories engineers P. Grover and C. Laughman. The work was supported by MIT’s Department of Nuclear Science and Engineering, the Department of Energy, the National Science Foundation, and Mitsubishi Electric Research Laboratories.

    See the full article here .


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  • richardmitnick 10:42 pm on October 2, 2018 Permalink | Reply
    Tags: , , , Fusion technology, , , ,   

    From SLAC National Accelerator Lab: “Peering into 36-million-degree plasma with SLAC’s X-ray laser” 

    From SLAC National Accelerator Lab

    October 2, 2018
    Ali Sundermier
    For commnication
    communications@slac.stanford.edu

    1
    At the Matter in Extreme Conditions (MEC) instrument at LCLS, the researchers zapped knuckle-shaped samples with a laser to create plasma, then used an X-ray scattering technique to watch it expand and collide. (Matt Beardsley/SLAC National Accelerator Laboratory)

    When you hit a piece of metal with a strong enough laser pulse you get a plasma – a hot, ionized gas found in everything from lightning to the sun. Studying it helps scientists understand what’s going on inside stars and could enable new types of particle accelerators for cancer treatment.

    Now a team of researchers has used an X-ray laser to measure, for the first time, how a plasma created by a laser blast expands in the hundreds of femtoseconds (quadrillionths of a second) after it’s created. Their technique could eventually reveal tiny instabilities in the plasma that swirl like cream in a cup of coffee.

    The experiments at the Department of Energy’s SLAC National Accelerator Laboratory involved scientists from SLAC, German research center Helmholtz-Zentrum Dresden-Rossendorf (HZDR) and other institutions, and was reported in Physical Review X in September.

    Blasting cancer cells

    Led by scientist Thomas Kluge at HZDR, the researchers have been working to harness the behavior of plasma to create a new type of particle accelerator for proton therapy, an existing cancer treatment that involves blasting tumors with charged particles rather than X-rays. This approach is gentler on the surrounding healthy tissue than traditional radiation therapy.

    When solid matter is zapped with a laser the interaction forms a plasma, causing a steady stream of protons to burst out of the back side of the sample. The researchers hope to use the proton streams to storm tumors and obliterate cancer cells. But producing these fast protons in a reliable way requires a better understanding of how plasma changes as it expands.

    “Instabilities can arise from the complex streams of electrons and ions moving back and forth in the plasma,” Kluge says. “You probably know one of these instabilities from the mushroom-shaped clouds that form when you drip milk into your morning coffee.”

    Hotter than ever

    Until now, it was difficult to probe plasma changes directly because they’re so tiny and happen on extremely fast time scales. This work, says Josefine Metzkes-Ng, co-author and junior group leader at HZDR, could only be done at SLAC where the researchers used a high-power, short-pulse optical laser beam to create the plasma and the Linac Coherent Light Source X-ray free-electron laser to probe it.

    SLAC/LCLS

    At the Matter in Extreme Conditions (MEC) instrument at LCLS, researchers create incredibly hot and dense matter that mimics the extreme conditions in the hearts of stars and planets. Simulations show that the researchers achieved a new temperature record for matter studied with a free-electron laser: 36 million degrees Fahrenheit, almost 10 million degrees hotter than the sun’s core.

    The researchers fabricated solid samples that consisted of raised silicon bars, like knuckles sticking out from a fist. They found that in the quadrillionths of seconds after they zapped the sample with intense, short pulses from the optical laser, tiny amounts of plasma stacked up between the knuckles. A special form of scattering that uses X-ray pulses from LCLS allowed them to peer inside the plasma to follow its evolution.

    This technique will pave the way for better understanding plasma instabilities, allowing researchers to create proton sources for cancer therapy with relatively small footprints that, unlike conventional accelerators, can be operated within a hospital. It will also be useful in research relevant to fusion energy, other types of novel particle accelerators and laboratory astrophysics.

    Speedy cosmic particles

    Siegfried Glenzer, director of the High Energy Density Division at SLAC, who helped with the paper, is especially excited about the prospect of using this technique to better understand the astrophysical processes that give cosmic rays – subatomic space particles that plunge into Earth’s atmosphere at almost the speed of light – their extreme energies.

    The highest-energy cosmic rays can pack a force comparable to that of a major league fastball hurtling toward a batter at 100 mph, condensed into a single subatomic particle. To accelerate a proton to the same energies as these cosmic rays, scientists would have to build an accelerator that sends particles traveling from Earth to Saturn and back.

    Using LCLS, scientists are able to recreate some of the astrophysical processes that may produce these high-energy cosmic rays, such as energetic jets that shoot out from the turbulent hearts of active galaxies. Now the new technique will allow them to directly observe the plasma instabilities that might be responsible for accelerating cosmic rays.

    “Cosmic rays are the largest particle accelerators known to mankind,” Glenzer says. “They have a million times higher energy than particles accelerated in the Large Hadron Collider. Recently, astronomers traced a cosmic ray particle to an active galactic nucleus jet. Our goal is to produce these types of jets in the laboratory so we can study the formation of these instabilities and show whether they can accelerate particles to such high energies and, if so, how it happens.”

    Flipping the light switch

    According to Kluge, “This research has opened the black box of how short-pulse lasers interact with solids, allowing us to directly see a little of what’s going on, which previously could only be simulated with largely unverified atomic models.

    “It’s a little like switching on a light,” he says. “Although we have some ideas, we don’t know what we will find, but surely it will help us develop the next generation of laser-based ion accelerators and could shape new applications in astrophysics, medicine and plasma physics. For me as a theorist and simulation guy, the most exciting thing about this project is that I can now lay my simulations aside and look at the real thing.”

    The research team also included scientists from Technical University Dresden, European XFEL, University of Siegen, Friedrich Schiller University Jena and Leibniz Institute of Photonic Technology, all in Germany.

    LCLS is a DOE Office of Science user facility. Funding was provided by the DOE Office of Science.

    See the full article here .


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  • richardmitnick 11:24 am on September 22, 2018 Permalink | Reply
    Tags: , Fusion technology, ,   

    From U Tokyo via ScienceAlert: “Scientists Just Created a Magnetic Field That Takes Us Closer Than Ever Before to Harnessing Nuclear Fusion” 

    From University of Tokyo

    via

    ScienceAlert

    1
    (Zoltan Tasi/Unsplash)

    22 SEP 2018
    KRISTIN HOUSER

    They were able to control it without destroying any equipment this time.

    Inexpensive clean energy sounds like a pipe dream. Scientists have long thought that nuclear fusion, the type of reaction that powers stars like the Sun, could be one way to make it happen, but the reaction has been too difficult to maintain.

    Now, we’re closer than ever before to making it happen — physicists from the University of Tokyo (UTokyo) say they’ve produced the strongest-ever controllable magnetic field.

    “One way to produce fusion power is to confine plasma — a sea of charged particles — in a large ring called a tokamak in order to extract energy from it,” said lead researcher Shojiro Takeyama in a press release.

    ITER Tokamak in Saint-Paul-lès-Durance, which is in southern France

    September 18, 2018

    Physicists from the Institute for Solid State Physics at the University of Tokyo have generated the strongest controllable magnetic field ever produced. The field was sustained for longer than any previous field of a similar strength. This research could lead to powerful investigative tools for material scientists and may have applications in fusion power generation.

    Magnetic fields are everywhere. From particle smashers to the humble compass, our capacity to understand and control these fields crafted much of the modern world. The ability to create stronger fields advances many areas of science and engineering. UTokyo physicist Shojiro Takeyama and his team created a large sophisticated device in a purpose-built lab, capable of producing the strongest controllable magnetic field ever using a method known as electromagnetic flux compression.

    “Decades of work, dozens of iterations and a long line of researchers who came before me all contributed towards our achievement,” said Professor Takeyama. “I felt humbled when I was personally congratulated by directors of magnetic field research institutions around the world.”

    Physicists from the Institute for Solid State Physics at the University of Tokyo have generated the strongest controllable magnetic field ever produced. The field was sustained for longer than any previous field of a similar strength. This research could lead to powerful investigative tools for material scientists and may have applications in fusion power generation.

    Magnetic fields are everywhere. From particle smashers to the humble compass, our capacity to understand and control these fields crafted much of the modern world. The ability to create stronger fields advances many areas of science and engineering. UTokyo physicist Shojiro Takeyama and his team created a large sophisticated device in a purpose-built lab, capable of producing the strongest controllable magnetic field ever using a method known as electromagnetic flux compression.

    “Decades of work, dozens of iterations and a long line of researchers who came before me all contributed towards our achievement,” said Professor Takeyama. “I felt humbled when I was personally congratulated by directors of magnetic field research institutions around the world.”

    2
    The megagauss generator just before it’s switched on. Some parts for the device are exceedingly rare and very few companies around the world are capable of producing them. Image: ©2018 Shojiro Takeyama

    3
    Sparks fly at the moment of activation. Four million amps of current feed the megagauss generator system, hundreds of times the current of a typical lightning bolt. Image: ©2018 Shojiro Takeyama

    But what is so interesting about this particular magnetic field?

    At 1,200 teslas – not the brand of electric cars, but the unit of magnetic field strength – the generated field dwarfs almost any artificial magnetic field ever recorded; however, it’s not the strongest overall. In 2001, physicists in Russia produced a field of 2,800 teslas, but their explosive method literally blew up their equipment and the uncontrollable field could not be tamed. Lasers can also create powerful magnetic fields, but in experiments they only last a matter of nanoseconds.

    The magnetic field created by Takeyama’s team lasts thousands of times longer, around 100 microseconds, about one-thousandth of the time it takes to blink. It’s possible to create longer-lasting fields, but these are only in the region of hundreds of teslas. The goal to surpass 1,000 teslas was not just a race for the sake of it, that figure represents a significant milestone.

    4
    Earth’s own magnetic field is 25 to 65 microteslas. The megagauss generator system creates a field of 1,200 teslas, about 20 million to 50 million times stronger. Image: ©2018 Shojiro Takeyama

    “With magnetic fields above 1,000 Teslas, you open up some interesting possibilities,” says Takeyama. “You can observe the motion of electrons outside the material environments they are normally within. So we can study them in a whole new light and explore new kinds of electronic devices. This research could also be useful to those working on fusion power generation.”

    This is an important point, as many believe fusion power is the most promising way to provide clean energy for future generations. “One way to produce fusion power is to confine plasma – a sea of charged particles – in a large ring called a tokamak in order to extract energy from it,” explains Takeyama. “This requires a strong magnetic field in the order of thousands of teslas for a duration of several microseconds. This is tantalizingly similar to what our device can produce.”

    The magnetic field that a tokamak would require is “tantalizingly similar to what our device can produce,” he said.

    To generate the magnetic field, the UTokyo researchers built a sophisticated device capable of electromagnetic flux-compression (EMFC), a method of magnetic field generation well-suited for indoor operations.

    They describe the work in a new paper published Monday in the Review of Scientific Instruments.

    Using the device, they were able to produce a magnetic field of 1,200 teslas — about 120,000 times as strong as a magnet that sticks to your refrigerator.

    Though not the strongest field ever created, the physicists were able to sustain it for 100 microseconds, thousands of times longer than previous attempts.

    They could also control the magnetic field, so it didn’t destroy their equipment like some past attempts to create powerful fields.

    As Takeyama noted in the press release, that means his team’s device can generate close to the minimum magnetic field strength and duration needed for stable nuclear fusion — and it puts us all one step closer to the unlimited clean energy we’ve been dreaming about for nearly a century.

    See the full article here .

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  • richardmitnick 4:40 pm on August 24, 2018 Permalink | Reply
    Tags: , Fusion technology, ,   

    From MIT: “Pushing the plasma density limit” 

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    From MIT News

    1
    Seung Gyou Baek and his colleagues performed experiments on the Alcator C-Mod tokamak to demonstrate how microwaves can be used to overcome barriers to steady-state fusion reactor operation. Photo: Paul Rivenberg/PSFC

    August 23, 2018
    Paul Rivenberg | Plasma Science and Fusion Center

    For decades, researchers have been exploring ways to replicate on Earth the physical process of fusion that occurs naturally in the sun and other stars. Confined by its own strong gravitational field, the sun’s burning plasma is a sphere of fusing particles, producing the heat and light that makes life possible on earth. But the path to a creating a commercially viable fusion reactor, which would provide the world with a virtually endless source of clean energy, is filled with challenges.

    Researchers have focused on the tokamak, a device that heats and confines turbulent plasma fuel in a donut-shaped chamber long enough to create fusion. Because plasma responds to magnetic fields, the torus is wrapped in magnets, which guide the fusing plasma particles around the toroidal chamber and away from the walls. Tokamaks have been able to sustain these reactions only in short pulses. To be a practical source of energy, they will need to operate in a steady state, around the clock.

    Researchers at MIT’s Plasma Science and Fusion Center (PSFC) have now demonstrated how microwaves can be used to overcome barriers to steady-state tokamak operation. In experiments performed on MIT’s Alcator C-Mod tokamak before it ended operation in September 2016, research scientist Seung Gyou Baek and his colleagues studied a method of driving current to heat the plasma called Lower Hybrid Current Drive (LHCD).

    Alcator C-Mod tokamak at MIT, no longer in operation

    The technique generates plasma current by launching microwaves into the tokamak, pushing the electrons in one direction — a prerequisite for steady-state operation.

    Furthermore, the strength of the Alcator magnets has allowed researchers to investigate LHCD at a plasma density high enough to be relevant for a fusion reactor. The encouraging results of their experiments have been published in Physical Review Letters.

    Pioneering LHCD

    “The conventional way of running a tokamak uses a central solenoid to drive the current inductively,” Baek says, referring to the magnetic coil that fills the center of the torus. “But that inherently restricts the duration of the tokamak pulse, which in turn limits the ability to scale the tokamak into a steady-state power reactor.”

    Baek and his colleagues believe LHCD is the solution to this problem.

    MIT scientists have pioneered LHCD since the 1970s, using a series of “Alcator” tokamaks known for their compact size and high magnetic fields. On Alcator C-Mod, LHCD was found to be efficient for driving currents at low density, demonstrating plasma current could be sustained non-inductively. However, researchers discovered that as they raised the density in these experiments to the higher levels necessary for steady-state operation, the effectiveness of LHCD to generate plasma current disappeared.

    This fall-off in effectiveness as density increased was first studied on Alcator C-Mod by research scientist Gregory Wallace.

    “He measured the fall-off to be much faster than expected, which was not predicted by theory,” Baek explains. “The last decade people have been trying to understand this, because unless this problem is solved you can’t really use this in a reactor.”

    Researchers needed to find a way to boost effectiveness and overcome the LHCD density limit. Finding the answer would require a close examination of how lower hybrid (LH) waves respond to the tokamak environment.

    Driving the current

    Lower hybrid waves drive plasma current by transferring their momentum and energy to electrons in the plasma.

    Head of the PSFC’s Physics Theory and Computation Division, senior research scientist Paul Bonoli compares the process to surfing.

    “You are on a surf board and you have a wave come by. If you just sit there the wave will kind of go by you,” Bonoli says. “But if you start paddling, and you get near the same speed as the wave, the wave picks you up and starts transferring energy to the surf board. Well, if you inject radio waves, like LH waves, that are moving at velocities near the speed of the particles in the plasma, the waves start to give up their energy to these particles.”

    Temperatures in today’s tokamaks — including C-Mod — are not high enough to provide good matching conditions for the wave to transfer all its momentum to the plasma particles on the first pass from the antenna, which launches the waves to the core plasma. Consequently, researchers noticed, the injected microwave travels through the core of the plasma and beyond, eventually interacting multiple times with the edge, where its power dissipates, particularly when the density is high.

    Exploring the scrape-off layer

    Baek describes this edge as a boundary area outside the main core of the plasma where, in order to control the plasma, researchers can drain — or “scrape-off” — heat, particles, and impurities through a divertor. This edge has turbulence, which, at higher densities, interacts with the injected microwaves, scattering them, and dissipating their energy.

    “The scrape-off layer is a very thin region. In the past RF scientists didn’t really pay attention to it,” Baek says. “Our experiments have shown in the last several years that interaction there can be really important in understanding the problem, and by controlling it properly you can overcome the density limit problem.”

    Baek credits extensive simulations by Wallace and PSFC research scientist Syun’ichi Shiraiwa for indicating that the scrape-off layer was most likely the location where LH wave power was being lost.

    Detailed research on the edge and scrape-off-layer conducted on Alcator C-Mod in the last two decades has documented that raising the total electrical current in the plasma narrows the width of the scrape-off-layer and reduces the level of turbulence there, suggesting that it may reduce or eliminate its deleterious effects on the microwaves.

    Motivated by this, PSFC researchers devised an LHCD experiment to push the total current by from 500,000 Amps to 1,400,000 Amps, enabled by C-Mod’s high-field tokamak operation. They found that the effectiveness of LCHD to generate plasma current, which had been lost at high density, reappeared. Making the width of the turbulent scrape-off layer very narrow prevents it from dissipating the microwaves, allowing higher densities to be reached beyond the LHCD density limit.

    The results from these experiments suggest a path to a steady-state fusion reactor. Baek believes they also provide additional experimental support to proposals by the PSFC to place the LHCD antenna at the high-field (inboard) side of a tokamak, near the central solenoid. Research suggests that placing it in this quiet area, as opposed to the turbulent outer midplane, would minimize destructive wave interactions in the plasma edge, while protecting the antenna and increasing its effectiveness. Principal Research scientist Steven Wukitch is currently pursuing new LHCD research in this area through PSFCs’ collaboration with the DIII-D tokamak in San Diego.

    Although existing tokamaks with LHCD are not operating at the high densities of C-Mod, Baek feels that the relationship between the current drive and the scrape-off layer could be investigated on any tokamak.

    “I hope our recipe for improving LHCD performance will be explored on other machines, and that these results invigorate further research toward steady-state tokamak operation,” he says.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.


    Stem Education Coalition

    MIT Seal

    The mission of MIT is to advance knowledge and educate students in science, technology, and other areas of scholarship that will best serve the nation and the world in the twenty-first century. We seek to develop in each member of the MIT community the ability and passion to work wisely, creatively, and effectively for the betterment of humankind.

    MIT Campus

     
  • richardmitnick 4:53 pm on August 22, 2018 Permalink | Reply
    Tags: , , Fusion technology, , , PPPL's QUEST journal,   

    From PPPL: Two Items 


    From PPPL

    Advances in plasma and fusion science are described in Quest, PPPL’s research magazine.

    1

    July 9, 2018
    Larry Bernard

    From analyzing solar flares to pursuing “a star in a jar” to produce virtually limitless electric power, scientists at the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL) have developed insights and discoveries over the past year that advance understanding of the universe and the prospect for safe, clean, and abundant energy for all humankind.

    “Our research sheds new light on the function of plasma, the state of matter that comprises 99 percent of the visible universe,” writes Steve Cowley, new director of PPPL, in the 2018 edition of Quest, PPPL’s annual research magazine. Quest, just published in July 2018, summarizes in short, easy-to-digest format, much of the research that occurred at PPPL over the last year.

    Among the stories are descriptions of how scientists are finding ways to calm instabilities that can lead to the disruption of fusion reactions. Such research is critical to the next steps in advancing fusion energy to enable fusion devices to produce and sustain reactions that require temperatures many times hotter than the core of the sun.

    Fusion, the power that drives the sun and stars, fuses light elements and releases enormous energy. If scientists can capture and control fusion on Earth, the process could provide clean energy to produce electricity for millions of years.

    Plasma, the state of matter composed of free electrons and atomic nuclei that fuels fusion reactions and makes up 99 percent of the visible universe, unites PPPL research from astrophysics to nanotechnology to the science of fusion energy. Could planets beyond our solar system be habitable, for example? PPPL and Princeton scientists say that stellar winds — the outpouring of charged plasma particles from the sun into space — could deplete a planet’s atmosphere and dry up life-giving water over hundreds of millions of years, rendering a blow to the theory that these planets could host life as we know it.

    Quest details efforts to understand the scientific basis of fusion and plasma behavior. For example, in the section on Advancing Fusion Theory, physicists describe how bubble-like “blobs” that arise at the edge of the plasma can carry off heat needed for fusion reactions. Improved understanding of such behavior could lead to better control of the troublesome blobs.

    Another story outlines how researchers are using a form of artificial intelligence called “machine learning” to predict when disruptions that can halt fusion reactions and damage fusion devices occur. The innovative technique has so far yielded outstanding results.

    Included in Quest are descriptions of collaborations PPPL scientists and engineers have working on fusion devices around the world. These collaborations include ITER, the large multinational fusion device under construction in France, as well as research on devices in China, South Korea, and at the National Ignition Facility in the United States.

    Read also about PPPL’s long-standing efforts to educate students, teachers, and the public around STEM (science, technology, engineering, and math), as well as some of the award-winning work by scientists and inventors at PPPL.

    Quest can be accessed here, or at this web address: https://www.pppl.gov/quest

    See the full article here .

    PPPL diagnostic is key to world record of German fusion experiment
    July 9, 2018
    John Greenwald

    2
    PPPL physicist Novimir Pablant, right, and Andreas Langenberg of the Max Planck Institute in front of the housing for the x-ray crystal spectrometer prior to its installation in the W7-X. (Photo by Scott Massida )

    When Germany’s Wendelstein 7-X (W7-X) fusion facility set a world record for stellarators recently, a finely tuned instrument built and delivered by the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL) proved the achievement.

    Wendelstein 7-AS built in built in Greifswald, Germany

    The record strongly suggests that the design of the stellarator can be developed to capture on Earth the fusion that drives the sun and stars, creating “a star in a jar” to generate a virtually unlimited supply of electric energy.

    The record achieved by the W7-X, the world’s largest and most advanced stellarator, was the highest “triple product” that a stellarator has ever created. The product combines the temperature, density and confinement time of a fusion facility’s plasma — the state of matter composed of free electrons and atomic nuclei that fuels fusion reactions — to measure how close the device can come to producing self-sustaining fusion power. (The triple product was 6 x 1026 degrees x second per cubic meter — the new stellarator record.)

    Spectrometer maps the temperature

    The achievement produced temperatures of 40 million degrees for the ions and an energy confinement time, which measures how long it takes energy to leak out across the confining magnetic fields of 0.22 seconds. (The density was 0.8 x 1020 particles per cubic meter.) Measuring the temperature was an x-ray imaging crystal spectrometer (XICS) built by PPPL physicist Novimir Pablant, now stationed at W7-X, and engineer Michael Mardenfeld at PPPL. “The spectrometer provided the primary measurement,” said PPPL physicist Sam Lazerson, who also collaborates on W7-X experiments.

    Pablant implemented the device with scientists and engineers of the Max Planck Institute of Plasma Physics (IPP), which operates the stellarator in the Baltic Sea town of Greifswald, Germany. “It has been a great experience to work closely with my colleagues here on W7-X,” Pablant said. “Installing the XICS system was a major undertaking and it has been a pleasure to work with this world-class research team. The initial results from these high-performance plasmas are very exciting, and we look forward to using the measurements from our instrument to further understanding of the confinement properties of W7-X, which is a truly unique magnetic fusion experiment.”

    Researchers at IPP welcomed the findings. “Without XICS we could not have confirmed the record,” said Thomas Sunn Pedersen, director of stellarator edge and divertor physics at IPP. Concurred physicist Andreas Dinklage, lead author of a Nature Physics (link is external) paper confirming a key feature of the W7-X physical design: “The XICS data set was one of the very valuable inputs that confirmed the physics predictions.”

    PPPL physicist David Gates, technical coordinator of the U.S. collaboration on W7-X, oversaw construction of the instrument. “The XICS is an incredibly precise device capable of measuring very small shifts in wavelength,” said Gates. “It is a crucial part of our collaboration and we are very grateful to have the opportunity to participate in these important experiments on the groundbreaking W7-X device.”

    PPPL provides added components

    PPPL has designed and delivered additional components installed on the W7-X. These include a set of large trim coils that correct errors in the magnetic field that confines W7-X plasma, and a scraper unit that will lessen the heat reaching the divertor that exhausts waste heat from the fusion facility.

    The recent world record was a result of upgrades that IPP made to the stellarator following the initial phase of experiments, which began in December 2015. Improvements included new graphite tiles that enabled the higher temperatures and longer duration plasmas that produced the results. A new round of experiments is to begin this July using the new scraper unit that PPPL delivered.

    Stellarators, first constructed in the 1950s under PPPL founder Lyman Spitzer, can operate in a steady state, or continuous manner, with little risk of the plasma disruptions that doughnut-shaped tokamak fusion facilities face. But tokamaks are simpler to design and build, and historically have confined plasma better, which accounts for their much wider use in fusion laboratories around the world.

    An overall goal of the W7-X is to show that the twisty stellarator design can confine plasma just as well as tokamaks. When combined with the ability to operate virtually free of disruptions, such improvement could make stellarators excellent models for future fusion power plants.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition


    PPPL campus

    Princeton Plasma Physics Laboratory is a U.S. Department of Energy national laboratory managed by Princeton University. PPPL, on Princeton University’s Forrestal Campus in Plainsboro, N.J., is devoted to creating new knowledge about the physics of plasmas — ultra-hot, charged gases — and to developing practical solutions for the creation of fusion energy. Results of PPPL research have ranged from a portable nuclear materials detector for anti-terrorist use to universally employed computer codes for analyzing and predicting the outcome of fusion experiments. The Laboratory is managed by the University for the U.S. Department of Energy’s Office of Science, which is the largest single supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.

     
  • richardmitnick 3:00 pm on August 8, 2018 Permalink | Reply
    Tags: Fusion technology, , Touring IPP’s fusion devices per virtual-reality viewer,   

    From Max Planck Institute for Plasma Physics: “Touring IPP’s fusion devices per virtual-reality viewer” 

    MPIPP bloc

    From Max Planck Institute for Plasma Physics

    Max-Planck-Institut für Plasmaphysik
    Press office
    Phone:+49 89 3299-2607Fax:+49 89 3299-2622
    info@ipp.mpg.de

    August 07, 2018

    ASDEX Upgrade and Wendelstein 7-X – as if you were there / 360° view of fusion research

    Wendelstgein 7-X stellarator, built in Greifswald, Germany

    2
    Visit IPP’s research devices any time by virtual reality cardboard viewer and smartphone. Illustration: IPP, Reinald Fenke

    You seem to be standing in the plasma vessel looking around: Where otherwise plasmas with temperatures of several million degrees are being investigated, with a virtual-reality viewer you can now roam around there.

    he viewer gives access at any time to the plasma vessel of the ASDEX Upgrade fusion device at Max Planck Institute for Plasma Physics (IPP) in Garching, upstairs, downstairs and in the control room. The plasma vessel of IPP’s Wendelstein 7-X device at Greifswald is likewise always open for a virtual visit, as well as the experimentation hall and the facilities for microwave heating.

    Here’s the way to ASDEX Upgrade and Wendelstein 7-X:
    http://www.sonnenmaschine-vr.de and
    http://www.sternenmaschine-vr.de

    A cardboard viewer or a VR headset provides virtual access by smartphone (with gyro function and acceleration sensor) or directly on the screen of a PC or tablet, depending on the type of viewer used*. And here’s how it works: Select the web address of the device wanted and click there the viewer symbol to select the virtual-reality mode. The screen then splits in two, one bit for each eye, thus providing a spatial image. Now put on the headset or attach the smartphone to the viewer and then you can look in any direction. The VR Setup link on the split screen adapts the image to the smartphone or headset used. Selector switches put you through to the various sites.

    The panoramas were photographed by Volker Steger and the VR conversion was done by Eduard Plesa.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    MPIPP campus

    The Max Planck Institute of Plasma Physics (Max-Planck-Institut für Plasmaphysik, IPP) is a physics institute for the investigation of plasma physics, with the aim of working towards fusion power. The institute also works on surface physics, also with focus on problems of fusion power.

    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 IPP has two sites: Garching near Munich (founded 1960) and Greifswald (founded 1994), both in Germany.

    It owns several large devices, namely

    the experimental tokamak ASDEX Upgrade (in operation since 1991)
    the experimental stellarator Wendelstein 7-AS (in operation until 2002)
    the experimental stellarator Wendelstein 7-X (awaiting licensing)
    a tandem accelerator

    It also cooperates with the ITER and JET projects.

     
  • richardmitnick 8:02 pm on August 7, 2018 Permalink | Reply
    Tags: Fusion technology, Lauren Garrison, ,   

    From Oak Ridge National Laboratory: Women in STEM: “Lauren Garrison: Testing materials for the future of fusion” 

    i1

    From Oak Ridge National Laboratory

    August 7, 2018
    Sean Simoneau
    Communications
    simoneausm@ornl.gov
    865.241.0709


    Lauren Garrison

    The materials inside a fusion reactor must withstand one of the most extreme environments in science, with temperatures in the thousands of degrees Celsius and a constant bombardment of neutron radiation and deuterium and tritium, isotopes of hydrogen, from the volatile plasma at the heart of the device.

    Conventional materials cannot endure such punishing conditions, requiring tougher novel materials to be researched and designed before fusion reactors can move from basic science to potential future energy sources. One of the fusion materials researchers looking to find a possible candidate is Lauren Garrison, a Weinberg Fellow in the Nuclear Materials Science and Technology Group at the Department of Energy’s Oak Ridge National Laboratory.

    “I’m drawn to plasma facing materials because it is such a challenging environment, so unique and complex, trying to understand how we can have a material that can withstand all of these very difficult conditions,” Garrison said.

    Working with plasma-facing materials is especially tricky, as the environment inside a fusion reactor is like no place on Earth, so the long, arduous process of testing new materials can sometimes feel like assembling a puzzle with no edge pieces to provide a helpful framework.

    “Many of the structural and cooling components have some comparable materials that would be used in a fission reactor, so there is some sort of jumping-off point,” Garrison said. “But the plasma-facing region, which is extremely hot and fusing on one side and connected to structural materials on the other side, has nothing comparable in fission, so it is very specific to this application.”

    Garrison first studied nuclear engineering during her time as an undergrad at the University of Illinois and had several diverse research internship experiences before finding nuclear materials, which she found distinctly interesting and wished to pursue as a career.

    She interned at the university’s Center for Plasma-Materials Interaction, researching plasma processing and plasma modification of surfaces. It was the first research area that caught her attention and gave her experience with lab testing that she hadn’t previously seen in her other classes.

    She then interned at a chemistry lab at the National Polytechnic Institute of Lorraine in Nancy, France, which provided an incredible opportunity to branch out into other subjects and gain a perspective on science culture in another country.

    “As an engineering or science student, having internship experiences is crucial for both getting the hands-on work and getting a sense for the field, for the actual work environment and for different companies or labs,” Garrison said.

    She worked for a short time in the Cryogenic Dark Matter Search research group at Fermi National Accelerator Laboratory before being selected for the DOE Office of Science graduate fellowship program, where she first got to visit ORNL and learn how it supported many nuclear materials projects, especially in fusion materials, that were relevant to her interests.

    “No other national lab had the same range of capabilities as ORNL, matched with these amazing materials analysis techniques,” Garrison said. “Whereas smaller labs or universities might be experts in one specific technique, what we have here is the combined benefit of expert scientists in many subareas and the tools to perform all the tests together and compare everything.”

    Garrison had found a place that aligned with her interests and would allow her to push the boundaries of her knowledge. ORNL, as a leader in the field of neutron irradiated materials, enabled her to collaborate with other research groups from around the world to test new materials and processes on a wider scale than was possible at other facilities.

    Garrison is currently collaborating with Japanese researchers on Project PHENIX, an experiment designed to evaluate tungsten and tungsten-based materials for possible use in future fusion reactors.

    The team built a specially instrumented capsule with four different temperature zones to hold more than 1,100 material samples for irradiation in the High Flux Isotope Reactor, a DOE Office of Science User Facility.

    ORNL High Flux Isotope Reactor

    After exposing the capsule to several fuel cycles in HFIR and a cooldown period in a hot cell, Garrison and the project team are now examining the materials to gauge the effects of high heat flux and neutron damage on their microstructures and physical properties.

    The goal of her work is to use the results of these varied tests and create a more well-rounded database of potential fusion materials, connect new information together and fill in the knowledge gaps in the field.

    “At this point, we’re not going to find a magic material that’s perfect in every different condition it needs to withstand, so we are going to have to make a compromise or understand where the weaknesses are,” Garrison said. “The only way we can move towards building something successful is with the broad testing of materials on many different axes to be able to compare them to each other.”

    Garrison would love to see a working fusion reactor in her lifetime and hopes that her work will help contribute to its creation. For now, though, fusion research is still based in basic science, which allows her to pursue questions without specific constraints or a final product in mind.

    “It’s very rewarding for me to be able to think creatively and have some freedom to investigate different avenues,” she said.

    As time goes on and more of the big questions in plasma science are answered, Garrison hopes the public will come to recognize the potential of fusion energy and how the current investments will pay off in the future.

    “I love the big picture of fusion and I think it is easy to get people excited about how great it is for energy,” she said. “Every time I get to talk about it, I get inspired and remember why I’m writing these long reports and doing all this work, because it has really cool applications that it is going towards.”

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    ORNL is managed by UT-Battelle for the Department of Energy’s Office of Science. DOE’s Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time.

    i2

     
  • richardmitnick 11:37 am on July 31, 2018 Permalink | Reply
    Tags: Cori at NERSC, Fusion technology, , ,   

    From PPPL: “Newest supercomputer to help develop fusion energy in international device” 


    From PPPL

    July 25, 2018
    John Greenwald

    Scientists led by Stephen Jardin, principal research physicist and head of the Computational Plasma Physics Group at the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL), have won 40 million core hours of supercomputer time to simulate plasma disruptions that can halt fusion reactions and damage fusion facilities, so that scientists can learn how to stop them. The PPPL team will apply its findings to ITER, the international tokamak under construction in France to demonstrate the practicality of fusion energy. The results could help ITER operators mitigate the large-scale disruptions the facility inevitably will face.

    ITER Tokamak in Saint-Paul-lès-Durance, which is in southern France

    Receipt of the highly competitive 2018 ASCR Leadership Computing Challenge (ALCC) award entitles the physicists to simulate the disruption on Cori, the newest and most powerful supercomputer at the National Energy Research Scientific Computing Center (NERSC) at Lawrence Berkeley National Laboratory.

    NERSC Cray Cori II supercomputer at NERSC at LBNL, named after Gerty Cori, the first American woman to win a Nobel Prize in science

    NERSC, a U.S. Department of Energy Office of Science user facility, is a world leader in accelerating scientific discovery through computation.

    Model the entire disruption

    “Our objective is to model development of the entire disruption from stability to instability to completion of the event,” said Jardin, who has led previous studies of plasma breakdowns. “Our software can now simulate the full sequence of an ITER disruption, which could not be done before.”

    Fusion, the power that drives the sun and stars, is the fusing of light elements in the form of plasma — the hot, charged state of matter composed of free electrons and atomic nuclei — that generates massive amounts of energy. Scientists are seeking to replicate fusion on Earth for a virtually inexhaustible supply of power to generate electricity.

    The award of 40 million core hours on Cori, a supercomputer named for Nobel Prize-winning biochemist Gerty Cori that has hundreds of thousands of cores that act in parallel, will enable the physicists to complete in weeks what a single-core laptop computer would need thousands of years to accomplish. The high-performance computing machine will scale up simulations for ITER and perform other tasks that less powerful computers would be unable to complete.

    On Cori the team will run the M3D-C1 code primarily developed by Jardin and PPPL physicist Nate Ferraro. The code, developed and upgraded over a decade, will evolve the disruption simulation forward in a realistic manner to produce quantitative results. PPPL now uses the code to perform similar studies for current fusion facilities for validation.

    The simulations will also cover strategies for the mitigation of ITER disruptions, which could develop from start to finish within roughly a tenth of a second. Such strategies require a firm understanding of the physics behind mitigations, which the PPPL team aims to create. Together with Jardin and Ferraro on the team are physicist Isabel Krebs and computational scientist Jin Chen.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition


    PPPL campus

    Princeton Plasma Physics Laboratory is a U.S. Department of Energy national laboratory managed by Princeton University. PPPL, on Princeton University’s Forrestal Campus in Plainsboro, N.J., is devoted to creating new knowledge about the physics of plasmas — ultra-hot, charged gases — and to developing practical solutions for the creation of fusion energy. Results of PPPL research have ranged from a portable nuclear materials detector for anti-terrorist use to universally employed computer codes for analyzing and predicting the outcome of fusion experiments. The Laboratory is managed by the University for the U.S. Department of Energy’s Office of Science, which is the largest single supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.

     
  • richardmitnick 12:29 pm on July 6, 2018 Permalink | Reply
    Tags: ELISE, Fusion technology, , MIPP   

    From Max Planck Institute for Plasma Physics: IPP’s ELISE test rig achieves first ITER objective 

    MPIPP bloc

    From Max Planck Institute for Plasma Physics

    July 04, 2018
    Isabella Milch

    Neutral-particle heating for ITER / Fast-hydrogen-particle beam for plasma heating.

    The heating beam in the ELISE test rig at Max Planck Institute for Plasma Physics (IPP) at Garching near Munich has attained the values needed for ITER: It can maintain for 1,000 seconds a particle beam composed of negatively charged hydrogen ions with the current strength of 23 amperes desired by ITER.
    ELISE is serving to prepare one of the heating methods that are to bring the plasma of the international ITER test reactor to several million degrees. The core piece is a novel high-frequency ion source developed at IPP that produces the high-energy particle beam.

    1
    One of the accelerator grids that get the hydrogen atoms in the ELISE ion source to the right velocity. The particle beam is extracted as individual beams through 640 small apertures in the grid surface of about a square metre. Photo: IPP

    The international ITER (Latin for ‘the way’) test reactor, now being built in France as a world-wide cooperation, is to demonstrate that a fusion fire supplying energy is possible.

    Iter experimental tokamak nuclear fusion reactor that is being built next to the Cadarache facility in Saint Paul les-Durance south of France

    Like the sun, a future fusion power plant is to derive energy from fusion of atomic nuclei. The fuel, viz. a hydrogen plasma, has to be confined without wall contact in a magnetic field cage and be heated to ignition temperatures exceeding 100 million degrees. ITER is to produce 500 megawatts of fusion power, this being ten times as much as needed beforehand to heat the plasma.

    About half of this plasma heating will be provided by the neutral-particle heating: Fast hydrogen atoms injected through the magnetic field cage into the plasma transfer their energy to the plasma particles by way of collisions. For this purpose, an ion source produces from hydrogen gas charged hydrogen ions that are accelerated by high voltage and finally re-neutralised so that, as fast hydrogen atoms, they can penetrate into the plasma unhampered by the magnetic field.

    This method enables present-day heating systems, e.g. that for IPP’s ASDEX Upgrade fusion device at Garching, to bring the plasma to a multiple of the sun’s temperature at the click of a button. The ITER large-scale device, however, presents higher requirements: For example, the particle beams have to be much thicker and the individual particles be much faster than hitherto so that they can penetrate the voluminous ITER plasma to a sufficient depth. Two particle beams with cross-sections about the size of an ordinary door are to feed 16.5 megawatts of heating power into the ITER plasma. ITER will thus greatly surpass the particle beams used in today’s fusion devices, which make do with cross-sections about the size of a dinner plate and much lower velocity.

    Therefore, instead of the positively charged ions used hitherto, which cannot be effectively neutralised at high energies, for ITER it is necessary to use negatively charged ions, which are extremely fragile. A high-frequency ion source developed for the purpose at IPP was incorporated in the ITER design. At the end of 2012 IPP was given a contract for further development and adaptions to ITER requirements.

    The ELISE (Extraction from a Large Ion Source Experiment) test rig constitutes a source half as large as that for ITER later. ELISE generates an ion beam with a cross-sectional area of about a square metre. The increased format made it necessary to revise the previous technical solutions for the heating method (see PI 2/2015). ELISE has advanced step by step to new orders of magnitude. “Now we are able to produce the desired 23-ampere particle beam of negatively charged hydrogen ions, stable, homogeneous and lasting 1,000 seconds”, states Professor Dr Ursel Fantz, head of IPP’s ITER Technology and Diagnostics division. “The gas pressure in the source and the quantity of electrons retained also meet ITER’s requirements”. It was only the current density of the ion beam that was not quite attained, this being due to the limited power capability of the high-voltage supply available.

    Where does it go from here?

    Now that ELISE has attained the ion current required by ITER with ordinary hydrogen it is time to tackle the second part of the task and produce ion beams from deuterium, the heavy isotope of hydrogen, albeit not just for 1,000 seconds, but for a whole hour. The system in the original size will be investigated by Italy’s fusion institute, ENEA, in Padua, who will collaborate with IPP. The SPIDER (Source for Production of Ions of Deuterium Extracted from Radio-frequency Plasma) test device was commissioned at Padua in early June. The target data: one-hour pulses with full ITER beam cross-section and 6 megawatts of power in hydrogen and deuterium.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    MPIPP campus

    The Max Planck Institute of Plasma Physics (Max-Planck-Institut für Plasmaphysik, IPP) is a physics institute for the investigation of plasma physics, with the aim of working towards fusion power. The institute also works on surface physics, also with focus on problems of fusion power.

    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 IPP has two sites: Garching near Munich (founded 1960) and Greifswald (founded 1994), both in Germany.

    It owns several large devices, namely

    the experimental tokamak ASDEX Upgrade (in operation since 1991)
    the experimental stellarator Wendelstein 7-AS (in operation until 2002)
    the experimental stellarator Wendelstein 7-X (awaiting licensing)
    a tandem accelerator

    It also cooperates with the ITER and JET projects.

     
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