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  • richardmitnick 2:02 pm on January 1, 2015 Permalink | Reply
    Tags: , , Plasma Physics   

    From physicstoday: “Plasma wakefield acceleration shows promise” 

    physicstoday bloc

    physicstoday

    January 2015
    Johanna L. Miller

    When electrons are precisely positioned in a region of high electric field, they can pick up a lot of energy in a small space.

    In their quest to test the standard model. and search for new physics beyond it, particle physicists have sought ever larger and more powerful facilities for accelerating and colliding charged particles.

    sm
    The Standard Model of elementary particles, with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth.

    Conventionally, accelerators rely on metal plates and resonators to generate electric fields and RF waves. The magnitude of those fields is limited to tens of megavolts per meter, so to accelerate particles to 125 GeV (the energy of the Higgs boson) or more requires a path of many kilometers. Protons and heavier particles can be accelerated in circles, but electrons and positrons must be accelerated in straight lines, lest they lose all their energy to synchrotron radiation. The 3-km linear accelerator at SLAC is currently the world’s longest; reaching the high energies relevant to particle physics with a conventional electron accelerator would require a much larger, costlier facility.

    Accelerators based on plasmas, which can sustain electric fields up to tens of gigavolts per meter, have the potential to be a smaller and cheaper alternative. An electron-density wave in a plasma, co-propagating with a charged-particle bunch, can keep the bunch in a high-field region over a path of a meter or more, thereby imparting a lot of energy to the particles in a compact space. But the precision engineering required to accelerate particles efficiently and uniformly has been a challenge.

    Now Chandrashekhar Joshi (at UCLA), Michael Litos, Mark Hogan (both at SLAC), and their colleagues have taken a leap forward. In their plasma wakefield accelerator, the plasma wave is created by a 20-GeV electron bunch from SLAC’s linac. A second bunch of equally energetic electrons follows close behind. With SLAC’s purpose-built Facility for Advanced Accelerator Experimental Tests, the researchers could place the trailing bunch at just the right spot in the plasma wave to increase the bunch energy by 1.6 GeV over just 30 cm of plasma.

    SLAC FACET Line
    SLAC FACET

    Energy boost

    Plasma acceleration schemes, first proposed by John Dawson in the 1970s, come in two basic types. (See the article by Joshi and Thomas Katsouleas, Physics Today, June 2003, page 47.) In laser wakefield acceleration, the plasma wave is created by the radiation pressure of an intense laser pulse. Because the wave can accelerate particles almost from rest, the scheme offers a way to create self-contained tabletop accelerators for moderate-energy applications, such as medicine and materials science. (See the article by Wim Leemans and Eric Esarey, Physics Today, March 2009, page 44.)

    In plasma wakefield acceleration, on the other hand, one bunch of fast-moving particles drives the plasma wave that accelerates another bunch. Both bunches must start out at ultrarelativistic energies, traveling so close to the speed of light that their separation doesn’t change even as the first bunch loses energy and the second gains energy. The scheme is therefore not suitable for free-standing accelerators; instead it is being developed as a way to boost the energy of large linacs. (For the same reason, it’s far better suited to accelerating electrons than protons, which would need 2000 times as much energy to reach the ultrarelativistic starting point.)

    Litos likens the plasma wakefield accelerator to an electrical transformer converting a large bunch of moderate-energy electrons into a smaller bunch at higher energy. That capability would be useful for particle-physics experiments, in which high collision energies are critical in the search for new physics. It also has the potential to reduce the size and cost of x-ray free-electron lasers. The Linac Coherent Light Source at SLAC, currently the only operating XFEL, uses electrons accelerated over 1 km of the linac. (See Physics Today, August 2009, page 21.) Plasma wakefield boosters on a smaller linac could, says Litos, “make XFELs more palatable to universities rather than just national labs.”

    SLAC LCLS
    SLAC LCLS Inside
    SLAC LCLS

    Riding the wave

    Figure 1 shows a simulation of the process under the conditions used in the new experiment. The drive bunch pushes away the plasma electrons, leaving a region of net positive charge in its wake. (The plasma ions, not shown in the figure, are heavy enough to be unaffected.) At the back of the wake, the longitudinal electric field E z is strongly negative, capable of accelerating electrons in the direction of travel.

    2
    Figure 1. Simulations of a plasma wakefield interaction, with beam density shown in orange, plasma-electron density in blue, and the longitudinal electric field E z as an orange curve. (a) The drive bunch clears away the plasma electrons, leaving a region of strong but inhomogeneous electric field in its wake. (b) If the trailing bunch is large enough and positioned in the right spot, it can flatten the electric field so that the trailing bunch is uniformly accelerated.

    But the field in the wake of the drive bunch alone, shown in figure 1 a, is far from homogeneous. Electrons separated by just a few microns would gain energy at vastly different rates. That’s bad for collider experiments, which require particles as close to a single energy as possible.

    Fortunately, if the trailing bunch is large enough, its own effect on E z can be significant. As shown in figure 1 b, E z is reduced in magnitude, but also flattened, to a near constant −5 GV/m. Using a denser plasma would yield a stronger E z . But it would also reduce the size of the wake and make positioning the trailing bunch more difficult.

    Beam gymnastics

    Earlier proof-of-principle plasma wakefield experiments have used, instead of a pair of electron bunches, a single elongated bunch. The physics is the same—the electrons at the back of the bunch are accelerated by the wake produced by those at the front. But to achieve the desired small energy spreads, it’s necessary to use two discrete bunches separated by about 100 µm, or 300 fs. The only way to make such closely spaced bunches is by crafting them out of a single linac bunch.

    To accomplish that, the researchers first used magnets to elongate the bunch to about 2 mm, with the highest-energy electrons in the front. Then, as shown in figure 2 , they rotated the bunch and allowed it to collide with a thin tantalum bar. Electrons that struck the bar were scattered and removed from the beam, whereas those on either side kept going. Rotating the bunch again and compressing it down to submillimeter size gave the desired two-bunch structure.

    3
    Figure 2. Two bunches from one. An electron bunch from the SLAC linear accelerator is dispersed according to its energy—here, the high-energy end of the bunch is shown in red and the low-energy end in blue. The bunch is then allowed to collide with a thin tantalum bar, which scatters the middle portion of the bunch out of the beam.

    The plasma was created from a chamber full of lithium vapor; 100 ps before the electrons’ arrival, the researchers shot a laser pulse through the vapor to ionize the Li atoms and create a 1-mm-wide tunnel of plasma, which remained ionized for several nanoseconds, plenty of time for the plasma wake to do its work.

    The researchers then measured the outgoing electrons to see what had happened. Figure 3 shows the energy spectrum of one of their trials compared with the outcome of the simulation from figure 1 b. In each case, both bunches started at 20.35 GeV; the drive bunch lost energy and broadened, whereas the trailing bunch gained energy and remained sharply peaked. The red dashed line shows a fit to the energetic core of the trailing bunch, with an energy spread of 2%.

    4
    Figure 3. Energy profiles of the simulated and actual electron bunches after they interact with the plasma. In both cases, the drive bunch, which begins with an energy just above 20 GeV, loses energy and broadens. The trailing bunch gains energy and is dominated by the sharply peaked core.

    What lies ahead

    Clearly, much work remains to be done: An energy gain of less than 10% is hardly going to revolutionize high-energy physics. Furthermore, of the 800 pC that started out in the trailing bunch, only 74 pC remained in the accelerated core. Better preservation of the beam is a priority for the SLAC team’s future work.

    One way to reach higher energies is simply by making the plasma chamber longer. With the setup as it is, plasma wakefield acceleration can continue for several meters before the drive bunch runs out of energy. The researchers are working on ways to daisy-chain several plasma accelerators together to pass the same trailing bunch from one to the next but use a fresh drive bunch each time.

    A high-energy collider experiment would need not just accelerated electrons but also positrons of equal energy. Plasma wakefield acceleration of positrons is tricky because of their positive charge: They draw the plasma electrons toward them rather than clearing them away, and the resulting wake structure is much less conducive to accelerating a trailing bunch. “But we’ve been making progress,” says Litos, “and we hope to publish some results soon.”

    Some simulations of plasma wakefield acceleration have predicted a phenomenon called the hosing instability, in which the electric field perpendicular to the direction of travel causes the trailing bunch to wobble back and forth with increasing amplitude and eventually break apart. But not only did the researchers see no sign of the hosing instability in their experiments, they couldn’t produce it even when they tried. “That was an interesting surprise, and rather encouraging,” says Litos. “The hosing instability had been predicted to be a potential show stopper.”

    See the full article here.

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  • richardmitnick 5:32 pm on November 20, 2014 Permalink | Reply
    Tags: , , , Plasma Physics,   

    From NSF: “A deep dive into plasma” 

    nsf
    National Science Foundation

    November 20, 2014
    No Writer Credit

    Renowned physicist uses NSF-supported supercomputer and visualization resources to gain insight into plasma dynamic

    Studying the intricacies and mysteries of the sun is physicist Wendell Horton’s life’s work. A widely known authority on plasma physics, his study of the high temperature gases on the sun, or plasma, consistently leads him around the world to work on a diverse range of projects that have great impact.

    Fusion energy is one such key scientific issue that Horton is investigating and one that has intrigued researchers for decades.

    “Fusion energy involves the same thermonuclear reactions that take place on the sun,” Horton said. “Fusing two isotopes of hydrogen to create helium releases a tremendous amount of energy–10 times greater than that of nuclear fission.”

    It’s no secret that the demand for energy around the world is outpacing the supply. Fusion energy has tremendous potential. However, harnessing the power of the sun for this burgeoning energy source requires extensive work.

    Through the Institute for Fusion Studies at The University of Texas at Austin, Horton collaborates with researchers at ITER, a fusion lab in France and the National Institute for Fusion Science in Japan to address these challenges. At ITER, Horton is working with researchers to build the world’s largest tokamak–the device that is leading the way to produce fusion energy in the laboratory.

    ITER Tokamak
    ITER tokamak

    “Inside the tokamak, we inject 10 to 100 megawatts of power to recreate the conditions of burning hydrogen as it occurs in the sun,” Horton said. “Our challenge is confining the plasma, since temperatures are up to 10 times hotter than the center of the sun inside the machine.”

    Perfecting the design of the tokamak is essential to producing fusion energy, and since it is not fully developed, Horton performs supercomputer simulations on the Stampede supercomputer at the Texas Advanced Computing Center (TACC) to model plasma flow and turbulence inside the device.

    “Simulations give us information about plasma in three dimensions and in time, so that we are able to see details beyond what we would get with analytic theory and probes and high-tech diagnostic measurements,” Horton said.

    The simulations also give researchers a more holistic picture of what is needed to improve the tokamak design. Comparing simulations with fusion experiments in nuclear labs around the world helps Horton and other researchers move even closer to this breakthrough energy source.

    Plasma in the ionosphere

    Because the mathematical theories used to understand fusion reactions have numerous applications, Horton is also investigating space plasma physics, which has important implications in GPS communications.

    GPS signaling, a complex form of communication, relies on signal transmission from satellites in space, through the ionosphere, to GPS devices located on Earth.

    “The ionosphere is a layer of the atmosphere that is subject to solar radiation,” Horton explained. “Due to the sun’s high-energy solar radiation plasma wind, nitrogen and oxygen atoms are ionized, or stripped of their electrons, creating plasma gas.”

    These plasma structures can scatter signals sent between global navigation satellites and ground-based receivers resulting in a “loss-of-lock” and large errors in the data used for navigational systems.

    Most people who use GPS navigation have experienced “loss-of-lock,” or instance of system inaccuracy. Although this usually results in a minor inconvenience for the casual GPS user, it can be devastating for emergency response teams in disaster situations or where issues of national security are concerned.

    To better understand how plasma in the ionosphere scatters signals and affects GPS communications, Horton is modeling plasma turbulence as it occurs in the ionosphere on Stampede. He is also sharing this knowledge with research institutions in the United States and abroad including the UT Space and Geophysics Laboratory.

    Seeing is believing

    Although Horton is a long-time TACC partner and Stampede user, he only recently began using TACC’s visualization resources to gain deeper insight into plasma dynamics.

    “After partnering with TACC for nearly 10 years, Horton inquired about creating visualizations of his research,” said Greg Foss, TACC Research Scientist Associate. “I teamed up with TACC research scientist, Anne Bowen, to develop visualizations from the myriad of data Horton accumulated on plasmas.”

    Since plasma behaves similarly inside of a fusion-generating tokamak and in the ionosphere, Foss and Bowen developed visualizations representing generalized plasma turbulence. The team used Maverick, TACC’s interactive visualization and data analysis system to create the visualizations, allowing Horton to see the full 3-D structure and dynamics of plasma for the first time in his 40-year career.

    p
    This image visualizes the effect of gravity waves on an initially relatively stable rotating column of electron density, twisting into a turbulent vortex on the verge of complete chaotic collapse. These computer generated graphics are visualizations of data from a simulation of plasma turbulence in Earth’s ionosphere. The same physics are also applied to the research team’s investigations of turbulence in the tokamak, a device used in nuclear fusion experiments.Credit: Visualization: Greg Foss, TACC Visualization software support: Anne Bowen, Greg Abram, TACC Science: Wendell Horton, Lee Leonard, U. of Texas at Austin

    “It was very exciting and revealing to see how complex these plasma structures really are,” said Horton. “I also began to appreciate how the measurements we get from laboratory diagnostics are not adequate enough to give us an understanding of the full three-dimensional plasma structure.”

    Word of the plasma visualizations soon spread and Horton received requests from physics researchers in Brazil and researchers at AMU in France to share the visualizations and work to create more. The visualizations were also presented at the XSEDE’14 Visualization Showcase and will be featured at the upcoming SC’14 conference.

    Horton plans to continue working with Bowen and Foss to learn even more about these complex plasma structures, allowing him to further disseminate knowledge nationally and internationally, also proving that no matter your experience level, it’s never too late to learn something new.
    — Makeda Easter, Texas Advanced Computing Center (512) 471-8217 makeda@tacc.utexas.edu
    — Aaron Dubrow, NSF (703) 292-4489 adubrow@nsf.gov

    Investigators
    Wendell Horton
    Daniel Stanzione

    Related Institutions/Organizations
    Texas Advanced Computing Center
    University of Texas at Austin

    Locations
    Austin , Texas

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    Leadership-Class System Acquisition – Creating a Petascale Computing Environment for Science and Engineering

    See the full article here.

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  • richardmitnick 7:02 pm on July 14, 2014 Permalink | Reply
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    From PPPL: “Students try out PPPL plasma physics experiment that can be accessed from anywhere in the world” March 2014 


    PPPL

    March 13, 2014
    Jeanne Jackson DeVoe

    Students at West Windsor-Plainsboro High School South in West Windsor, N.J. were enthralled when they watched a glowing pink plasma appear on a screen in their classroom in a video stream of PPPL’s Remote Glow Discharge Experiment (RGDX) five miles away.

    The March 12 event marked the first public demonstration of an invention that fills a gap in online education by providing students anywhere in the world with a way to take part in an actual experiment online.

    Students in one class shouted out, “Whoa!” when the plasma first appeared. “I think it’s really cool!” said Paige Kunkler, a senior. “It’s an opportunity to do something that’s never been done before.”

    Online learning has become increasingly popular: Thousands of people are taking advantage of Massive Open Online Courses (or MOOCs) and a variety of online courses available at every level from K-12 to graduate-level courses, together with virtual simulations and YouTube science demonstrations. However, it is difficult to find a real online experiment like RGDX that anyone in the public can use from anywhere in the world.

    An online physics experiment for students and teachers

    While the high school is only a few miles from the Science Education Laboratory at the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL) in Plainsboro, physicist Arturo Dominguez of PPPL’s Science Education Department, pointed out that the RGDX could just as easily be used by students in Japan. It can be used by anyone with access to a computer and can easily be accessed by physics teachers or as an experimental component of an online physics course.

    pc
    more
    Controlling a lab from home

    The Remote Control Glow Discharge (RGDX) is a plasma that you can control from the comfort of your browser. YOU have control of the entire experiment including the gas pressure inside the tube, the voltage produced by the power supply that makes the plasma, and the strength of an electromagnet surrounding the plasma. You can perform experiments from any computer anywhere in the world!

    In 2002, we began developing plasma sources for educational purposes and one of our devices won 2nd place in the National Apparatus Competition sponsored by the American Association of Physics Teachers. In 2003, we began controlling our plasma sources by computer for a plasma exhibit in a science museum. The progression of this has led to remote control of a plasma from any location by anyone with an internet connection. This type of control could serve as an experimental component of an online physics class or for a school that typically does not have plasma physics equipment.

    As with all other Science Education Department labs, the RGDX has been developed in large part by high school and undergraduate interns.

    The Remote Glow Discharge Experiment was officially released to the public on 3/12/2014.

    “We’re very excited about what we’re unveiling,” Dominguez told the class. “It’s created specifically for students and those who are interested in science. We believe this is the next step in online education. It’s bringing the laboratory to students.”

    Dominguez explained that the RGDX provides a hands-on way for students to learn about plasma — a hot, charged gas that is the fourth state of matter — and observe what happens when they change the conditions in the machine through the online controls. Students using a personal computer can easily go to http://scied-web.pppl.gov/rgdx/, sign on to the queue and get started with the experiment.

    The RGDX, developed by Dominguez and Andrew Zwicker, head of the Science Education Department, allows students to manipulate a plasma and make it glow inside a glass tube in a device located in the Science Education laboratory. Students see their results in real time through a streaming video of the plasma in the device and can see how the plasma changes as they use the controls to change the conditions inside the glass tube.

    The tube is connected to a vacuum pump. It is encircled by two electromagnetic coils and connected to electrodes at either end of the device. Students can use the controls to change the pressure in the tube, the voltage between the electrodes and the strength of the magnetic field to create the plasma and to make it glow.

    After the demonstration, Dominguez placed a video conference call that appeared on the screen to Liutauras Rusaitis, a software developer in the Science Education laboratory who works on the RGDX. Rusaitis showed the students the Science Education laboratory and the actual machine through a Google Hangout session. “I was here when you were controlling the experiment and it felt sort of magical,” he said.

    Taking students through easy and difficult physics topics

    Dominguez pointed out that the online site guides students through the experiment, taking them from relatively easy concepts like, “What is a plasma?” to more difficult concepts like, “What does the electromagnet do to the plasma?” The tasks themselves range from relatively simple ones as students set the controls to the suggested levels, to more advanced tasks in which students can determine how much voltage makes the plasma glow. In the process, students learn the physics of plasmas and of pressure, electrode voltage and electromagnets. All these concepts are related to the study of plasma physics at the Princeton Plasma Physics Laboratory, where researchers are developing the science required to produce magnetic fusion as a clean and abundant source of energy for generating electricity.

    “There’s nothing like it in the world,” said Andrew Zwicker, head of the Science Education Department, who developed the device with Dominguez and their students. “The idea of doing something similar for educational purposes has been around for some time, but this is the first prototype of a fully open remote-controlled laboratory available for learners of all backgrounds. The best way to learn science is by doing, and this is the next step for online science education.”

    Both students and teachers were enthusiastic about the RGDX demonstration. “I think it’s amazing,” said Barbara Fortunato, the high school physics teacher whose classes tried out the device. “I think it’s great to bring plasma as a topic to high school science because it really doesn’t appear anywhere else.”

    High school junior Snigdha Kasi said the experiment brings a new dimension to her class. “We get taught about this stuff and this just opens it up and lets people look into something so much deeper,” she said.

    The RGDX currently works on PC and Mac personal computers. Dominguez plans to add features that will allow users to access the site using tablets and smart phones. Students were very interested in how the experiment will be developed in the future. “I’m really excited to see where it goes from here,” Kasi said. “There are so many different possibilities!”

    See the full article here.

    Princeton Plasma Physics Laboratory is a U.S. Department of Energy national laboratory managed by Princeton University.


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  • richardmitnick 2:42 pm on April 16, 2014 Permalink | Reply
    Tags: , , , , Plasma Physics   

    From M.I.T.: “A river of plasma, guarding against the sun” 

    March 6, 2014
    Jennifer Chu, MIT News Office

    MIT scientists identify a plasma plume that naturally protects the Earth against solar storms.

    The Earth’s magnetic field, or magnetosphere, stretches from the planet’s core out into space, where it meets the solar wind, a stream of charged particles emitted by the sun. For the most part, the magnetosphere acts as a shield to protect the Earth from this high-energy solar activity.

    But when this field comes into contact with the sun’s magnetic field — a process called “magnetic reconnection” — powerful electrical currents from the sun can stream into Earth’s atmosphere, whipping up geomagnetic storms and space weather phenomena that can affect high-altitude aircraft, as well as astronauts on the International Space Station.

    magrec
    Magnetic Reconnection: This view is a cross-section through four magnetic domains undergoing separator reconnection. Two separatrices divide space into four magnetic domains with a separator at the center of the figure. Field lines (and associated plasma) flow inward from above and below the separator, reconnect, and spring outward horizontally. A current sheet (as shown) may be present but is not required for reconnection to occur. This process is not well understood: once started, it proceeds many orders of magnitude faster than predicted by standard models.

    Now scientists at MIT and NASA have identified a process in the Earth’s magnetosphere that reinforces its shielding effect, keeping incoming solar energy at bay.

    sun

    By combining observations from the ground and in space, the team observed a plume of low-energy plasma particles that essentially hitches a ride along magnetic field lines — streaming from Earth’s lower atmosphere up to the point, tens of thousands of kilometers above the surface, where the planet’s magnetic field connects with that of the sun. In this region, which the scientists call the merging point, the presence of cold, dense plasma slows magnetic reconnection, blunting the sun’s effects on Earth.

    “The Earth’s magnetic field protects life on the surface from the full impact of these solar outbursts,” says John Foster, associate director of MIT’s Haystack Observatory. “Reconnection strips away some of our magnetic shield and lets energy leak in, giving us large, violent storms. These plasmas get pulled into space and slow down the reconnection process, so the impact of the sun on the Earth is less violent.”

    Foster and his colleagues publish their results in this week’s issue of Science. The team includes Philip Erickson, principal research scientist at Haystack Observatory, as well as Brian Walsh and David Sibeck at NASA’s Goddard Space Flight Center.

    Mapping Earth’s magnetic shield

    For more than a decade, scientists at Haystack Observatory have studied plasma plume phenomena using a ground-based technique called GPS-TEC, in which scientists analyze radio signals transmitted from GPS satellites to more than 1,000 receivers on the ground. Large space-weather events, such as geomagnetic storms, can alter the incoming radio waves — a distortion that scientists can use to determine the concentration of plasma particles in the upper atmosphere. Using this data, they can produce two-dimensional global maps of atmospheric phenomena, such as plasma plumes.

    These ground-based observations have helped shed light on key characteristics of these plumes, such as how often they occur, and what makes some plumes stronger than others. But as Foster notes, this two-dimensional mapping technique gives an estimate only of what space weather might look like in the low-altitude regions of the magnetosphere. To get a more precise, three-dimensional picture of the entire magnetosphere would require observations directly from space.

    Toward this end, Foster approached Walsh with data showing a plasma plume emanating from the Earth’s surface, and extending up into the lower layers of the magnetosphere, during a moderate solar storm in January 2013. Walsh checked the date against the orbital trajectories of three spacecraft that have been circling the Earth to study auroras in the atmosphere.

    As it turns out, all three spacecraft crossed the point in the magnetosphere at which Foster had detected a plasma plume from the ground. The team analyzed data from each spacecraft, and found that the same cold, dense plasma plume stretched all the way up to where the solar storm made contact with Earth’s magnetic field.

    A river of plasma

    Foster says the observations from space validate measurements from the ground. What’s more, the combination of space- and ground-based data give a highly detailed picture of a natural defensive mechanism in the Earth’s magnetosphere.

    “This higher-density, cold plasma changes about every plasma physics process it comes in contact with,” Foster says. “It slows down reconnection, and it can contribute to the generation of waves that, in turn, accelerate particles in other parts of the magnetosphere. So it’s a recirculation process, and really fascinating.”

    Foster likens this plume phenomenon to a “river of particles,” and says it is not unlike the Gulf Stream, a powerful ocean current that influences the temperature and other properties of surrounding waters. On an atmospheric scale, he says, plasma particles can behave in a similar way, redistributing throughout the atmosphere to form plumes that “flow through a huge circulation system, with a lot of different consequences.”

    “What these types of studies are showing is just how dynamic this entire system is,” Foster adds.

    Tony Mannucci, supervisor of the Ionospheric and Atmospheric Remote Sensing Group at NASA’s Jet Propulsion Laboratory, says that although others have observed magnetic reconnection, they have not looked at data closer to Earth to understand this connection.

    “I believe this group was very creative and ingenious to use these methods to infer how plasma plumes affect magnetic reconnection,” says Mannucci, who was not involved in the research. “This discovery of the direct connection between a plasma plume and the magnetic shield surrounding Earth means that a new set of ground-based observations can be used to infer what is occurring deep in space, allowing us to understand and possibly forecast the implications of solar storms.”

    See the full article here.


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  • richardmitnick 8:12 pm on March 18, 2014 Permalink | Reply
    Tags: , , , , Plasma Physics, ,   

    From PPPL: “PPPL extends system for suppressing instabilities to long-pulse experiments on KSTAR” 

    March 18, 2014
    John Greenwald

    PPPL collaborations have been instrumental in developing a system to suppress instabilities that could degrade the performance of a fusion plasma. PPPL has built and installed such a system on the DIII-D tokamak that General Atomics operates for the U.S. Department of Energy in San Diego and on the Korea Superconducting Tokamak Advanced Research (KSTAR) facility in South Korea — and now is revising the KSTAR design to operate during extended plasma experiments. Suppressing instabilities will be vital for future fusion facilities such as ITER, the huge international project under construction in France.

    controller
    A look into the microwave launcher showing the steering mirrors that guide the beam into the plasma (Photo by PPPL)

    The system developed on DIII-D and then installed on KSTAR aims high-power microwave beams at instabilities called islands and generates electrical current that eliminates the islands. The process links software-controlled mirrors to detection equipment, creating a system that can respond to instabilities and suppress them within milliseconds. “It works like a scalpel that removes the island,” said PPPL physicist Raffi Nazikian, the head of the Laboratory’s collaboration with DIII-D.

    Revising the unit on KSTAR calls for adding a water-cooling system to keep the mirrors that direct the high-power microwaves into the plasma from overheating. KSTAR’s superconducting magnets can confine the plasma for up to 300 seconds during long-pulse experiments that reach temperatures far hotter than the 15-million degree Celsius core of the sun. “Once you get beyond 10 seconds you have to remove the heat as you put it in,” said PPPL engineer Robert Ellis, who designed the copper and copper-and-steel mirrors.

    Ellis was part of a team of PPPL physicists and engineers who worked closely with their counterparts at General Atomics to develop the original system on DIII-D. PPPL Physicist Egemen Kolemen, an expert in plasma control, created much of the software that automatically steers the mirrors and directs the microwave beams to their target. PPPL engineer Alexander Nagy also shared responsibility for the system, providing onsite support in San Diego.

    The microwave beams not only remove instabilities, but enable researchers to mimic the way that the alpha particles produced by fusion reactions will heat the plasma in ITER. While current heating methods typically heat the ions in plasma, these microwave beams act on the electrons instead. This process parallels what will happen in ITER. “By putting microwave power into the electrons,” Nazikian said, “we can experimentally simulate and study how a fusion plasma will be heated in ITER.”

    The revised KSTAR unit will extend such research to long-pulse plasma experiments when work on the water-cooled mirrors is completed later this year.

    See the full article here.

    Princeton Plasma Physics Laboratory is a U.S. Department of Energy national laboratory managed by Princeton University.


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  • richardmitnick 3:13 pm on February 11, 2014 Permalink | Reply
    Tags: , , , Plasma Physics,   

    From PPPL: “Solution to plasma-etching puzzle could mean more powerful microchips” 

    February 11, 2014
    John Greenwald

    Research conducted by PPPL in collaboration with the University of Alberta provides a key step toward the development of ever-more powerful computer chips. The researchers discovered the physics behind a mysterious process that gives chipmakers unprecedented control of a recent plasma-based technique for etching transistors on integrated circuits, or chips. This discovery could help to maintain Moore’s Law, which observes that the number of transistors on integrated circuits doubles nearly every two years.

    chip
    An integrated-circuit microchip with 456 million transistors
    (Photo by John Greenwald/PPPL Office of Communications)

    The recent technique utilizes electron beams to reach and harden the surface of the masks that are used for printing microchip circuits. More importantly, the beam creates a population of “suprathermal” electrons that produce the plasma chemistry necessary to protect the mask. The energy of these electrons is greater than simple thermal heating could produce — hence the name “suprathermal.” But how the beam electrons transform themselves into this suprathermal population has been a puzzle.

    The PPPL and University of Alberta researchers used a computer simulation to solve the puzzle. The simulation revealed that the electron beam generates intense plasma waves that move through the plasma like ripples in water. And these waves lead to the generation of the crucial suprathermal electrons.

    This discovery could bring still-greater control of the plasma-surface interactions and further increase the number of transistors on integrated circuits. Insights from both numerical simulations and experiments related to beam-plasma instabilities thus portend the development of new plasma sources and the increasingly advanced chips that they fabricate.

    See the full article here.

    Princeton Plasma Physics Laboratory is a U.S. Department of Energy national laboratory managed by Princeton University.


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  • richardmitnick 12:03 pm on November 30, 2012 Permalink | Reply
    Tags: , , , Plasma Physics,   

    From PPPL: “PPPL-designed coil critical to experiment arrives in stellar condition” 

    July 10, 2012 (posted by PPPL 11.30.12)
    John Greenwald

    Engineers at the U.S. Department of Energy’s Princeton Plasma Physics Laboratory (PPPL) have designed and delivered a crucial barn-door size component for a major device for developing fusion power. The component, called a ‘trim coil,’ marks the initial installment of one of the largest hardware collaborations that PPPL has conducted with an international partner.

    tc
    The crated coil arrives at Max Planck Institute for Plasma Physics.

    The 2,400-pound trim coil is the first of five coils that PPPL is producing for the Wendelstein 7-X stellarator, or W7-X, that the Max Planck Institute for Plasma Physics (IPP) is building in Greifswald, Germany. The powerful coils will fine-tune the shape of the superhot, charged gas called plasma that the W7-X will use to study conditions required for fusion when the machine begins operating in 2015.”

    See the full article here.

    Princeton Plasma Physics Laboratory is a U.S. Department of Energy national laboratory managed by Princeton University.


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