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Now, the analysis of measured data from the first round of experiments, carried out from December 2015 to March 2016, has confirmed that both requirements – good particle confinement and a small bootstrap current – have been successfully implemented in the optimized field geometry of Wendelstein 7-X. “The first experimental campaign has therefore already succeeded in verifying key aspects of the optimization,” says the paper’s first author, Dr. Andreas Dinklage. “This will be followed by a more precise and systematic evaluation in future experiments with a significantly higher heating power and plasma pressure.”
Inside your home and office, low-voltage alternating current (AC) powers the lights, computers and electronic devices for everyday use. But when the electricity comes from remote long-distance sources such as hydro-power or solar generating plants, transporting it as direct current (DC) is more efficient — and converting it back to AC current requires bulky and expensive switches. Now the General Electric (GE) company, with assistance from scientists at the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL), is developing an advanced switch that will convert high- voltage DC current to high-voltage AC current for consumers more efficiently, enabling reduced-cost transmission of long-distance power. As a final step, substations along the route reduce the high-voltage AC current to low-voltage current before it reaches consumers.
GE is testing a tube filled with plasma [...] that the company is developing as the conversion device. The switch must be able to operate for years with voltage as high as 300 kilovolts to enable a single unit to cost-effectively replace the assemblies of power semiconductor switches now required to convert between DC and AC power along transmission lines.
The results from the PPPL model are both scientifically interesting and favorable for high-voltage gas switch design.
-Timothy Sommerer, GE physicist
The American Physical Society (APS) has recognized MIT Plasma Science and Fusion Center (PSFC) principal research scientists John Wright and Stephen Wukitch [Alcator C-Mod], [...] Yevgen Kazakov and Jozef Ongena [JET] of the Laboratory for Plasma Physics in Brussels, Belgium, with the Landau-Spitzer Award for their collaborative work.
Given biennially to acknowledge outstanding plasma physics collaborations between scientists in the U.S. and the European Union, the prize this year is being awarded “for experimental verification, through collaborative experiments, of a novel and highly efficient ion cyclotron resonance heating scenario for plasma heating and generation of energetic ions in magnetic fusion devices.”
One of the key fusion challenges is confining the very energetic fusion product ions that must transfer their energy to the core plasma before they escape confinement. This heating scenario efficiently generates energies comparable to that of those produced by fusion and can be used to study energetic ion behavior in present day devices such as JET and the stellarator Wendelstein 7-X (W-7X). It will also allow study in the non-nuclear phase of ITER, the next-generation fusion device being built in France.
“It will be the icing on the cake to use this scenario at W-7X,” says Wright. “Because stellarators have large volume and high-density plasmas, it is hard for current heating scenarios to achieve those fusion energies. With conventional techniques it has been difficult to show if stellarators can confine fast ions. Using this novel scenario will definitely allow researchers to demonstrate whether a stellarator will work for fusion plasmas.”
There's a sort of radio wave that bangs its way around Earth, knocking around electrons in the plasma fields of loose ions surrounding our planet and sending strange tones to radio detectors. It's called a "whistler." And now, scientists have observed bursts like this in more detail than ever before.
In December 2017 improvements in... LTS magnet technology, together with advances in... HTS materials, produced another change in magnet development. The successful demonstration of a 32 T all-superconducting magnet by the National High Magnetic Field Laboratory (NHMFL) in Florida, US, was a significant milestone in the field. The new super-magnet is expected to become available to users in 2019, and its high, stable field will help scientists break new ground in studies of nuclear magnetic resonance, electron magnetic resonance, molecular solids and quantum oscillation studies of complex metals, among other areas.
NbTi was developed in the 1970s and has been the “workhorse” of [LTS] superconducting magnets ever since. However, NbTi material can only function as a superconductor at fields of up to 10 T at 4.2 K (and not more than 11.7 T at 2.2 K) for magnets with narrow bores of less than 60 mm. For larger-bore magnets, the maximum field is even lower, limiting the material’s usefulness in high-field magnets. Coils made from Nb3Sn material can remain superconducting at up to 23 T at 2.2 K, much higher than is possible for NbTi, but they also need to have a very fine filament-like structure to prevent a phenomenon known as flux jumping that dissipates energy in the superconductor and can cause the coil to quench prematurely. Hence, the manufacture of Nb3Sn wire has to be done with stringent quality-control procedures in place to ensure that it will perform stably at high fields.
The NHMFL 32 T magnet uses a second-generation HTS wire made from YBCO, a superconducting ceramic composed of yttrium, barium, copper and oxygen. Production of YBCO wires and tapes has increased during the last few years, and their mechanical properties are better than for Bi-2212, but they display anisotropic effects with respect to field orientation that need to be accounted for in magnet design. They also require more sophisticated quench-management systems. In short, both materials have their challenges, but also some advantages, and are strong candidates for high-field magnets.
A scant few μJ of additional energy – equivalent to the potential energy of a pin dropped from the height of just a few centimetres – would be enough to raise the temperature above the point where the coils become resistive, and the magnet undergoes a quench. When that happens, the helium boils off and all the energy stored in the magnet is released very quickly, risking damage to its structure if the quench process is not properly managed. The potential for damage is significant, too: at the maximum field of 32 T, the energy stored in the NHMFL magnet is more than 8.3 MJ, approximately equal to the energy in 2 kg of TNT.[!!!]
The result was a precedent-setting achievement. "We show for the first time the full 3-D field operating window in a tokamak to suppress ELMs without stirring up core instabilities or excessively degrading confinement," said Park, whose paper—written with 14 coauthors from the United States and South Korea—is published in Nature Physics. "For a long time we thought it would be too computationally difficult to identify all beneficial symmetry-breaking fields, but our work now demonstrates a simple procedure to identify the set of all such configurations."
Researchers reduced the complexity of the calculations when they realized that the number of ways the plasma can distort is actually far fewer than the range of possible 3-D fields that can be applied to the plasma. By working backwards, from distortions to 3-D fields, the authors calculated the most effective fields for eliminating ELMs. The KSTAR experiments confirmed the predictions with remarkable accuracy.
To heat the plasma we used an experimental technique called merging compression – joining two rings of plasma and then compressing it with an intense magnetic field. We didn’t have any external heating from things like neutral beams, which is an additional way to heat plasma. We’re now starting to upgrade to use neutral beams; we want to achieve 100 million °C in the next year or so.
A group of scientists at the University of Tokyo has recorded the largest magnetic field ever generated indoors—a whopping 1,200 tesla, as measured in the standard units of magnetic field strength.
...
The high magnetic field also has implications for nuclear fusion reactors, a tantalizing if unrealized potential future source of abundant clean energy. To reach the quantum limit or sustain nuclear fusion, scientists believe magnetic field strengths of 1,000 tesla or more may be needed.
The article "Record indoor magnetic field of 1200 T generated by electromagnetic flux-compression" by D. Nakamura, A. Ikeda, H. Sawabe, Y.H. Matsuda and S. Takeyama appears in the journal Review of Scientific Instruments (2018).
During the 23 years Alcator C-Mod has been in operation at MIT, it has repeatedly advanced the record for plasma pressure in a magnetic confinement device. The previous record of 1.77 atmospheres was set in 2005 (also at Alcator C-Mod). While setting the new record of 2.05 atmospheres, a 15 percent improvement, the temperature inside Alcator C-Mod reached over 35 million degrees Celsius, or approximately twice as hot as the center of the sun. The plasma produced 300 trillion fusion reactions per second and had a central magnetic field strength of 5.7 tesla. It carried 1.4 million amps of electrical current and was heated with over 4 million watts of power. The reaction occurred in a volume of approximately 1 cubic meter (not much larger than a coat closet) and the plasma lasted for two full seconds.
Pressure, which is the product of density and temperature, accounts for about two-thirds of the challenge. The amount of power produced increases with the square of the pressure — so doubling the pressure leads to a fourfold increase in energy production.
Using the device, they were able to produce a magnetic field of 1,200 teslas [... and] 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...
In the fast ignition scheme, first, fusion fuel is compressed to a high density using nanosecond laser beams. Next, a high-intensity picosecond laser rapidly heats the compressed fuel, making the heated region a hot spark to trigger ignition.
The REB [elativistic electron beam], which is generated by a high-intensity short-pulse laser and accelerated to nearly the speed of light, travels through high-density nuclear fusion fuel plasma and deposits a portion of kinetic energy in the core, making the heated region the hot spark to trigger ignition. However, REB accelerated by high-intensity lasers has a large divergence angle (typically 100 degrees), so only a small portion of the REB collides with the core. (Figure 2)
A kilo-tesla level magnetic field [600 T] is necessary to guide high-energy electrons at the speed of light, so the researchers employed magnetic fields of several hundreds of tesla. Because electrons, which are charged and have a small mass, easily move along a magnetic field line, they guided the high energy REB of 1MeV along the magnetic field lines to the core (the fusion fuel of 100 microns or less), achieving efficient heating of high-density plasma. They called the scheme magnetized fast isochoric heating.
FLF [First Light Fusion] - based in Oxford, England - announced today that the first test 'shot' was fired in late July. The company said it was able to repeat the test a few days later after all parts of Machine 3 had been checked and the data produced analysed, "proving the limb functions as designed".
Machine 3 will be capable of discharging up to 200,000 volts and in excess of 14 million ampere - the equivalent of nearly 500 simultaneous lightning strikes - within two microseconds, FLF said. The GBP3.6 million (USD4.6 million) machine will use some 3km of high voltage cables and another 10km of diagnostic cables.
So scientists use other forms of energy to bring hydrogen atoms as close as possible to each other. Heating the hydrogen gas using radio waves, for instance, forces the atoms to travel at incredible speeds, collide, and, on occasion, fuse. The easiest way to quantify the heat energy added to the system using radio waves is to measure the temperature of the gas. Experiments have shown that fusion can occur above temperatures of 100 million °C, many times higher than that at the center of the sun.
No known material can withstand (and thus contain) such an incredibly hot gas....
At temperatures over 100 million °C, atoms are stripped of their electrons, creating a soup of charged particles called plasma, which can interact with magnetic forces. By creating a strong magnetic force, you can direct the plasma along a specific pathway—and if the magnetic lines are set up in the right way, the movement of plasma particles can be confined so as to not come in contact with other non-plasma matter. This is magnetic confinement.
Another trick is to create mini bombs. If you take a frozen pellet of hydrogen (the fuel) and heat it extremely quickly using high-energy lasers, it creates an envelope of plasma on the surface of the pellet (step 1 in the diagram below). As the plasma blows off, it creates rocket-like forces that compress the fuel (step 2). The compression causes the pellet to heat up to 100 million °C (step 3) and the atoms inside the pellet to undergo fusion and explode as it releases lots of high-energy neutrons (step 4).
Though there are other companies pursuing fusion technology, CFS has a number of advantages over its competitors. One—which Quartz can now report for the first time—is that it’s funded, in part, by Breakthrough Energy Ventures led by a group of billionaires, including Bill Gates, Jeff Bezos, Jack Ma, Mukesh Ambani, and Richard Branson.
We didn’t compare the different types of nuclear-fusion reactors in a bake-off competition before deciding on investing in CFS. We knew the team; they had a promising idea; they needed our help.
Carmichael Roberts, head of investing at Breakthrough Energy Ventures (same source)
The point of building a magnet in the 1,000-plus tesla range, Takeyama said, is to study hidden physical properties of electrons that are invisible under normal circumstances. He and his team will put different materials inside their magnet to study how their electrons behave.
Under those extreme conditions, he said, conventional models of electrons break down. Takeyama doesn't know exactly what happens to electrons in such extreme situations, but said that studying them in the moments before the coil's self-destruction should reveal properties of electrons normally invisible to science.
Instead of using TNT to generate their magnetic field, the Japanese researchers dumped a massive amount of energy—3.2 megajoules—into the generator to cause a weak magnetic field produced by a small coil to rapidly compress at a speed of about 20,000 miles per hour. This involves feeding 4 million amps of current through the generator, which is several thousand times more than a lightning bolt. When this coil is compressed as small as it will go, it bounces back. This produces a powerful shockwave that destroyed the coil and much of the generator.
To protect themselves from the shockwave, the Japanese researchers built an iron cage for the generator. However they only built it to withstand about 700 Teslas, so the shockwave from the 1,200 Teslas ended up blowing out the door to the enclosure.
“I didn’t expect it to be so high,” Shojiro Takeyama, a physicist at the University of Tokyo, told IEEE Spectrum. “Next time, I’ll make [the enclosure] stronger.”
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.
The Duke of Cambridge said "it's incredible, it really is" after being shown an experimental fusion reactor which the UK Atomic Energy Authority (UKAEA) believes could help make the power source commercially viable.
Standing in the shadow of the Mast (Mega Amp Spherical Tokamak) Upgrade fusion experiment - a large cylindrical machine covered in wires and pipes - the duke joked with senior staff, saying: "It's very exciting, no pressure."
After the tour, William was taken to the nearby control room at the UKAEA's Culham Science Centre near Oxford and asked to press a large red button to start up the machine to mark the end of its five-year construction.
When William pushed the button, everyone turned towards a screen which showed the inside of the reactor, and when a purple plasma cloud was seen after a long wait, there was a spontaneous round of applause.
At present one-tenth of generated electricity is lost in the grid because of the cables we use.
Better cables require better materials, and mixing copper (Cu) with carbon nanotubes (CNTs) can help to solve the problem.
Large research investments are made world-wide to develop Cu-CNTs ultra- conductive wires able to transport electricity with improved energy efficiency.
ESRI Director Prof Andrew Barron is leading research in advanced ultra-conductive wires, and Dr Ewa Kazimierska is working alongside him to achieve this goal.
Professor Andrew Barron said:
"Making a good mix from carbon nanotubes and copper is challenging. There have been several reports that a combination of copper and carbon nanotubes has significantly higher ampacity than copper alone, which makes it very promising for future power distribution for the grid, automotive and aerospace applications."
The successful Royal Society Research Grant, entitled "Tuneable plasma oxidation of CNTs and its effect on dispersion and metal integration", aims to solve the CNT-Cu incompatibility problem.
Plasma is an ionised gas that can be used to modify CNTs and improve their dispersion in water. With both CNTs and dissolved copper salt in water it should be easier to combine the two in a working ultra-conductive wire.