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Researchers one step more closer to Cold Fussion Power – Vancouver Technology Time
Research on magnetic fusion energy shows that plasma can be contained using magnetic fields. The plasma is heated to a temperature much hotter than the sun’s core, which leads to the fusion of ions and the release of excess energy that can be transformed into electricity , according to new experimental results achieved by the first U.S.-China fusion research team.
The team is led by Dr. Xianzu Gong of ASIPP and Dr. Andrea Garofalo of General Atomics (GA) in San Diego
Using both China’s EAST facility and the DIII-D National Fusion Facility, operated by GA for the U.S. Department of Energy, the team has investigated the “high-bootstrap current” scenario, which enhances self-generated (“bootstrap”) electrical current to find an optimal tokamak configuration for fusion energy production.
Magnetic fusion energy research uses magnetic fields to confine plasma (ionized gas) heated to temperatures hotter than the Sun’s core. This enables the ions to fuse and release excess energy that can be turned into electricity, harnessing the Sun’s power on Earth. The most developed configuration is the tokamak, and the team’s work helps prepare for the 500-megawatt ITER fusion research facility that is currently being built in France by a consortium of 35 nations, including China and the U.S.
This joint U.S.-China experiment directly demonstrates the stabilizing effect of reducing the plasma-wall distance in tokamaks with high plasma pressure and large bootstrap current fraction, according to Dr. Gong, who said, “I think, in simple terms, these experiments may provide better physics and operation foundation for ITER plasmas.”
The focus was on resolving the “kink mode” instability, a wobbling effect that reduces performance, by moving the plasma closer to the vessel’s wall, Dr. Garofalo explained . Operating closer to the wall suppresses the kink mode and enables higher pressure inside the tokamak, the toroidal or doughnut-shaped steel-lined fusion device. This gives rise to “pressure-driven” plasma flows that maintain the confinement quality even with lower external injection of velocity.
“This is unlike any other regime,” said Dr. Garofalo. “It’s very risky to move the plasma that close to the wall. The chief operator said ‘You can’t do that anymore, you’re going to damage the machine,’ so it was a struggle to prove our theory was correct.”
The gambit paid off. Moving the plasma closer to the wall removed the kink mode and enabled higher plasma pressure, which, in turn, makes the plasma less dependent on externally injected flow. This is important because in a tokamak reactor, such as ITER, it is very difficult and expensive to drive a rapid plasma flow with external means.
The team performed the most recent bootstrap exploration in DIII-D, following-up work on the record-setting milestone achieved at China’s EAST tokamak, where GA scientists have also been collaborating. An ASIPP scientist Dr. Qilong Ren will deliver the invited talk on the topic of Magnetic Confinement-Experiments.
While fusion has been in the public domain since the 1950s and its advances have been achieved by teams around the world, this U.S.-China team is setting new milestones in global cooperation. For realization of magnetic fusion energy, global cooperation is needed, said Dr. Gong of ASIPP, who cited the EAST/DIII-D partnership as “an efficient and effective new model” for international science collaborations that benefits both partners and the field of study.
“We have made a very good start of international collaboration in fusion research between China and the U.S., and we are very proud to be a pioneer in this field,” said Dr. Gong.
Tokamak confinement is an advanced configuration for this process. The International Thermonuclear Experimental Reactor (ITER) is an international project which aims to design and construct an experimental fusion energy reactor based on the tokamak concept
“ITER is based on the ‘tokamak’ concept of magnetic confinement, in which the plasma is contained in a doughnut-shaped vacuum vessel. Strong magnetic fields are used to keep the plasma away from the walls; these are produced by superconducting coils surrounding the vessel, and by an electrical current driven through the plasma,” says the ITER website.
A team of American and Chinese researchers are currently helping in the development of a facility for the 500-megawatt ITER fusion research in France. The facility is a joint project of 35 nations, including the United States and China.
The plasma found in the confined areas are dubbed as magnetic islands. These ‘islands’ do not have a temperature incline, which leads to turbulence. If the turbulence rises outside the magnetic islands where there is a temperature gradient, the turbulence eventually moves into the islands. The turbulence’s intensity is the determining factor of the magnetic island’s confinement state. Improving the confinement state of these magnetic islands holds the key to the future of fusion plasma.
Scientists in the joint project found a new confinement state that could lead to the improvement of fusion reactor plasma and eventually pave the way to fusion energy research in the future
Led by Andrea Garofalo of General Atomics in San Diego and Xianzu Gong of the Institute of Plasma Physics at the Chinese Academy of Sciences, the team investigated a scenario called the “high-bootstrap current” which improves self-generated electrical current. This scenario aims to determine the ideal tokamak setting for the production of fusion energy.
Reducing the distance of plasma from the tokamak wall using large bootstrap current fraction and high plasma pressure showed a stabilizing effect. Moving the plasma closer to the wall made high pressure inside the tokamak possible. This operation resulted in the stable flow of pressure-driven plasma in a confined state even with reduced outside injected flow.
“This is unlike any other regime. It’s very risky to move the plasma that close to the wall. The chief operator said ‘You can’t do that anymore, you’re going to damage the machine,’ so it was a struggle to prove our theory was correct,” said Garofalo.
The results of the experiment will be beneficial in the improvement of a tokamak reactor capable of generating fusion energy.
Meet “Super H mode,” a newly discovered state of tokamak plasma that could sharply boost the performance of future fusion reactors. This new state raises the pressure at the edge of the plasma beyond what previously had been thought possible, creating the potential to increase the power production of the superhot core of the plasma.
Discovery of this mode has led to a new line of research within plasma physics that aims to define a path to higher power. The route could prove particularly promising for ITER, the international experiment under construction in France to demonstrate the feasibility of fusion energy.
Researchers led by Wayne Solomon of the U.S. Department of Energy’s Princeton Plasma Physics Laboratory (PPPL) accessed the new state on the DIII-D National Fusion Facility that General Atomics operates for DOE in San Diego. Motivating their findings were theoretical predictions of a plasma state beyond H-mode, the current regime for high-level plasma performance.
Philip Snyder, director of Theory and Computational Science for General Atomics’ Energy and Advanced Concepts Group, developed the predictions. His surprising discovery was that a model called EPED predicted more than one type of edge region in tokamak plasmas, with the previously unknown Super H-mode among them.
Such regions are called “pedestals” because they serve as ledges in H-mode plasmas from which the pressure drops off sharply. The higher and wider the pedestal the greater the density and pressure, which together act like thermoses to contain the man-made plasma at more than 100 million degrees C. “It’s an important way that we can reach fusion conditions efficiently,” said Snyder, whose model predicted a new pedestal height that corresponds to the super H-mode.
Verification of this prediction is what the researchers found. Their experiments reached the higher Super H-mode regime by steadily increasing density in a quiescent state that naturally avoids pedestal collapses. The results caused the plasma to follow a narrow path to the Super H-mode, the physics equivalent of steering a boat through rocky shores.
http://www.albanydailystar.com/scie...ion-power-vancouver-technology-time-9681.html
