News from the 58th Annual Meeting of the APS Division of Plasma Physics
Researchers at General Atomics (GA) have invented a new kind of gamma ray camera that can image beams of energetic electrons inside ultra-hot fusion plasma.
The device is used in ongoing global research that is developing fusion into a new clean energy source. Turning fusion fuel into extractable energy requires it to be hotter than the center of the sun, hence in the plasma state. If the shutdown phase of operation is not controlled well, released magnetic energy can drive a population of electrons to relativistic speeds. If this population is not controlled, the electrons impact the inner walls of the plasma chamber, leading to material damage.
A team of researchers is working to better understand the properties of these electrons at the DIII-D National Fusion Facility operated by GA in San Diego for the U.S. Department of Energy. They designed and built a Gamma Ray Imager to capture the image of these particles.
The Gamma Ray Imager works on the principle of a standard pinhole camera (Figure 1), except that it is made of lead and weighs 420 pounds (190.5 kilograms). The imager actually records images of equally energetic gamma rays that are emitted by the electrons, and the lead is necessary to achieve a good focus (Figure 2). These gamma ray measurements provide information about the energy, direction, and quantity of electrons in the relativistic population, giving researchers an unparalleled view of how the energetic electrons evolve and interact with the fusion plasma.
"This system allows us to see with unprecedented detail how different plasma properties can mitigate these electrons," said Dr. Carlos Paz-Soldan, the scientist who led the first experiments utilizing the new camera. The results, to be presented at the American Physical Society Division of Plasma Physics conference Oct. 31-Nov. 4, demonstrate experimentally that radiation "reaction" forces are able to sap the highest energy electrons while collisions with other electrons are most effective at low energy (Figure 3).
These measurements imply that energetic electron control is not one-size-fits all, and that different energies require different control strategies.
With the new measurements, scientists can compare the behavior of the electron populations to theoretical models being developed by research teams worldwide. These models are, in turn, crucial to predict how the electron populations will behave in new reactors, such as the ITER tokamak now under construction in Cadarache, France, and thus ensure they can be adequately controlled.
Dr. Carlos Paz-Soldan
Synchrotron and collisional damping effects on runaway electron distributions
2:00 PM-5:00 PM, Monday, October 31, 2016, Room: 230 A
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The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.
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Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.
During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....
The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.
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