Researchers at Tohoku University have discovered a new plasma wave phenomenon, leading to the development of a negative ion source for fusion plasma heating.
Led by Associate Prof K. Takahashi and Prof A. Ando, the team demonstrated adjoining generations of high and low electron temperature plasmas, based on the presently discovered plasma wave physics.
Development of neutral beam injection (NBI) heating system utilizing a hydrogen/deuterium (H/D) negative ion source, is significant for a fusion plasma reactor, which is one of the potential solutions to future energy-resource problems.
A very high temperature plasma state above 1.2 hundred billion degrees C (>10 keV) has to be sustained to maintain the fusion reaction; the NBI system plays an important role in heating the plasma. Once the negative ions are produced in a low-temperature plasma source, they are extracted electrostatically as an energetic beam. The negative ions are then neutralized via a gas neutralizer system and injected into the magnetically-confined plasma core.
Seeds of the negative ions are the H/D positive ions or atoms, which can be produced by collisions with high temperature electrons (~ 10 eV) and H/D molecules. On the other hand, it is well known that the energetic electrons destroy the negative ions.
Therefore, it would be favorable that the high electron temperature region for the seeds production exists close to the low temperature one for maintaining the negative ions. This inconsistent situation is realized in the present experiment by the newly discovered wave behavior.
The researchers found that the radiofrequency wave for the plasma production, called a helicon wave, is reflected by a local change of the refractive index (contour plot in Fig), which is introduced by the rapidly bent magnetic field structure (white arrows in Fig). Although there is no axial physical boundary downstream of the source, the wave recognizes the bent magnetic field structure as the boundary and is reflected there (black arrow in Fig).
As a result of the wave reflection, a standing wave yielding the high temperature electrons is generated upstream of the vertical magnetic fields. Since the wave energy cannot go inside the vertical magnetic fields, which also play a role in separating the high and low energy electrons, the low temperature electrons can be obtained downstream of the vertical magnetic fields.
The experiment has just started and currently only shows the low temperature plasma production; the detailed investigations on the negative ion production and the beam extraction will be progressed hereafter. The above-mentioned plasma source based on the wave physics will provide various applications for plasma processing devices, in addition to the application to the negative ion source.
Kazunori Takahashi | EurekAlert!
What happens when we heat the atomic lattice of a magnet all of a sudden?
18.07.2018 | Forschungsverbund Berlin
Subaru Telescope helps pinpoint origin of ultra-high energy neutrino
16.07.2018 | National Institutes of Natural Sciences
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
19.07.2018 | Materials Sciences
19.07.2018 | Earth Sciences
19.07.2018 | Life Sciences