A major fusion collaboration between Chinese and US research teams has made an attempt to reduce the distance between the plasma and the wall of the chamber that contains it. By doing this, the system can become more stable. This process allows the researchers to create higher-pressure plasmas, which in turn achieves the all-important threshold of ignition, and a self-sustaining fusion reaction.
This has led to an important finding that can help alter the way fusion devices are designed to function.
Andrew J. Cole, a new Assistant Professor of Applied Physics, had earlier stated that the magnetic reconnection leads to significantly large “magnetic islands” that lets heat and particles from the hot fusion core contact cooler edge plasma. Magnetic islands puts a limit to fusion performance, and if large enough, can lead to a complete loss of plasma confinement.
The new confinement state inside a magnetic island by applying the “momentary heating propagation method” to the DIII-D plasma was discovered by Professor Katsumi Ida, Assistant professor Tatsuya Kobayashi, and the LHD experiment group, together with Professor Shigeru Inagaki at Kyushu University, have, together with Dr. T. Evans, a DIII-D senior researcher.
Superconductors, which endure no resistive loss of power, are utilized to create the magnetic fields that keep the 100 million degree C plasma, in combination reactor designs.
Researchers led by Wayne Solomon of the U.S. Department of Energy’s Princeton Plasma Physics Laboratory (PPPL) made an attempt to access the new state on the DIII-D National Fusion Facility that General Atomics operates for DOE in San Diego. The current regime for high-level plasma are performance theoretical predictions of a plasma state beyond H-mode, which motivated them to pursue their research.
Dr. Xianzu Gong of ASIPP and Dr. Andrea Garofalo of General Atomics (GA) in San Diego led the team. While raising the magnetic field force offers a way to develop reactors, usual low-temperature superconductors undergo remarkable drops in current carrying capacity at high magnetic fields. A new, lower-cost path to fusion energy has opened up with the materialization of high-temperature superconductors that are functional in high magnetic fields.
A distinctive amount of fusion plasma development is called “plasma beta,” which is the ratio of plasma pressure to magnetic field pressure. The cost of the superconducting magnets used in a fusion reactor can be reduced if a very high beta, creating the required plasma pressure with low magnetic field, can be achieved. This leads to several visions of fusion reactors trying to optimize plasma beta at reasonable magnetic field strengths. Plasma stability however can become a complicated thing as operation at upper beta pushes the plasma up against many performance limits.
But, the issue is not plasma beta alone and there are other aspects to it. The size of the confined plasma is another ratio that is compared to the ion gyroradius, which are helical path ions that are forced to follow strength of the magnetic field, and it decides the overall energy confinement and states plasma performance.
There is a decrease in ion gyroradius when magnetic field strength increases. When this is done, a reduction in the size of the fusion device happens with performance loss. When this approach is taken, it lowers beta and the plasma not operating under stability limits or away from a “safe zone.”
Plasma or ionized gas is confined to high temperatures when magnetic fields are used. This high temperature is at times higher than the temperature of the core of Sun. A group of 35 nations is making a 500-megawatt ITER fusion research facility in France.
Some unwanted hot spots are made to ‘chill’ with pellets of frozen neon and deuterium straight into the hot plasma by Dr. Eidietis, along with a team, led by Dr. Daisuke Shiraki of Oak Ridge National Laboratory.
According to GA physicist Nicholas W. Eidietis, it is important to cool down hot plasma quickly. It is vital to maintain the temperature right as problems can be caused if the plasma is cooled too much or too little.
For tokamak design, the toroidal or doughnut-shaped steel-lined fusion device, allowable stresses set the field strength limits. This stress lies in the structural components that hold the magnet together, and not by the basic limits of the superconductors.
The limit of the aggressive tokamak designs with conventional superconductor technology is set to about 6 Tesla on-axis toroidal magnetic fields.
There are many physics and technology challenges that need to be solved, these tokamak experiments experience provide the basis to support a new path of exploration into compact, power producing reactors.
