Dartmouth Journal of Undergraduate Science February 24, 2018 | Ted Northup
According to a recent report on nuclear fusion, scientists may have discovered an optimal model for regulating plasma turbulence while still achieving desired functional results.
A Brazilian researcher, Vinicius Duarte of the Princeton Plasma Physics Laboratory, recently developed a conceptual regulation of plasma turbulence that would minimize the loss of heat in a reactor. Plasma turbulence disruption is one of many significant hurdles facing the development of nuclear fusion as a widespread energy source due to the difficulty of trying to replicate the conditions of the sun—but in a box.
While there are many models that government researchers and private companies have been pursuing, the most well-known and most advanced model for fusion research is the tokamak. This donut-shaped chamber uses extremely powerful magnets to create an electromagnetic field that contains extremely hot and charged particles in the form of a gas, known as plasma, inside the chamber, which can be viewed as analogous to jelly stuck in a donut, isolated from the surface.
The concept behind achieving nuclear fusion is getting sub-atomic particles to have enough energy to overcome repulsion forces and ‘smash’ into each other, releasing huge amounts of energy. In natural nuclear fusion occurring within the sun, the huge effect of the sun’s gravity is enough to crush particles together and release energy that produces the heat and light we receive from the sun. In the absence of this huge gravitational force on Earth, scientists have to heat plasmas in tokamak chambers to over ten times the temperature of the sun to give the particles enough energy to collide.
Coming back to the jelly-in-the-donut analogy, the plasma must be kept isolated to prevent heat loss to the walls of the tokamak chamber. The aforementioned powerful electromagnets provide the containment with a magnetic field 10,000 times stronger than the Earth’s.
A huge problem arises when these powerful magnetic fields, combined with the high temperatures, result in turbulence in the plasma and resulting magnetic fields, leaking thermal energy and disrupting the reaction.
A potential solution has emerged. Physicist Ricardo Galvao, head of Brazil’s National Space Research Institute, explains that “what Duarte found is that this outcome happens in a self-organized manner, with the production of chirping, if the plasma is not very turbulent. If turbulence is high, however, it doesn’t.” In a somewhat counter-intuitive concept, lower plasma turbulence leads to the disruption of the reaction, while this is largely ignored if plasma turbulence in high. Increasing the turbulence of the plasma, as Galvao says, “prevents the creation of a self-organized system that sustains an undesirable associated electromagnetic wave.” As a result, fusion energy loss would not occur and the reaction could be sustained.
Researchers have not yet tested this “goldilocks” theory of plasma turbulence, but the issue is sure to be addressed when the experimental fusion reactor ITER (International Thermonuclear Experimental Reactor) comes online in the 2020s. Currently in development, the ITER is the most expensive scientific project ever undertaken, and will allow plasma physics researchers to determine whether fusion energy is viable.
With positive results from this test stage, the commercial fusion industry could achieve a lift-off and displace fossil fuels and even current renewable sources as the king of sustainable energy around the globe.
Source: Wikimedia commons
Duarte, V. N., H. L. Berk, N. N. Gorelenkov, W. W. Heidbrink, G. J. Kramer, R. Nazikian, D. C. Pace, M. Podestà, and M. A. Van Zeeland. 2017. “Theory and observation of the onset of nonlinear structures due to eigenmode destabilization by fast ions in tokamaks.” Physics of Plasmas 24 (12): 122508. doi:10.1063/1.5007811.
“Fusion conditions.” 2018. EUROfusion. EUROfusion. Accessed February 5. https://www.euro-fusion.org/fusion/fusion-conditions/.
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