PPPL physicist Gerrit Kramer with conceptual image of SPARC fusion reactor. Credit: Collage and Kramer photo by Elle Starkman / PPPL Office of Communication. SPARC image licensed by Commonwealth Fusion Systems
The US Department of Energy (DOE)’s Princeton Plasma Physics Laboratory (PPPL) collaborates with the private industry on cutting-edge fusion research aimed at achieving commercial fusion energy. This work, made possible by a public-private DOE grant program, supports efforts to develop high-performance fusion grade plasmas. In one such project, PPPL works in collaboration with MIT‘s Plasma Science and Fusion Center (PSFC) and Commonwealth Fusion Systems, a startup of MIT that is developing a tokamak fusion device called SPARC.
The aim of the project is to predict the leakage of fast “alpha” particles produced during the fusion reactions in SPARC, given the size and possible misalignment of the superconducting magnets that the plasma. These particles can create a largely self-heating or ‘burning plasma’ that stimulates fusion reactions. The development of burning plasma is an important scientific objective for fusion energy research. However, leakage of alpha particles can delay or stop the production of fusion energy and damage the inside of the SPARC plant.
New superconducting magnets
Key features of the SPARC machine include the compact size and powerful magnetic fields that can be done by the ability of new superconducting magnets to operate at higher fields and voltages than existing superconducting magnets. These features enable the design and construction of smaller and cheaper fusion facilities, as described in recent publications by the SPARC team – assuming that the fast alpha particles generated in fusion reactions may be long enough to keep the plasma warm.
“Our research suggests that it may be,” said PPPL physicist Gerrit Kramer, who is participating in the project through the DOE Innovation Network for Fusion Energy (INFUSE) program. The two-year-old program, which serves PPPL physicist Ahmed Diallo as deputy director, aims to accelerate the development of fusion energy in the private sector through partnerships with national laboratories.
Well restrained
“We have found that the alpha particles are indeed well confined in the SPARC design,” said Kramer, co-author of an article in the Journal of Plasma Physics which reports the findings. He has worked closely with lead author Steven Scott, a Commonwealth Fusion Systems consultant and former physicist at PPPL.
Kramer uses the SPIRAL computer code developed at PPPL to verify the particle confinement. “The code, which simulates the wavy pattern or wrinkles in a magnetic field that allows the escape of fast particles, showed good confinement and lack of damage to the SPARC walls,” Kramer said. In addition, he added, “the SPIRAL code is in good agreement with the ASCOT code from Finland. Although the two codes are completely different, the results were similar. ”
The findings pleased Scott. “It’s gratifying to see the calculation of our understanding of wrinkle – induced losses,” he said, “as I studied the issue experimentally in my early 1980s for my doctoral dissertation.”
Fusion reactions combine light elements in the form of plasma – the warm, charged state of matter made up of free electrons and atomic nuclei, or ions, which make up 99 percent of the visible universe – to generate massive amounts of energy. Scientists around the world are trying to create fusion as a virtually unlimited power source for generating electricity.
Important guidance
Kramer and colleagues noted that the incorrect layout of the SPARC magnets would increase the wrinkle-induced losses of fused particles, leading to increased force hitting the walls. Their calculations should give the SPARC engineering team the most important guidelines on how well the magnets should be in line to prevent excessive power loss and wall damage. Well magnets magnets will for the first time make it possible to do plasma self-heating and develop improved techniques for plasma control in future fusion power plants.
Reference: “Fast-ion physics in SPARC” by online by SD Scott, GJ Kramer, EA Tolman, A. Snicker, J. Varje, K. Särkimäki, JC Wright and P. Rodriguez-Fernandez, September 29, 2020, Journal of Plasma Physics.
DOI: 10.1017 / S0022377820001087
Support for this research comes from Commonwealth Fusion Systems. Support for Kramer comes from the DOE Office of Science INFUSE program. Contributors to the project include physicists from PSFC; Aalto University in Espoo, Finland; and research intensive University of Gothenburg, Sweden, which was founded in 1829 after a donation by William Chalmers, a director of the Swedish East India Company. It focuses on technology, science, architecture and shipping. “Class =” glossaryLink “> Chalmers University of Technology in Gothenburg, Sweden.