New device demonstrates potential for long-time fusion plasma
New device demonstrates potential for long-time fusion plasma lead image
One obstacle to large-scale magnetic fusion energy using tokamaks is the need to continuously drive a large electrical current within the high-temperature plasma in order to achieve fusion confinement. Devices called stellarators can confine the plasma without such currents but have their own drawback. The strong magnets that surround the plasma have a complicated configuration that requires careful design, and without optimization, the energy loss is larger than in tokamaks.
An international team of researchers constructed and operated an optimized stellarator, called Wendelstein 7-X, and report the results from initial experiments that could potentially operate for 30 minutes straight.
Co-author Robert Wolf said the instrument works thanks to an “elaborate optimization procedure” that helped overcome the device overcome the known limitations of stellarators. For controlling the removal of heat used to generate and sustain the plasma, the team installed a magnetic island divertor, which extended the device’s energy limit from 4 to 80 megajoules, a hydrogen pellet injection system, which allowed the stellarator to achieve record-breaking performance in only a few weeks, and a microwave heating system, which enabled operation at very high plasma densities.
Despite such promising results, Wolf added the device must still be optimized to achieve longer operation times.
“The cooling capability and thus the plasma durations are still limited,” Wolf said. “Many of the fundamental properties of (Wendelstein 7-X) could still be tested from the first campaigns, which took place from 2016 to 2018.”
The team’s next major step is to lengthen the plasma’s duration from seconds to minutes. To do this, the researchers are building a massive cooling system to help dissipate heat effectively.
Source: “Performance of Wendelstein 7-X stellarator plasmas during the first divertor operation phase,” by R. C. Wolf, A. Alonso, S. Äkäslompolo, J. Baldzuhn, M. Beurskens, C. D. Beidler, C. Biedermann, H.-S. Bosch, S. Bozhenkov, R. Brakel, H. Braune, S. Brezinsek, K.-J. Brunner, H. Damm, A. Dinklage, P. Drewelow, F. Effenberg, Y. Feng, O. Ford, G. Fuchert, Y. Gao, J. Geiger, O. Grulke, N. Harder, D. Hartmann, P. Helander, B. Heinemann, M. Hirsch, U. Höfel, C. Hopf, K. Ida, M. Isobe, M. W. Jakubowski, Y. O. Kazakov, C. Killer, T. Klinger, J. Knauer, R. König, M. Krychowiak, A. Langenberg, H. P. Laqua, S. Lazerson, P. McNeely, S. Marsen, N. Marushchenko, R. Nocentini, K. Ogawa, G. Orozco, M. Osakabe, M. Otte, N. Pablant, E. Pasch, A. Pavone, M. Porkolab, A. Puig Sitjes, K. Rahbarnia, R. Riedl, N. Rust, E. Scott, J. Schilling, R. Schroeder, T. Stange, A. von Stechow, E. Strumberger, T. Sunn Pedersen, J. Svensson, H. Thomson, Y. Turkin, L. Vano, T. Wauters, G. Wurden, M. Yoshinuma, M. Zanini, D. Zhang, and the Wendelstein 7-X Team, Physics of Plasmas (2019). The article can be accessed at https://doi.org/10.1063/1.5098761 .
