MHD properties of low-aspect ratio RFP in RELAX

S. Masamune, A. Sanpei, R. Ikezoe, T. Onchi, K. Oki, T. Yamashita, H. Shimazu, H. Himura, R. Paccagnella

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The low-aspect-ratio (A) reversed field pinch (RFP) offers attractive properties such as enhanced bootstrap current and simpler MHD mode dynamics. The RELAX (REversed field pinch of Low-Aspect ratio eXperiment) machine with the world's lowest A of 2 (R/a = 0.5 m/0.25 m) has been constructed to explore the RFP properties in low-A regime. In flat-topped low-A RFP discharges in RELAX, plasma current of ~50 kA has been attained with discharge duration of ~2 ms. In round-topped discharges with plasma current of ~70 kA, quasi-periodic growth of a single helical mode has been observed. When the dominant m = 1/n = 4 mode grows, the toroidal mode spectrum looks like that of the quasi-single helicity (QSH) RFP state with higher amplitude. MHD equilibrium analyses using a reconstruction code have shown that the bootstrap current fraction is lower than ~5% in the present RELAX plasmas, and it will be ~25% if we could achieve the plasma density of 4 × 1019m-3and electron temperature of 300 eV at plasma current of ~100 kA. © 2008 Springer Science+Business Media, LLC.
Original languageEnglish
Pages (from-to)187 - 190
Number of pages4
JournalJournal of Fusion Energy
Issue number2 SPEC. ISS.
Publication statusPublished - Jun 2009
Externally publishedYes


All Science Journal Classification (ASJC) codes

  • Nuclear and High Energy Physics
  • Nuclear Energy and Engineering

Cite this

Masamune, S., Sanpei, A., Ikezoe, R., Onchi, T., Oki, K., Yamashita, T., ... Paccagnella, R. (2009). MHD properties of low-aspect ratio RFP in RELAX. Journal of Fusion Energy, 28(2 SPEC. ISS.), 187 - 190.