Model C stellarator

Model C stellarator
Device typeStellarator
LocationPrinceton, New Jersey, United States
AffiliationPrinceton Plasma Physics Laboratory
Technical specifications
Major radius12.0 m (39.4 ft) (total non-circular length)
1.91 m (6 ft 3 in) (equivalent effective radius)
Minor radius0.05–0.075 m (2.0 in – 3.0 in)
Plasma volume0.1–0.2 m3
Magnetic field3.5 T (35,000 G)
Heating power4 MW (RF)
Plasma current0–8 kA
Plasma temperature< 400 eV
Plasma density< 1×1020 m−3
History
Date(s) of construction1961
Year(s) of operation1962–1969
Preceded byModel A/B stellarators
Succeeded bySymmetrical Tokamak (ST)

The Model C stellarator was the US flagship fusion experiment in the 1960s. At the time, only the US operated stellarators which were invented by Lyman Spitzer at Princeton University. Model C followed the smaller Model A and Model B stellarators. Construction began in 1961 at what became Princeton Plasma Physics Laboratory (PPPL). Model C had unfavorable properties for confining hot fuel plasma, notably suffering from Bohm diffusion. Its measured electron temperatures were only in the range of 10-400 eV, when ~10,000 was needed for a power plant.

In 1968, the Soviet T-3 tokamak presented much better results at an international conference, which were then verified by British scientists. The tokamak confined plasma fuel twenty to thirty times better than predicted by Bohm diffusion, and was reaching temperatures of 1000 eV. PPPL and the US Department of Energy decided to convert Model C to a tokamak, the Symmetrical Tokamak. Stellarator development in the US ended until 1984. At PPPL it did not resume until NCSX in the early 2000s, which was also unsuccessful.

Design and concept

The Model C had a racetrack shape. The total length of its magnetic axis was 12 m, combining curved and straight sections. The plasma could have a 5-7.5 cm minor radius. Magnetic coils could produce a toroidal field (along the tube) of 50,000 Gauss, although it was more typically operated at 35,000 Gauss. It was only capable of pulsed operation.

It had a divertor in one of the straight sections. In the other it could inject 4 MW of 25 MHz ion cyclotron resonance heating (ICRH).

It had helical windings on the curved sections.

Results

At the 1968 3rd IAEA Fusion Energy Conference in Novosibirsk, USSR, Model C reported results, for plasmas where particles were confined for more than one length of the machine, of 10 eV electron temperatures, and 4×1016 m−3 density. Confinement time was about five times longer than predicted by Bohm diffusion.

At the same conference, the West German Wendelstein II-A stellarator reported achieving confinement time one hundred times longer than predicted by Bohm diffusion, although its temperature and density were low due to its small size, weaker magnets, and use of Barium rather than hydrogen plasma.

Several months later, in its final paper before reconstruction as a tokamak, it was claimed that Model C achieved a peak average ion temperature of 400 eV in 1969.

History

Construction funding/approval was announced in April 1957 with the design based on Katherine Weimer's efforts in fundamental research.

It started operating March 1962. The leader of Model C experiments was Princeton physicist Shoichi Yoshikawa.

The Model C was reconfigured as a tokamak in 1969, becoming the Symmetrical Tokamak (ST).

References

  1. 1 2 3 4 5 6 7 8 9 Yoshikawa, S.; Stix, T.H. (1985-09-01). "Experiments on the Model C stellarator". Nuclear Fusion. 25 (9): 1275–1279. doi:10.1088/0029-5515/25/9/047. ISSN 0029-5515.
  2. 1 2 3 4 Stix, T. H. (1998). "Highlights in early stellarator research at Princeton" (PDF). J. Plasma Fusion Res. 1: 3–8.
  3. ↑ Grove, D.J.; et al. "Confinement of Gun-Injected Hydrogen Plasmas and Microwave-Produced Xenon Plasmas in the C Stellarator". Plasma Physics and Controlled Nuclear Fusion Research, Conference Proceedings, Novosibirsk, 1-7 August 1968.
  4. ↑ Berkl, E.; et al. "Confinement of Contract-Ionized Barium Plasma in the Wendelstein Stellarator W II". Plasma Physics and Controlled Nuclear Fusion Research, Conference Proceedings, Novosibirsk, 1-7 August 1968.
  5. ↑ Iiyoshi, A. (20 April 1991). Development of the Stellarator/Heliotron Research (PDF) (Report). National Institute for Fusion Science, Japan. Retrieved 9 October 2026.
  6. ↑ Princeton Alumni Weekly, Volume 57. April 19. p9
  7. ↑ Johnson, John L.; Greene, John M. (September 2000). "Katherine Ella Mounce Weimer". Physics Today. 53 (9): 88. doi:10.1063/1.1325250. ISSN 0031-9228.
  8. ↑ See 1962
  9. ↑ A Celebration of the Life and Work of Shoichi Yoshikawa, April 9, 1934–November 4, 2010 (PDF). Princeton Plasma Physics Laboratory.
  10. ↑ See 1969,1970

Further reading