Field-reversed configuration

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Field-Reversed Configuration: a toroidal electric current is induced inside a cylindrical plasma, creating a poloidal magnetic field, reversed in respect to the direction of an externally applied magnetic field. The resultant high-beta axisymmetric compact toroid is self-confined.

A Field-Reversed Configuration (FRC) is a device developed for magnetic fusion energy research that confines a plasma on closed magnetic field lines without a central penetration.[1]

History[edit]

The FRC has been first observed in laboratory in the late 1950s during theta pinch experiments with a reversed background magnetic field.[2] The first studies about the effect started at the United States Naval Research Laboratory (NRL) in the 1960s, and considerable data is available since then, with over 600 published papers.[3] Almost all research was conducted during Project Sherwood at Los Alamos National Laboratory (LANL) from 1975 to 1990,[4] and during 18 years at the Redmond Plasma Physics Laboratory of the University of Washington,[5] with the large s experiment (LSX).[6] More recently some research has been done at the Air Force Research Laboratory (AFRL),[7] the Fusion Technology Institute (FTI) of the University of Wisconsin-Madison[8] and the University of California, Irvine.[9] Some private companies now theoretically and experimentally study FRCs in order to use this configuration in future fusion power plants they try to build, like General Fusion, Tri-Alpha Energy, Inc., MSNW LLC and Helion Energy.[10]

The FRC is also considered for deep space exploration, not only as a possible nuclear energy source, but as means of accelerating a propellant to very high levels of specific impulse (Isp) for electrically powered spaceships and fusion rockets, with interest expressed by NASA[11][12][13][14][15][16] and the media.[17][18]

Operation[edit]

One approach to producing fusion power is to confine the plasma with magnetic fields. This is most effective if the field lines do not penetrate solid surfaces but close on themselves into circles or toroidal surfaces. The mainline confinement concepts of tokamak and stellarator do this in a toroidal chamber, which allows a great deal of control over the magnetic configuration, but requires a very complex construction. The Field-Reversed Configuration offers an alternative in that the field lines are closed, providing good confinement, but the chamber is cylindrical, allowing easy construction and maintenance.[19]

A Field-Reversed Configuration is formed in a cylindrical coil which produces an axial magnetic field. First, an axial bias field is applied, then the gas is pre-ionized, which "freezes in" the bias field, finally the axial field is reversed. At the ends, reconnection of the bias field and the main field occurs, producing closed field lines. The main field is raised further, compressing and heating the plasma and providing a vacuum field between the plasma and the wall.

Field-reversed configurations and spheromaks are together known as compact toroids. Unlike the spheromak, where the strength of the toroidal magnetic field is similar to that of the poloidal field, the FRC has little to no toroidal field component and is confined solely by a poloidal field. The lack of a toroidal field means that the FRC has no magnetic helicity and that it has a high beta. The high beta makes the FRC attractive as a fusion reactor. Spheromaks have β ≈ 0.1 whereas a typical FRC has β ≈ 1.[20]

Plasma stability[edit]

Charged particles inside an FRC follow large betatron orbits (their average gyroradius is about half the size of the plasma) which are typical in accelerator physics rather than plasma physics. FRCs are very stable because the plasma is not dominated by usual small gyroradius particles like other thermodynamic equilibrium or nonthermal plasmas. Its behavior is not described by classical magnetohydrodynamics, hence no Alfvén waves and almost no MHD instabilities despite their theoretical prediction,[21] and it avoids the typical "anomalous transport", i.e. all processes in which loss of particles or energy occurs.[22][23][24]

As of 2000, several remaining instabilities are being studied:

  • The tilt and shift modes. Those instabilities can be mitigated by either including a passive stabilizing conductor, or by forming very oblate plasmas (i.e. very elongated plasmas),[25] or by creating a self-generated toroidal field.[26] The tilt mode has also been stabilized in FRC experiments by increasing the ion gyroradii.[27]
  • The magnetorotational instability. This mode causes a rotating elliptical distortion of the plasma boundary, and can destroy the FRC when the distorted plasma comes in contact with the confinement chamber.[28] Successful stabilization methods include the use of a quadrapole stabilizing field,[29][30] and the effects of a rotating magnetic field (RMF).[31][32]

See also[edit]

External links[edit]

References[edit]

  1. ^ Freidberg, Jeffrey P. (2007). Plasma Physics and Fusion Energy. Cambridge University Press. ISBN 0-521-85107-6. 
  2. ^ Kolb, A.C.; Dobbie, C.B.; Griem, H.R. (1 July 1959). "Field mixing and associated neutron production in a plasma". Physical Review Letters 3 (1): 5–7. Bibcode:1959PhRvL...3....5K. doi:10.1103/PhysRevLett.3.5. 
  3. ^ Tuszewski, M. (November 1988). "Field reversed configurations". Nuclear Fusion 28 (11): 2033. doi:10.1088/0029-5515/28/11/008. 
  4. ^ McKenna, K.F.; Armstrong, W.T.; Barnes, D.C; Bartsch, R.R; Chrien, R.E.; Cochrane, J.C.; Klingner, P.L.; Hugrass, W.W; Linford, R.K.; Rej, D.J.; Schwarzmeier, J.L.; Sherwood, E.G.; Siemon, R.E.; Spencer, R.L.; Tuszewski, M. (1985). "Field-reversed configuration research at Los Alamos". Nuclear Fusion 25 (9): 1317. doi:10.1088/0029-5515/25/9/057. 
  5. ^ "Web page of the Redmond Plasma Physics Laboratory". 
  6. ^ Hoffman, Alan L.; Carey, Larry L.; Crawford, Edward A.; Harding, Dennis G.; DeHart, Terence E.; McDonald, Kenneth F.; McNeil, John L.; Milroy, Richard D.; Slough, John T.; Maqueda, Ricardo; Wurden, Glen A. (March 1993). "The Large-s Field-Reversed Configuration Experiment". Fusion Science and Technology (American Nuclear Society) 23 (2): 185–207. OSTI 6514222. 
  7. ^ Kirtley, David; Brown, Daniel L.; Gallimore, Alec D.; Haas, James (June 2005). Details on an AFRL Field Reversed Configuration Plasma Device (Technical report). Air Force Research Laboratory. 
  8. ^ "Web page of the Fusion Technology Institute, University of Wisconsin-Madison". 
  9. ^ Harris, W.S.; Trask, E.; Roche, T.; Garate, E.P.; Heidbrink, W.W.; McWilliams, R. (20 November 2009). "Ion flow measurements and plasma current analysis in the Irvine Field Reversed Configuration". Physics of Plasmas (American Institute of Physics) 16 (11). Bibcode:2009PhPl...16k2509H. doi:10.1063/1.3265961. 
  10. ^ Poddar, Yash (11 March 2014). "Can Startups Make Nuclear Fusion Possible?". Stanford University. 
  11. ^ Wessel, F. J. (2000). "Colliding beam fusion reactor space propulsion system". "AIP Conference Proceedings" 504. p. 1425. doi:10.1063/1.1290961.  edit
  12. ^ Cheung, A. (2004). "Colliding Beam Fusion Reactor Space Propulsion System". "AIP Conference Proceedings" 699. p. 354. doi:10.1063/1.1649593.  edit
  13. ^ Slough, John T. (28 November 2000). Propagating Magnetic Wave Plasma Accelerator (PMWAC) for Deep Space Exploration (Technical report). MSNW LCC and NASA Institute for Advanced Concepts. Phase-I Final Report. 
  14. ^ Slough, John; Pancotti, Anthony; Pfaff, Michael; Pihl, Christopher; Votroubek, George (November 2012). "The Fusion Driven Rocket". NIAC 2012. Hampton, VA: NASA Innovative Advanced Concepts. 
  15. ^ Pancotti, A.; Slough, J.; Kirtley, D.; Pfaff, M.; Pihl, C.; Votroubek, G. (2012). "Mission Design Architecture for the Fusion Driven Rocket". "48th AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit". doi:10.2514/6.2012-4113. ISBN 978-1-60086-935-8.  edit
  16. ^ Slough, John; Pancotti, Anthony; Kirtley, David; Votroubek, George (6–10 October 2013). "Electromagnetically Driven Fusion Propulsion" (PDF). 33rd International Electric Propulsion Conference (IEPC-2013). Washington, D.C.: George Washington University. 
  17. ^ "Nuclear Fusion Rocket Could Reach Mars in 30 Days". Space.com. 10 April 2013. 
  18. ^ Brian Heather (12 September 2013). "Professor John Slough on how nuclear power could get us to Mars in 30 days". Engadget. 
  19. ^ Ryzhkov, Sergei V. (2002). "Features of Formation, Confinement and Stability of the Field Reversed Configuration". Problems of Atomic Science and Technology. Plasma Physics 7 (4): 73–75. ISSN 1682-9344. 
  20. ^ Ono, Y (1999). "New relaxation of merging spheromaks to a field reversed configuration". Nuclear Fusion 39 (11Y): 2001–2008. doi:10.1088/0029-5515/39/11Y/346.  edit
  21. ^ Asai, T.; Takahashi, T. (2012). "MHD Activity in an Extremely High-Beta Compact Toroid" (PDF). "Topics in Magnetohydrodynamics". doi:10.5772/37375. ISBN 978-953-51-0211-3.  edit
  22. ^ Rostoker, N.; Wessel, F.J.; Rahman, H.U.; Maglich, B.C.; Spivey, B. (22 March 1993). "Magnetic Fusion with High Energy Self-Colliding Ion Beams". Physical Review Letters (American Physical Society) 70 (1818). Bibcode:1993PhRvL..70.1818R. doi:10.1103/PhysRevLett.70.1818. Archived from the original on 30 December 2005. 
  23. ^ Binderbauer, M.W.; Rostoker, N. (December 1996). "Turbulent Transport in Magnetic Confinement: How to Avoid it". Journal of Plasma Physics (Cambridge University Press) 56 (3): 451–465. Bibcode:1996JPlPh..56..451B. doi:10.1017/S0022377800019413. Archived from the original on 30 December 2005. 
  24. ^ Rostoker, N.; Binderbauer, M. W.; Wessel, F. J.; Monkhorst, H. J. "Colliding Beam Fusion Reactor" (PDF). Invited Paper, Special Session on Advanced Fuels APS-DPP. American Physical Society. 
  25. ^ Gerhardt, S. P.; Belova, E.; Inomoto, M.; Yamada, M.; Ji, H.; Ren, Y.; Kuritsyn, A. (2006). "Equilibrium and stability studies of oblate field-reversed configurations in the Magnetic Reconnection Experiment". Physics of Plasmas 13 (11): 112508. doi:10.1063/1.2360912.  edit
  26. ^ Omelchenko, Yu. A. (27–29 March 2000). "Stabilization of the FRC Tilt Mode by a Self-Generated Toroidal Field" (PDF). Sherwood 2000 International Fusion/Plasma Theory Conference. UCLA, Los Angeles, California: General Atomics Fusion Energy Research. 
  27. ^ Slough, J. T.; Hoffman, A. L. (1988). "Observation of tilt stability of field reversed configurations at large s". Nuclear Fusion 28 (6): 1121. doi:10.1088/0029-5515/28/6/016.  edit
  28. ^ Tuszewski, M. (1984). "Experimental study of the equilibrium of field-reversed configurations". Plasma Physics and Controlled Fusion 26 (8): 991. doi:10.1088/0741-3335/26/8/004.  edit
  29. ^ Ohi, S.; Minato, T.; Kawakami, Y.; Tanjyo, M.; Okada, S.; Ito, Y.; Kako, M.; Gotô, S.; Ishimura, T.; Itô, H. (1983). "Quadrupole Stabilization of the n=2 Rotational Instability of a Field-Reversed Theta-Pinch Plasma". Physical Review Letters 51 (12): 1042. doi:10.1103/PhysRevLett.51.1042.  edit
  30. ^ Hoffman, A. L. (1983). "Suppression of the n=2 rotational instability in field-reversed configurations". Physics of Fluids 26 (6): 1626. doi:10.1063/1.864298.  edit
  31. ^ Guo, H.; Hoffman, A.; Milroy, R.; Miller, K.; Votroubek, G. (2005). "Stabilization of Interchange Modes by Rotating Magnetic Fields". Physical Review Letters 94 (18). doi:10.1103/PhysRevLett.94.185001.  edit
  32. ^ Slough, J.; Miller, K. (2000). "Enhanced Confinement and Stability of a Field-Reversed Configuration with Rotating Magnetic Field Current Drive". Physical Review Letters 85 (7): 1444. doi:10.1103/PhysRevLett.85.1444. PMID 10970525.  edit