Self Consistently Generated Charge Cylinder in BETA Device


This paper presents a study on near cathode space charge region in BETA (Basic Experiments in Toroidal Assembly), a toroidal plasma device with purely toroidal magnetic field. A charge cylinder has been found to be embedded in the plasma center corresponding to the hot filament cathode location in poloidal cross section. This charge cylinder has been created by the primary electrons emitted from the filament surface, which in turn, leads to the formation of a potential well in the core plasma. We have proposed a model, which shows that a tiny fraction of injected energetic electrons is sufficient to sustain the observed potential well. We have examined the equilibrium of the charge cylinder in poloidal cross-section and found that it exhibits equilibrium configuration by forming circulation pattern of primary electrons. The circulation pattern is formed by vertical drift due to toroidal magnetic field and self-consistent poloidal E×B drift. We have concluded that the self-consistency is in adjusting the poloidal drift to the vertical drift of the trapped primary electrons.

Share and Cite:

R. Kaur, A. Sree and S. Mattoo, "Self Consistently Generated Charge Cylinder in BETA Device," Journal of Modern Physics, Vol. 3 No. 10A, 2012, pp. 1697-1702. doi: 10.4236/jmp.2012.330208.

Conflicts of Interest

The authors declare no conflicts of interest.


[1] S. Roy, B. P. Pandey, J. Poggie and D. V. Gaitonde, Physics of Plasmas, Vol. 10, 2003, pp. 2578-2585. doi:10.1063/1.1572491
[2] R. Iiyoshi and E.-J. Surf, Sci. Nanotech., Vol. 4, 2006, pp.339-344. doi:10.1380/ejssnt.2006.339
[3] R. Iiyoshi, E.-J. Surf. Sci. Nanotech., Vol. 1, 2003, pp. 147-151. doi:10.1380/ejssnt.2003.147
[4] M. S. Benilov, “Understanding and Modelling Plasma-Electrode Interaction in High-Pressure Arc Discharges: A Review,” Journal of Physics D: Applied Physics, Vol. 41, No. 14, 2008, p. 144001. doi:10.1088/0022-3727/41/14/144001
[5] M. S. Benilov and A. Marotta, “A Model of the Cathode Region of Atmospheric Pressure Arcs,” Journal of Physics D: Applied Physics, Vol. 28, No. 9, 1995, pp. 1869- 1882. doi:10.1088/0022-3727/28/9/015
[6] J. R. Ahn, C. J. Park, Nuc. Inst. Meth. Phys. Res. Sec. A: Accel., Spect., Det. Ass. Equip. Vol. 645, 2011, pp. 345-349.
[7] M. R. B. Ghadikolaee, B. Fateh and E. T. Ghadikolaee, “Design and Study of an Enhanced Filament Ion Source,” Vacuum, Vol. 86, No. 1, 2011, pp. 44-47. doi:10.1016/j.vacuum.2011.03.028
[8] H. Somacal, H. Huck, D. E. DiGregario, J. O. F. Niello and M. Igarzabal, Nuc. Inst. Meth. Phys. Res. Sec. A: Accel., Spect., Det. Ass. Equip., Vol. 490, 2002, pp. 9-15.
[9] R. Kaur and S. K. Mattoo, Plasma Sources Sc. and Tech., Vol. 18, 2009, pp. 015993-1-8.
[10] R. Kaur, A. S. Sree, A. K. Singh and S. K. Mattoo, “Life Cycle of Density Structures in a Simple Magnetized Torus,” New Journal of Physics, Vol. 12, 2010, pp. 103013-103018. doi:10.1088/1367-2630/12/10/103013
[11] R. Kaur, A. K. Singh, R. Singh, A. S. Sree and S. K. Mat-too, “Territorial Characteristics of Low Frequency Electrostatic Fluctuations in a Simple Magnetized Torus,” Physics of Plasmas, Vol. 18, No. 1, 2011, pp. 12109- 12111. doi:10.1063/1.3551514
[12] R. Singh, S. Mahajan and K. Avinash, “Equilibrium and Fluctuations in a Plasma Confined in a Pure Toroidal Field,” Physical Review Letters, Vol. 77, No. 8, 1996, pp. 1504-1507. doi:10.1103/PhysRevLett.77.1504
[13] S. Mahajan, R. Singh and K. Avinash, “Theory of Plasma Confinement in Devices with Pure Toroidal Field,” Physics of Plasmas, Vol. 4, No. 7, 1997, pp. 2612-2618. doi:10.1063/1.872349
[14] K. Rypdal, E. Gronvoll, F. J. Oynes, A. Fredriksen, R. J. Armstrong, J. Trulsen and H. L. Pecseli, “Confinement and Turbulent Transport in a Plasma Torus with no Rotational Transform,” Plasma Physics and Controlled Fusion, Vol. 36, No. 7, 1994, pp. 1099-1114. doi:10.1088/0741-3335/36/7/002
[15] R. Van Nieuwenhove and G. Van Oost, “Charge Neutralization by Poloidal Plasma Rotation,” Plasma Physics and Controlled Fusion, Vol. 34, No. 5, 1992, pp. 873-880. doi:10.1088/0741-3335/34/5/015
[16] E. Wagner, et al., “Regime of Improved Confinement and High Beta in Neutral-Beam-Heated Divertor Discharges of the ASDEX Tokamak,” Physical Review Letters, Vol. 49, No. 19, 1982, pp. 1408-1412. doi:10.1103/PhysRevLett.49.1408
[17] E. J. Strait, et al., “Enhanced Confinement and Stability in DIII-D Discharges with Reversed Magnetic Shear,” Physical Review Letters, Vol. 75, No. 24, 1995, pp. 4421-4424. doi:10.1103/PhysRevLett.75.4421
[18] K. K. Jain, “Observation of Improved Behavior by Electrode Biasing of a Toroidal Plasma Having no Poloidal Magnetic Field,” Physical Review Letters, Vol. 70, No. 6, 1993, pp. 806-809. doi:10.1103/PhysRevLett.70.806
[19] K. K. Jain, “Poloidal Plasma Rotation and Its Effect on Fluctuations in a Toroidal Plasma,” Nuclear Fusion, Vol. 36, No. 12, 1996, pp. 1661-1669. doi:10.1088/0029-5515/36/12/I06

Copyright © 2022 by authors and Scientific Research Publishing Inc.

Creative Commons License

This work and the related PDF file are licensed under a Creative Commons Attribution 4.0 International License.