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Plasma Opening Switches

Plasma Opening Switches. Matthew Brickell ELEC 6750 Dr. Tzeng Spring 2004. OVERVIEW. Terminology Highlight typical applications Operation of a plasma switch Experiments: Past and Present. Questions. What does PEOS stand for? What are the two main phases of plasma opening switches?.

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Plasma Opening Switches

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  1. Plasma Opening Switches Matthew Brickell ELEC 6750 Dr. Tzeng Spring 2004

  2. OVERVIEW • Terminology • Highlight typical applications • Operation of a plasma switch • Experiments: Past and Present

  3. Questions • What does PEOS stand for? • What are the two main phases of plasma opening switches?

  4. Terminology • POS – Plasma Opening Switch • PEOS – Plasma Erosion Opening Switch

  5. Applications • Pulsed-Power • The main application of plasma opening switches is in conjunction with pulsed power generators. • Some applications of pulsed power generators are: • Inductive energy storage • Inertial confinement fusion research • Magnetic fusion research • High power radiation production • Quantum electronics • Electromagnetic accelerators • Charged-particle-beam technology • High-power lasers • Mass drivers • High density plasmas

  6. Conceptual Circuit Diagram of a Typical POS • Used for the application of inductive energy storage • A plasma is injected into the vacuum gap between the output conductors of a pulse generator. W. Rix, D. Parks, J. Shannon, J. Thompson, E. Waisman, “Operation and Empirical Modeling of the Plasma Opening Switch,” IEEE Trans. Plasma Sci., vol. 19, p. 400, April 1991.

  7. Plasma sources used over the years • Flashboards • Carbon guns • Ion beams • Laser ablative sources • Coaxial plasma guns • Capillary discharge source -- Ones that have provided sufficient plasma mass for practical use.

  8. POS Operation Schematic of Gamble 2 • Ion species is primarily C++. • The plasma will conduct current as a short circuit and then “open” • Conduction is primarily by emitted electrons passing through the background plasma B. V. Weber, R. J. Commisso, P.J. Goodrich, J.M. Grossmann, D.D.Hinshelwood, J.C. Kellogg, P.F. Ottinger, IEEE Trans. Plasma Sci., vol.19, p. 758, October 1991.

  9. Conduction Phase Emitted electron current density vs. ion current density for C++ Bipolar current density limit Bipolar, space-charge-limited emission Ion (electron) current density Ion (electron) mass Ion charge state Electron density Maximum ion collection rate B.V. Weber et al., “Investigation of plasma opening switch conduction and opening mechanisms.”, IEEE Trans. Plasma. Sci. vol.19 pp.757-766 Oct.1991

  10. Conduction Phase axial displacement by magnetic pressure • Switching could be induced by magnetic forces at current levels far lower than the bipolar value in the earlier slide. Axial plasma displacement by magnetic pressure B.V. Weber et al., “Investigation of plasma opening switch conduction and opening mechanisms.”, IEEE Trans. Plasma. Sci. vol.19 pp.757-766 Oct.1991

  11. Open Phase • At high power levels, a • magnetically insulated gap • forms near the cathode. • This gap prevents electron • conduction between the • switch electrodes. Magnetic insulation gap near the cathode B.V. Weber et al., “Investigation of plasma opening switch conduction and opening mechanisms.”, IEEE Trans. Plasma. Sci. vol.19 pp.757-766 Oct.1991

  12. Gap Size and Critical Current • Gap size must roughly equal the electron gyroradius • The critical current is a formula used to aid in the • formation of a gap of the correct size. Critical Current for “Opening” of POS: r = cathode raduis D = gap size γ = related to voltage across the gap B.V. Weber et al., “Investigation of plasma opening switch conduction and opening mechanisms.”, IEEE Trans. Plasma. Sci. vol.19 pp.757-766 Oct.1991

  13. Method 1: Erosion Opening • Begins when the influx of ion current is insufficient to maintain a steady gap. • The boundary between conduction and erosion opening can be found by multiplying the bipolar current density limit(JBP) by the emission area. Conduction current limit: is the length of the emitting area of the cathode. where • If this limit is exceeded, the gap may grow by the erosion • mechanism. B.V. Weber et al., “Investigation of plasma opening switch conduction and opening mechanisms.”, IEEE Trans. Plasma. Sci. vol.19 pp.757-766 Oct.1991

  14. Method 1: Erosion Opening • Erosion of the plasma occurs when ions are • removed from the plasma surface faster than they • can be replaced. l0 The rate at which this occurs is: Erosion opening mechanism B.V. Weber et al., “Investigation of plasma opening switch conduction and opening mechanisms.”, IEEE Trans. Plasma. Sci. vol.19 pp.757-766 Oct.1991

  15. Method 2: Magnetic Pressure • Magnetic pressure pushes open the switch gap. • Plasma displacement is related to axial current, ρis the mass density BΦis the azimuthal magnetic field B.V. Weber et al., “Investigation of plasma opening switch conduction and opening mechanisms.”, IEEE Trans. Plasma. Sci. vol.19 pp.757-766 Oct.1991

  16. Method 2: Magnetic Pressure Recall the figure of the POS during conduction: If current flows along the tilted plasma surface, magnetic pressure forces open the switch. B.V. Weber et al., “Investigation of plasma opening switch conduction and opening mechanisms.”, IEEE Trans. Plasma. Sci. vol.19 pp.757-766 Oct.1991

  17. BLACKJACK 5 • BLACKJACK 5 experiments on the use of POS for the production of short electrical pulses were initiated in 1986. • BLACKJACK 5 is a 10terawatt, 0.6 ohm accelerator which delivers an electrical pulse with a 100 ns pulse width. • Experiments were discontinued in 1987. • Yielded data relevant to POS performance. W. Rix, D. Parks, J. Shannon, J. Thompson, E. Waisman, “Operation and Empirical Modeling of the Plasma Opening Switch,” IEEE Trans. Plasma Sci., vol. 19, p. 400, April 1991.

  18. Experimental Results From BLACKJACK 5 • BLACKJACK 5 POS current waveform configuration with a 0.6 ohm impedance e-beam. • The switch current is derived by taking the difference between the measured upstream and load currents. • dI/dt > 1014 A/s This is a factor of five gain over the dI/dt available without a POS. W. Rix, D. Parks, J. Shannon, J. Thompson, E. Waisman, “Operation and Empirical Modeling of the Plasma Opening Switch,” IEEE Trans. Plasma Sci., vol. 19, p. 400, April 1991.

  19. ACE 1 • Started around the time BLACKJACK 5’s experimentation was discontinued. • Consists of a 250kJ capacitor bank which discharges its energy into a parallel plate transmission line and POS shorted diode frontend. • Quarter-cycle time is approximately 3microseconds. W. Rix, D. Parks, J. Shannon, J. Thompson, E. Waisman, “Operation and Empirical Modeling of the Plasma Opening Switch,” IEEE Trans. Plasma Sci., vol. 19, p. 400, April 1991.

  20. Experimental Results of ACE-1 • POS-conducted peak currents between 100 and 900kA. • POS conduction time varied between 100 and 2000ns. W. Rix, D. Parks, J. Shannon, J. Thompson, E. Waisman, “Operation and Empirical Modeling of the Plasma Opening Switch,” IEEE Trans. Plasma Sci., vol. 19, p. 400, April 1991.

  21. Parameters of various research facilities N. U. Barinov, G. S. Belen’ki, G. I. Dolgachev, et al., in Proceedings of the 11th IEEE Pulsed Power Conference, Baltimore, 1997, Vol. 2, p. 1222.

  22. Coaxial Nanosecond POS http://plasma-gate.weizmann.ac.il/NSPOS/nspos_photo.jpg

  23. Questions • What does PEOS stand for? Plasma Erosion Opening Switch • What are the two main phases of plasma opening switches? Conduction and open

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