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Ph .D. Thesis by Gua-qiang ZHU Toulouse University ,2012

Modeling of plasma dynamics and patern formation during high pressure microwave breakdown in the air. Presented by Mehmet Serhan Yıldız 28 November 2013 Boğaziçi University , İstanbul. Ph .D. Thesis by Gua-qiang ZHU Toulouse University ,2012. Content. Gas Breakdown

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Ph .D. Thesis by Gua-qiang ZHU Toulouse University ,2012

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  1. Modeling of plasma dynamics and patern formation during high pressure microwave breakdown in the air Presentedby Mehmet Serhan Yıldız 28 November 2013 Boğaziçi University, İstanbul Ph.D. ThesisbyGua-qiang ZHUToulouseUniversity,2012

  2. Content • Gas Breakdown • Gas Breakdown History • Types of Gas Discharge • High Pressure Microwave Discharge • Numerical Method • Results

  3. GasBreakdown R

  4. GasBreakdownHistory • 17 th century Coulomb proved experimentally in that charge leaks through air. • 19th century first vacuum tube experiment by Faraday (P=1 torr, V=1000V) • In 1889 Friedrich Paschen published his work in which he investigated the minimum potential that is necessary to generate a spark in the gap between the two electrodes in gas discharge tubes.

  5. GasBreakdownHistory Figure.1 PaschenCurveforAir [1]

  6. GasBreakdownHistory At thebegining of 1900 Townsendexplaindevelopment of current in thegas.

  7. Gas Breakdown History • The discharge phenomenon in microwave field was first extensively investigated in the late 1940s in order to solve the problem of discharge formation within a waveguide in a radar system. • The free located microwave discharges that are considered in this thesis work were first observed during the 1980s.

  8. High Pressure Microwave Breakdown

  9. High Pressure Microwave Breakdown • Diffusive dischargedoesn’t absorb microwave energy due tolower electron neutral momentum transfer frequency. • Streamer form is characterized by high energy coupling.

  10. High Pressure Microwave Breakdown

  11. High Pressure Microwave Breakdown

  12. Numerical Model IonizationFrequency Electronİonrecombination AttachmentFrequency DiffusionCofficient

  13. Ambient PlasmaDensityGoestoZero AmbipolarDiffusion FreeDiffusion PlasmaDimensions < DebyLength FreeDiffusion PlasmaDimensions >= DebyLength AmbipolarDiffusion

  14. Numerical Model ChracteristicLength DebyeLength

  15. Numerical Model n J u

  16. Numerical Model CriticalFieldionizationbalanceattachment

  17. Results

  18. Results

  19. Results

  20. References • Characterization of Paschen Curve Anomalies at High P*D values W.J.Carey et.al ARC tech.USA • Paschen Test in Superconducting Coils,Knaster J.,IEEEtransactionon applied superconductivity,vol.22,No.3,June 2012

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