MODELING OF PLASMA DYNAMICS AND PATERN FORMATION DURING HIGH PRESSURE MICROWAVE BREAKDOWN IN THE AIR Ph.D. Thesis by Gua-qiang ZHU Toulouse University,2012 Presented by Mehmet Serhan Yıldız 28 November 2013 Boğaziçi University, İstanbul
Feb 23, 2016
MODELING OF PLASMA DYNAMICS AND PATERN FORMATION DURING
HIGH PRESSURE MICROWAVE BREAKDOWN IN THE AIR
Ph.D. Thesis by Gua-qiang ZHU Toulouse University,2012
Presented by Mehmet Serhan Yıldız28 November 2013
Boğaziçi University, İstanbul
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CONTENT Gas Breakdown
Gas Breakdown History
Types of Gas Discharge
High Pressure Microwave Discharge
Numerical Method
Results
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GAS BREAKDOWN
R
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Gas Discharges
Non Self Sustaining
Self Sustaining
Break down
Sustaining non
equiblirium
SustainingEquiblirium
DC low freq.and pulsed
Radio freq.
microwave
Optical fields
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GAS BREAKDOWN HİSTORY 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.
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GAS BREAKDOWN HİSTORY
Figure.1 Paschen Curve for Air [1]
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GAS BREAKDOWN HİSTORY
At the begining of 1900 Townsend explain development of current in the gas.
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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.
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HIGH PRESSURE MICROWAVE BREAKDOWN
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HIGH PRESSURE MICROWAVE BREAKDOWN Diffusive discharge doesn’t absorb microwave
energy due to lower electron neutral momentum transfer frequency.
Streamer form is characterized by high energy coupling.
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HIGH PRESSURE MICROWAVE BREAKDOWN
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HIGH PRESSURE MICROWAVE BREAKDOWN
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NUMERİCAL MODELIonization Frequency
Attachment Frequency Diffusion Cofficient
Electron İon recombination
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Free Diffusion
Ambipolar Diffusion
AmbientPlasma Density Goes to Zero
Plasma Dimensions < Deby Length Free Diffusion
Plasma Dimensions >= Deby Length
Ambipolar Diffusion
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NUMERİCAL MODEL
Debye Length
Chracteristic Length
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NUMERİCAL MODEL
nJ
u
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NUMERİCAL MODEL
Critical Field ionization balance attachment
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RESULTS
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RESULTS
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RESULTS
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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.,IEEE transaction on applied superconductivity,vol.22,No.3,June 2012