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