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Jianjun Shi, Fangchuan Zhong, Jing Zhang and Michael Kong

Control of operation modes in radio frequency Atmospheric pressure glow Discharges by excitation frequency. Jianjun Shi, Fangchuan Zhong, Jing Zhang and Michael Kong. College of Science, Donghua University, Shanghai, 201620 China

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Jianjun Shi, Fangchuan Zhong, Jing Zhang and Michael Kong

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  1. Control of operation modes in radio frequency Atmospheric pressure glow Discharges by excitation frequency Jianjun Shi, Fangchuan Zhong, Jing Zhang and Michael Kong College of Science, Donghua University, Shanghai, 201620 China Dept of Electronic and Electrical Eng, Loughborough University, Loughborough, UK Towards stable & cold atmospheric plasmas

  2. Towards stable & cold atmospheric plasmas Outlines • Introductions • Operation modes in RF APGDs • Numerical characteristics; • Experimental studies; • Excitation frequency on RF APGDs • Mode expansion studied by simulation • Experimental studies on excitation frequency; • Conclusions Chengdou- 2007: page-2

  3. Towards stable & cold atmospheric plasmas Introductions Widely applied low pressure radio frequency plasmas Atmospheric pressure radio frequency plasmas Chengdou- 2007: page-3

  4. Towards stable & cold atmospheric plasmas Modes in RF APGDs-Numerical Operation modes in RF APGDs  Mode: Volumetric Differential conductivity: Positive  Mode: dominated in sheath region Differential conductivity: Negative Ref: J. J.Shi and M. G. Kong, J. Appl. Phys., 97, 023306 (2005). Chengdou- 2007: page-4

  5. Towards stable & cold atmospheric plasmas Modes in RF APGDs-Numerical Modes characterization Sheath thickness: Change of slope Sheath voltage: Change of differential conductivity Mode transition dependent on secondary emission coefficient. Ref: Jianjun Shi and Michael G. Kong, IEEE Transaction on Plasma Science, 33, 624 (2005) Chengdou- 2007: page-5

  6. Towards stable & cold atmospheric plasmas Modes in RF APGDs-Experimental Operation modes in RF APGDs  Mode: Volumetric across the discharge gap  Mode: Constricted single column Ref: J. J. Shi, X. T. Deng, R. Hall, J. D. Punnett and M. G. Kong, J. Appl. Phys., 94, 6303-6310 (2003) Ref: J.J. Shi, D. W. Liu and M. G. Kong, Applied Phys. Lett.,90, 031505 (2007) Chengdou- 2007: page-6

  7. Towards stable & cold atmospheric plasmas Modes in RF APGDs-Experimental Evolution of RF APGD Taken by nano-second ICCD. Sheath region formed above two electrodes alternatively. Chengdou- 2007: page-7

  8. Towards stable & cold atmospheric plasmas Frequency on modes-Numerical Excitation frequency on modes Ref: J.J. Shi and M. G. Kong, Applied Phys. Lett.,87, 201501 (2005) Chengdou- 2007: page-8

  9. Towards stable & cold atmospheric plasmas Frequency on modes-Numerical Excitation frequency on modes Plasma reactivity: • Mean electron energy increases; • Electron density increases. Sheath structure: • Sheath voltage: similar to applied voltage; • Sheath thickness: sustain in  mode and collapse in  mode. Ref: J.J. Shi and M. G. Kong, Applied Phys. Lett.,87, 201501 (2005) Chengdou- 2007: page-9

  10. Towards stable & cold atmospheric plasmas Frequency on modes-Experimental Excitation frequency on modes Excitation frequency: double & triple • Discharge current range expanded; • Applied voltage reduced. With increasing excitation frequency: • Stable operation  region expanded. Chengdou- 2007: page-10

  11. Towards stable & cold atmospheric plasmas Frequency on modes-Experimental Voltage regime in  modes Breakdown voltage: • Decreases with excitation frequency; • maintain in higher frequencies. With increasing excitation frequency: • Voltage regime is constricted. Chengdou- 2007: page-11

  12. Towards stable & cold atmospheric plasmas Frequency on modes-Experimental Excitation frequency on modes With increasing excitation frequency: • More reactive species are obtained in RF APGDs. Using optical emission intensity to indicate the energetic electron density. Chengdou- 2007: page-12

  13. Towards stable & cold atmospheric plasmas Conclusions • Different operation modes (- and -mode) are found in RF APGDs in numerical simulation and experiments; • The  mode in RF APGDs is suggested to be expanded by higher excitation frequencies in simulation results. • The expansion of  mode in RF APGDs by higher excitation frequency is also found in experimental studies. Chengdou- 2007: page-13

  14. Towards stable & cold atmospheric plasmas Thank you! Chengdou- 2007: page-14

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