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Advanced Probe Measurement for Atmospheric Pressure Discharge Plasma

Advanced Probe Measurement for Atmospheric Pressure Discharge Plasma. APSPT7 ( 2012/ 4 / 15 、 Taipei). Radiation Research Center, Osaka Prefecture University Hiroto Matsuura Graduate School of Engineering, Osaka Prefecture University Ken Nakano and Taku Kiriishi.

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Advanced Probe Measurement for Atmospheric Pressure Discharge Plasma

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  1. Advanced Probe Measurement for Atmospheric Pressure Discharge Plasma APSPT7 (2012/4/15、Taipei) Radiation Research Center, Osaka Prefecture University Hiroto Matsuura Graduate School of Engineering, Osaka Prefecture University Ken Nakano and Taku Kiriishi

  2. Contents of this presentation • Introduction of Radiation Research Center and a new division of OPU. • Background of atmospheric plasma • DC discharge plasma parameters obtained with the probe method • Heat flux of Dielectric Barrier Plasma Jet • Conclusion

  3. Largest tomb of ancient emperor

  4. Outline of Radiation Research Center 1959: Establishment of RCOP　　　　　 1962: Installation of the electron linear accelerator (linac) 1990: merged in OPU and reorganized 2011: reorganized to RRC in Research Organization for University- Community Collaborations 2013 new Division will start the Division of Quantum and Radiation Engineering We can provide your students with the basic and practical education. Radiation Laser Beam Plasma Physics Chemistry Biology

  5. The irradiation rooms and the accelerator rooms.

  6. Division of Quantum and Radiation Engineering (Apr. 2013) • A new division of graduate school of engineering of our university will start next year.(我們大學工程研究生院的一個新部門將於明年啟動。) • We will accept students from all of the world.(我們將接受來自世界各地的學生。) • http://www.eng.osakafu-u.ac.jp/English/02senko/senko.htm

  7. Background Atmospheric pressure plasma is now attractive for decontamination of environmental waste and medical technology, because of low cast without vacuum pumping system applicability for biomaterial that does not less tolerate vacuum large process speed Although many production methods have been proposed, parameters of plasma produced with them are not well studied. Electro static probe method has been widely used for low pressure discharge plasma. And even for Atmospheric pressure plasma, some literature reported its application as following. O.Sakai et al.: J.Phys. D: Appl. Phys, 38, 431(2005). M.R.Talukder et al.: J.Appl.phys., 91, 9529(2002). H.Matsuura, et al.:AIP conf. Proc., 1084, 871(2008). Key issue is the choice of probe tip material which tolerate plasma heat load and analysis of I-V characteristic with collisional sheath effect.

  8. Cathode Probe DC atmospheric discharge device Ip Vp Idis

  9. Air plasma and He plasma （1）Air(w/o flow) （2） He flow

  10. Ar plasma （3）Ar（high) （４）Ar（low)

  11. DC plasma parameters Comparison of plasma parameters in air/He/Ar plasma( Normal ) a. Data from previous work Space potential varies with gas spicis. Ion current for He/Ar plasma is too large.(metastable and 2nd electron?)

  12. How about heat flux measurement? New J. Phys. 11 (2009) 115012 Are these guys insensitive? http://www.drexel.edu/research/img/mri_plasma.jpg http://www.maximizingprogress.org/2010/02/plasma-medicine-disinfection.html http://www.jsap.or.jp/ap/2008/ob7704/cont7704.html

  13. Yambe's work on calorimetry Water temperature is monitored for He gas/plasma irradiation. (22P039-P, plasma conference 2011, Kanazawa) The difference of two case corresponds to plasma heat flux. They said 3.81E-5[J] energy was carried by 13[kHz] micro pulse, which consists plasma jet. Average heat flux is 0.5[W]. He plasma He gas Is the thermal isolation of water vessel sufficient? Is temperature in water homogeneous?

  14. Atmospheric Pressure Plasma Jet Power supply LHV-13AC(Logy Electric Co.LTD.) Input AC100V/2A Output 10KV/120mA RMS 9～12KHz Size 140×92×175 Weight 1.4kg

  15. Heat flux measurement with a metal target Material: Cu, Mo Electrically isolated Easy to modify for Q-V characteristic Heat flux determination Type-T TC Temperature gradient method Type-K TC Fitting/cut method This target was provided by Dr. Osakabe(NIFS).

  16. First result of target temperature This data gives us heat flux of about 2(kW/m2) or 0.15(W) as a whole.

  17. Estimation of heat flux(Fitting) 12 4 0 dT decay time t is obtained by fitting. Target moved 0.5 0.17 Estimation with exponential fitting Q（~dT/t) = 0.5 [W] Heat flux depends upon measurement position.

  18. Estimation of heat flux(Cut) before after Estimation with discharge cut Q（~jump of dT/dt) = 0.2 [W]

  19. Plasma heat flux • Electron positive bias • Ion Negative bias • Metastable atom Atmospheric He/Ar • Radical Atmospheric N2/O2 • Surface recombination • Surface condensation Is it possible to decompose these contribution? with bias? Tip material?

  20. Effect on TC raw data of target bias Al though data is limited and Although data is limited, TC signal seems to depend upon bias voltage applied to target. Although data is limited and At positive bias, target current becomes negative and TC signal shows large fluctuation. Although discharge itself might be changed with biasing, positive bias seems to reduce heat flux.(Ion, surface reaction?)

  21. Consideration • If heat flux of 0.5W is composited only electron and ion contribution, particle flux ( equivalently 50mA ) must be flowed into the target depending on bias voltage. But by now, such a large current has not been observed. • For previous work on DC discharge, electron saturation current of 1mA was observed with a small probe.

  22. Consideration 2 • Heat from atmospheric plasma seems to be carried by mainly metastable or radical.( Different Q-V curve ?) • To confirm this, plasma current must be measured preciously. But, since plasma jet is composed of so many micro plasma bullet, current measurement needs to some integration procedure to compare with heat flux measurement.

  23. Conclusion • Probe measurement of atmospheric pressure plasma requires the heat conduction estimate for tip materials and careful analysis of I-V curve with collisional sheath theory. • It gives us valuable information of plasma parameter, which depends on discharge device, gas spices, and so on. • Heat flux of atmospheric plasma jet is measured with target TC data and thermal probe analysis, as like as for low pressure plasma. • Obtained flux agrees well with Yambe's estimation. But by considering heat flux response to bias voltage, heat flux contribution from charged particles seems small. • Comparison of Langmuire/thermal probe data would be interesting and left for future work.

  24. Thank you for kind attention. 多謝你的親切關懷。 Is there any questions? 有任何問題嗎？

  25. Appendix • DC atmospheric pressure plasma • Ion current abnormality • Thermal probe

  26. DC atmospheric plasma data With J.S.Chang's procedure, plasma density is about 1e17[m-3] for Ies=1[mA].

  27. Normal Reverse Discharge polarity (+) (-) Air plasma (+) (-)

  28. Ip-Vp特性 Ion current is too large. Secondary electron current from probe surface, which can not be distinguished from ion's. Ip Vp

  29. Air(wo flow) Reverse polarity discharge No anonymity in ion current No transition in Ar plasma Ar flow He flow

  30. DC plasma parameters ＊low current mode

  31. Ar ion saturation current

  32. This metastable density would produce secondary electron current, which is the same order as the observed ion current.

  33. Conventional thermal probe Probe tip size, material, thermometer, and so on must be optimized for target plasma.

  34. Heat flux measurement

  35. Various design of thermal probe tips for discharge plasma and divertor plasma

  36. Requirement of design tip size smaller than the plasma size larger to smooth out plasma movement tip material depends on expected flux and method thermometer thermocouple is experienced Pt thermistor is attractive(?) Trial measurement of heat flux is necessary.

  37. Usage of Pt thermistor Oxygen radicals recombine on platinum surface, which receive more heat than other metal( ex, tungsten). N.Haraki et al. EEJ 149(2004)14. Pt/W temperature can be estimated from its resistance(=V/I-R0). Its temperature is determined by heat balance between plasma heat flux, ohmic heating, heat loss. If Pt and W temperature can be set equal by adjusting R0 or V, excess of ohmic heating is equal to radical contribution to Pt sensor, which can be measure of radical flux( or density). Electron, ion, radical heat flux Heat loss Pt/W ohm heating I V Only an idea. But is it possible? R0

  38. Reduction of TC noise HR2500E Chart During discharge, TC signal shows large fluctuations in spite of large thermal diffusion time. electro-magnetic noise? movement of jet column? Data aqusition with NI9211 and averaging Discharge control( flow, power, distance) Relatively smooth TC signal is obtained.

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