advanced probe measurement for atmospheric pressure discharge plasma
DESCRIPTION
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. - PowerPoint PPT PresentationTRANSCRIPT
Advanced Probe Measurement for Atmospheric Pressure Discharge Plasma
Radiation Research Center, Osaka Prefecture University
Hiroto Matsuura
Graduate School of Engineering,
Osaka Prefecture University
Ken Nakano and Taku Kiriishi
APSPT7(2012/4/15 、 Taipei)
Contents of this presentation
• Introduction of Radiation Research Center and a new division of OPU.
• Background of atmospheric plasma• DC discharge plasma parameters obtaine
d with the probe method• Heat flux of Dielectric Barrier Plasma Jet• Conclusion
Largest tomb of ancient emperor
1959: Establishment of RCOP 1962: Installation of the electron linear accelerator (linac)1990: merged in OPU and reorganized2011: reorganized to RRC in Research Organization for University-Community Collaborations
Outline of Radiation Research Center
2013 new Division will startthe Division of Quantum and Radiation Engineering
RadiationLaserBeamPlasma
PhysicsChemistryBiology
We can provide your students with the basic and practical education.
The irradiation rooms and the accelerator rooms.
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
Background
Atmospheric pressure plasma is now attractive for decontamination of environmental waste and medical technology, because of
low cast without vacuum pumping systemapplicability for biomaterial that does not less tolerate vacuumlarge 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 loadand analysis of I-V characteristic with collisional sheath effect.
DC atmospheric discharge device
Ip
Cathode
Probe
Idis
Vp
Air plasma and He plasma
( 1 ) Air(w/o flow) ( 2 ) He flow
Ar plasma
( 3 ) Ar ( high) (4) Ar ( low)
DC plasma parameters Comparison of plasma parameters in air/He/Ar plasma( Normal )
Parameter Working gas
Air He Ar(high) a Ar(low)
Idis(mA) 70 58 85 68
Iis(mA) 0.02 0.7 0.2 0.4
Ies(mA) 0.8 1.2 0.9 1.3
Vs(V) 100 250 35 200
Te(eV) 9 10 9 8
Ne(10 17 m -3 ) 1.6 2.3 1.2 2.7
a. Data from previous work
Space potential varies with gas spicis.Ion current for He/Ar plasma is too large.(metastable and 2nd electron?)
How about heat flux measurement?
http://www.jsap.or.jp/ap/2008/ob7704/cont7704.html
http://www.maximizingprogress.org/2010/02/plasma-medicine-disinfection.html
http://www.drexel.edu/research/img/mri_plasma.jpg
New J. Phys. 11 (2009) 115012
Are these guys insensitive?
Yambe's work on calorimetry
He gas He plasma
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].
Is the thermal isolation of water vessel sufficient?
Is temperature in water homogeneous?
Atmospheric Pressure Plasma Jet
Power supplyLHV-13AC(Logy Electric Co.LTD.) Input AC100V/2A Output 10KV/120mA RMS 9 ~ 12KHz Size 140×92×175 Weight 1.4kg
Heat flux measurement with a metal target
Heat flux determination
Type-T TC Temperature gradient methodType-K TC Fitting/cut method
Electrically isolated
Easy to modify for Q-V characteristic
Material: Cu, Mo
This target was provided by Dr. Osakabe(NIFS).
First result of target temperature
This data gives us heat flux of about 2(kW/m2) or 0.15(W) as a whole.
Estimation of heat flux(Fitting)
0
4
8
12
16
20
1000 1200 1400 1600 1800 2000 2200 2400 2600 2800 3000
TC(center)
time[s]
TC[deg.]
Estimation with exponential fitting Q ( ~dT/t) = 0.5 [W]
12
4
0
0.5 0.17
Target moved
Heat flux depends upon measurement position.
dTdecay time t is obtained by fitting.
Estimation of heat flux(Cut)
0
2
4
6
0 500 1000 1500 2000 2500 3000
TC(center)
t ime[s]
TC[deg.]
0
2
4
6
2100 2200 2300 2400 2500 2600 2700 2800 2900 3000
TC(center)
time[s ]
TC[deg.]
Estimation with discharge cut Q ( ~jump of dT/dt) = 0.2 [W]
before
after
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?
Effect on TC raw data of target bias
0 2000 400012
16
20
LF plasma(2012/2/14)
time[s]
Tar
get T
emp.
[deg
.C]
Although data is limited andAlthough data is limited and
Although data is limited, TC signal seems to depend upon bias voltage applied to target.
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?)
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.
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.
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.
Thank you for kind attention.多謝你的親切關懷。Is there any questions?有任何問題嗎?
Appendix
• DC atmospheric pressure plasma• Ion current abnormality• Thermal probe
DC atmospheric plasma data
With J.S.Chang's procedure, plasma density is about 1e17[m-3] for Ies=1[mA].
Discharge polarityNormal
Reverse Air plasma
(-)
(-)
(+)
(+)
Ip-Vp 特性
Ion current istoo large.
Secondary electron currentfrom probe surface,which can not be
distinguished from ion's.
Ip Vp
Reverse polarity discharge
Air(wo flow) He flowAr flow
No anonymity in ion current
No transition in Ar plasma
DC plasma parametersNormal Reverse
Air Ar (*) He Air Ar He
Dis. curr.[mA] 70 68 58 40 65 58
Float. pot.Vf[V] 30 190 245 395 225 180
Space Pot.Vs[V] 100 200 250 440 310 200
Ele. temp.Te[eV] 9 8 10 8 9 10
Ele. sat.curr.Ies[mA] -0.8 -1.3 -1.2 ? -1.1 -0.90
Ion sat.curr.Iis[mA] 0.02 0.4 0.7 0.055 0.1 0.15
Ele.den.ne×1017[m-3] 1.6 2.7 2.3 1.3 2.2 1.7
* low current mode
Ar ion saturation current
This metastable density would produce secondary electron current, which is the same order as the observed ion current.
Conventional thermal probe
Probe tip size, material, thermometer, and so on must be optimized for target plasma.
Heat flux measurement
Various design of thermal probe tips for discharge plasma and divertor plasma
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.
Usage of Pt thermistorOxygen radicals recombine on platinum surface, which receive more heat than other metal( ex, tungsten). N.Haraki et al. EEJ 149(2004)14.
Pt/W
Electron, ion, radical heat flux
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).
I
R0
V
Heat loss
ohm heating
Only an idea. But is it possible?
Reduction of TC noise
0 1000 2000 300010
20
30LF plasma(2011/12/22)
time[s]
Tem
p.[d
eg.C
]
During discharge, TC signal shows large fluctuations in spite of large thermal diffusion time. electro-magnetic noise? movement of jet column?
HR2500E Chart
Data aqusition with NI9211 and averagingDischarge control( flow, power, distance)
Relatively smooth TC signal is obtained.