quantitative estimation of heat flux of atmospheric pressure plasma jet
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Quantitative Estimation of Heat Flux of Atmospheric Pressure Plasma Jet
Radiation Research Center, Osaka Prefecture University
Hiroto Matsuura
IC-PLANTS 2012(2012/3/9 、 Inuyama)
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 notis 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.
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?
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
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?
Measurement of target heat flux
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
Heat flux measurement
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 inspit 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.
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
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, traget 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.
DC atmospheric plasma data
With J.S.Chang's procedure, plasma density is about 1e17[m-3] for Ies=1[mA].
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
• Heat flux from atmospheric plasma jet was measured with target TC data and thermal probe analysis, as like as for low pressure plasma.
• Considering heat flux value and its response to bias, heat flux contribution from charged particles seems small.
• Present plasma jet has smaller density compared with DC discharge.
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