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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
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

Contents of this presentation
Contents of this presentation Discharge Plasma

  • 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

Outline of Radiation Research Center Discharge Plasma

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.








T Discharge Plasmahe irradiation rooms and the accelerator rooms.

Division of quantum and radiation engineering apr 2013
Division of Quantum and Radiation Engineering Discharge Plasma(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。)


Background Discharge Plasma

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.

Dc atmospheric discharge device

Cathode Discharge Plasma


DC atmospheric discharge device




Air plasma and he plasma
Air plasma and He plasma Discharge Plasma

(1)Air(w/o flow)

(2) He flow

Ar plasma
Ar plasma Discharge Plasma



Dc plasma parameters
DC plasma parameters Discharge Plasma

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?)

How about heat flux measurement? Discharge Plasma

New J. Phys. 11 (2009) 115012

Are these guys insensitive?

Yambe s work on calorimetry
Yambe's work on calorimetry Discharge 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].

He plasma

He gas

Is the thermal isolation of water vessel sufficient?

Is temperature in water homogeneous?

Atmospheric pressure plasma jet
Atmospheric Pressure Plasma Jet Discharge Plasma

Power supply

LHV-13AC(Logy Electric Co.LTD.)

Input AC100V/2A

Output 10KV/120mA RMS


Size 140×92×175

Weight 1.4kg

Heat flux measurement with a metal target Discharge Plasma

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).

First result of target temperature
First result of target temperature Discharge Plasma

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

Estimation of heat flux(Fitting) Discharge Plasma





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.

Estimation of heat flux cut
Estimation of heat flux(Cut) Discharge Plasma



Estimation with discharge cut

Q(~jump of dT/dt) = 0.2 [W]

Plasma heat flux
Plasma heat flux Discharge Plasma

  • 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
Effect on TC raw data Discharge Plasmaof target bias


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?)

Consideration Discharge Plasma

  • 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
Consideration 2 Discharge Plasma

  • 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 Discharge Plasma

  • 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. Discharge Plasma


Is there any questions?


Appendix Discharge Plasma

  • DC atmospheric pressure plasma

  • Ion current abnormality

  • Thermal probe

Dc atmospheric plasma data
DC atmospheric plasma data Discharge Plasma

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

Discharge polarity

Normal Discharge Plasma


Discharge polarity



Air plasma



I p v p
I Discharge Plasmap-Vp特性

Ion current is

too large.

Secondary electron current

from probe surface,

which can not be

distinguished from ion's.



Reverse polarity discharge

Air(wo flow) Discharge Plasma

Reverse polarity discharge

No anonymity in ion current

No transition in Ar plasma

Ar flow

He flow

Dc plasma parameters1
DC plasma parameters Discharge Plasma

*low current mode

Ar ion saturation current
Ar ion saturation current Discharge Plasma

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

Conventional thermal probe
Conventional thermal probe current, which is the same order as the observed ion current.

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

Heat flux measurement current, which is the same order as the observed ion current.

Requirement of design
Requirement of design and divertor plasma

tip size

smaller than the plasma size

larger to smooth out plasma movement

tip material

depends on expected flux and method


thermocouple is experienced

Pt thermistor is attractive(?)

Trial measurement of heat flux is necessary.

Usage of pt thermistor
Usage of Pt thermistor and divertor plasma

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


ohm heating



Only an idea. But is it possible?


Reduction of tc noise
Reduction of TC noise and divertor plasma

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.