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.
Radiation Research Center, Osaka Prefecture University
Graduate School of Engineering,
Osaka Prefecture University
Ken Nakano and Taku Kiriishi
Largest tomb of ancient emperor Discharge Plasma
Outline of Radiation Research Center Discharge Plasma
1959: Establishment of RCOP
1962: Installation of the electron linear
1990: merged in OPU and reorganized
2011: reorganized to RRC in Research
Organization for University-
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.
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.
Cathode Discharge Plasma
ProbeDC atmospheric discharge device
（2） He flow
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?
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?
LHV-13AC(Logy Electric Co.LTD.)
Output 10KV/120mA RMS
Heat flux measurement with a metal target Discharge Plasma
Material: Cu, Mo
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).
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.
Estimation with exponential fitting
Q（~dT/t) = 0.5 [W]
Heat flux depends upon measurement position.
Estimation with discharge cut
Q（~jump of dT/dt) = 0.2 [W]
Is it possible to decompose these contribution? with bias? Tip material?
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?)
Thank you for kind attention. Discharge Plasma
Is there any questions?
With J.S.Chang's procedure, plasma density is about 1e17[m-3] for Ies=1[mA].
Normal Discharge Plasma
Ion current is
Secondary electron current
from probe surface,
which can not be
distinguished from ion's.
Air(wo flow) Discharge PlasmaReverse polarity discharge
No anonymity in ion current
No transition in Ar plasma
＊low current mode
This metastable density would produce secondary electron 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.
Various design of thermal probe tips for discharge plasma and divertor plasma
smaller than the plasma size
larger to smooth out plasma movement
depends on expected flux and method
thermocouple is experienced
Pt thermistor is attractive(?)
Trial measurement of heat flux is necessary.
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
Only an idea. But is it possible?
During discharge, TC signal shows large fluctuations in spite of large thermal diffusion time.
movement of jet column?
Data aqusition with NI9211 and averaging
Discharge control( flow, power, distance)
Relatively smooth TC signal is obtained.