22P003-O
Atmospheric Pressure Argon Plasma Jet Generated
with Penning Discharge
ペニング放電を利用した
小型大気圧アルゴンプラズマジェットの生成
Hiroshi Akamatsu1, Tomohiro Kaneda1, Kazunori Ichikawa1,Kingo Azuma2, and Masahiro Onoi3
1
赤松 浩 ，金田知大1，市川和典1，東 欣吾2，尾ノ井正裕31

Electrical Engineering, Kobe City College of Technology,
8-3 Gakuenhigashi-machi, Nishi-ku, Kobe 651-2194, Japan
2
Dept. Electrical Engineering and Computer Science, Graduate School of Engineering, University of Hyogo
2167 Shosha, Himeji 671-2208, Japan
3
Metal Technology Co. Ltd.
713 Shake Aza Narihira, Ebina 243-0424, Japan1
神戸市立工業高等専門学校電気工学科，〒651-2194 神戸市西区学園東町8-32
兵庫県立大学大学院工学研究科電気系工学専攻，〒671-2280 姫路市書写2167
3金属技研株式会社，〒243-424 海老名市社家字業713
An atmospheric pressure plasma jet generated with argon gas has been compared with the one with heliumgas. The length of argon plasma jet was shorter than the helium plasma jet because the argon is difficult tomaintain glow discharge. On the other hand, the argon plasma jet had much more hydroxyl radicals thanthe helium. In the argon plasma, metastable argon atoms with energy of 11.5 eV can be formed bybombardment of argon atoms and electrons. The metastable species dissociated H2O molecules to OH
radicals in the argon plasma.

1. Introduction
Atmosphericpressureplasmasarenon-thermal and glow discharge plasma operating
at an atmospheric pressure. In the plasmas, there
are chemically active species such as hydroxyl
radical and ozone. Therefore the plasmas can beapplied on surface modification of materials
and bio application [1-3].
In our early work, an atmospheric pressureplasma jet device with a high voltage modulator
driven by dry cells of 12 V has been developed[4]. The plasma generated by the device hascarried out decomposition of water-solubleorganic dye and surface treatment of highly
crystalline graphite [5]. The running cost,
however, isn’t economical because the plasma
was generated with helium gas of 1-5 l/min.
In the present work, we have generated an
atmospheric pressure plasma jet with argon
instead of helium in order to cut the running cost.
This paper reports on a comparison of plasmas
generated by helium and argon.
2. Experimental
Plasma jet nozzle has a dielectric tube and twocylindrical electrodes geometry. The quartz tube
with the diameter of 1.5 mm and thickness of 0.6

mm is used as a dielectric barrier. A powered
electrode is in the tube and a grounded electrode isrolled on the tube. Helium or argon gas iscontrolled by 1-5 l/min by a flow meter andintroduced to the tube.
The plasma jet is generated by an AC power
supply with 6 kV and 16 kHz. Chemically active
species in the plasmas were evaluated by fiber optic
spectrometer (SEC2000, BAS).
3. Results
Figure 1 shows photographs of the plasmasgenerated with (a) helium and (b) argon gas. The
flow rate was adjusted at 2 l/min. It is clear from(a) He: 2 l/min(b) Ar: 2 l/min
10 mm

Fig. 1 Observation of plasmas generated with (a)helium and (b) argon.

Fig. 1 that the length of plasma plume with helium
is longer than that with argon. The difference in theplasma length results from easiness of maintaining
glow discharge.
The helium has metastable level Em=20.6 eV
under the ionization one Ei = 24.5 eV. On the otherhand, the argon has also metastable and ionizationlevel of Em=11.5 eV and Ei = 15.8 eV, respectively.
The difference between Ei and Em levels for argon ismore than that of helium. It is difficult for argon tomaintain the glow discharge.
Figure 2 shows spectra of the plasmas with (a)helium and (b) argon. The helium plasma jet has
hydroxyl radical OH, nitrogen molecule N2, andmetastable helium He*. The argon plasma jet has
OH and metastable argon Ar*. The OH peak in theargon plasma is 7 times higher than that in thehelium plasma.

Flow meterN2ArPlasma jet deviceMass flowcontroller

He*

Ethanol(b) Ar: 2 l/min

Ar*

Intensity [A.U.]

OH(a) He: 2 l/min(CH3CH2OH) [6]. The breakdown voltage for argon
was reduced by adding ethanol due to Penningeffect:Ar* + CH3CH2OH → B1+ + D1 + e,(1)+where B1 and D1 stand for the products of ions andneutrals, respectively, while e represents theelectrons.
We propose an experimental setup for
generation of argon plasma jet with dry cells asshown in Fig. 3. A small amount of the argon wasmixed by ethanol in a flask. In this system, we
experimentally generate argon plasma jet.

200 300 400 500 600 700 800 900
Wave length λ [nm]Fig. 2 Optical emission spectra of plasmas
generated with (a) helium and (b) argon.
In generally, electron energy in the plasma jet is~10 eV, which is comparable with the one ofmetastable argon. Therefore metastable argon
species can be generated by bombardment ofelectron and argon atom. Dissociation energy from
H2O to OH is 5.1 eV. In the argon plasma jet, H2O
molecules can be dissociated to OH bybombardment of H2O and metastable argon.
4. Discussion
A breakdown voltage of argon is much higher
than that of helium although the argon plasma hasmore OH radicals than the helium. The breakdown
voltage must be reduced in order to generate argon
plasma jet by dry cells. Wen-Ting Sum et.al. hasreported on generation of atmospheric pressure
glow plasma with argon added ethanolFig. 3 Scheme of experimental setup for generationof argon plasma jet with Penning ionization.
5. Conclusion
In this paper, comparison of plasma jet generated
with helium and argon. The argon plasma jet has
much more OH radicals than the helium plasma jet.
The breakdown voltage for argon is higher than thatof helium. The voltage can be reduced by mixing ofethanol and argon due to Penning ionization.
Acknowledgement
This study was supported by research grants(R-22107) from Research Foundation for theElectrotechnology of Chubu.
References[1] J.Goree, B.Liu, D.Drake and E.Stoffels: IEEE Trans.
Plasma Sci. 34 (2006) 1317.
[2] S.Ikawa, K.Kitano and S.Hamaguchi: Plasma
Process. Polym. 7 (2010) 33.
[3] H.Jung, B.Gweon, D.B.Kim and W.choe: Plasma
Process. Polym. 8 (2011) 535.
[4] H.Akamatsu and R.Kiriyama: Frontier of Applied
Plasma Technology 2 (2009) 7.
[5] H.Akamatsu, K.Ichikawa, K.Azuma and M.Onoi:
AIP Conference Proceedings 1282 (2010) 92.
[6] W.T.Sun, G.Li, G.P Li, C.Y.Bao, H.B.Wang, S.Zeng,
X.Gao and H.Y.Luo: J. Appl. Phys. 101 (2007)
123302.