22P036-P
Development of Temperature Controllable Atmospheric Plasma Jet Source
温度可変プラズマジェットの開発	 
Takaya Oshita1, Toshihiro Takamatsu1, Ryota Sasaki1,2, Naoki Nakashima1,2,Hidekazu Miyahara1 and Akitoshi Okino1
大下貴也, 高松利寛，佐々木良太，中島尚紀，宮原秀一，沖野晃俊
1Department of Energy Sciences, Tokyo Institute of Technolog

J2-32, 4259 Nagatsuta, Midori-ku, Yokohama 226-8502, Japan
東京工業大学創造エネルギー専攻	  〒226-8502	  横浜市緑区長津田	  4259-J2-32
2Plasma Factory, Co. Ltd.
YVP W402, 4259-3 Nagatsuta, Midori-ku, Yokohama 226-8510, Japan
プラズマファクトリー株式会社	  〒226-8502	  横浜市緑区長津田	  4259-3	  YVP W402	 
Atmospheric pressure plasma source in which the gas temperature of the plasma can be accurately
controlled from below freezing point up to a high temperature have been developed. In it, the gas that is tobe supplied to the plasma generator is first cooled by using a gas cooler and then heated by a heater. The
temperature of the produced plasma is measured, and feedback is sent to the heater. Thus, plasma at adesired temperature can be generated. Gas temperature control of the plasma over a range from −28°C to+150°C with a standard deviation of ± 0.8°C was realized.

1. Introduction
Atmospheric pressure plasma does not require avacuum chamber; therefore, processes can beperformed continuously, the plasmas can begenerated at higher densities than conventional
low-pressure plasmas, and living bodies and large
objects that cannot be put in a vacuum chamber canbe processed. Consequently, benefits such as higher
speed processing, lower costs, and a wider range ofprocessing subjects are available. In particular,
because the production of atmospheric pressureplasma at low temperatures—from roomtemperature to around 100°C—has been feasible fora number of years, there has been increasing use ofatmospheric plasma in industry. 1 For example, thesurfaces of semiconductors can be cleaned andhydrophilized by oxygen included plasmas; 2 oxidesurfaces on metal can be removed with hydrogenincluded plasmas; 3 and plasmas have been used forsterilization, surface coating, and so on. 4,5	  Processing of materials that are sensitive totemperature, such as living bodies and polymer
materials is difficult. In addition, most kinds ofplasma processing are chemical reactions withradicals or high reactive spices, so that there aresuitable temperatures for each process.
The conventional atmospheric plasma source
shown in Fig. 1 generates plasma by an electricaldischarge through a gas supplied at around room
temperature, so the gas temperature of the generated
plasma is somewhat higher than room temperature.
When there is a need to suppress the temperaturerise, a technique such as limiting the discharge

power or increasing the gas flow rate is used.
However, the energy per unit volume provided tothe plasma is reduced by these techniques, andprocessing effectiveness of the produced plasma
decreases.
In the developed temperature controllable plasma
source, shown in Fig. 2, gas supplied from acylinder is cooled by a gas-cooling device that uses
liquid nitrogen (−196°C), after which the gas isheated to a desired temperature by a heater, andPlasma
sourcePlasmaHeHigher thanRoom temperature room temperature
Gas temperature

Fig. 1. Conventional atmospheric plasma source

Gas-coolingdeviceHe

Liquidnitrogen

Roomtemperature

About-195 ℃

HeaterPlasmasourceInputpower

Feed backControlledby Input power
to heater

Desiredtemperature

Gas temperature

Fig. 2. Temperature controllable atmospheric plasma
sourcethen plasma is generated. Feedback on the gas
temperature of the generated plasma is sent to theheater, and the gas temperature of the plasma can becontrolled to the desired value.
2. Experimental
In testing, helium plasma was generated. The
flow rate of the helium gas was 10 slm, ring-shaped
copper electrodes spaced 10 mm apart wereprovided at the periphery of a glass tube with 3 mm
i.d. and 5 mm o.d., 9 kV electric power at 16 kHz
was applied, and thus a plasma bullet was generated.
Before generating plasma, the gas temperature was22℃. After generating plasma, the gas temperature
raised up to 36℃. From heat capacity of helium andtemperature change, calculated power to heat
plasma was 2.1 W.
3. Result and Discussion
Figure 3 shows the relationship between the input
power to the heater and the gas temperature of thegenerated plasma. The gas temperature wasmeasured with a thermocouple. When the heater
was not used, the plasma gas temperature was−28°C. The gas temperature rose by heat loss
between the gas-cooling device and the plasma
source. When a water droplet was irradiated withthis plasma, it was frozen in 10 seconds. As theinput power of the heater was raised, the plasma gas
temperature rose linearly, rising to 150°C at 84 W.
Thus, with the device we have developed, by
feedback of the temperature to the power applied tothe heater, control of the plasma gas temperature
over a range from −28°C to 150°C with a standard
deviation of ±0.8°C was achieved. Figure 4 shows
the relationship between the plasma gas
temperature and the helium excitation temperature.
The excitation temperatures were measured using
Boltzmann's plot from a spectrum of 402.62 nm,492.19 nm, 501.57 nm and 587.56 nm. The

Fig. 4. Relationship between plasma gas temperatureand helium excitation temperature

excitation temperatures were 3,600°C to 4,900°C
higher than the gas temperatures. Thus, it wasconfirmed that the generated plasma is a kind of
non-equilibrium plasma.
4. Summary	  Atmospheric pressure plasma source in which thegas temperature of the plasma can be accurately
controlled from below freezing point up to a hightemperature have been developed. By it, Gas
temperature control of the plasma over a range from−28°C to +150°C with a standard deviation of ±0.8°C was realized.
With this plasma source, all kind of materials canbe irradiated by the plasma that are weak intemperature rise, and the plasma irradiation can beperformed under the optimum temperature for theprocess requires. As a result, plasma irradiation ofmaterials with low melting points, which aredifficult to treat with conventional devices, ispossible.
Acknowledgments
This study was partly supported by Plasma
Concept Tokyo Inc..
References[1] Akitoshi Okino et al., J. Plasma Fusion Res., 86, 1,40 (2010).
[2] Ryota Sasaki et al., IEEJ Trans. FM, 129, 12, 903(2009).
[3] Moe Shibata et al., The 30th International
Conference on Phenomena in Ionized Gases (ICPIG2011), D13-271 (2011).
[4] Kaoru Tamazawa, Bokin Bobai, 32, 1, 13 (2004).
[5] Barry Twomey et al., Surface & Coatings
Technology 203, 2021 (2009).

Fig. 3. Relationship between power applied to heaterand plasma gas temperature