22P039-P
Plasma Current and Temperature Measurements ofAtmospheric Pressure Plasma
大気圧非平衡プラズマにおけるプラズマ電流及び温度測定
Kiyoyuki Yambe, Takaki Shinada and Kazuo Ogura
山家清之, 品田隆貴，小椋一夫
Niigata University, 8050, Igarashi 2-Nocho, Nishi-ku Niigata 950-2181, Japan
新潟大学 〒950-2181 新潟市西区五十嵐２の町8050
We have studied atmospheric pressure plasma jets using a quartz tube, helium gas and electrodes byapplying radio frequencies and high voltages. To study the characteristics of the jet, the plasma current wasmeasured using by a current probe. The plasma current was estimated from the displacement current fromcurrent with plasma to current without plasma. The plasma current flowed for about 5 μs and the peakcurrent was about 22 mA at 1 slm of helium gas flow. On the other hand, the net increase temperature withplasma heat was the water temperature difference between with and without plasmas.

1. Introduction
Recently, plasma techniques under atmosphericpressure have been adopted for industrial andbiological applications. Atmospheric pressureplasmas such as plasma jets are typically
produced using an arc discharge, which produces
a high-temperature plasma, whereas dielectricbarrierdischarge(DBD)
producesalow-temperature plasma, which results in lessthermal damage to a material surface [1,2]. As
one of the applications of DBD, atmosphericpressure plasma jet have been demonstrated using
a quartz tube and copper electrodes, to which a
low frequency of kilohertz band and a highvoltage were applied [3,4]. A plasma plume is infact a small bullet-like volume of plasma
traveling at unusually high velocities [5-9]. The
plasma density and temperature have beeninvestigated by some measurements for thepotential to be used as an effective plasma
supplement for various types of discharge system.
The plasma density and temperature are evaluatedfrom the plasma current.
In this study, we present the dependences ofthe plasma current on the helium gas flow.
Moreover, to study the plasma temperature, theplasma heat capacity is measured using by athermometer in the irradiated water.

are made of copper foil with 20 mm x 20 mm and a
thickness of 0.1 mm. The distance between theelectrodes is set at 40 mm. The helium gas flow iscontrolled by a gas flow meter. The power supplysystem (LHV-13A, Logy Electric) has a voltage of+9 kV to -6 kV and a frequency of ~13 kHz. The
applied high voltage and circuit current aremeasured by high voltage probe (P6015A,Tektronix) and current probe (CURRENTMONITOR MODEL 4100, PEARSON). The
plasma jet irradiates to pure water 50 ml. The watertemperature is measured using by thermometer(1521 FLUKE).
3. Experimental Results
The time evolutions of the applied voltage andcircuit currents with and without plasmas are shownin Fig. 2 at 1.0 slm of helium gas flow. The total
circuit current with plasma contains the plasma
current and supply current. The plasma current isestimated as the displacement current on the circuitcurrent. The time evolutions of the displacement
current are shown in Fig. 3. It is found that theplasma current flows for 5 μs and the peak current
is about 22 mA. The rise time of plasma current isabout 0.5 μs and the fall time is 4.0 μs. It isPlasma

Electrodes

Quartz tubeHe gas

2. Experimental SetupFigure 1 shows schematic diagrams of theatmospheric pressure discharge system using a tube
and electrodes, and measurement system. The
dielectric tube is made of quartz, and its inner andouter diameters about φ1.5 mm and φ3.0 mm,
respectively. The powered and grounded electrodes

Currentprobe

High voltage probe

Power supply

Fig. 1. Schematic drawing of atmospheric pressure
discharge and measurement systems

30202810Temperature [oC]

Voltage [kV], Current [mA]

300-10-20-30
Voltagewithout plasma
with plasma-40-50-40-200Time [μs]2040Fig. 2. Time evolutions of applied voltage and circuitcurrents with and without plasmas.
30Current [mA]

250.5 slm
1.0 slm
2.0 slm

20151050-10123Time [μs]45Fig. 3. Time evolutions of displacement currents at
0.5, 1.0 and 2.0 slm.

confirmed that the plasma is generated with rapid
rising voltage phase. The plasma electric energy isestimated as about 0.36 mJ from the applied voltage
and the plasma current. Figure 3 shows that thepeak current increases in proportion to gas flow.
The electric charge increases also with gas flow.
The plasma density and temperature areevaluated from the plasma current. However, theplasma temperature does not depend on thethermal velocity of electron on the atmosphericpressure. In order to investigate the plasma heateffect, the time evolutions of the water temperatureswith and without irradiated are shown in Fig. 4 at
50 ml of pure water and 1.0 slm of helium gas flow.
The water temperature without heating is equal toroom temperature. In the case without plasma, thewater temperature decreases by the influence ofinsulation expansion of helium gas from the gas
cylinder. In the case with plasma, the watertemperature increases by the plasma heat. The netincrease temperature with plasma heat is thetemperature difference between with and without

2624
Water only
without plasma
with plasma

22
2001234Time [min]567Fig. 4. Time evolutions of water temperatures withand without plasmas of pure water 50 ml.

plasmas, and the increase temperature is estimatedas about 0.385 ℃/min. Here, the cycle of plasma
generation is about 13 kHz, the single-plasma
electric energy is estimated as about 0.1 mJ. The
rate of the plasma jet which diffuses to theatmospheric is about 28 %.
4. Summary
We studied the dependence of plasma current on
the helium gas flow and the plasma heating effect.
The plasma current was estimated from thedisplacement current on the circuit current. The
plasma current increased in proportion to gas flow.
The water temperature increased by plasma
irradiated. The plasma electric energy wasestimated from the increase water temperature.
Thus, the plasma temperature will be able toestimate with a drift velocity of electron current bytime of flight method of the plasma bullet.
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