Chang-Seung Ha

Properties of dielectric-barrier-free atmospheric pressure microplasma driven by submicrosecond dc pulse voltage

Atmospheric pressure microplasma driven by dc pulse is developed. This device has a simple structure comprised of a flowing helium (He) feed gas and dielectric-free metal electrodes without an external current limiting resistor. It is shown that a stable glow mode plasma can be sustained without arc runaway by limiting the voltage pulse width to shorter than 300 ns. The properties of the device are reported in terms of discharge current waveforms, rotational temperature of N 2 + , and spatiotemporally resolved optical emission characteristics.

Images of Nanosecond Pulse-Driven Low Temperature Atmospheric Pressure Plasma Using Dielectric-Free Parallel Electrodes

Images of intensified charged coupled device and optical emission spectra are presented for a low temperature atmospheric pressure plasma jet, which is pulse-driven with a duration of 350 ns at a frequency of 40 kHz. He gas is injected with a gas flow rate of 5-30 L/min through two parallel electrodes that are exposed to the air and have a submillimeter gap. Driving voltage ranges from 400 to 600 V. The total power consumption is less than 2 W, and the plasma does not transit to an arc mode because of the short pulse duration.

Surface treatment of glass and poly(dimethylsiloxane) using atmospheric-pressure plasma jet and analysis of discharge characteristics

An atmospheric-pressure plasma jet source based on dielectric barrier discharge (DBD) was prepared for the hydrophilic surface treatment of poly(dimethylsiloxane) (PDMS). Discharge characteristics were investigated from intensified charge coupled device (ICCD) images and by optical emission spectroscopy (OES). Different optical emission profiles were observed in plasmas with argon (Ar) and helium (He) feed gases. For Ar plasma, OH and N2 related emission lines are dominant. On the other hand, relatively strong peaks of N2+ and O excited species were observed in He plasma, suggesting that a metastable He atom plays an important role in the downstream plasma region. Ar plasma was further found to be more effective than He plasma for hydrophilic surface modification. The surface reverted to being hydrophobic about 40 h after plasma irradiation.

A Study on the Dielectric Barrier Discharges Plasmas of Flat Atmospheric Pressure Using an AC Pulse Voltage

Various types of dielectric-barrier-discharge (DBD) devices have been developed for diverse applications for the last decade. In this study, a flat non-thermal DBD micro plasma source under atmospheric pressure has been developed. The flat-panel type plasma is generated by bipolar pulse voltages, and driving gas is air. In this study, the plasma source was investigated with intensified charge coupled device (ICCD) images and Optical Emission Spectroscopy (OES). The micro discharges are generated on the crossed electrodes. For theoretical analysis, 2-dimensional fluid simulation was performed. The plasma source can be driven in air, and thus the operation cost is low and the range of application is wide.

Discharge Images of a Dielectric-Barrier-Free Atmospheric-Pressure Microplasma Controlled by an External Ballast Capacitor

A direct-current pulse-driven dielectric-free atmospheric-pressure microplasma controlled by an external capacitor is developed. Discharge images show that the electrical energy stored in the ballast capacitor controls effectively the discharge energy per pulse in air, He, and Ar gas flows. The effect of the ballast capacitance on the discharge from 22 pF to 10 nF is presented. This configuration provides a wide and stable microplasma operational regime, i.e., from a glow to a near-arc discharge.

Development of an energy controlled DC pulse discharge for atmospheric pressure plasma applications

An atmospheric pressure plasma jet driven by energy controlled DC pulse has been developed. Unlike the most commonly used dielectric barrier atmospheric discharge sources, the proposed device utilize dielectric-free metal electrode with externally controllable ballast capacitor. Discharge energy per pulse can easily and precisely be controlled by voltage and capacitance of ballast capacitor. It is shown that wide range of plasma, from stable glow mode to near arc state, is obtained by varying the injection energy per pulse. The properties of proposed plasma device such as current-voltage waveforms, optical emission spectra and spatio-temporal evolution of discharge were investigated as a function of injection energy, feed gas (Ar or He), and electrode gap distance (200 urn to 1 mm). As well as pulse mode operation, this device can be driven by sinusoidal voltage waveform, the difference between DC pulse mode and AC sinusoidal discharge was also investigated in the voltage range of 500 V ~ 1 kV. The experimental results demonstrate that the proposed plasma device can be used as useful tool for atmospheric plasma applications including bio-medical field.

Development of a Microplasma Source under Atmospheric Pressure using an External Ballast Capacitor

A pulse driven atmospheric plasma jet controlled by external ballast capacitor is developed. Unlike the most commonly use DBD sources, the proposed device utilizes bare metal electrode. The discharge energy per pulse can precisely be determined by changing voltage and capacitance of the ballast capacitor. It is shown that the device can provide wide range of plasma, from stable glow mode to near arc state. Current-voltage waveforms, optical emission spectra and discharge images are investigated as a function of an injection energy. The OES shows that He and oxygen lines are increased as a function of the external ballast capacitor. Ozone and rotational temperature have similar tendency with a power consumption. The feeding gas is He and the applied DC voltage is from 400V to 800V when the gap distance is .

Line-array atmospheric pressure plasma jet device for medical treatment

Currently, several types of atmospheric pressure plasma jet (APPJ) were introduced by many groups and widely used. In this study, we introduce a panel type APPJ which was developed using a plasma display panel (PDP) process. This device consists of facing glasses with barrier rib for feeding gas guide and electrode gap, where He gas flows between two dielectric-free Titanium metal electrodes with a voltage pulse shorter than 500 ns. He gas is injected with a gas flow rate of 0.1~5 liter per minutes through the electrodes that are exposed to the air and have a sub-millimeter gap. Unipolar DC pulse (25~50 kHz and 500~1000 V) or sinusoidal (50 kHz and 1 kVrms) power was applied to the electrode. The discharge characteristics were investigated with an intensified charge coupled device (ICCD) and optical emission spectroscopy measurement. The results for medical treatment with this device are to be discussed.

Development of a pulse driven micro-electrical discharge machining for micro-hole boring

Recently, the needs of integrated system for micro-machining and measurement have been increased with the appearance of micro-factory system. For boring electro-conductive high hardness material such as tungsten carbide (WC), an electrical discharge machining (EDM) is much more practical than conventional machining to bore these materials since hardness is not a dominant parameter in EDM. In this study, a pulse driven micro-EDM device for the treatment of conductive high-hardness material is suggested and the micro-hole machining by arc erosion is presented using the method. The characteristics of the developed EDM were analyzed in terms of the electro-optical observation. The discharge images were captured by ICCD camera. Resistance and capacitance are important parameters for EDM. They determine the time constant (tau=RC), so that they decide discharge frequency. Pulsed power broadens the restriction of RC parameters compare with a RC discharge EDM. The pulse driven EDM can change both the discharge frequency and the capacitance for discharge.