Achieving Plasma Density Control in a Dielectric Barrier Discharge (DBD) Cell by Using a Laser Engraved Pattern
S. Naovaratpong, I. Boonyaroonate and A. Nathakaranakule
Directly a creating thin dielectric layer on conductive material is a recently new technique for dielectric barrier discharge (DBD) cell. It can be done by plasma spray and micro arc oxidation. These dielectric film layers can generate plasma at lower voltage and provide more plasma uniformity. It has better heat conduction property than using a thick dielectric layer such as borosilicate glass (Pyrex glass) or ceramic tubes, which have been used in ozone generators for more than 30 years. But despite the many advantages of these dielectric film layers, they still have some problems as their previous technology is limited: tt needs a much higher starting voltage than its operating point and cannot design the plasma density pattern.
Applying a modern laser engraving process to DBD cell can make micro spots of high-density discharge pattern by partial removal of the dielectric layer. It is very useful to reduce discharge starting voltage by pre-ionising spots and having a more stable discharge at lower power. This technique explores a designed plasma field distribution, which can increase the performance of many parallel electrode gas discharge processes.
This paper presents DBD cells, which had some dielectric layer removed by laser engraving as compared to normal DBD cells in terms of discharge property. The discharge area of testing cell is 10 × 10 mm2 with a 0.2 mm gap. It was driven by a high voltage-high frequency inverter at 2000 V maximum and 50 kHz in a nitrogen gas environment. The experiment shows that the engraved dielectric layer can reduce 18% of starting voltage and lower minimum operating voltage at 15%. Moreover, it demonstrates a plasma pattern designed property, which has not been studied in conventional DBD cells before.
Keywords: Dielectric barrier discharge (DBD), laser engraving, CO2 laser, ozone generator, plasma