Volume 107, Number 6, September 2014
|Number of page(s)||6|
|Section||Physics of Gases, Plasmas and Electric Discharges|
|Published online||23 September 2014|
Temporal evolution of atmosphere pressure plasma jets driven by microsecond pulses with positive and negative polarities
1 Institute of Electrical Engineering, Chinese Academy of Sciences - Beijing 100190, China
2 Key Laboratory of Power Electronics and Electric Drive, Chinese Academy of Sciences - Beijing 100190, China
3 School of Automation and Electrical Engineering, Nanjing University of Technology - Nanjing 210009, China
4 Department of Electrical & Computer Engineering, University of New Mexico - Albuquerque, NM 87131, USA
Received: 18 June 2014
Accepted: 1 September 2014
Current-voltage characteristics, discharge images, and optical spectra of atmospheric pressure plasma jets (APPJs) are studied using a microsecond pulse length generator producing repetitive output pulses with different polarities. The experimental results show that the APPJs excited by the pulses with positive polarity have longer plume, faster propagation speed, higher power, and more excited species, such as , O, He, , than that with the negatively excited APPJs. The images taken using an intensified charge-coupled device show that the APPJs excited by pulses with positive polarity are characterized by a bullet-like structure, while the APPJs excited by pulses with negative polarity are continuous. The propagation speed of the APPJs driven by a microsecond pulse length generator is about tens of km/s, which is similar to the APPJs driven by a kHz frequency sinusoidal voltage source. The analysis shows that the space charge accumulation effect plays an important role during the discharge. The transient enhanced electric field induced by the accumulated ions between the needle-like electrode and the nozzle in the APPJs excited by pulses with negative polarity enhances electron field emission from the cathode, which is illustrated by the bright line on the time-integrated images. This makes the shape of the APPJ excited using pulses with negative polarity different from the bullet-like shape of the APPJs excited by pulses with positive polarity.
PACS: 51.50.+v – Electrical properties (ionization, breakdown, electron and ion mobility, etc.)
© EPLA, 2014
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