Division of Environmental Physics -
Students Faculty of Mathematics, Physics and Informatics, Comenius University Bratislava
Adriana NIKLOVÁ alumni student
MSc. study 2006 - 2010
Supervisor: Mário Janda Title:
Abstract: Presented work was focused on electrical and optical diagnostic of relatively new type of streamer-to-spark transition discharge named transient spark (TS). Despite the DC applied voltage, TS has a pulsed character with short (<100 ns) high current (>1 A) pulses, with repetitive frequencies of a few kHz. TS generates non-thermal plasma leading to production of many radicals and excited species. The emission of N2 2nd and 1st positive, N2+ 1st negative, and atomic N and O lines, was detected in time integrated emission spectra. The non-equilibrium character of TS was confirmed by calculated
vibrational (~350 K) and rotational (450-850 K) temperatures.
Temporal profiles of total emission, emission of N2 2nd positive system and
emission of atomic O line a 777 nm were also obtained using PMT measurements.
It was found that emission profiles of TS depend strongly on the average discharge frequency. Below 5 kHz, streamer and spark phases of the discharge can be well distinguished. Despite the small currents, streamer leads to a strong emission peak, mainly due to emission of 2nd positive system of N2. During the spark phase current reaches ~ 5 A, causing secondary peak of emission intenzity. This can be mostly contributed to emission of excited atomic O species.
For higher frequencies, the transition from streamer to spark is almost instantenous and only one emission peak was observed. Emission cause by streamer and spark pulse cannot be separated, but major part of the emission is probably caused by streamer. The majority of the emission is coming from the 2nd positive system of N2.