Comparison of laser induced breakdown spectroscopy and fast ICCD imaging for spatial and time resolved measurements of atmospheric pressure helium plasma jet

Abstract

In this paper we compared the fast Intensified Charge Coupled Device (ICCD) imaging with the newly developed diagnostic method that utilizes laser induced breakdown in plasma jet. Our helium plasma jet was powered by an 80 kHz high-voltage sine wave and propagated into the ambient air. Pulsed laser beam 1064 nm (4 ns pulse duration and 5 Hz repetition rate) was focused with the lens into the plasma jet at energy below breakdown threshold in helium. Laser pulses and the jet powering signal were synchronized. Laser induced plasma is highly dependent on the concentration of seed electrons and other charged particles in the plasma jet channel. We compared the radial profiles of the plasma jet obtained with these two methods. For laser induced breakdown it was ±0.5 mm and for ICCD measurement it was ±1.75 mm, while the ionization wave velocities obtained with these two methods were 15 km s−1 and 20 km s−1 respectively. Electrical characteristics of the plasma jet were also presented and one can see a large hysteresis effect when the applied power to the plasma jet was reducing. We show that the laser induced breakdown spectroscopy can be used as a complementary diagnostics technique with ICCD measurements.