Details

Autor(en) / Beteiligte

• Urabe, Keiichiro
• Morita, Tadasuke
• Tachibana, Kunihide
• Ganguly, Biswa N

Titel

Investigation of discharge mechanisms in helium plasma jet at atmospheric pressure by laser spectroscopic measurements

Ist Teil von

• Journal of physics. D, Applied physics, 2010-03, Vol.43 (9), p.095201-095201

Ort / Verlag

IOP Publishing

Erscheinungsjahr

2010

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• We have measured spatiotemporal structures of excited species by laser spectroscopic methods in a plasma jet, which was driven by a bipolar impulse voltage pulse train of the order of kilohertz repetition rate applied across a pair of electrodes wrapped around a glass tube with a helium gas flow. We noticed the differences between the positive and the negative phases of the voltage applied to the front-side electrode placed closer to the tube exit while the back-side electrode was grounded. The experimental results showed that the radial distribution of the excited species had a hollow shape at the centre in the positive voltage phase, while it had a more uniform shape in the negative phase. The peak density of the helium metastable atom in the positive phase was almost constant irrespective of the peak applied voltage. However, it increased with the increase in the peak applied voltage in the negative phase. The mechanism causing these differences was argued from the respects of positive and negative corona discharges. We have also investigated the property of the plasma plume under conditions similar to material processing with a conductive substrate placed in front of the plasma jet. In this case, the plasma production by electron impact ionization became dominant near the substrate as was revealed from the spatiotemporal distributions of helium metastable atom and nitrogen ion densities.