1P-34 PDF
Influences of Ambient Air on Ion Chemistry in Atmospheric Pressure Helium Plasma
Ionic species generated by atmospheric pressure helium plasma were investigated using an atmospheric pressure ionization mass spectrometry (API-MS). The plasma generator used in this experiment was composed of a union-tee, a glass tube and a stainless steel rod. An alternating high voltage of 1.6 kVpp at a frequency of 42 kHz was applied to the rod inside the glass tube relative to the grounded outer electrode (copper tape) to generate the dielectric barrier discharge. The measurements were conducted at different positions between the plasma jet and the ion sampling orifice to see the influences of the ambient air on the ion chemistry in the helium plasma. O+, OH+, H2O+, H3O＋, N2+, and O2＋were detected in the positive ion mass spectra in the plasma jet, while O- dominated in the negative ion spectra. Influences of the constituents of ambient air such as water vapor were observed to increase from the center to the outer region of the plasma jet.