| This thesis presents the design and characterization of a novel pulsed miniature capacitively-coupled Atmospheric Pressure Glow Discharge Torch (APGD- t) aimed at localized biomedical applications. Amplitude modulation of the 13.56 MHz carrier signal allows to continuously vary the power level applied to the APGD-t. Typically, the APGD-t produces a plasma jet with a 150-500 mum diameter and ≈2.5 mm length. Helium (He) is the plasma-forming gas with a flow rate ranging from 0.5 to 1.5 slm. The use of a small capillary electrode enhances the electric field, lowering the breakdown voltage (typically 220 Vpk-to-0) and allows the injection of small amounts (0-50 sccm) of a source of reactive species (O2) downstream of the plasma-forming region, in the plasma afterglow. The O2 is electronically dissociated in the plasma afterglow to create atomic oxygen (O) with no effect on the electrical properties. A ratio of 0.3% v/v, O2/He generates a maximum in O production.; Careful electrical probe measurements and circuit analyses reveal the strong effect of commercial passive voltage probes on the total load impedance of the APGD-t circuit. The larger the probe capacitance and cable length, the larger the component of the phase angle between the load voltage and circuit current signals induced by the probe. The calibration of the phase angles induced by the voltage probes allows to estimate that a resistive power of ∼0.24-1 W is dissipated in the APGD- t under nominal operating conditions.; The gas kinetic and atomic He excitation temperatures, and the electron density near the APGD-t nozzle exit are estimated at ≈323 K, ≈1914 K and ≈1011 cm-3, respectively. This confirms that the APGD-t plasma jet near the nozzle exit is in a non-thermal equilibrium state. The emission spectroscopy study reveals the entrainment of air molecules (N2, O2 and H2O) in the plasma jet, and that their excitation by the plasma creates new reactive species (O and OH). A preliminary survey of the chemical reactions taking place in the plasma afterglow reveals that metastable He as well as OH, O, O2(a1Deltag), O2(b 1sumg+), N2, N2+ and O3 are plasma species that can reach and react with organic or biological surfaces located a few mm downstream of the APGD-t nozzle exit. This thesis demonstrates that the APGD-t is a promising tool for localized biomedical applications. |
