Characterisation of Sub-Millimetre Plasmas

High pressure molecular gas hollow cathode (HC) plasmas have potential biomedical applications[1,2]. Issues however remain with geometries presented by realistic applications. Here we investigate the electrical {\&} optical characteristics of such a geometry, a 2~mm diameter HC with a variable precisely positioned anode cathode gap. We present HC electrical measurements including static IV, Paschen curves {\&} other derived scaling characteristics eg j/p$^{2}$[3] for various gases (inert and molecular), pressures ($>$100mTorr) {\&} gaps ($<$1 mm). Analysis of these discharge characteristics sheds light on the HC effect in our sub-mm geometries, including instabilities, oscillations {\&} self-pulsing. Investigations of electron distribution {\&} gas temperature via optical emission spectroscopy are under way; plasma density may also be attainable. Other studies include molecular gas dissociation and detection of NxOy {\&} other molecular gases via FTIR spectroscopy using optics developed for point source plasma measurement.\\[4pt] [1] McLaughlin et al 2008 \textit{Diamond {\&} Related Mat} \textbf{17} 873\\[0pt] [2] Mariotti et al 2004 \textit{PSST} \textbf{13} 207\\[0pt] [3] Petrovic et al 2008 \textit{J Phys D }\textbf{41} 194002