A plasma generating system comprises a plasma gun including a hollow cylindrical anode member, a hollow cylindrical intermediate member electrically isolated from and juxtaposed coaxially with the anode member to form a plasma-forming gas passage through the intermediate member and the anode member,...http://www.google.com.au/patents/US4780591?utm_source=gb-gplus-sharePatent US4780591 - Plasma gun with adjustable cathode
