Patent ID: 6693253
Filing Date: 2004-02-17
Classification: H05H

Abstract:
An induction plasma torch comprising:a tubular torch body having proximal and distal ends, and including a cylindrical inner surface having a first diameter; a plasma confinement tube (a) made of material having a high thermal conductivity, (b) defining an axial chamber in which high temperature plasma is confined, and (c) including a cylindrical outer surface having a second diameter slightly smaller than the first diameter; the plasma confinement tube being mounted within the tubular torch body, and the cylindrical inner and outer surfaces being coaxial to define between said inner and outer surfaces a thin annular chamber of uniform thickness; a gas distributor head mounted on the proximal end of the torch body for supplying at least one gaseous substance into the axial chamber defined by the plasma confinement tube; a cooling fluid supply connected to the thin annular chamber for establishing a high velocity flow of cooling fluid in said thin annular chamber, the high thermal conductivity of the material forming the confinement tube and the high velocity flow of cooling fluid both contributing in efficiently transferring heat from the plasma confinement tube, heated by the high temperature plasma, into the cooling fluid to thereby efficiently cool the confinement tube; a first power supply having a higher frequency output; a second power supply having a lower frequency output including first and second terminals; a series of induction coils mounted to the tubular torch body generally coaxial with said tubular torch body between the proximal and distal ends of the torch body, the series of induction coils comprising; a first induction coil connected to the higher frequency output of the first power supply to inductively apply energy to the at least one gaseous substance supplied to the axial chamber; and a plurality of second induction coils between the first induction coil and the distal end of the tubular torch body, the second induction coils having respective terminals; and an interconnection circuit interposed between (a) said first and second terminals of the lower frequency output of the second power supply and (b) the terminals of the second induction coils, to connect the second induction coils in a series and/or parallel arrangement between said first and second terminals in order to: substantially match an input impedance of the second induction coils with an output impedance of the second power supply; and inductively apply energy to said at least one gaseous substance supplied to the axial chamber.