IMPROVEMENTS IN OR RELATING TO INDUCTION PLASMA GENERATORS

1,223,455. Induction plasma torch. HUMPHREYS CORP. 11 June, 1968, No. 27731/68. Heading H5H. In order that an induction plasma torch may be used for monatomic and diatomic gases, the gas is caused to flow through induction chamber 30 as an annular sheath engaging the chamber wall and means is provided to control independently a tangential swirl stabilization component and a radial component of said gas flow. The gas injector structure 32 is spaced from the wall of chamber 30 to define a cylindrical passage 152 which is supplied with gas through a circular array of radial apertures 118 and through a circular array of tangential swirl stabilizing apertures 120. A circular array of axial apertures 114 is also provided for gas supply. Radial apertures 118 are supplied from conduit 142 via passages 138; tangential apertures 120 are supplied from conduit 150 via a radial passage 148 an annular passage 102, and an axial passage; and axial apertures 114 are supplied from conduit 130 via passages 128, 126. The induction coil 12 is wound on a quartz tube 22 coated internally at 24 with gold to reflect heat. Tube 22 is resiliently supported by O-ring seals 26 at both ends. Coolant flows from coil terminal 62 through channel 64 to an annular groove 100 in injector 32, thence through a channel 66 to a cylindrical channel 68 containing the coil. A parallel flow path exists direct from channel 64 to channel 68. Coolant flows from channel 68 to chamber 70 to cool nozzle 40 and emerges via passage 74 from the other coil terminal 76. A metal probe 42 through which material can be injected into the plasma passes through injector 32 and has a double annular wall supplied with coolant from conduits 48, 50. The nozzle 40 may be provided with copper inserts for different functions. One such nozzle insert has an annular coolant chamber and another may have radial ports for introducing material to be spheroidized. The plasma may be initiated by sparking at conductive lining 24 of quartz tube 22, by a temporary graphite rod, by earthing either nozzle 40 or injector end plate 38, or by an auxiliary D.C. arc. Monatomic e.g. argon is introduced through axial inlet 130, no gas is introduced through radial inlet 142, and argon is introduced through tangential inlet 150. Once a plasma has been established the generator may be switched to diatomic gas e.g. nitrogen or oxygen by supplying the diatomic gas to inlets 142 and 150. Thereupon the argon supplies are cut off and the power supply