APPARATUS FOR PRODUCING A VITREOUS INNER LAYER ON A FUSED SILICA BODY, AND METHOD OF OPERATING SAME

An apparatus for producing a layer of vitreous silica adjacent at least a portion of an inner surface of a fused silica body is described, comprising a heat source disposed to apply sufficient heat to at least a portion of the inner surface to cause a layer of said at least a portion of the inner surface to vitrify. In certain embodiments the heat source is configured to heat at one time a relatively small area of the inner surface, and the apparatus comprises a positioning mechanism for moving the heat source with respect to the inner surface. In certain embodiments the heat source is a hydrogen-oxygen surface-mix fueled torch that is moved helically with respect to the inner surface of the body under the control of a programmed CNC motion control system.