Patent ID: 7861557

Claim:
A plasma torch for making synthetic silica comprising: an outer quartz glass tube having a first length and a first cross-section diameter and a first end connected to a base and a second end oriented towards a substrate, said outer quartz glass tube encircled by an induction coil; an inner quartz glass tube having a second length and a second cross-section diameter and a first end connected to said base and a second end oriented towards said substrate, said second cross-section diameter being smaller than said first cross-section diameter such that said inner quartz glass tube is located substantially parallel to and inside of said outer quartz glass tube; a middle quartz glass tube having a third length and a third cross-section diameter and a first end connected to said base and a second end oriented towards said substrate, said third cross-section diameter being less than said first cross-section diameter and greater than said second cross-section diameter such that said middle quartz glass tube is located substantially parallel to and between said outer quartz glass tube and said inner quartz glass tube for providing a pathway between said middle quartz glass tube and said outer quartz glass tube for a screen gas, and for providing a pathway between said inner quartz glass tube and said middle quartz glass tube for a plasma gas to produce a plasma flame when said induction coil is energized; a first quartz glass ring disk concentrically connected to said second end of said outer quartz glass tube; a second quartz glass ring disk concentrically connected to said second end of said middle quartz glass tube, wherein the flow pattern of said screen gas is determined by said first quartz glass ring disk and said second quartz glass ring disk; and at least one chemical injection nozzle located between said first quartz glass ring disk and said second quartz glass ring disk for injecting a chemical source gas into said plasma flame.