Radio frequency coaxial feedthrough device

Claim 1

A high voltage radio frequency coaxial feedthrough device for transmitting high voltage radio frequency energy between first and second coaxial transmission lines of different dielectric mediums and pressures, comprising: a tapered inner coaxial conductor including means for electrical connection at an upstream end thereof to an inner coaxial conductor of said first coaxial line and at a downstream end thereof to an inner coaxial conductor of said second coaxial line; a tapered outer coaxial conductor including means for electrical connection at the upstream end thereof to an outer coaxial conductor of said first coaxial line and at the downstream end thereof to an outer coaxial conductor of said second coaxial line; a coaxially disposed cylindrical insulator formed of a rigid, impermeable, electrically insulating material including first and second conductive metal mounting rings sealably brazed to the upstream and downstream ends respectively of said cylindrical insulator, said first ring having an axially extending portion forming a first guard ring which extends axially over a portion of the outer surface of said cylindrical insulator to form a corona shield about the upstream end of said cylindrical insulator, said second ring having an axially extending portion forming a second guard ring which extends over a portion of the inner surface of said cylindrical insulator to form a corona shield about the downstream end of said cylindrical insulator; and means for removably connecting said cylindrical insulator in a leak-tight sealing arrangement between said first mounting ring of said cylindrical insulator and said inner conductor at the upstream end of said cylindrical insulator and said second mounting ring of said cylindrical insulator and said outer conductor at the downstream end of said cylindrical insulator so that a leak-tight seal is provided between the different pressurized dielectric mediums of said first and second coaxial transmission lines, said inner and outer coaxial conductors being spaced apart and separately tapered uniformly along the outer and inner surfaces respectively inwardly from said upstream end of said cylindrical insulator toward the central axis of said coaxial feedthrough device and said inner surface of said upstream end of said outer conductor being formed of an enlarged diameter axial segment axially aligned with said first mounting ring of said cylindrical insulator so that a constant characteristic impedance is provided along the entire length of said feedthrough device while minimizing the insertion-voltage standing wave ratio of said feedthrough device.