The Spallation Neutron Source (SNS) facility utilizes a Superconducting linac to provide a 1 GeV Hbeam with an average power of 2 MW. A critical part of the accelerator structure is the superconducting radio frequency (SRF) niobium cavities, which are housed in a titanium liquid helium pressure vessel. These vessels maintain the operating temperature of 2.1 Kelvin while facilitating the mechanical support, tuning and alignment of the SRF cavities. The design, fabrication and operation of the

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... erconducting support structure will be presented with an emphasis on the design criteria as they pertain to the operation of the cavity. These criteria will be discussed with respect to the titanium liquid helium pressure vessels, higher order mode couplers, fundamental power coupler, field probe and tuning requirements.