TESLA vertical test dewar cryogenic and mechanical design

Collaborators on the design of a Tevatron Superconducting Linear Accelerator (TESLA) are working toward construction of a test cell consisting of four full length cryostats, 12 meters long, each containing eight, 9-cell superconducting RF cavities. In order to ensure that each cavity meets its performance requirements, 'as received' structures will be tested in a vertical dewar prior to installation in the cryostat vessels. In addition, the dewar system will accommodate cavities installed in their helium containment vessels far testing if performance problems occur during later stages of fabrication. The vertical dewar system permits testing of the RF performance and high power processing of the cavity structures at their operating temperature of 1.8 K. The design of the cryogenic system, vacuum system, RF input, test instrumentation, and tuning system are be described in detail. >