Design and Fabrication of a Large Cryostat for Testing SMES Apparatus

Abstract

The design and fabrication of a large liquid helium cryostat for testing of SMES components is described. The cryostat was built in 1996 and 1997 by Meyer Tool & Mfg., Inc. for the Westinghouse Science and Technology Center and the US Navy, for installation at the National High Magnetic Field Laboratory in Tallahassee, FL. The cryostat is a system of stainless steel pressure/vacuum vessels designed for containment of liquid helium at atmospheric pressure and 4.2 K. The outer containment is an eleven-foot (3.35 m) diameter vacuum vessel with a dished bottom head and a full-body flange at the top. The other components are supported from the flat annular top head of the vacuum vessel. These include an annular background magnet case, a seventy-nine inch (2.0 m) diameter test vessel, and a thirty-six inch (9.14m) diameter lead vessel. The overall height of the system is about twelve feet (3.66 m). Large lateral magnetic interaction loads are transferred within the cryostat by three 1.75-inch (44.45 mm) diameter Nitronic 50 rods and a system of brackets and gussets on the vessel heads. Heat leaks are controlled by multilayer vacuum insulation and a system of nitrogen-cooled aluminum shields. Design details will be described, as will the rationale behind various design decisions.