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Investigation of the combined thermal performance of the stacks and vaporcooled leads for the Mirror Fusion Test Facility-"B" (MFTF-B) (Figure 1) demonstrates considerable interdependency. For instance, the heat transfer to the vapor-cooled lead (VCL) from warm bus heaters, environmental enclo sure, and stack is a significant additional heat load to the joule heating in the leads, proportionately higher for the lower current leads that have fewer current-carrying, counter flow coolant copper tubes. Consequently, the specific coolant flow (G/sec-kA-lead pair) increases as the lead current decreases. The definition of this interdependency and the definition of necessary thermal management has required an integrated thermal model for the entire stack/VCL assemblies.Computer simulations based on finite difference thermal analyses computed all the heat interchanges of the six different stack/VCL configurations. These computer simulations verified that the heat load of the stacks benefically alters the lead temperature profile to provide added stability against' thermal runaway. Significant energy is transferred tdrough low density foam filler in the stack from warm ambient sources to the vapor-cooled leads.Stack-contributed heat transfer has such a significant influence on lead performance that grossly erroneous conclusions may evolve if vapor-cooled leads are analyzed independent of their stack assemblies. • amt

Teiis dacimtcnt «*s prepared »s A& atcosni of work sponsored by alt «stn(}' of ihc I'ltired MAGNET COLD MASS HIGH LOAD SUPPORTSIn addition to capabilities of determining thermal response, optimization of thermal performance through adjusting location of the LNo-cooled heat intercepts, Liycooled liners, and radiation shields is also discussed.

Several finite difference, finite element detailed analyses of propagation velocities in up to three dimensions in pool-boiling windings have been con ducted for different electromagnetic and cryogenic environments. Likewise, a few full scale simulated winding and magnet tests have measured propagation velocities. These velocity data have been correlated in terms of winding thermophysical parameters. This analysis expresses longitudinal and trans verse propagation velocities in the form of power function regression equations for a wide variety of windings and electromagnetic and thcrmohydraulic environments. The generalized velocity equations are considered applicable to well-ventilated, monolithic conductor windings. These design equations are used piecewise in a gross finite difference mode as functions of field to predict the rate of normal zone growth during quench conditions. A further check of the validity of these predictions is available through total predicted quench durations correlated with actual quench durations of large magnets.