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Office of Science Project Review Cryostat, WBS171

NCSX. Office of Science Project Review Cryostat, WBS171. Fabrication, Operations, and Maintenance Division Engineering Department Princeton Plasma Physics Laboratory. August 15-17, 2007.

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Office of Science Project Review Cryostat, WBS171

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  1. NCSX Office of Science Project Review Cryostat, WBS171 Fabrication, Operations, and Maintenance Division Engineering Department Princeton Plasma Physics Laboratory August 15-17, 2007

  2. The cryostat (WBS 171) is an insulating, semi-hermetic barrier that will allow the surrounding of the stellarator core with a cold, dry nitrogen blanket down to a temperature of 77K. The semi-hermetic nature of the cryostat excludes the components of atmosphere from approaching the stellarator core in the design temperature range (77K to 311K). Introduction: What is the Cryostat?

  3. The cryostat’s many versions have all had the same basic shape: One that be affords access to the port extension flanges.

  4. Must be gas-tight to tolerate slight internal positive pressure Must provide penetrations for vessel extensions, electrical & hydraulic lines, stellarator supports, etc. Shall be of *demountable* design Shall withstand vacuum boundary displacements due to thermal expansion/contraction The cryostat design, including penetrations and joint sealing, shall limit the influx of ambient heat to about 13.9 kW (includes WBS 172, machine base) Cryostat Requirements

  5. Interface Control • The cryostat has interfaces with many systems (buswork, coil cooling, cryostat cooling, diagnostics, etc.) • Notably, Diagnostics will have ever-evolving interfaces

  6. Current Concept • The current cryostat concept has double mechanical strut located at the upper, outer, and lower aspects of each TF coil • Basic shape is described by struts on radial planes

  7. Current Concept • An FRP panel bridges two struts as a substrate • A glued 16 cm pyramid of polyurethane foam is applied to the substrate

  8. Current Concept • Lapped layers of flexible foam laid into the steps of the rigid foam pyramids with clamping/beauty panels finish the assembly

  9. Thermal Characteristics of Materials

  10. The 0.033 W/mK associated with the candidate foams suggest a constant heat load of about 5 kW through the panels only. 5 kW suggests the vaporization of 4900 gallons of LN2 or ¾ trailers per week The GRD requires a maximum non-bakeout parasitic load of 2.12 trailers per week The panels claim 36% of this number Heat Load

  11. Differential Thermal Expansion Differential expansion between the vessel and the penetrations is not trivial at 1 cm & 1.5 cm! The cold innermost seals must tolerate this displacement

  12. Dow Super-Tuff R Closed cell polyisocyanurate foam available for $0.60 per board foot Why closed cell? Avoids condensation of moisture in bulk with consequent increase of k-factor Main Insulation

  13. Main Insulation • Coil Test Facility’s pump skid and coil cryostat used 17 cm of Dow Super Tuff-R • Very successful, no condensation

  14. Inspec’s Solomide polyimide open-cell foam has a k-factor of .040 W/mK and retains its resiliency at 77K. Open cell nature is undesirable Sub-mil Mylar is required between layers $8.50/bd ft Flexible Insulation

  15. Development jobs Edge seal demonstration fixture is required Development

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