Thermal and flow considerations for the 80 K shield of the SSC magnet cryostats
- Superconducting Super Collider Lab., Dallas, TX (United States)
- Centre for Advanced Technology, Indore (India)
The nominal temperatures in the SSC cryostat range between 4.2 K in the superconducting magnet and 300 K on the cryostat outer wall. To minimize the 4 K heat load, a thermal shield cooled by liquid and vapor nitrogen flows at 84 K and one a 20 K cooled by helium flow are incorporated in the cryostat. Tubes attached to the shields serve as conduits for cryogens. The liquid nitrogen tube in the cryostat is used for cryostat refrigeration and also for liquid distribution around the SSC rings. The second nitrogen line is used to return the vapor to the helium refrigerators for further processing. The nominal GN2 flow from a 4.3-km long cryogenic string (4 sections) to the surface is 64 g/s. The total liquid nitrogen consumption of approximately 5000 g/s will be supplied at one, two or more locations on the surface. The total heat load of the 80 K shield is estimated as 3.2 W/m. About 50% is composed of infrared radiation and remaining 50% by heat conduction through supports, vacuum barriers and other thermal connections between the shield and the 300 K outer wall. The required LN2 flow rate depends on the distribution and circulation schemes. The LN2 temperature will in turn vary depending on the flow rate and on the recooling methods used. For example, with a massflow of 400 g/s of LN2 the temperature rises from 82 K to 86 K between two compact recoolers 1 km apart. This temperature is higher thin desired. The temperature can be reduced by increasing the flow rate of the liquid or by using the continuous recooling. This paper discusses some thermal problems caused by certain mechanical designs of the 80 K shielding the possible improvement by using continuous recooling. In the following, we present results of the 80 K shield temperature distribution analysis, the 20 K shield heat load augmentation resulting from the increased 80 K shield temperatures, the continuous nitrogen recooling scheme and some flow timing related analysis.
- Research Organization:
- Superconducting Super Collider Lab., Dallas, TX (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC35-89ER40486
- OSTI ID:
- 82453
- Report Number(s):
- SSCL-Preprint--212; CONF-930537--118; ON: DE95011193
- Country of Publication:
- United States
- Language:
- English
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