Heat transfer through the flat surface of Rutherford superconducting cable samples with novel pattern of electrical insulation immersed in He II

• Published in: Cryogenics (Guildford) 2014-05, Vol.61, p.79-85
• Main Authors: Strychalski, M., Chorowski, M., Polinski, J.
• Format: Article
• Language: English
• Subjects: Cables; Coils; Electric cables; Electrical insulation; Heat transfer; Helium; Magnets; Permeability; Rutherford type cables; Superfluid helium
• ISSN: 0011-2275; 1879-2235
• DOI: 10.1016/j.cryogenics.2014.02.007

•Experimental verification of heat transfer through SC cables characterized by different electrical insulation wrapping schemes.•We measured the heat flux in the direction perpendicular to the side of the SC cable on which a compression force was applied.•These tests were performed in a pressurized superfluid helium environment.•We investigated the effect of pre-stress at room temperature to pressure applied on the samples at low temperature. Future accelerator magnets will be exposed to heat loads that exceed even by an order of magnitude presently observed heat fluxes transferred to superconducting magnet coils. To avoid the resistive transition of the superconducting cables, the efficiency of heat transfer between the magnet structure and the helium must be significantly increased. This can be achieved through the use of novel concepts of the cable’s electrical insulation wrapping, characterized by an enhanced permeability to helium while retaining sufficient electrical resistivity. This paper presents measurement results of the heat transfer through Rutherford NbTi cable samples immersed in a He II bath and subjected to the pressure loads simulating the counteracting of the Lorentz forces observed in powered magnets. The Rutherford cable samples that were tested used different electrical insulation wrapping schemes, including the scheme that is presently used and the proposed scheme for future LHC magnets. A new porous polyimide cable insulation with enhanced helium permeability was proposed in order to improve the evacuation of heat form the NbTi coil to He II bath. These tests were performed in a dedicated Claudet-type cryostat in pressurized He II at 1.9K and 1bar.