Experimental study of gas-cooled current leads for superconducting magnets

• Published in: Cryogenics (Guildford) 1979-01, Vol.19 (10), p.563-566
• Main Author: Warren, R.P.
• Format: Article
• Language: English
• ISSN: 0011-2275; 1879-2235
• DOI: 10.1016/0011-2275(79)90028-6

Design details and experimental test results from several design variations of the gas-cooled, copper current leads used in conjunction with the superconducting dipole magnets for ESCAR (Experimental Superconducting Accelerator Ring) are reported. Thermal acoustic oscillations, which were experienced with an initial design, were eliminated in subsequent designs by a reduction of the hydraulic diameter. The occurrence of these oscillations is in general agreement with the stability analysis of Rott, 1 but the observed gas flow dependence is not in agreement with some other recently reported results for leads operated with supercritical phase coolant. 2 An empirically determined correlation was obtained by plotting lead resistance vs enthalpy gain of the coolant gas. The resulting family of curves can be reduced to a single line on a plot of effective resistivity vs, the product of current and cross-sectional area divided by the product of the square of the mass flow of the coolant and the lead length. This correlation, which should be applicable to other designs of copper current leads in which ideal heat transfer to the coolant gas is approached, predicts that the enthalpy gain of the coolant, and therefore the peak lead temperature, is proprtionalo to the cube of the ratio of current to coolant mass flow. The effective value of the strongly temperature-dependent kinematic viscosity of the coolant gas was found to vary linearly with the effective resistivity of the lead.