PEFORMANCE TEST AND THERMAL ANALYSIS OF CONDUCTION-COOLED OPTIMIZED CURRENT LEADS AT NON-OPTIMUM OPERATION

摘要

Current leads are the key components which make an electrical connection between room temperature power supply and superconducting magnets at 4.2 K. In any cryogen-free magnet system, major heat input comes from the copper current leads of the magnet. The dimensional optimization of the copper part of the hybrid current leads is done for a particular operating current between room temperature to the operating temperature of the 1st stage of cryocooler (CCR). The conduction-cooled magnet may not necessarily be operated at the optimized current all the time. Hence for non-optimum current, the heat input per unit current will be increased both at under-current and over-current operation. The stabilized temperature, of the 1st stage of CCR corresponding to each operating current, would mainly be governed by the dynamic heat input by the current lead. A pair of copper current leads working between the temperatures 300 K to 33 K has been optimized for 85 A optimum current. A simple analytical technique has been used for estimation of dynamic heat load at non-optimum operation. This paper describes the optimization procedure, estimation of dynamic heat input, measurement and detailed thermal analysis of conduction-cooled current leads at non-optimum operation.