Construction of Superconducting Solenoid Generating Homogeneous Field along Axial Distance

Abstract

The design and construction of a superconducting solenoid to be used for gas laser spectroscopy is described. The solenoid was qualified to produce a field up to 60 kOe along the axial distance of about 30cm with the highest possible homogeneity. A computational recepie to determine the coil cross section which meets above requirement is given in §1. Here the least-square method was applied to determining the coil geometry, and was treated by the local linearization as to the given set of dimensional parameters. Following the dictates of digital computation we wound the Nb-Ti wire of 0.375mm diameter, 22km in one length with great care to uniformity of winding. The number of turns were 74x103, and the coil inductance was about 78H. The cryostat in which our solenoid was mounted yielded the room temperature space of 40mm clear bore along the horizontal solenoid axis. The details of wire winding process and the design of cryostat are described in §2 and 3, respectively. The performance test is described in §4. The relative inhomogeneity as measured by the proton NMR was less than 10-4 along the axial distance of 28cm. The crytical current was 32A. at which the field strength of 72 kOe was achieved.