Low-temperature sample-rotating cryostat with two degrees of freedom for measuring the anisotropy of the upper critical field of superconductors

An apparatus is described for measuring the anisotropy of the upper critical field, Hc2 . It can rotate a sample through large angles about two orthogonal axes in a magnetic field. Three Hall probes determine the orientation of the sample relative to an applied magnetic field, giving an angular precision of less than 0.1°. This is an order of magnitude improvement in angular precision over previously reported devices. Its performance, operation, and advantages are discussed.