Losses in Nb Ti multifilamentary composites subjected to a rotating magnetic induction

The purpose of the present investigation is to study losses in a superconducting multifilamentary composite submitted to a rotating magnetic induction. We have designed an experimental apparatus in which loss measurements are made by measuring the retarding torque undergone by the sample when it rotates in a magnetic induction. This torque is proportional to the losses which take place in the sample. The experimental apparatus essentially consists of a superconducting split coil arrangement in which the sample is rotated through a rotating support fitted out with a strain gauges torque cell. This equipment may be rotated in the 2.5 to 230 r.p.m. range in a magnetic induction up to 6 T, which is equivalent to time dependent magnetic induction up to 145 T/s. Measurements of losses have been made in Nb Ti multifilamentary composites which differ in the nature of the matrix, the twist pitch length, the diameter and the number of filaments. In the low values range of the product of the angular velocity by the magnetic induction, experimental results are analyzed with respect to present loss theories. Calculated values of losses are very close to experimental ones within 15%.