Avoiding quenching in superconducting rings
A procedure for avoiding the quenching associated to a previously reported method for inducing currents in superconducting rings [H. Gonzalez-Jorge et al., Appl. Phys. Lett. 81, 4207 (2002)] is proposed. High persistent currents are induced in two textured YBCO rings (1536 and 2870 A) using a modified version of the original procedure that consist on a straightforward magnetic circuit made up of an iron core and a permanent magnet. The insertion of an iron core into the ring reduces the current to an exent sufficing to avoid quenching as the critical temperature is overcame and preserving thus the structures of the samples. Such a simple operation can be extended to other situations involving quenching (e. g. the use of superconducting coils):