Investigations on trapped flux in cryogenic continuous film memory cells

This paper is concerned with measurements on trapped flux in superconducting continuous film memory cells in the stationary case. For investigating the frozen-in magnetic field with the drive currents switched on and off, a superconducting tin film is used as a probe. The memory cell is deposited in the usual way with the sense line consisting of tin. With an adequately chosen sense current, the voltage along the sense line changes depending on the field which penetrates the memory plane. This method allows observation of small or slow flux changes like creation and migration of vortexes. Effects of this kind cause, for instance, flux degradation by half select pulses. The method is further used to investigate the differences in trapped flux when slow and fast rise time pulses are applied.