a—Diagram of doubly connected superconductor (DCS) with a point contact, through which a constant transport current is passed; and —currents in the branches of the superconducting circuit of DCS with inductances and ; —frozen current in the DCS circuit; FB—ferroprobe for measuring the magnetic field of the current of the branch with conductance ; ×—position of the point contact between niobium conductors. b—Current-voltage characteristic of a point contact with an open DCS ring.
Experimental dependence of the current in the branch No. 1 with the FB (branch with inductance ) versus the magnitude of the transport current through the DCS, —some transport current added to such that the section 7–8 of the “plateau” is shifted relative to the axis by , in contrast to similar “plateaus” arising as the current decreases from (lines of several “plateaus” in the regions 1-2-3-0 and 4-5-6-0).
Model dependences of the reduced (with respect to ) values of the currents: total current in the branch No. 1 with the FB , parts of the current in the same branch in the form of a frozen current in the DCS circuit and part of the transport current of this branch , decreasing in connection with a decrease of , versus the magnitude of the reduced transport current . The figures in parentheses indicate the initial and final values of the decreasing transport current . The arrows indicate the directions of change of the currents and with increasing current from zero to four and with it decreasing from , to zero.
a—Diagram of a doubly connected superconductor with transport current fed through a superconducting interferometer with two Josephson contacts (1, 2) with critical currents . b, c, d—Model dependences of the critical current of an interferometer on the relative magnitude of the transport current for : and with alternating values of the transport current from to , respectively. e—Relative current in branch No. 1 with FB versus , constructed on the basis of the dependence shown in Fig. 4d.
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