Magnetic field patterns in Josephson junctions

The critical currents of Pb/Ag/Pb Josephson junctions have been measured as a function of magnetic field and temperature in order to study the types of magnetic field distributions that occur in superconductor-normal metal-super-conductor (SNS) junctions. A study is made of the quantum interference regime near the critical temperature where the junction is filled with vortices and the crossover to Meissner-like behavior at low temperature occurs. Special emphasis is placed on the changes in effective area of the junction as the London and Josephson penetration depths change with temperature. A mapping of the crossover regime in the temperature-magnetic field plane is given.