PHASE-LOCKING OF STACKED ALL-NIOBIUM JUNCTION ARRAYS TO EXTERNAL RF-IRRADIATION

We have experimentally investigated the range of locking to external r f-bias current for large 3D arrays. Up to 2000 series connected stacks with two junctions ina stack and 84 series connected stacks with four junctions in a stack were incorporated into a microstripline. Our mea surement showed a drastic reduction of the phase locking range with an increasing number of junctions in an individual stack of the array. W e investigated the dependence of the attenuation in the microstripline for different numbers of junctions in a stack In addition, the attenu ation of the rf current in the neighboring junctions in a stack was me asured.