Dynamics of some single flux quantum devices: II. Inhomogeneous flux shuttle

In this report we discuss the properties of a "flux shuttle", similar to that described recently but with its parameters depending periodically on the coordinate along the length of the structure. In the case of a proper choice of the parameters a one-directional shift of vortices (flux quanta) appears to be possible along the structure, induced by ac current flowing directly in the superconducting electrodes. The shift for one structure period takes typically one psec and does not pertrub the relative distance between vortices of any sign (orientation).