We have studied the flux dynamics in superconducting strips patterned from
both Nb and weak-pinning amorphous MoGe films using a Scanning SQUID Micros
cope (SSM). The unparalleled flux sensitivity of the SSM allows us to image
the vortices in the strip under a variety of field and cooling conditions
with single vortex resolution for low flux density. We are able to apply tr
ansport currents while imaging the strip and observe the shift of the vorte
x distributions due to the Lorentz force. Surface steps etched into the str
ips significantly alter the flux patterns and introduce asymmetry in the vo
rtex motion under applied transport currents. Both the change in vortex lin
e energy across the step and the screening currents which flow along the st
ep influence the vortex distributions and flux dynamics. We are studying th
e relationship between the vortex distributions from the SSM images and the
transport characteristics of the strips.