  In this paper I first analytically calculate the magnetic-field and
sheet-current distributions generated in an infinite stack of thin
superconducting strips of thickness d, width 2a >> d, and arbitrary separation
D when adjacent strips carry net current of magnitude I in opposite directions.
Each strip is assumed to have uniform critical current density Jc, critical
sheet-current density Kc = Jc d, and critical current Ic = 2a Kc, and the
distribution of the current density within each strip is assumed to obey
critical-state theory. I then derive expressions for the ac losses due to
magnetic-flux penetration both from the strip edges and from the top and bottom
of each strip, and I express the results in terms of integrals involving the
perpendicular and parallel components of the magnetic field. After numerically
evaluating the ac losses for typical dimensions, I present analytic expressions
from which the losses can be estimated.
