  In a magnetic field, vortices significantly contribute to the dark counts of
single-photon detectors made of superconducting wires, and they are also
limiting the critical current of such devices. To address this issue, we
prepared superconducting microwires with a pinhole grid from WSi thin films and
report on corresponding critical-current and count-rate measurements in an
external magnetic field B. When compared to corresponding devices without
pinholes, the critical current only weakly depends on the magnetic field at B <
16 mT and it is even larger already at B > 10 mT. Moreover, dark counts are not
only suppressed in zero field, but particularly in magnetic fields B < 16 mT,
while photon counts are virtually field insensitive in the same range of the
magnetic field.
