  The performance of scintillator counters with embedded wavelength-shifting
fibers has been measured in the Fermilab Meson Test Beam Facility using 120 GeV
protons. The counters were extruded with a titanium dioxide surface coating and
two channels for fibers at the Fermilab NICADD facility. Each fiber end is read
out by a 2*2 mm^2 silicon photomultiplier. The signals were amplified and
digitized by a custom-made front-end electronics board. Combinations of 5*2
cm^2 and 6*2 cm^2 extrusion profiles with 1.4 and 1.8 mm diameter fibers were
tested. The design is intended for the cosmic-ray veto detector for the Mu2e
experiment at Fermilab. The light yield as a function of the transverse and
longitudinal position of the beam will be given.
