  Auger Muons and Infill for the Ground Array) is an upgrade of the Pierre
Auger Observatory to extend its range of detection and to directly measure the
muon content of the particle showers. It consists of an infill of surface
water-Cherenkov detectors accompanied by buried scintillator detectors used for
muon counting. The main objectives of the AMIGA engineering array, referred to
as the Unitary Cell, are to identify and resolve all engineering issues as well
as to understand the muon-number counting uncertainties related to the design
of the detector. The mechanical design, fabrication and deployment processes of
the muon counters of the Unitary Cell are described in this document. These
muon counters modules comprise sealed PVC casings containing plastic
scintillation bars, wavelength-shifter optical fibers, 64 pixel photomultiplier
tubes, and acquisition electronics. The modules are buried approximately 2.25 m
below ground level in order to minimize contamination from electromagnetic
shower particles. The mechanical setup, which allows access to the electronics
for maintenance, is also described in addition to tests of the modules'
response and integrity. The completed Unitary Cell has measured a number of air
showers of which a first analysis of a sample event is included here.
