  The instantaneous luminosity of the Large Hadron Collider at CERN will be
increased up to a factor of five with respect to the present design value by
undergoing an extensive upgrade program over the coming decade. The most
important upgrade project for the ATLAS Muon System is the replacement of the
present first station in the forward regions with the so-called New Small
Wheels (NSWs). The NSWs will be installed during the LHC long shutdown in
2018/19. Small-Strip Thin Gap Chamber (sTGC) detectors are designed to provide
fast trigger and high precision muon tracking under the high luminosity LHC
conditions. To validate the design, a full-size prototype sTGC detector of
approximately 1.2 $\times$ $1.0\, \mathrm{m}^2$ consisting of four gaps has
been constructed. Each gap provides pad, strip and wire readouts. The sTGC
intrinsic spatial resolution has been measured in a $32\, \mathrm{GeV}$ pion
beam test at Fermilab. At perpendicular incidence angle, single gap position
resolutions of about $50\,\mathrm{\mu m}$ have been obtained, uniform along the
sTGC strip and perpendicular wire directions, well within design requirements.
Pad readout measurements have been performed in a $130\, \mathrm{GeV}$ muon
beam test at CERN. The transition region between readout pads has been found to
be $4\,\mathrm{mm}$, and the pads have been found to be fully efficient.
