  Future measurements of the flavor-separated spin structure of the proton via
parity-violating W boson production at RHIC require an upgrade of the forward
tracking system of the STAR detector. This upgrade will allow the
reconstruction of the charge sign of electrons and positrons produced from
decaying W bosons. A design based on six large area triple GEM disks using GEM
foils produced by Tech-Etch Inc. has emerged as a cost-effective solution to
provide the necessary tracking precision. We report first results from a beam
test of three test detectors using Tech-Etch produced GEM foils and a laser
etched two dimensional strip readout. The detectors show good operational
stability, high efficiency and a spacial resolution of around 70 um or better,
exceeding the requirements for the forward tracking upgrade. The influence of
the angle of incidence of the particles on the spatial resolution of the
detectors has also been studied in detail.
