  Investigations of He II Ly-alpha (304 A rest) absorption toward a half-dozen
quasars at z~3-4 have demonstrated the great potential of helium studies of the
IGM, but the current critically small sample size of clean sightlines for the
He II Gunn-Peterson test limits confidence in cosmological inferences, and a
larger sample is required. Although the unobscured quasar sightlines to high
redshift are extremely rare, SDSS DR6 provides thousands of z>2.8 quasars. We
have cross-correlated these SDSS quasars with GALEX GR2/GR3 to establish a
catalog of 200 higher-confidence (~70% secure) cases of quasars at z=2.8-5.1
potentially having surviving far-UV (restframe) flux. We also catalog another
112 likely far-UV-bright quasars from GALEX cross-correlation with other
(non-SDSS) quasar compilations. Reconnaissance UV prism observations with HST
of 24 of our SDSS/GALEX candidates confirm 12 as detected in the far-UV, with
at least 9 having flux extending to very near the He II break; with refinements
our success rate is even higher. Our SDSS/GALEX selection approach is thereby
confirmed to be an order of magnitude more efficient than previous He II quasar
searches, more than doubles the number of spectroscopically confirmed clean
sightlines to high redshift, and provides a resource list of hundreds of
high-confidence sightlines for upcoming He II and other far-UV studies from
HST. Our reconnaissance HST prism spectra suggest some far-UV diversity,
confirming the need to obtain a large sample of independent quasar sightlines
across a broad redshift range to assess such issues as the epoch(s) of helium
reionization, while averaging over individual-object pathology and/or cosmic
variance.
