  We present the results of the first observations, taken with FLAMES during
Science Verification, of red giant branch (RGB) stars in the globular cluster
NGC 2808. A total of 137 stars was observed, of which 20 at high resolution
(R=47,000) with UVES and the others at lower resolution (R=19,000-29,000) with
GIRAFFE in MEDUSA mode, monitoring ~ 3 mag down from the RGB tip. Spectra were
taken of the Halpha, Na I D and Ca II H and K lines. This is by far the largest
and most complete collection of such data in globular cluster giants, both for
the number of stars observed within one cluster, and for monitoring all the
most important optical diagnostics of chromospheric activity/mass
motions.Evidence of mass motions in the atmospheres was searched from asymmetry
in the profiles and coreshifts of the Halpha, Na I D and Ca II K lines, as well
as from Halpha emission wings. We have set the detection thresholds for the
onset of Halpha emission, negative Na D_2 coreshifts and negative K_3
coreshifts at log L/Lsun ~ 2.5, 2.9 and 2.8, respectively. These limits are
significantly fainter than the results found by nearly all previous studies.
Also the fraction of stars where these features have been detected has been
increased significantly with respect to the previous studies. Our observations
confirm the widespread presence of chromospheres among globular cluster giants,
as it was found among Population I red giants. Some of the above diagnostics
suggest clearly the presence of outward mass motions in the atmosphere of
several stars.
