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We present homogeneous abundances for Fe and some of the elements involved inthe proton-capture reactions (O, Na, Mg, Al, and Si) for 202 red giants in 17Galactic globular clusters (GCs) from the analysis of high resolution UVESspectra obtained with FLAMES@ESO-VLT2. Our programme clusters span almost thewhole range in metallicity of GCs and were selected to sample the widest rangeof global parameters (HB morphology, masses, concentration, etc). Here we focuson the discussion of the Na-O and Mg-Al anticorrelations and related issues.Our study finds clear Na and O star-to-star abundance variations in all GCs.Variations in Al are present in all but a few GCs. Finally, a spread inabundances of Mg and Si are also present in a few clusters. Mg is slightly lessoverabundant and Si slightly more overabundant in the most Al-rich stars. Thecorrelation between Si and Al abundances is a signature of production of 28Sileaking from the Mg-Al cycle in a few clusters. The cross sections required forthe proper reactions to take over in the cycle point to temperatures in excessof about 65 MK for the favoured site of production. We used a dilution model toinfer the total range of Al abundances starting from the Al abundances in theUVES spectra, and the Na abundance distributions found from analysis of themuch larger set of stars for which GIRAFFE spectra were available. We foundthat the maximum amount of additional Al produced by first generation polluterscontributing to the composition of the second generation stars in each clusteris closely correlated with the same combination of metallicity and clusterluminosity that reproduced the minimum O abundances found from GIRAFFE spectra.We then suggest that the high temperatures required for the Mg-Al cycle areonly reached in the most massive and most metal-poor polluters.

Na-O Anticorrelation and HB. VIII. Proton-capture elements and metallicities in 17 globular clusters from UVES spectra