  We present the X-ray source detection procedure that we have developed for
the purpose of assembling and characterizing controlled samples of cluster of
galaxies for the XMM Large Scale Structure Survey. We describe how we model the
selection function by means of simulations: this leads us to define source
classes rather than flux limited samples. Focussing on the CFHTLS D1 area, our
compilation suggests a cluster density higher than previously determined from
the deep ROSAT surveys above a flux of 2.10^(-14) erg cm-2 s-1. We also present
the L-T relation for the 9 brightest objects in the area. The slope is in good
agreement with the local correlation. The relation shows luminosity enhancement
for some of the 0.15<z<0.35 objects having 1<T<2 keV, a population that the
XMM-LSS is for the first time systematically unveiling.
