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 \times 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 .