The WFI survey will take ~25% of the first four years of planned observations, and will be made of a wide (80-90 ks exposures), medium (900-1000 ks) and deep (1.4Ms) tier.
The survey is designed to detect hundreds of z>6 AGN, and in particular at least 10 with 10^43.0 < LX <10^43.5 erg/s at z=6-7, Aim(1), and at least 10 AGN with 10^44.0 < LX <10^44.5 erg/s at z=7-8, Aim(1b). In the figure below the flux-area coverage of the WFI survey is compared with existing surveys and with the forthcoming eROSITA all sky survey.
At OAS we (G. Lanzuisi, A. Comastri, R. Gilli) are developing end-to-end simulations to test the WFI survey performances for different instrumental configurations. To this purpose we use the multi-mission X-ray simulator SIXTE. The input catalogs comprise millions of AGN from the Gilli et al. 2007 population synthesis model, passive galaxies and extended emission.
On the left below is shown a false color X-ray image of a 1Ms pointing with WFI. ~3000 AGN can be detected (a few at z>6) together with more than 1000 galaxies. On the right panel is shown the redshift-luminosity distribution of all the sources detect over 10 fields. Both Aim1 and Aim1b can be achieved with the current configuration.