  We present the results of a Chandra ACIS-I survey of a high latitude region
at 13h +38 which was earlier observed with ROSAT (McHardy et al. 1998) and
which has recently been observed by XMM-Newton for 200ksec. XMM-Newton will
provide good quality X-ray spectra for over 200 sources with fluxes around the
knee of the logN/logS, which are responsible for the bulk of the X-ray
background (XRB). The main aim of the Chandra observations is to provide
arcsecond, or better, positions, and hence reliable identifications, for the
XMM-Newton sources. The ACIS-I observations were arranged in a mosaic of four
30ksec pointings, covering almost all of the 15' radius XMM-Newton/ROSAT field.
We detect 214 Chandra sources above 5 sigma significance, to a limiting flux of
\~1.3e-15 erg/cm2/s (0.5-7 keV). Optical counterparts are derived from a Subaru
SuprimeCam image reaching to R~27. The very large majority of the Chandra
sources have an optical counterpart, with the distribution peaking at 23<R<24,
although 14 have no counterpart to R=27. The fraction of X-ray sources with no
identification brighter than R=27 is similar to that found in deeper Chandra
surveys. The majority of the identifications are with galaxies. As found in
other Chandra surveys, there is a very wide range of optical magnitude for
given X-ray flux, implying a range of emission mechanisms, and many sources
have high L_X/L_opt ratios, implying absorption at moderate redshift.
Comparison with the earlier ROSAT survey shows that the accuracy of the ROSAT
positions agrees very well with the predictions from simulations in McHardy et
al. (1998) and that the large majority of the identifications were correct
(abridged).
