  We studied the central regions of the Galactic Centre to determine if the
CircumNuclear Disk (CND) acts as an absorber or a barrier for the central
X-rays diffuse emission. After reprocessing 4.6Ms of Chandra observations, we
were able to detect, for the first time, a depression in the X-ray luminosity
of the diffuse emission whose size and location correspond to those of the CND.
We extracted the X-ray spectra for various regions inside the CND footprint as
well as for the region where the footprint is observed and for a region located
outside the footprint. We simultaneously fitted these spectra as an optically
thin plasma whose absorption by the interstellar medium and by the local plasma
were fitted independently using the MCMC method. The hydrogen column density of
the ISM is 7.5x10^22 cm^-2. The X-ray diffuse emission inside the CND footprint
is formed by a 2T plasma of 1 and 4keV with slightly super-solar abundances
except for the iron and carbon which are sub-solar. The plasma from the CND, in
turn, is better described by a 1T model with abundances and local hydrogen
column density which are very different to those of the innermost regions. The
large iron abundance in this region confirms that the CND is dominated by the
shock-heated ejecta of the Sgr A East supernova remnant. We deduced that the
CND rather acts as a barrier for the Galactic Centre plasma and that the plasma
located outside the CND may correspond to the collimated outflow possibly
created by Sgr A* or the interaction between the wind of massive stars and the
mini-spiral material.

High Energy Astrophysical Phenomena