The radiation length map in units of $X/X_{0}$ ina zoomed-in part of the active detector area as a function of the pseudorapidityand the azimuthal angle, calculated from the geometry inAliRoot (the colour scale has a suppressed zero). The positions of the MCMs and the cooling pipes are visible as hot spots. The radiation length was calculated for particles originating from the collision vertex. Therefore the cooling pipes of the six layers overlap for small, but not large $\eta$