
 --- DETECTOR : Add, at the end of the current detector,
     another absorber layer and then another active layer,
     with the following specifics:

       * extra absorber layer: 

            - a cone of Lead
                 Z = 82
                 a = 207.19 g/mole
                 density = 11.35 g/cm3;

            - of internal radius = 0, 
                 initial (left) external radius of 25 cm, 
                 full length along the x-axis of 30 cm, 
                 final (right) external radius of 50 cm.
  
       * There is a gap of 1 cm between the end of the
         previous active layer and this extra absorber layer.

       * extra active layer: 

            - a tube (cylinder) of Silicon
                 Z = 14
                 a = 28.09 g/mole
                 density = 2.33 g/cm3;

            - internal radius = 0, 
              radius of 50 cm, 
              and full length along the x-axis of 300 microns.


     NB) Be careful that the solids usually are defined
         with z-axis as symmetry axis, whereas in our
         case we want them with x-axis (beam direction).
         Therefore a rotation is necessary when the
         logical volume is placed...
 

