Moderators for the Endcaps
    Updated by Dave Cockerill, 26.5.99

    Based on the ECAL TDR, p349-353
** + new calculations for the cylindrical moderator (march 1999)
     +extra  z allocation, from HE, for electronics (Nov 1998)
     +new backplate position due to HT circuitry now placed inside SC (May 26, 1999)

     Geometry input :
                                        EE front                         at 3170 mm
                                        Back of support plate    at 3650 mm
                                        Back of EE                     at 3988 mm

1)  A 'conical' moderator behind the EE 'plug' region

                        length in z                                 = 33.8 cm     (from back of EE support plate to HE)

                        inner radius, at   z = 3650 mm, = 36.4 cm  (eta=3 )
                        outer radius, at   z = 3650 mm, = 43.4 cm

                        inner radius, at   z = 3988 mm, = 39.8 cm  (eta=3 )
                        outer radius, at   z = 3988 mm, = 46.8 cm

                        This moderator must be 7 cm thick radially at all points along z

2) A vertical moderator mounted behind the endcap support plate

                        thickness       8 cm ,
                        inner radius  43.4 cm (meets the conical moderator)
                        outer radius 100 cm          

          then thinning down to
                        thickness       4 cm
                        inner radius 100 cm
                        outer radius 130 cm

3) A vertical moderator mounted in front of HE

                        thickness           2 cm
                        inner radius  46.8 cm (meets the conical moderator)
                        outer radius   130 cm

4) A vertical scintillator 'moderator' which is part of the HE

                        thickness             0.9 cm
                        inner radius       ~40 cm (eta = 3)
                        outer radius  ~176.6 cm (eta = 1.5)

Notes

1) Moderator of 2 cm in front of HE assumes an existing scintillator on HE of 0.9 cm thickness

2) If the HE scintillator were to be removed this moderator would need to be increased to 2.5 cm
     thickness (because PE is CH2, but scintillator is CH, with only a slightly higher density).

3) Packing moderator in the seating elements, on the support plate, or in parts of the supercrystal
    may enable the vertical moderator thicknesses behind the support plate to be reduced.