From Guennadi.Alexeev@cern.ch Mon Dec  8 09:28:41 2003
Date: Sun, 7 Dec 2003 21:39:41 +0100 (CET)
From: Guennadi Alexeev <Guennadi.Alexeev@cern.ch>
To: a.magnon@cern.ch, g.mallot@cern.ch, s.platchkov@cern.ch,
     maggiora@to.infn.it, DANIELE.PANZIERI@UNIPMN.IT, denisov@to.infn.it,
     s.dalla-torre@cern.ch, f.tessarotto@cern.ch, vladimir.polyakov@cern.ch,
     i.savin@cern.ch, v.anosov@cern.ch
Cc: g.alexeev@cern.ch, a.samartsev@cern.ch
Subject: Rich Wall drawings



  Dear Colleagues,

  This is to inform you that after number of multi- and bi-lateral discussions
of Rich Wall structure, dimensions and its optimal position on the beam we 
came to consensus which allows us (Dubna team) starting the production of 
working RW drawings. These drawings will be used for manufacturing of the 
system soon after the final aproval (signature) of Torino-Dubna contract by 
INFN and JINR authorities, hopefully by the end of this year. Let us fix the 
main issues/numbers: 

1. The Rich Wall will serve as RW itself, preshower for ECal 1 and 
   wide-aperture tracker.

2. Its geometrical sizes are (in mm): 5275 x 3915 for outer perimeter,
                                      1185 x  675 for inner beam hole,
                                        about 380 thickness (incl. Pb 
                                                             convertor)         

3. If we let 50 mm fields/gaps along Z-axis on both sides of RW, one to
   RICH structure and another to ECal 1, it leads to about + 90 mm shift
   of ECal 1 from its nominal position. At this point we may serve RW
   electronics on bottom edge of detector (even with rigidity bar of ECal 
   installed).

4. The lead convertor (4 layers, 3Xo total thickness) overlaps in aperture
   with ECal 1 and has the central hole for the beam of 1185mm x 675mm. 
   Each layer is made of few pieces for simple installing on and off.

5. The RW suspension system should provide for centering the detector 
   depending on lead convertor configuration, thus minimizing to zero
   the suspension torque.
  
  Please, have 'a last sight' on attached RW conceptual picktures and let 
me know asap, preferably by the end of COMPASS week, if something is stll
to be changed (slightly though). The absense of remarks we will interprete
as an agreement with present version. 

  Regards,
             Gena
 

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