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[lcdds 270] Re: CMS-like assembly

Subject:   [lcdds 270] Re: CMS-like assembly
From:   "Seryi, Andrei" <seryi@xxxxxxxxxxxxxxxxx>
Date:   Wed, 13 Sep 2006 09:57:44 -0700

 Dear Sugimoto san and all, 

1) Is it a correct conclusion, from your message, 
that if GLD is built with pure CMS assembly, 
it has to have gaps between barrel rings and
thus it cannot be self-shielded, in radiation sense? 

If so, this is very important point and 
need to be studied very carefully. 


2) In the detector model, when you calculate the leaking 
field, one would need to include an antisolenoid. 
It could change (reduce?) the leaking field. 
Could you please include it? 

Could you please think about other questions
that were raised in lcdds-266? 

 Best regards
  Andrei


-----Original Message-----
From: Yasuhiro Sugimoto [mailto:yasuhiro.sugimoto@xxxxxx] 
Sent: Wednesday, September 13, 2006 12:29 AM
To: lcdds@xxxxxxxxxxxxxx
Subject: [lcdds 268] CMS-like assembly

Dear Andrei, and all,

   Thank you very much for forwarding  Jean-Luc's
comments on CMS-like assembly.
   I would like to point out several disadvantages
of pure CMS-like assembly which Jean-Luc did not
mentioned.

    If we adopt pure CMS-like assembly, we need small
gaps between barrel rings in order to extract cables,
pipes, etc.  As a result,  the leakage field is stronger
than the case without gaps.  I  calculated the leakage
field assuming 5 rings with 5cm gaps between them,
and 2 endcap segments with a 5cm gap. The leakage field
at Z=10m is 220G, while it is 70G if we don't put these
additional gaps.
    I think the top of the detector can be used as a space
for electronics hut. But if there are gaps between rings,
the leakage field around the detector  becomes strong,
and  we might need a large distance between the detector
and the electronics hut. That could increase the size (height)
of the experimental hall.
    The increase of gaps  would increase the leakage of neutron
background. Then, we need more radiation shield and more cost.

     I think pure CMS-like assembly takes more time to
construct  the iron yoke. The barrel part of CMS  consists of
180 (=12 sectors x 3 layers x 5 rings ) iron slabs. In case of GLD,
we need 540 (= 12 sectors x 9 layers x 5 rings ) iron slabs
if we adopt the pure CMS assembly method.  If the number
of cranes  in the surface assembly hall is same, it will take
quite a long time to assemble  the iron yoke rings.
The number of muon detector modules   will be also
5/2 times  more, and fabrication of the modules  will take longer.


Yasuhiro Sugimoto
KEK