[Hbi-svt] [Fwd: SVT to MicroMegas Boundary]

[Marc McMullen]

Hi Jacques,

Recently Amrit was informed by Volker that you were unaware of the work 
being done to mitigate the current interference between the Micromegas 
(MM) and the SVT.  This is to inform you that we are working  on the 
redesign of the SVT layout to accommodate the polarized target. To 
accomplish this we had to increase our region module counts from 8-12-16 
to 10-14-18. The new layout region count was determined by the 
Engineering group to give enough space to accommodate the support 
structure, cooling fixtures  and readout cables. The result of the new 
count is an interference between SVT R3 and the inner most MM region 
(please read the attached email).

We have looked at the MM layout provided in CLAS-NOTE 2010-003 and 
considered the possible option of the reduction of space between MM 
regions to 20mm. This would mitigate the interference.
 Currently we are in the process of evaluating the SVT layout by 
studying various options of the layout so we cannot give concrete 
suggestions at this time.

Please feel free to contact us on this matter or any other issue 
concerning he central tracker at Hallb_svt at jlab.org. If you would like 
we could set up a meeting, in person, phone, or video conference to 
discuss this further.

Attached is a layout diagram of one version of the SVT layout as well as 
the layout used in CLAS-NOTE 2010-003 (this uses the old SVT layout).

Thank You,
Marc McMullen


-------- Original Message --------
Subject: 	[Hbi-svt] SVT to MicroMegas Boundary
Date: 	Fri, 11 Jun 2010 11:07:04 -0400
From: 	Marc McMullen <mcmullen at jlab.org>
To: 	hbi-svt at jlab.org



Hi All,

The current SVT layout consist of a 10-14-18 region configuration.This 
increase from the previous layout of 8-12-16, was done to mitigate 
interference with the target. However, with the increased radius of  SVT 
region 3 there is a new interference with the Micromegas barrel 
detector. Hall B Instrumentation is working with Hall B Engineering to 
resolve boundary issues between the SVT and other central detector 
fixtures.

We have calculated a necessary distance of 30mm from the inside/bottom 
surface of SVT region 3 (120mm radially from target center). This 
clearance will provide enough space for the module cooling fixtures, 
flex cable passage ways, and the carbon fiber exterior shell of the SVT. 
This clearance distance would create an outer boundary line at 150mm 
from target center for the SVT.

Amrit has reviewed the information provided in CLAS-NOTE 2010-003 (this 
document uses the previous SVT layout, 8-12-16) and has determined that 
the MM encroachment of the needed SVT boundary can be mitigated via a 
reduction in the spaces between the MM regions. These spaces ( 40mm 
between the inner set of MM barrel detectors and the middle set, and 
35mm between the middle set and the outer set) could be reduced to 20mm 
each by moving the MM inner and middle barrel sets 20mm and 15mm , 
respectively, away from target center.

This change in MM barrel detector spacing will allow enough clearance 
for the SVT without encroaching on the Central Detector Time of Flight.

Thanks
Marc McMullen


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