[Hbi-svt] SVT to MicroMegas Boundary

[Marc McMullen]

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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