Revision 10 as of 2009-11-10 11:33:08

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To Do List


Resp. Person




Estabilish the GEM segmentation



Estabilishing the contact pattern





Design the GEM




Test the effect of the glue into the GEM holes


Prepare a testing setup for the new GEMs


Prepare a framing setup for the GEMs


Choose the stack setup


Simulate the stack setup



Status Summary

Because we want to build a module with the maximum possible sensitive area we need to use custom GEM which can fit the size allotted in the endplate. The total area of this module is almost 400 cm^2 which means it's almost 4 times the area of the standard CERN GEM. Because of this reason we choose to segment one of the GEM electrodes in 4 parts to limit the total energy stored in each sector thus limit the possibility for damaging discharges on the GEM.

Having decided the number of segmentation we also decided to align the gap between the segments with the ceraming framing to limit the total loss in the sensitive area. Because of this reason the gap will be 1 mm wide, as much as the ceramic frame itself. The gap area will be glued to the framing structure itself to make the structure more rigid. To avoid the glue to go inside the GEM holes we decided to set to 0.5 mm the distance between the kapton gap and the pierced area of the GEM

The other important feature that we needed to estabilish to design the GEM of the module is the power supply scheme for the device. After much consideration we decided to power all the segments of the GEM from the upper side of the module. Because we want to have a module where to install up to 4 GEMs (3 amplification plus an optional fourth gating GEM) and we need 5 power supply contact for each GEM (4 on the segmented side and one on the unsegmented electrode) we need a total of 20 power contacts on the GEM on a total width of the upper side of the GEM of about 23 cm. Morevor this contact need to be far enough from one another to avoid discharges between the power contacts. The pattern of this power contact has been estabilished so that each contact is 4 mm wide and distant from the closest one not less than 5 mm, 11 for the contacts which will be used by the gating GEM where the potential difference will be maximum.