April 5, 2023, FCAL Insert Installation Meeting

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  • Discussion on using thermally conductive rubber at side edges of lead glass blocks and all edges of the crystals to reduce sharp contact points. Generally a good idea and we will look into what is available.
  • We need to make sure when squeezing horizontally that we don not press on the 7mm offeset portion of the glass module.
  • Matt suggested the torque required to compress the rows was much higher than 20 in-lbs. We will need to monitor this as we assemble and come up with the actual values as to what is required.
  • A quick calculation of thermal shrinkage of the aluminum supports over 10C, 2 meters is about 400 microns. Should not significantly change anything. As far as adding spring loading to the beam left side, I do not believe this will be needed to compensate. The conductive rubber should accommodate. We need to pay close attention at the crystal/glass interfaces to ensure we get the proper shimming to get the edges as flat as possible. A conductive rubber sheet can take up small imperfections. The top surface ( or all interface surfaces) may require a thin sheet (200 microns)sheet between to ensure no edge loading.
  • We looked at the side plates compressing 15 rows of glass blocks (same as original FCAL). Sasha is concerned that it is too many at once. A couple of rows would be compressed and released. Sasha is concerned with spring back as seen on the ComCal. How much is this spring back? We are looking at breaking this into 3 sections (5 rows each) to reduce the concern.
  • We will take a close look at the force and spring back of the rows on the existing FCAL as we remove the modules.
  • Sasha presented a concern on the interface of the top crystal layer with the glass layer above. The cg is more towards the downstream end of the crystal. Sasha is concerned that the glass could put a force on the crystal that may be concentrated at the downstream edge. Being that the housings are attached with 50 micron brass straps and of mylar covering, this should not be an issue (I believe the straps are located on the top and bottom surfaces). The iron pmt housing also extends downstream.