April 20, 2023, FCAL Insert Installation Meeting

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Meeting Time and Place

Wednesday April 20, 2023 9am At Jefferson Lab, Hall D Counting House and on Zoom https://jlab-org.zoomgov.com/j/1619449114?pwd=UFlVQ1dWTGZ0ZkVYSEx5QzE4YUI3dz09&from=addon meeting ID: 161 944 9114 Passcode: 562689



  • Went over minutes of last meeting
  • We discussed unstacking the first (top) row and how to do it. Malte and Tim will look at it tomorrow morning
  • Discussed adding plastic sheet around shelves to keep out dust
  • We will blow off modules with N2 gas before restacking
  • Malte looked at shelving and we have enough for 2400 modules (400 will not be used) if we use the top wall mounted shelf. Scot has bought (2) 2' high platforms to enable easy access.
  • It was pointed out that the modules should not be rotated when unstacked to keep the bases all pointing in the proper position
  • We discussed the interface between the crystals
    • the consensus is that the 1.6mm thick thermacool silicone rubber sheet will be adequate on both sides as long as the edge of the glass blocks are as flat as possible
    • the top and bottom crystal row interface will have a 160 micron thick stainless steel sheet separating from the glass to ensure no high stress points
    • The glass blocks will be compressed beam right before installing crystals. This can be done one or more rows at a time
  • We will use some "bad" glass modules to develop the horizontal compression requirement on the bottom row before installation. The total dimension should equal the existing FCAL dimension
  • It seems like a good idea to put 800 micron thermacool between the cooling blocks and the outer glass modules to soften and act as a spring
  • Malte pointed out that on the existing LMS the LED boards did not all stay adhered to the acrylic. We should screw them in place for the FCAL2
  • It was discussed that the sanding spec for the acrylic should be verified
  • No final decision on crystal LMS as far as the fibers being glued to the crystals. The remaining designs for the tungsten, rohacel and outer acrylic support depend on this decision

Action Items

  • Tim to get samples of the thermocool sheets with and without adhesive (160 and 80 micron)
  • Scot to procure clear plastic sheets to put around shelving
  • Tim to update procedure to include items discussed
  • Malte/Tim to setup torque testing for horizontal compression
  • Malte/Scot to make acrylic sanding sample
  • Sasha to decide on crystal LMS configuration