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August 29, 2013 FDC meeting


  1. Installation preparations [1]
  2. Engineering [2],[3],[4],[5] (Bill)
  3. Electronics (Chris, Nick)
  4. Tests at EEL126
    • Diffusion measurements [6] (Vlad)
  5. Other


Participants: Bill, Eugene, Chris, Simon, Vlad, and Lubomir.

Installation preparations

- Bill: for the cooling system in the Hall if the hard piping is not ready we can still have a temporary solution using plastic pipes. However, we need chill water supply.

- Expectations are to start the FDC installation sometimes in October. Before that we need to install the skin and do some small fixes on the FDC: fix the HV connectors, replace a couple of pre-amps. Need also to connect the cooling system between the packages.


- Bill showed his new design of the mesh attachment using the main rails (drawings attached). Additional support at the end of the mesh, right between the CDC and FDC is needed; done with a stock T-shape Al profile (1/8"). Similar structure would be needed even with the old design using additional rails for the mesh attachment. The bearing for the mesh is glued to a holder. Same bearing is at the other (upstream) end of the mesh but it is removable. The drawings show also the plate connecting the packages and the grounding cable.

- After testing the FDC with HV we will start working on the skin; the g10 sheets for that have been cut to the right sizes.

Tests at EEL126

- We started applying HV on the FDC package by package; will keep the HV for at least 24 hours on each. For that the flow was increased from 100ccpm total to 200ccpm or 50ccpm per package. Gas mixture is 40/60. All the packages were bubbling already at 25ccpm per package.

- While testing the top two cells of the spare package we had to increase the fADC samples up to 2500 resulting in a huge event size. This was a stress test for CODA: Beni, Elliot and others found a bug in CODA. Vlad is now analyzing the data from these cells at 40/60 Ar/CO2.

- Vlad presented his results of analyzing the data from the top two cells with a scope at Blue Crab (talk attached above). He estimated the diffusion coefficient for 40/60 Ar/CO2 which turned out to be lower than the Garfield prediction at 100-200V/cm electric field. New results will come from the fADC data.