July 22, 2009 CDC Meeting

Meeting Time and Place

Friday July 22, 2009 at 3:00pm At Jefferson Lab, the meeting will be held in room ARC 428

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Agenda

• CDC

Action Items/Decisions from Previous Meeting

• Discussed high prices for tight tolerance components
  • Prices for plastic parts come down by 66% if tolerances opened to .003 in.(from .0005) Curtis to determine in the next day or 2 if these are acceptable.
• Checked IDEAL tool and manufacturing in Chicago. No listing
• Tim to discuss with vendor repair of end plates if hole messed up
• Carnegie Mellon to use GARFIELD to check electric field around crimp pin insert
• CMU to look over to see if piece tolerances can be loosened to ± .001 in
  • These are ok for hole position. We had tightened them for gluing purposes.
• OK if we open end plate to .005 tolerance on hole positions, need to reduce straw diameter to prevent interferences
• Conductive rubber tubes cover 30% of gas holes - ok
• Add holes for 1/4 inch survey balls in top downstream plete to match upstream (2 at 90°)
• CMU to send list of glues
  • Silver Epoxy: Tra-Con TRA-DUCT 2929
  • Scotchweld 190 & 270
• JLAB to specify glue for rohacel to mylar joint
  • Hysol RE2039 & HD 3561 (3:1)

Comments on Inner Shell

In going over the latest drawings, We have a number of small concerns about how the inner shell is attached.

• 1 First, by gluing the shell to the inside of the downstream endplate, we automatically introduce any errors in radial matching of the shell with the endplates. We need to rotate the two plates relative to each other to align them, and by introducing an uncertainty at the place where we hold the plates, we make this job much more difficult.
• 2 The area with which we have to glue the plates to the shells seems minimal. We are worried about not being able to get the solid glue joint we need for the shell to become a rigid part of the chamber construction.
• 3 Gary is very concerned about holding the chamber (particularly on the Carbon Fiber end), He would feel a lot more comfortable if we were holding it directly by the endplates.

Our very minor modification would be to machine a groove in each endplate into which we can glue a thin ring about ~1" long. This ring would then slide into the inner shell and provide a large surface area for glue. We note that because of the 12 bolts on the upstream end, a continuous groove is probably not possible, but a the part between the bolts could be machined (an intermittent groove). We feel that this small change would solve the above three issues with very little impact on the design.

• 4 We also note that while it may not be possible, we had hoped to have a 1/4" radially of free space on the endplates after the plenums were installed. This would allow us to hold the chamber with our fixture even after the gas plenums were put on. While there may really be no such space availabe, it did appear that it was present on the downstream ends of the rohocell piece was not so thick radially. Because of the bolted on hub on the upstream end, this does not appear possible, so we assume that we will use the gas plenum to hold the chamber if we need to.