FDC Weekly Meeting
Date: June 22, 2007
Participants: Daniel, Simon, Brian, Kim, Roger, Tim, Chuck
Next Meeting: July 11, 2007
- Brian sent out the Gerber file for our full-scale cathode boards to Optiprint and Sierra in the last week. He heard back from Optiprint that they cannot handle this request. He expects word back from Sierra in the next week. - Our plan is that if Sierra cannot do this work, we will immediately go back to CCT Marketing and pay the $14k for setup charges and have them make the +/-75 deg boards for the small-scale prototype and also nominally plan on using them for the full-scale boards. - We do not presently have a plan to measure the flatness of our non-backed full-scale cathode prototype as the boards need to be measured when they are in a vertical orientation (so that gravity is eliminated). We appear to have more options with the backed boards, which can be measured laying flat. - We discussed the plans for future cathode prototyping: > we will make one more prototype without backing focussing on the issues that arose during the first attempts. We need to come up with plans to handle the alignment and overlap of the multi-piece cathodes and we need to be sure that the air-bubble problem is mitigated. > we will make another prototype with backing, but with a reduce Rohacell thickness. Our nominal thickness is 5-mm, but we believe that we can use less material here. Brian will contact the manufacturer to find out what they can provide. Tim will work on some calculations to compare the 5-mm thicknesses to 2 and 3-mm thicknesses. The plan would be to use the thinner Rohacell plus a filler piece (to give a total thickness of 5-mm) during manufacture. After the cathode is glued in place, the filler material would be removed.
- Brian has completed a full-scale prototype of a composite wire frame. His construction used two 1/32-in skins of G10 and a 5-mm thick Rohacell core. The test appears to be a success and presents us with a viable wire frame that should be able to handle the wire load without significant distortion. Brian will still perform a load test to give us more information (he would like to compare this to results that Tim can provide from calculation). - The weight of the 5-mm thick G10 frame is 7.9lbs and that of the composite is 2.9lbs. This amounts to nearly a factor of 3 reduction in thickness of these boards. Good news. - In the final composite design, the composite frame would be a total of 5-mm thick, and one side of the board would be tiled with the 1/32-in STBs, HVTBs, and filler pieces. (The Rohacell would need to be 3.4 mm thick.)
Magnetic Field Tests
- DSC has taken some pictures of the magnet and surrounding area and will post them in the FDC logbook. - DSC has had discussions with Arne, and it appears that the mini-torus power supply can supply sufficient current to ramp the magnet to full-field regardless of its lead configuration. Stepan plans on mapping field strength vs. current first thing in the shutdown period. - We are still in a bind with finding detectors to define an external track through the FDC prototype. It appears we have talked to all folks at JLab. Brian will talk to folks at SLAC and BNL. Simon will talk to Elke. - Simon and Brian have been talking with Bogdan from Hall A, and he has 3 2-cm diameter silicon detectors. There is a fourth detector, but it is broken. Simon will talk to Bogdan about whether these are single axis detectors. If they are, then having only 3 detectors is insufficient. Also, the small size is a big worry for us. The counting rate will be miniscule.
- Joe was going to provide some numbers on the thicknesses of the original readout cables and the modified (no-shield) version. Simon will follow up with him to get this information.
- The FDC short-term work list has been posted on the FDC web site (see http://www.jlab.org/Hall-D/detector/fdc/). This is continually being updated and DSC welcomes any feedback or comments from the group.
Minutes prepared by Daniel. Send any comments or corrections along.