FDC Weekly Meeting
Date: June 6 2007
Participants: Daniel, Simon, Brian, Kim, Roger, Fernando, Tim, Chuck, Joe
Next Meeting: Friday, June 22, 2007 @ 1:30 p.m.
New Prototype Cathodes
- Brian has heard from CCT regarding our cathode boards. They believe that they now have a solution to making our boards that involves a two-step etching process. They will require that we pay an additional $14k for setup charges to be able to do what we need. It appears that this is a one time charge that would cover both the boards for the small-scale prototype chamber, as well as the boards for the full-scale prototype. - Brian is also working on contacting other board manufacturers to find out if they can make our boards and also if they can make the boards for our full-scale prototype out of a single piece of materials. More to come. - The time line is getting somewhat tight. We would like to have the boards for the small-scale prototype in our hands so that we can complete the studies with the +/-75 deg cathodes before the magnet tests in July/August. - Fernando has been in touch with the folks at Sierra. They told him that they can produce boards with 1 micron of Cu on 1-mil Kapton. The attraction here is that they would also supply the cathode material, cutting out the middle man. The maximum width boards they can make is 24 in. - Brian will send them a Gerber file of our small-scale and full-scale boards for quotes.
- Kim has been improving the layout of the STB boards based on comments from our last meeting. The main issue was to improve the spacing between the signal traces at HV and the capacitor legs at ground. The spacing in the current layout looks acceptable. - Kim will start roughing out the traces from the resistors to the connectors as a check on real estate. - Fernando showed us a connector and cable that he has selected for making power connections to the STBs for the daughter boards. - We discussed LV bussing options and possibilities. It may be that we want a distribution panel on the downstream face of the last FDC package. - Fernando asked that we provide a Gerber file to Sierra to estimate the costs of an circuit board for the small-scale prototype made from HVPF instead of FR4.
- Brian has been thinking about an alternative design for the wire boards consisting of two 1/32-in thick G10 layers (one of which will be the STB and HVTB) and a Rohacell form core. Tim was not worried about increasing flexing due to the wire load. This design could serve to reduce the overall frame thickness by another factor of two. - Brian will make a full-scale mock-up to test the design. Tim will do some wire-load distortion calculations for this design.
FDC CD-2 Document
- David Lawrence worked to prepare the geometry files for our two design options (with and without cathode backing) based on files that Richard Jones had originally made. David then passed these onto the folks at IU. David has started some studies of momentum resolution We got some preliminary results for photon conversions from Mihajlo at IU. The results were very confusing, and we became convinced that there is a bug somewhere along the way. David and the IU folks are working on figuring things out. - As the Monte Carlo studies will not be completed and checked on the time scale needed for CD-2 documentation, we agreed that we would write up what we have now. Simon and DSC will complete the work on this document before Friday.
Magnetic Field Tests
- Simon will talk to Bogdan in Hall A to get a commitment for their small silicon detectors as a backup plan. Brian will contact BNL and FNAL to see what they may have available. Brian will also talk to Elke to see if she has any suggestions for contacts in Germany. - DSC will talk to Stepan and Doug about how the magnet will be configured. The magnet has been configured so that each of the six coils in each pole are driven in parallel. However, in order to achieve the 1.4T field, the magnet would have to be configured in series. The question then is whether the mini-torus power supply has a high enough current rating.
- Brian talked to Paul Brindza about the use of carbon fiber in our cathode support frames. He stated that this will not be an issue because the orientation of the frames is orthogonal to the field direction. This limits severely the current that can flow in the carbon fiber, and the direction that the current would flow in is resistive in the material.
- Brian reported that he has done some investigations of other foams and talked to Youri. He cannot find any large bubble foam with a density lower than Rohacell. He will continue looking. We can also consider using a backing of Rohacell that is less than 5-mm thick.
- As Joe was at today's meeting, we took the opportunity to talk about the cabling of the FDCs. The current plan is to use the 50-conductor cables for both anodes and cathodes. Note, as the anodes only have 34-pin readout, 16 conductors in the 50-conductor cable will not be used (but they will be configured with 34-pin connectors). This was decided as the nominal choice as the 50-conductor cables actually have less copper in them than the 34-conductor cables. - As the cables will surround the entire detector, Joe will work to produce a drawing showing the cable packing. - Joe will contact the manufacturer about making cables with a thinner outer jacket to reduce material thickness. - As the signal cables can have jackets of any color we choose, Joe suggested we use different color cables for each FDC package to allow for easier identification in the cable trays and electronics. This was viewed as a good idea. - Joe asked that we consider purchasing cables for him to study. The minimum order is $10k.
- We discussed the work needed to be able to readout the small-scale prototype with the ASIC preamps. Fernando will need to complete a daughter board and a jumper to connect to the chamber. Given that we would not be able to get very far in our studies without the FADCs from Gerard, we decided that the daughter boards and connectors for the small-scale prototype would not be needed until after the magnet tests this summer. So, the right time frame is September. - Fernando stated that UPenn will most likely be responsible for testing all preamps and that possible UAlberta might be testing the stuffed daughter boards. More to come.
- 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.