FDC Weekly Meeting
Date: November 19, 2009
Participants: Daniel, Roger, Mark S., Beni, Bill, Casey, Simon, Mark I., Eugene, Glenn, Brian
Next Meeting: November 26, 2009 @ 1:30 a.m.
General Construction Updates
- We are still battling with leak isses associated with the gas spacers. We have two different versions. One uses a harder o-ring (50 durometer) and the other a softer o-ring (8 durometer) built up with an 8-mil tape shim down in the o-ring trough. On frame P1, which is installed in the single-layer prototype, it also has a few gas leaks up through the vias on one protion of the STB. Casey has attempt to seal these up. Given also that the spacer ring must pass across signal traces that stick up by 3 to 4 mils (!), it may be that we will just have to do the best we can and make do. But there has got to be a better design solution so that we are not forced to battle a leaky chamber until the end of time. - Fernando has completed his test plan on the single layer prototype using a single anode preamp board and a single cathode preamp board, both stuffed with the new GAS-II preamps. He is preparing a write-up of his results that will be distributed soon. Fernando did not encounter any surprises and all seemed to follow expectations (chamber and preamp boards). As a quick summary, the signal-to-noise levels on the cathode strip signals were about 20 to 1. This is likely due to the jury-rigged readout connection and use of an oscilloscope that was known to generate significant EMF. Firmer numbers will be extracted at a later time. It looked like the performance of the long wires and the short wires was very similar. Same for the long cathode strips and the short cathode strips. - A comparison of the single-layer FDC prototype in a horizontal vs. a vertical configuration revealed no obvious differences in performance. This is good news as a sizeable portion of our test plan calls for using cosmic rays with the chamber in a horizontal orientation. - The issue with the voltage differences between the full-scale prototype and the small-scale prototype has been fully resolved. We took a sense wire sample from a small-scale prototype wire plane and measured its diameter to be 25 um. We have 20 um diameter wire in the full-scale prototype. This size difference explains the different plateau voltages. DSC verified this with GARFIELD calculations of the chamber gain. - It turns out that only a portion of the production wire order for the FDC and CDC has arrived. 4 spools of 20 um W wire and 4 spools of 80 um Cu-Be wire. Each spool holds 1000 m. DSC and Bill met with the SEM folks for an information exchange meeting. We prepared a set of testing instructions and circulated it to Curtis and Eugene. It has been turned over to the SEM folks who are working on a quote. - The plan for the next several days is to add the second layer to the prototype. The system will be leak checked and HV checks will be performed. We will spot check some of the wire and cathode signals to be sure that there are no gross differences with what we have already seen. We expect to be ready to add the third layer after that. - The parts n' pieces for the third full-scale prototype layer will not be ready until after Thanksgiving unless Mark and Casey can finish cathode preparations and cathode to wire frame lamination next week. The plan is to have the full-scale prototype assembly completed by December 4. - The preliminary FDC stack assembly document draft is located at: /u/group/halld/Engineering/PRELIMINARY DOCUMENTS. The document will continue to be fleshed out during the assembly procedure for the full-scale prototype. We will have to add steps in our construction plans for leak checking.
Wire Frame Update
- Wire frame P4 has completed its electrical QA check after several minor repairs associated with soldering problems with the preamp connectors. The components and regions that gave us HV breakdown problems on P1 have been potted in Humaseal. Wire frame P3 will then follow. - Wire frame P4 has been laminated to its associated cathode (that is part of a cathode sandwich). This frame structure is ready for inclusion as part of the second layer of the stack. - We need to have a dedicated meeting to design what the schedule for work on the Phase 3 wire winding will be. The highest priority for work scheduling will be doing work on upgrades of the wire winding facility. This includes a better strongback design, the design and construction of precision combs, modification to the wire winding table, and a list of other items with the system. Stay tuned, more to come. - The wire frame construction document is located at: /u/group/halld/Engineering/PRELIMINARY DOCUMENTS. We will include the information on the wire electroplating process shortly. - The parts of the jig to use for the wire electroplating operation are in our hands. They will be assembled as we find time. - We need to prepare a document for the electrical QA of the preamp connectors on the wire boards. - DSC, Bill, and Fernando will plan a meeting to go over the circuit board design work for Kim. - Kim is following up with the contacts obtained from Peter Monaghan regarding large-area PCBs. Kim is still in back and forth with the board house and the board material supplier. The outlook may be rosier than it was a few years ago. Stay tuned.
- Progress updates: * Casey has been working on soldering rigid-flex assemblies to the second of our two cathode sandwiches. Soldering work on the first sandwich has been completed and electrical QA checks are done. * Even though we are nearly done with the soldering of the rigid-flex assemblies, we ordered another stencil and will use it for the remaining soldering work. * The conducting epoxy used to attach the cathode board grounds between the three cathode boards that make up a single panel were starting to peel off. Casey has improved the design using copper tape. - Roger has been in contact with our cathode board material supplier to get an update on our order delivery. Stay tuned. - The current draft of the cathode construction document is located at: /u/group/halld/Engineering/PRELIMINARY DOCUMENTS. - We need to prepare a document for QA/stuffing/cleaning for the cathode boards and a similar document for the cathode daughter boards and ground boards.
- An order for more ASIC chips is expected very shortly. Fernando expects that we will have ~40 boards ready by the end of November.
Cosmic Ray Test Stand
- Several meetings ago we focussed on the wiggles seen in the reconstructed wire position from the cathodes (see log entry 419) in the FDC logbook. We believe that the periodicity seen is due to the algorithm Beni is using to determine the U and V centroids. Beni get back to this soon. Stay tuned.
- The FDC short-term work list has been posted on the FDC web site. 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.