October 21, 2010 FDC meeting
- Production (David)
- Electronics (Fernando, Chris, Roger)
- Update on PCBs
- Cathode foil and rigid-flex procurement 
- Engineering (Bill, David)
- Wire stringing
- Gluing and soldering materials
- Full-scale prototype tests (Lubomir)
- gas mixture studies FDC Log Book, page 526
Participants: Fernando, Bill, Al, David, Chris, Glenn, Simon, and Lubomir.
- We have a new technician, Al, joining the FDC group.
- David: Setting up the off-site space: temporary lights were installed, more cabinets to be moved there. Working on the safety papers. The use of Hysol requires eye wash station that will be put in place tomorrow. David will contact the clean room company so that our stuff doesn't interfere with the construction. They will start bringing materials at the beginning of November. We should use the space at the angle of the shelving fences, we have 18' our space (see the sketch linked above).
- We get 5 wire frames each week from the company and send another 5 laminated with the Rohacell rings, back for fly cut. For now 10 wire frames were laminated. David, Casey, and Al are doing this job.
- We should change the FastTrack for the FDC production to reflect the fact that we will have the wire frames ready before the full production starts. David will take care of this, but it's not first priority.
- Chris: Inspecting the first article (8, two of each) populated PCBs. Initially they could hold a maximum voltage of ~1500V.The problem: flux from the soldering under the capacitors. Chris cleaned 5 channels (using some flux-off spray) and they could hold 2500V without problems. Fernando decided to go ahead with the full production by requiring the company to improve the cleaning procedures.
- We discussed possible flux cleaning methods; we will need cleaning also after soldering the wires. Using flux-off is expensive (both materials and labor). Ultrasonic cleaner is also very expensive (Fernando) and even more difficult for large surfaces. Bill asked how much we can spend on ultrasonic cleaner. Glenn: up to ~$15K, otherwise manual cleaning is less expensive. The other problem Glenn pointed out is the power that we will need for large volumes. Bill will look for possible solutions.
- Good news about the cathode foil procurement: according to Ross Small only Allflex responded to the ad at FedBiz, he has all the paperwork (after some delay) from Allflex and will go ahead with the contract. There was some confusion about the shipment method (in tubes or boxes) but Roger will discuss it with Ross. Roger got the first quotation for the rigid-flex (linked above) and expects three more. Fernando is working also on the ASIC procurement which will be a sole source one.
- Wire stringing: Bill will soon have more time to start first prototyping. Pulley system is mounted, we can put the strongback on the table and use the old wire frame to exercise. Fernando proposed to use the laser system that we use for the cathode tension measurements, to detect the wire positions when doing position measurements. This should be experimented to see if there will be enough light reflecting from the wire.
- We discussed if we have to/can use the adhesive and soldering materials that were used at UVA for the Hall A chambers. At UVA they used high performance resin flux cored solder (KR-18 SHRMA QQ-S-571F Type RMA Alloy Sn60 Pb40 NIHONALMIT Co. Japan). Fernando says this material is no longer available. As for the glue, UVA used 2011 Araldite (www.araldite.com), while we use EPON epoxy. Same epoxy is used at IUCF, so it should be OK.
Full-scale prototype tests
- Comparison of the gas mixtures using premixed bottle 10.3/89.7 and MKS gas system of 10/90 CO2/Ar (FDC logbook page 526): MKS gives about 20% higher signals, meaning it puts more Ar in the mixture.
- Measurements using 55Fe source triggering with one top strip and looking at the wire signals with fADC. Spectra for 90/10 and 40/60 Ar/CO2 (page 527): the Ar peak has about the same width (~8%) for the two gas mixtures; this differs from the measurements with the CDC prototype where they see wider peak with 40/60. The background comes from CO2 plus the Ar escape peak; has to be investigated with Garfield. Page 528: spectra for all the channels; different (by ~5%) ranges can be explained by different pre-amp gains. After-pulses for one event (page 529): the fact that they affect also the neighbor wire means the after-pulses are initiated by photons. The timing between the pulses of 120-160ns is about the time for the electrons produced via photoeffect in the copper at the cathode, to drift to the wires.