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| | = Minutes = | | = Minutes = |
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| − | Participants: Bill, Dave, Chris, Beni, Simon, Casey, and Lubomir. | + | Participants: Bill, Dave, Chris, Beni, Simon, Glenn, and Lubomir. |
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| | == Production == | | == Production == |
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| − | - Dave: The construction tracking attached above has different structure now; it has the spare package with the first four wire frames (new epoxy used there) ready. Lubomir: as demonstrated with cell#2 just drying them for a week with nitrogen and/or Ar/CO2 would be enough to have them operational. Outside in the dirty area techs are laminating now the wire frames for the first package. After that (according to Dave) it will take less than a week per wire frame to finish the first package. Wire frame #5 was strung, wires taped and will be glued with the old Epoxy. | + | - Dave (see link above): all wire frames for the first package were laminated. Wire plane #5 ( the first to go in the package) will be populated tomorrow by Chris, followed by putting Humi-seal on the caps, and then wire deadening. Techs are working also on cathodes for cell#6: cathode type 1 is ready and the foils for type 2 are being cut. |
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| − | - Dave: we tested the electro-plating procedure this time on a full-scale wire frame, the one that was built at IUCF and shown on the open houses. Before that the frame was cleaned and HV applied to it in air. We were able to put on the two middle sectors 2200V with low current (~80 nA). | + | - Wire deadening: the wire deadening of the first production chamber (wire plane #2) was successful. The thickness of one sample was measured by a microscope from Olympus company and they found it ~66 microns along one wire. The surface looked very good. We have permission to use the W&M microscope to check samples. Bill is going to look at different wires to make sure the tickness is the same. |
| − | After electroplating the current at 2200V in air almost didn't change. Two issues related to the procedure were discussed:
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| − | *First, how to bypass the 1MOhm resistors on each wire and the 10KOhm on the HV sector; this is needed to use the HV paths to connect to the sense wires. Since we are plating only 6 or 8 wires this is not a big deal. Lubomir: the problem is that if by some reasons you had a bad connection to a wire and you don't know what was the current there, you can't repeat the electroplating to fix that wire. One way would be to unsolder the resistors and shorten the pads (as Dave did in this test), or simply to solder a wire on the top of the resistors, or to use a small alligator clamp (Chris) across the resistor. Bill proposed another option: after stringing not to cut these wires at the soldering pad, but to leave some length and use it to apply the voltage there. Related to that, Beni figured out that actually the current trough each individual wire is different, proportional the wire length that is in the chemical and that's why we have the same thickening on all the wires (Dave confirmed it by measurements with micrometer on the small prototype frames).
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| − | *Second, how to check the results of the wire deadening. So far, with the full-scale frame, we were not able to look at the wires with good enough magnification. Using microscope in the middle of the wires is not practical. We will try to use the position measurement system to see if the laser sensor can measure the thickness of the wires, at least relatively.
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| − | - Lubomir: wire frame #2 was keeping the HV (+2200/-500V) without any trips for almost a week (except some intentional interruptions) and the current is relatively low, ~200nA for the whole chamber. Before that it took ~5 days drying with nitrogen and the current between the field and sense wires was going down, but after changing the gas to Ar/CO2 the field-sense wire current dropped significantly from ~250nA to 20nA. Most likely there was some moister in the nitrogen bottle. | + | - The chamber from 126 with cell#1 was moved to Blue Crab and the wire plane #1 was replaced with wire plane #2. All the cathode channels were tested with the testing card. We found that several daughter card connectors didn't make good contact at some channels. After re-connection (sometimes several) finally we got them working. One bad connection was found between the flex at the cathode (the first one of this kind!) and it was fixed after re-heating/pressing without changing the conductive tape. |
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| | + | - Bill wants to try on one end window to use scotch-weld for gluing the thick mylar, he is afraid of the bubbles that appeared somewhere on the end windows. |
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| | == Engineering == | | == Engineering == |
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