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March 18, 2010 FDC meeting

Tentative Agenda

  1. FDC production
    • production space update
    • FDC procurement plans
      • procurement of cables, connectors (HV, signal, LV)
      • procurement of cathodes: 1)flex connection, 2)beam hole size tracking meeting
  2. Full scale prototype tests
    • prototype test updates FDC Log Book
    • HV tests
    • frame modification work: cathode sandwich and wire frame
    • plans for layer 3
  3. Wire frame update
  4. Cathode frame redesign
    • cathode redesign status
    • rigid-flex assembly
  5. Wire winding
    • IUCF phase 3 contract
    • plans for wire winding upgrades
    • tension specs
  6. Other


Participants: Lubomir, Eugene, Casey, Bill, Daniel, Roger, Brian, Mark, Beni, Fernando, Simon, Tim

FDC production

- Tim organized a visit to off-site properties (across the street) that could be used for FDC production/storage purposes. We are considering this as a possible option that needs to be further investigated. There was a second meeting after this one, discussing the requirements to use the space for the FDC production.

- Fernando is working on the procurement of the HV and signal cables/connectors. He wants to make sure the lengths of the cables corresponds to the up-to-date plans.

- procurement of the cathodes: Roger and Dan are finalizing the cathode modifications. Eugene suggested to investigate the failure rate in soldering the flexes. Another showstopper is the decision about the size of the hole of the cathode strips. This issue was discussed during the last tracking meeting and Alex will investigate the effect of the copper material on the detector rates. We aim to have the same hole size on all the FDC packages. Fortunately, the decision about the the size of the wire deadening area that defines the sensitive area of the chamber, can be done later.

Full scale prototype tests

- Beni finished the tests with Sr source, the prototype was moved back in the tent and the top layer was opened.

- Beni summarized the results of the plateau and drift time investigations with different gas mixtures. So far there's nothing unexpected. Nevertheless, there are concerns about the uniformity of the detector response and the quality of the gas inside the chambers. Systematic analysis of the full scale prototype tests will be prepared for the next meeting. Lubomir showed results from the tests with 55Fe: the energy resolution is about 7%.

- At the end of the testing, Beni made a series of HV studies with CO2 only. Before and after opening the chamber he repeated the same tests. At all of the sectors, except maybe few, he was able to reach much higher HV than with Ar - CO2 mixtures.

- We observed corona discharge (bluish light barely visible in the darkened tent) at several places in one HV sector (at about +2700V/-400V) of the opened top chamber. The light was visible on the soldering pad of the last (for the sector) sense wire, later along the whole wire, and then on all the wires in that sector. Also we saw different spots blinking for few seconds coming from some dust on the wires. The corona discharge requires conductivity between places with different potential (through the air, or on the board) but is visible at places like edges or thin wires with very high electric field.

- All this suggests that so far there are no indications that the HV problems are related to the boards, except maybe at few places due to impurities. The dust on the wires could explain at least some of the HV problems we had during the test. Dan suggested to clean the wires with alcohol and ionized nitrogen and continue the HV tests.

- Bill informed us about the frame modification work: the one-piece g10 wire frame came from the shop and Casey and Mark are working on the frames. The work will continue next week.

Wire frame update

- Fernado is reviewing the modified PCBs, waiting also the diagnosis of the HV problems

- new wire sample measurements were posted

Wire winding

- Keith Solberg is reviewing the plans for wire winding upgrades prepared by Bill

- Lubomir suggested to measure the capacitance of one wire, which parameter enters in the calculations of the tension specs. Fernando can provide a capacitance meter.

- Brian suggested to investigate the aging of the wire deadening. In this line, Eugene mentioned that the weight of the copper in that area should also be taken into account when calculating the tension specs.


- Lubomir prepared a short description of the FDC naming convention. There were several suggestions to improve the convention. A modified version will be ready for the next meeting.