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June 10, 2010 FDC meeting

Tentative Agenda

  1. Production
  2. Electronics
    • fADC125 status (Gerard, Fernando)
    • noise/grounding investigations(Fernando)
  3. Cathode redesign Bill's changes proposed on the last meeting (Bill, Roger)
  4. Full-scale prototype tests
  5. Other


Participants: Bill, Casey, Glenn, Roger, Beni, Chuck, Fernando, Simon, and Lubomir


- We discussed only the production planning. Bill with the help of Chuck put the cathode production on the FastTrack. When a pdf version will be available it will be linked to the minutes of this meting. The production of one cathode sandwich (cathode and ground planes) will take about four days with five people: four techs cutting, gluing, stretching the foil and one electrical tech doing the soldering work. The second type of cathode sandwich doesn't have a ground plane which makes the production by a half day faster, but if assuming the same time, we will have 8 days per chamber layer or for 30 layers, 240 days in total.

-Fernando had to go to another meeting, so moving to electronics:


- According Bryan Moffit, the fADC125 module shows problems when operated above 50 Hz rate. Fernando explained, this is just the initial version of the firmware made by Gerard that we can use for cosmic test. Gerard and Bryan are working to solve the issue.

- Bryan, Beni, and Lubomir connected the fADC125 with the Linux CPU to the FDC and are performing tests since Wednesday using the Gerard's code to read the fADC. The fADC was powered on for already 24 hours without heating problems; initially the temperature goes up to 53ded Celsius and stays there. Lubomir investigated the problem of the delay of the signals from one of the cathode cards w.r.t the anode signals. By swapping card inputs and fADC inputs, it turned out the the delay is caused by one of the pre-amp cards or by its cable. Fernando will look into that. Lubomir is analyzing the data from this second run with fADC. He showed a plot (page 483): vertical (perpendicular to the chamber plane) wire position as reconstructed from the ratio of the cathode signals vs wire number. The vertical position changes by 0.5mm from wire #0 (shortest wire) to wire #20. This issue will be investigated taking more data at different places of the chamber.

- Fernando posted doc-1543, linked above, explaining the noise investigations of the FDC prototype. Fernando identified the source that radiates noise: the UPS to which the CAEN HV supply and the gas system are connected. The noise depends on the load, that's why when we disconnect the HV system, the noise disappears. Still, this external noise served as a test of the chamber grounding. Fernando discussed ways to improve the grounding of the pre-amp cards by connecting the board's ground directly to the cathode's ground. Fernando, Bill and Roger discussed possible ways of flapping the cathode foil ground on the back of the g10 to be connected to the pre-amp cards. Fernando mentioned also that the noise on the bottom cathode (of the top layer chamber) was much bigger than the noise on the top cathode. Fernando suspects bad ground somewhere. Bill asked what is the difference in the design electrically between the top and the bottom cathode. Lubomir noted that the ground of the top cathode is connected directly to the ground plane above with 6 common flaps, while the ground of the bottom cathode has no direct connection to the ground plane bellow, it is connected through cables. Bill discussed with Fernando the type of the metal to be used for the cooling line so that it can be used also for grounding the cards.

Cathode redesign

- Bill has no more corrections/requirements to the last design. Fernando and Roger will work next week to implement the extra grounding of the cards, as discussed above. The hope is to finalize the cathode design by the end of the next week and then submit a PR.

Full-scale prototype test results

- Beni had several plots linked above, showing that the chamber efficiency is about 97% +/- few percents. The efficiency was estimated using the tracks from the Indiana chamber, projected on the FDC. Beni also mentioned that after removing the noise from the UPS, the strip resolution was improved (see the plots above). Further improvement will come after calibrating the gains of the strip channels.

- Lubomir already showed above some results from the second test with the fADC125. The plan is to scan some part of the top layer till Monday using the FADC, changing the positions of the cards, and then continue with the standard tests.