Minutes-6-10-2010
June 10, 2010 FDC meeting
Tentative Agenda
- Production
- 727 B.C. status
- production planning
- wire stringing
- tension measurement system
- Electronics
- fADC125 status (Gerard, Fernando)
- noise/grounding investigations(Fernando)
- Cathode redesign Bill's changes proposed on the last meeting (Bill, Roger)
- Full-scale prototype tests
- cosmics tests FDC Log Book, page 478 - 482 (Beni)
- new tests with fADC125 (Lubomir)
- Other
Minutes
Participants: Bill, Casey, Glenn, Roger, Beni, Chuck, Fernando, Simon, and Lubomir
Production
- 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 it 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 moved to electronics
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 Lunux 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 that 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 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.
