May 20, 2010 FDC meeting
- 727 B.C. status
- production planning
- fADC125 status (Fernando)
- PCB status (Kim, Fernando)
- grounding (Fernando, Lubomir)
- Cathode redesign Bill's changes proposed on the last meeting (Bill, Roger)
- Full-scale prototype test results
Participants: Bill, Mark, Casey, Simon, Eugene, Glenn, Fernando, Beni, Lubomir, and Gerard on the phone
- Bill has given updated drawings with our requirements for the off-site space to Ron Bartek. Ron will work on the infrastructure of that building.
- Bill has reviewed the production planing document linked above. There were several questions regarding the testing of the FDC layers and packages with cosmics. What we want to do will depend on the available time. For now we assume one day-night for testing per layer. We will come to this again after creating the production flowchart (Bill will take care about the latter). Fernando explained us the procedures related the the PCB inspections/tests. We need to set-up a place for testing, preferably in 117, and have one person trained for that. Bill mentioned that (from mechanical point of view) the most important is the quality of the PCB edges.
- Fernando and Gerard informed us about the last week fADC125 tests. The module was installed in the VXS crate in 126 and connected to three FDC cards (top, bottom cathode and an anode). The tests were done using Gerard's code to configure the module and read the data into a file. Beni wrote a code to read the file from root. The DAQ group will work on incorporating the fADC125 into CODA system. For the beginning, they promised us (within two weeks) to write a simple interface to the module so that Beni can include it in the cosmics set-up. We discussed the heating issues we had with the modules in the VXS crate. Beni said there were problems with the F1TDCs there. Gerard asks us to be cautious and not have the fADC powered for long time (hours).
- Kim received the third quotation for the PCBs from TriLab; the price is more than $200K, which is factor of 5 higher than the CEM's price. Fernando generated the step files for the PCBs, Bill checked for consistency with his 3D model: three holes had to be modified and Kim did it. Kim will submit the PR for the PCBs.
- We discussed the noise bursts we observed on the FDC signals. Beni identified the source: the CAEN HV crate used for the scintillator PMTs. At the same time we discussed why the noise on the bottom cathode is stronger than on the top (see FDC logbook page 457, linked above). Possible explanantions: additional ground plane on the top, different grounding on the different cathodes. Bill, Fernando, Mark and Lubomir looked at the prototype after the meeting. It is also strange that the bursts are correlated with the trigger (seen from the same picture); Beni's explanation: the noise is induced also on the trigger input.
Roger is working on the Bill's modifications, will have the cathode design ready soon.
Full-scale prototype test results
- Lubomir is analyzing the data from the fADC125 tests and showed two pictures. The firs one (linked as "one event using fADC125" above) shows the raw signals from all the channels (different cards with different colors) on the left. The right panel shows the signals induced on the top (blue) and bottom (green) cathodes, summed over three strips with max signal and normalized to the wire signal; the black curve is the averaged of the above two curves (not the sum!). It is not clear why the top/bottom cathode picks up much more/less charge at the beginning of the peak. The larger signals on the top cathode can be explained (Bill) by the wires being closer to the top cathode. The second picture (FDC logbook, page 456) shows the correlation between the centers of the gravity as reconstructed on the two cathode planes, shown with different colors for the different wire hits.
- Beni: no new results yet from the cosmics tests using conventional ADCs. Beni was trying to reduce the noise effects by looking for correlations between neighboring channels. He doesn't see such correlations, that are otherwise visible with the fADC. There were several explanations, but certainly this has to be investigated further.
- Bill had a good news: the machine shop is getting a CNC horizontal milling machine. This will expedite the machining of the FDC frames.