March 2, 2011 Tracking CDC/FDC

Meeting Time and Place

Wednesday March 2, 2011 at 11:00am At Jefferson Lab, the meeting will be held in F326

To connect from the outside, please use ESNET

Participants: Naomi, Gary, Beni, Lubomir, Simon, Dave, Mark and Tim.

Naomi and Gary reported on status of CDC construction.
1. Row 16 is in progress.
2. We have enough straws to finish row 20, if the new straws are delayed then we will start stringing the straight rows.
Gary has tested using silver beads for the HVB connector wires instead of solder balls. He prefers the beads to the solder ball approach because the process is easier and the results are more consistent (very uniform) and have better conductivity. The cost is a few hundred $ in total. He is going to go ahead with this.
Beni has the drawings from Slava to estimate the HVB connector wire lengths required, this should be done by the end of the week.
Beni asked if the conductivity between the endplate and the inside of a few installed straws could be measured.
Tim asked for a video conference on CDC construction (swiss-cheese plate and HVB connections) to be scheduled for Monday. There are some details to be settled, eg O-rings, before the remaining small parts can be ordered.
Tim has tried to contact Lamina but Patrick has been elusive. Sheldahl are waiting to hear from Lamina about their samples.
Naomi has received the MFCs back from repair. Early results are broadly similar to the previous results, still do not agree with pre-mixed gas. She is constructing a plenum around the prototype straws to mitigate gas leaks and plans to order another bottle of premixed gas.

End of last week the stringing table was moved to Blue Crab and now we have there all the main equipment needed to start the production.
We glued a test PCB ring using old boards. We use these tests also to update the production procedures. Next, we start checking the thickness of the cathode frames.
The full scale prototype was operational for almost a year and we identified different problems. For the top chamber we found that the signals on the top strips are bigger (by ~30-50%) than on the bottom strips. To study this problem, we turned the chambers upside-down. It turned out that now we need to increase the HV by at least 250V, and even more to have the same gas gain as before. First test also showed that signals on the top strips (that were on the bottom before) are again bigger than the bottom ones. Preliminary conclusions are that there are geometrical changes due to sagging or deformation of the frame. The huge change in the gain in principle can be explained also by one of the cathode plane sagging, but it could also be due to gas contamination/leakage. Unfortunately we had to change the gas bottle at the same time when we turned the chamber upside-down.