Minutes-6-20-2013

June 20, 2013 FDC meeting

Agenda

1. Production spare package installed, and the people around it
   • Spare package tests (Vlad)
   • Thicker cell results (Lubomir) [1], [2], [3], [4], [5], [6], [7], [8], [9], [10], [11]
2. Engineering (Bill)
3. Electronics (Chris, Nick)
4. Full electronics test FDC E-log (Beni)
5. Other

Minutes

Participants: Bill, Beni, Simon, Vlad, and Lubomir. Due to the PAC, magnet test going on at the same time, Wiener people coming on site, the turnout was low for this meeting. The meeting was in A110.

Production

- End of last week we installed the last cell of the last package (see the photos of the package and the happy people around it, attached above). Vlad tested the new cells and found no problems. The top two cell have 3.5 instead of 0.5cm spacer ring. When using iron source Vlad had to increase the HV by 100V to see approximately the same amplitudes as from the regular cells. Very interestingly the last two cells showed very low dark current ~20-30nA, compared to 200-800nA for the other cells. We are not sure why, just because these were the last two wire frames produced, or there's something else related to the special geometry of the cells.

- First signals on the scope with definitely visible individual clusters over a very long drift time (up to 15 usec) are attached above. We some minimal grounding we were able to lower the noise to <5mV. At the same time we increased the gas gain to about 2-3 x 10^5 by going up with the HV up to 2450/-500V ! Amazingly the two cells were stable at this HV at least for several hours. Having such gas gain we were able to clearly see (see scope pictures above) individual electrons corresponding to ~20-30 mV signal. On average we have two electrons per cluster, and really we see some single peaks, and some double/triple peaks separated due to the diffusion.

- Plans: on Monday we will take the two gusset rings from the spare package since we will need them for a week to build the package spacers. For that, first we will replace the top gusset with a Lexan sheet, then will take the package out of the mounting table and put it upside down using some strong-back. Then we will replace the bottom gusset. After we are done with the spacers we will re-install the gusset rings in the same way. The spare package will go for testing in 126 after we are done with the third package there. The spacers will be installed between the packages and then we will do the practicing with the mock-up.

Engineering

- Bill started working on the fixture for the scintillators needed at the Hall for triggering: it is not a problem at all

Full electronics tests

- HV was set on the third package several days ago and there were no trips since then. Initially when the flow was 50ccpm only one channel had problems setting the HV, but already at 100ccpm it was stable. Now the flow is 200ccpm.

- This week we started working on the cabling (see first two pictures linked above). All the LV cables were connected. This is the first time we test the length of the LV cables between the four connectors on them on a real package. The only problem was at a place where the manifold is, where Vlad had to insert the cable behind the manifold, but it worked. One crate (12 fADC125, or two cells) was connected with signal cables and another one connected on the next day after the meeting. We need one more VXS crate for the last two cells, and Beni asked Fernando about this.

- The LV, together with the cooling system, is powered already second day and works without problems. We are using Beni's LV control system. When powering the LV, he increases the voltage up to a point (at about 7V) when the current no longer increases, corresponding to ~0.45A per preamp.

- Beni can read now the raw data from all the fADCs in all the crates (see picture of the monitor showing fADC samples linked above). Next on Beni's list is extracting the time and integral for the fired channels in the ROCs.

Other

- Beni is working on the control interface with the cooling system.

- We discussed also the requirements for the control of the gas system. Narciso wrote a document explaining it. Beni: the control system must be mostly "passive" except when the pressure in the mixing volume is out of the limits. In addition we need also automatic response in case of under/over-pressure in the packages or higher pressure difference between the cells.

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