June 13, 2013 FDC meeting
- Production Construction Tracking (Dave)
- Spare package status
- Engineering (Bill)
- Full electronics test , ,  (Beni, Lubomir)
Participants: Bill, Dave, Chris, Nick, Simon, Vlad, Beni, Eugene, and Lubomir.
- The spare package with four cells was opened last week on Thursday down to the top of the cell #5 (second from the bottom) to fix the gas leakage in an O-ring of the spacer ring there (the O-ring was mashed). The place on a wire showing a "point noise" in cell #4 (wire frame #27) was cleaned. Then we put again the four cells together, this time swapping the top two wire frames: #27 put on the top and #28 below it. The gas leakage was fixed.
- At the beginning of this week Vlad tested cells #5-3. The "point noise" disappeared. Another type of noise was also present at three places on the strips coming from wire frames #27 and #28. We observed it long time ago when tested these wire frames and it comes from positive HV traces on the back of the PCBs at the place where the are laminated to the solid part of the G10 wire frame. The frequency of this noise varies between 100-3000Hz and is visible only on the strips at the place where the traces leading to the strip connector are close to the HV trace. Definitely, it is the wire frame responsible since when we swapped the wire frames the noise showed up on the new cathodes. The only way to fix it is to drill the wire frame from the back, but it is not worth doing it since this is only in three places and the frequency is not that high.
- On Wednesday we installed one new cell and right after the meeting we installed the last cell of the last (spare) package! In these two cells we put the thicker version of the spacer ring to study the feasibility for cluster counting. Now the spare package is being flushed with gas.
- The water chiller was connected end of last week but there was a very small leak in two T-connectors outside of the package. On the next day after the meeting Bill replaced the connectors and now there's no leak.
- Spacers between the packages: the G10 sheets to be used to build the spacers have been glued. All the rods (three per spacer) have be made. Building the cylinders requires the use of the gusset rings that are now on the spare package. After the test of the spare package is finished we will take the gusset rings from the package for several days to finish the production of the spacers. Bill: the distance between the packages is defined by the width of the G10 sheets. It has been tested and there are several places that have to be grind. If needed we can use shims.
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.
- 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.