Revision as of 16:41, 17 January 2014

January 16, 2014 FDC meeting

Agenda

1. Installation [1],[2],[3],[4] (all)
2. Engineering (Bill)
   • Cooling system status
   • Gas system status
   • Other: FDC survey, cathode scan
3. Electronics (Chris, Nick)
4. Mini-DAQ results [5] (Beni)
5. Other

Minutes

Participants: Eugene, Fernando, Dave, Nick, Chris, Simon, Bill, Beni, and Lubomir.

Installation

- The top two quadrants were cabled (see first three pictures attached); Mike Klopf was working till his last minute at JLab, to arrange the cables nicely and uniformly (first picture). Nick is almost done with routing the second quadrant to the electronics. Casey and Tina are working now on the bottom right quadrant and have cabled already two packages (second picture).

- Discussions about the routing of the LV cables. They all have to run to the left side (looking downstream) and it is not clear yet how they will be attached to the face of the magnet in their final position. Therefore, Tom prefers to disconnect them from the LV panel during insertion and then route them again to the panel. Fernando, Bill and other disagree; Beni showed on a drawing how to route the bottom half in order to avoid disconnection from the panel. Lubomir discussed if the extra length of the big bundle at the top right cable tray is enough for the FDC insertion (third picture).

- On Monday we changed the gas to 40/60 Ar/CO2 pre-mixed bottle. The flow was initially increased from 400 to 1000 sccpm (using another mass flow controller with 6000 sccpm range and another rotameter), but at this point the bubblers stopped bubbling: the same old story and we suspect again that somehow gas channels with high impedance are created, making connection from the bubble meniscus to the air. Finally the flow was set to 800 sccpm (200 sccpm per package) so that the bubblers can work.

- Since Wednesday nominal HV, +2100/-500V, has been set on all channels except one (fourth picture showing its current) with +2000/-500V and there were no trips for more than 24 hours. After the meeting that channel was also set to the nominal HV and is stable: all the HV channels are now operational at the nominal HV and gas mixture.

Engineering

- On Wednesday morning we found the chiller off with an active alarm. It turned out that there was disruption in the chilled water supply for several minutes that most likely caused the chiller to fail. The top half of the LV channels were on at that night which increased the Fluorinert temperature to 27degC (as measured with the chiller when it was re-started). Everybody agrees that we need a hardware shutoff of the LV crate in case the chiller fails and this is urgent. Details how to do it were discussed on another meeting organized by Hovanes right after the FDC meeting.

- Even if the chiller failed due to the chilled water disruption, Bill wanted to make sure that the chiller itself didn't contribute to that. Dave measured the temperature difference of the water in/out of the chiller and it was 31degF. According to Bull this means we have ~0.5 GPM water flow, while it is recommended to be 1.3 GPM to have small temperature difference. Bill is looking for a flow meter to measure the actual water flow.

- Gas system: Bill sent to Brooks one of each: mass flow controller, control unit and cable to Brooks. Certainly there's a problem, most likely in the control unit. Other than that, most of the gas stuff is ready, still needs to be tested. So when we fix the flow controllers, the system can be used in principle with a manual control and using one bottle (of each, Ar and CO2) at a time. Because of the high flow we use now one bottle per week. According to Dave we expect the next gas delivery for Feb. 5 and we a little more than one bottle in the moment. Again, we need to find a temporary solution till Feb. 5, either reducing the flow or flushing with Nitrogen and postponing the tests.

- Bill talked to Jim Dahlberg, but there are no results yet from the last survey!?