Minutes-6-26-2014

June 26, 2014 FDC+CDC meeting

Agenda

1. Readiness review (Beni, Lubomir)
   • Wiki Page
   • Draft CDC Commissioning Plan
2. Gas system [1], [2]
3. DAQ (Beni)
4. CDC status (Beni)
   • noise studies
5. Electronics (Chris, Nick)
6. Engineering (Bill)
   • FDC chiller [3]
7. Other

Instructions for Bluejeans meeting connection

FDC meeting ID: 290664653

Minutes

Participants: Naomi (CMU), Curtis, Dave, Beni, Chris, Nick, Simon, Bill, Fernando, Eugene, and Lubomir (JLab).

Readiness review

- Curtis prepared (Elton requested) a draft of a commissioning plan for the CDC (linked above). Lubomir and Beni will do the same for the FDC. It doesn't have to be a final version. All the other documents needed for the review are ready.

Gas system

- On Wednesday Scott replaced quickly under pressure, the relief valves on the two mixing tanks (first picture). This morning he replaced also the too regulators outsides, because they had some silicon rubber inside, and installed two filters (for the CO2 and Ar lines) that will remove water and oil contaminations. Fernando was concerned about the silicon. Beni: it works with high rates (i.e. with beam), but we need to start bubbling with alcohol.

- Scott had to stop the gas to the detectors for about 4 hours and for this time the pressure in the CDC dropped almost to the atmospheric (~2-3Pa above). The fourth package dropped to about 39Pa, all the other FDC packages didn't show significant changes in the pressure. Naomi proposed to look with a borescope camera at the downstream mylar.

- We started using the Oxygen sensor set-up. There was a small issue: the pressure sensor is supposed to stop the pump if the pressure goes below some limit to prevent under-pressure in the chambers. However, the gas is taken just next to the bubbler and the pressure there varies a lot. To avoid this Beni set the pump to run always, and Dave added in the PLS control to shut down all the valves to the Oxygen sensor if the pressure in any chamber goes below 30Pa.

- We measured the Oxygen on Tuesday and Wednesday using the two sensors and (after some flushing) they gave more or less consistent results: CDC ~3-5ppm, FDC1 and FDC4 ~5-8ppm (extremely low values!). Bill is concerned that the sensors may need calibration. Beni: let's see first if we have problems (charge not constant with the drift time). Today Lubomir did measurements right after the gas was restored: CDC ~8ppm, FDC1 ~35ppm, FDC2 ~120ppm, FDC3 ~46ppm, and FDC4 ~25ppm. Very strangely, the chambers that had bigger leakage showed smaller Oxygen percentages.