May 22, 2013 Tracking CDC/FDC

Meeting Time and Place

Wednesday May 22, 2013 at 11:00am At Jefferson Lab, the meeting will be held in F326

Connections

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Hardware Agenda

1. Announcement
2. Collaboration Meeting
3. FDC Update
4. CDC Update straight straws early results

Minutes

Present: Naomi, Beni, Simon, Eugene, Lubomir, Mark

1. Collaboration meeting
   • We do not need the 3rd timeslot.
2. FDC Update
   1. The second cell of the spare package was opened once more. All the channels were tested before and worked fine, but the HV was unstable over the weekend. One wire soldering was fixed and some additional cleaning done. The cell will be tested once more at the end of the week.
   2. The test of the cooling system is going on. The Fluorinert chiller produces a lot of heat and the water chiller has not enough power to cool it. Bill is in contact with the experts.
3. CDC Update
   1. HV - All 3522 wires have been up to 2200V; at 2200V they all drew less than 8uA shared between 3 HVBs (most drew much less). We have found signals on every wire and have pedestal measurements for every wire. For almost all of these, the pedestal width is 15-20 channels (ADC range 0-4095) and at 2100V the HVBs draw less than 0.08uA current shared between 3 boards. There are 7 straws, each on a different transition board, with pedestal width larger than 20 channels (between 24 and 50). Using these transition boards the HVBs draw less than 8uA (the trip setting) at 2200V shared between 4 boards, perhaps unevenly. We think that the noisy pedestal may be associated with dust burning off the wires because our experience with other transition boards is that the current and the pedestal width both fall with time and then stabilize. We hope to be able to use any 4 boards at 2100V and less than 0.08uA (total) eventually.
   2. Drift time - CDC_straight_straws Naomi shared some drift time histograms from straws on transition boards E8, E9, E10 (3 o'clock looking downstream) and one resolution plot for all 72 straws. The histograms do not look quite as expected, the maximum edge is not as sharp as with the prototype, and the maximum drift time suggests that the gas mix is not 50/50 as intended (which would affect the resolution). The flammable gas detector is still indicating flammable gas leaving the CDC. The flow rate is 275sccm of each Ar and CO2.
   3. Tracks - CDC_events These were for stereo straws (9 o'clock looking downstream) but triggered by scints at the upstream endplate so not very different from the axial straws here. Naomi looked at every hit missed from the first 20 tracks in that run. Only 12 hits were missed out of a total of 147, for 5 of these the hit time found actually looked ok (hits are rejected if over 1mm from the track) and for another 5 the hit leading edge was obviously disturbed by noise; the leading edge disturbances could sometimes be found by comparing the high and low threshold crossing times.