July 3, 2013 Tracking CDC/FDC

Meeting Time and Place

Wednesday July 3, 2013 at 11:00am At Jefferson Lab, the meeting will be held in F326

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Hardware Agenda

1. Announcement
2. FDC Update
   1. single electron detection [1], [2], [3], [4]
3. CDC Update
4. Installation Timelines

Minutes

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

1. FDC Update
   1. Beni on the test of the 3rd package with full electronics: the noise is as low as in the previous tests. The main issue are several cathode channels that show signals from time to time. Re-seating the pre-amp card helps in most of the cases. There is one really problematic card with several channels not working at the same time, though we have seen signals from each channel.
   2. The three spacers between the packages were made; we are waiting for some hardware for the fiducial holders and will start putting all the packages together on the installation cart. After that the plan is to exercise with the cabling, connecting a quadrant of the packages.
   3. Lubomir on cluster counting: the top two cells of the spare package have thicker spacer rings resulting in a drift time of up to 20 usec. Due to the diffusion over such a long drift time we see individual electrons arriving on the wires operating at a gas gain of >2*10^5. Two parallel wires from the first and second cell were connected to a scope triggered if there were signals on both (first picture attached above). The number of clusters as counted by the two wires shows a clear correlation (second plot). The total number of clusters seen by the two cells is ~100 meaning already with only these two cells one can achieve PID with 10% resolution. Some of the electrons are lost due to the recombination (we had 60ppm oxygen contamination) as seen in the third plot showing the decrease of the electrons with the time. One can use these results to study the gas gain from the single electrons: the distribution (fourth plot) has exponential tail related to the gas gain.
2. CDC Update

• Large cooling ring - we set up the large cooling ring, as illustrated in the first picture, and switched on the air supply to it after assembling a group of 14 preamps together and letting them warm up. Those in the H ring were cooled 2C by the air supply (15cfm at 50psi).
• Small cooling rings - we made some smaller cooling rings which fit on top of the hookup wires and can be attached to the standoffs. We started with the D and E rings as the HVBs are packed closest there. These boards were cooled 4-6C by a smaller air supply (3.5cfm at 20psi shared between the 2 rings, we estimate 17-20cfm would be required by the full complement of rings).

Cooling rings

Cooling rings

• Naomi found that the unexpectedly long drift times from some straws are from hits theoretically just outside the volume of the straw, on the side away from the center of the CDC (identified by plotting the tracks fitted whilst excluding the straw in question). This implies that at some point along their length these straws have become very slightly egg-shaped, perhaps caused during the packing of the next ring of straws. Drift-time tables from Garfield for straws of greater radius (10mm) can be used to make use of these long-drift-time-hits, as there is little or no difference in the drift times from closer drift radius. CDC_straight_straws
• Naomi also found that the new flash really does require a VXS crate not a VME64x one; Cody is getting one sent to CMU.