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| | = Minutes = | | = Minutes = |
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| − | Participants: Bill, Beni, Simon, Vlad, and Lubomir. Due to the PAC, magnet test going on at the same time, Wiener people coming on site, the turnout was low for this meeting. The meeting was in A110. | + | Participants: Bill, Dave, Chris, Nick, Simon, Vlad, Beni, Eugene, and Lubomir. |
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| | == Production == | | == Production == |
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| − | - End of last week we installed the last cell of the last package (see the photos of the package and the happy people around it, attached above). Vlad tested the new cells and found no problems. The top two cells have 3.5 instead of 0.5cm spacer ring. When using iron source Vlad had to increase the HV by 100V to see approximately the same amplitudes as from the regular cells. Very interestingly the last two cells showed very low dark current ~20-30nA, compared to 200-800nA for the other cells. We are not sure why, just because these were the last two wire frames produced, or there's something else related to the special geometry of the cells. | + | - Bill: two spacers are ready, the last one will be glued right after the meeting. Pictures of the spacers, the fixture and the gluing are attached above. The carbon fiber rods are glued to the g10 cylinder. The two gusset rings needed for this procedure were taken from the spare package which is sitting now on a granite table with two Lexan sheets on both sides. Tomorrow after the last spacer is ready, we will put the gussets back. This operation requires at least 4 people, since we use metal pins inserted in the six places when lifting the Lexan sheets. As in happened already when taking the gusset ring in the same way, the pin can lift some of the planes/cells up. |
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| − | - First signals on the scope with definitely visible individual clusters over a very long drift time (up to 15 usec) are attached above. We some minimal grounding we were able to lower the noise to <5mV. At the same time we increased the gas gain to about 2-3 x 10^5 by going up with the HV up to 2450/-500V !
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| − | Amazingly the two cells were stable at this HV at least for several hours. Having such gas gain we were able to clearly see (scope pictures above) individual electrons corresponding to ~20-30 mV signal. On average we have two electrons per cluster, and really we see some single peaks, and some double/triple peaks separated due to the diffusion. On some of the plots two neighboring channels are shown (with different colors; we used a second differential probe from Fernando) and you can see the transition from one wire to another when the track crosses the filed region between the two wires.
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| − | - Plans: on Monday we will take the two gusset rings from the spare package since we will need them for a week to build the package spacers. For that, first we will replace the top gusset with a Lexan sheet, then will take the package out of the mounting table and put it upside down using some strong-back. Then we will replace the bottom gusset. After we are done with the spacers we will re-install the gusset rings in the same way. The spare package will go for testing in 126 after we are done with the third package there. The spacers will be installed between the packages and then we will do the practicing with the mock-up. | + | - |
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| | == Engineering == | | == Engineering == |
![[1]](http://www.jlab.org/Hall-D/detector/fdc/photographs/IMG_0536.JPG){kind=link}
![[2]](http://www.jlab.org/Hall-D/detector/fdc/photographs/IMG_0537.JPG){kind=link}
![[3]](http://www.jlab.org/Hall-D/detector/fdc/photographs/IMG_0538.JPG){kind=link}
![[4]](http://www.jlab.org/Hall-D/detector/fdc/clucou/tek00077.png){kind=link}