Difference between revisions of "Minutes-7-8-2010"

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#* oxygen contamination measurements  [http://www.jlab.org/Hall-D/software/wiki/index.php/Image:Halld_gas_systemB_v2.gif Beni's scheme]
 
#* oxygen contamination measurements  [http://www.jlab.org/Hall-D/software/wiki/index.php/Image:Halld_gas_systemB_v2.gif Beni's scheme]
 
# Other
 
# Other
−
 
−
<!--
 
  
 
= Minutes =
 
= Minutes =
−
Participants: Bill, Roger, Mark, Simon, Casey, Bob, and Lubomir
+
Participants: Fernando, Bill, Roger, Mark, Bob, and Lubomir (fewer people
 +
because of the trigger meeting at CNU at the same time).
  
−
(A relatively short meeting with some of the key players in vacations, still there were some important and useful discussions) 
+
== Production ==
  
−
== Production ==       
+
- According to Tim, the PR for the clean room is awaiting Claus Rode's signature.
  
−
- Bill: the PR for the clean room is awaiting Teresa Danforth's signature (it's a vacation time). Bill placed a PR (that is signed already) for two granite tables with wheels to be delivered directly in 727 B.C. We will need also in total 11 formica tables for the production. Bill looked already to find some surplus tables. We could take one or two from 126. Before purchasing the rest ($500 each) we will look around to find some. On some of the tables we must be able to put 700-800lb.  
+
- Long discussion about the production procedures. Bill included in the Fast Track also the wire frame production, the wire stringing, and the testing of
 +
the chamber layers. The file is linked above (as jpeg) and is open for
 +
discussions and improvements. Bill asked Mark to look at the file (with Fast
 +
Track from Tom) and give his comments. 8 technicians will be involved full day
 +
and will produce one layer for 6 days, but realistically we assume 8 days. For
 +
30 layers it will be 240 working days. In addition, two scientists will
 +
assemble the stack and do HV and cosmics tests. The exact tests are not yet
 +
defined, but the idea is to use all the time available for such tests, but not
 +
more than needed for the layer production. Fernando asked about the cleaning
 +
of the wire frames after soldering and we discussed different options for
 +
ultrasonic cleaning. Fernando wanted to have a flow chart of the production
 +
with dates, so that he knows when the different components are needed for the
 +
production. One of the main unknown is when realistically we can move to the
 +
off-site space and start organizing the production. The plan is to have the
 +
wire frames by 8/24 (first article) and 9/20 (all 30). According to Fernando
 +
we will have the PCBs by 7/19 (first article) and by 8/19 (all). The PR for
 +
the cathode foils will be submitted next week and the timing of their
 +
production is not known yet, but Roger has contacted the company: they can do
 +
the first article by the middle of August (assuming the procurement doesn't
 +
take a lot of time). Using this information, Lubomir will start working on the
 +
flow chart with dates on it.
  
−
- Bill placed a PR for the g10 wire frames (30 pieces); the goal is to have them by middle of September. The template for the rochacell rings will be ready next week. The plan is to have two students (working now with Mark) working on the rochacell. Mark asked where to store the rings. Bill prefers to store them on a flat surface, maybe table. We will look to find some space for storage. Lubomir: today we got 6 more feet in EEL 126 from Hall C. After coordinating with Dave Mack, we rearranged their tables. We will use the extra space also for a new rack for the new gas equipment.
+
- Bill explained us his ideas about the wire stringing. He will use the strong-back that is at IUCF. Lubomir will take care of bringing the
 +
strong-back to JLab. The idea is to use tape pads to hold the wires at the
 +
right positions before gluing and soldering them. The wire positions will
 +
adjusted by hands (or with some tool) using the camera. We discussed once more
 +
different options for the tension measurements.
  
−
- Bill started working on the wire stringing fixtures. We agree that this work has highest priority right now. Bill discussed the way the wires will be pushed down locally, close to the soldering pads. His idea is to use a diffraction plate with grooves: 50 grooves/mm with about 10 microns depth. The grooves will keep the wires at the same spacing while pushing them down.
+
- the templates for the rohacell arcs will be ready next Wednesday. Two students will start cutting the arcs, supervised by Mark. Bill said the most
 +
important is to have the I.D. cut correctly. The arcs will be stored in a box
 +
and then they will start gluing the rings.
  
−
== Cathode redesign ==
+
== Electronics ==
  
−
- Roger prepared the drawings according to the modifications from the last week: increased O.D. with flaps to improve the grounding. Except for few minor modifications (extra flaps in the areas without cards) the design is ready to go, hopefully next week. Roger will send the design to the vendor. We discussed what our requirements will be. Bill suggested to ask for prices: 1) for 60 cathode foils and also 2) if we use the whole material for about 120 foils. We will have 4 foils in the first article and then 4-6 weeks time to check them and start the rest. We discussed how to transport and store the foils. Bill suggested to have them stored in rolls. Mark had suggestions about the material to separate the foils in the rolls.
+
- Fernando: CEM was awarded to produce the PCBs. After getting the first article (two of each) on 7/19, the PCBs will be tested by Fernando within
−
 
+
two weeks before starting the mass production. In parallel, the first boards
−
== Full-scale prototype test results  ==
+
will be given to an outside company for stuffing, they will be tested again and
 +
then we will continue with the stuffing of all the boards.
  
−
- Lubomir showed a [http://www.jlab.org/Hall-D/detector/fdc/tests_full_scale_prototype/DTvsMeanMaxPlusGarfieldOxygen0.1pc.pdf plot]: the mean signal vs drift time. One can see that the signal drops with the drift time. Normally this shouldn't happen: the electrons drift and, close to the sense wire, they are multiplied, so that the gain doesn't depend on the drift time. A possible explanation: the electrons while drifting can be attached to electronegative gas molecules. To check this, Garfield simulations were done adding small percentages of oxygen contamination in the gas mixture. The red dots in the plot represent the Garfield results with 0.1% oxygen contamination. The good agreement suggest that probably we have some oxygen in the chamber. Without oxygen, the Garfield simulations show that the signals do not change with the drift time, except for very small drift times.
+
- Lubomir looked with the differential probe at the output (with 18m cable) of the new anode and cathode cards. The dynamic range of the anode cards is
 +
about 2/3 of the range of the cathode cards; according to Fernando this is
 +
normal and comes from the difference in the gains. This explains the cutoff in
 +
the fADC spectra discussed before.
  
−
- We want to measure the oxygen contamination in the full scale prototype to make sure we understand the problem. Then, the plan is to measure the oxygen from the new design mechanical prototype, to be sure there's no oxygen there. If the problem really is in the oxygen contamination, then without it, we can expect to reach the plateau at about 75-100V ( a factor of ~2 in the gain) lower voltage. This will make also the dynamic range of the signals narrower. To test this we can use the new oxygen sensor, but before that we will try with the old one. We have to pump the gas because of the high impedance of the sensors, but the problem is how to regulate the flow through the sensor so that it doesn't disturb the flow through the chamber. We will go with the Beni's scheme, linked above, in which instead of the rotameter in front of the sensor we will use the current mass flow controller. The latter being used now in the gas system will be replaced by our new mass flow controller. The plan is to install the new gas equipment in a separate rack so that it can go altogether eventually to the shed in the hall. Brian Cross gave us a small pump that can be used in the above scheme.
 
  
−
- Beni prepared several plots, linked above, showing the drift time resolution. Two layers were used with the wires parallel. In one case the drift time in the two layers were compared but for tracks within a plane perpendicular to the layers and parallel to the wires. In the second case Beni included one of the layers in the track reconstruction and look at the predicted hit in the other layer. In both cases he got a resolution of about 200 microns which is encouraging.
+
== Cathode redesign ==
 +
 
 +
- Roger is ready with the design, except for a few cosmetic changes. He will send the Gerber files to the company by tomorrow and expects estimations
 +
from the company for 70 cathodes by the middle of the next week. At the same
 +
time he will start the PR paperwork, so that he can submit it as soon as he
 +
gets the quotation from the company.
 +
 
 +
== Full-scale prototype test results  ==
 +
 
 +
- Lubomir showed several Beni's plots, linked above. Based on high statistics cosmic data, the mean ADC, measuring the total charge from the wires, goes
 +
down with the drift time. Same was observed before for the maximum amplitude,
 +
using the fADC data. This can be explained by ~0.1% oxygen contamination. Beni
 +
also did measurements at different, by 20%, gas flow rates, but there's no
 +
visible change in the results.
  
−
-->
+
- To measure the oxygen contamination we need a pump at the end of the oxygen sensor, as discussed last time. The problem is that the pressure there should
 +
not be less than 0.5 atm, according to the documentation of the sensor. Beni
 +
also confirmed this talking to the company. We will look what are the
 +
parameters of the pump that we have. We may need a relieve valve to keep the
 +
pressure there above half atm.

Latest revision as of 18:40, 8 July 2010

July 8, 2010 FDC meeting

Tentative Agenda

  1. Production
  2. Electronics: update (Fernando)
  3. Cathode redesign: finalizing (Roger)
  4. Full-scale prototype tests
  5. Other

Minutes

Participants: Fernando, Bill, Roger, Mark, Bob, and Lubomir (fewer people because of the trigger meeting at CNU at the same time).

Production

- According to Tim, the PR for the clean room is awaiting Claus Rode's signature.

- Long discussion about the production procedures. Bill included in the Fast Track also the wire frame production, the wire stringing, and the testing of the chamber layers. The file is linked above (as jpeg) and is open for discussions and improvements. Bill asked Mark to look at the file (with Fast Track from Tom) and give his comments. 8 technicians will be involved full day and will produce one layer for 6 days, but realistically we assume 8 days. For 30 layers it will be 240 working days. In addition, two scientists will assemble the stack and do HV and cosmics tests. The exact tests are not yet defined, but the idea is to use all the time available for such tests, but not more than needed for the layer production. Fernando asked about the cleaning of the wire frames after soldering and we discussed different options for ultrasonic cleaning. Fernando wanted to have a flow chart of the production with dates, so that he knows when the different components are needed for the production. One of the main unknown is when realistically we can move to the off-site space and start organizing the production. The plan is to have the wire frames by 8/24 (first article) and 9/20 (all 30). According to Fernando we will have the PCBs by 7/19 (first article) and by 8/19 (all). The PR for the cathode foils will be submitted next week and the timing of their production is not known yet, but Roger has contacted the company: they can do the first article by the middle of August (assuming the procurement doesn't take a lot of time). Using this information, Lubomir will start working on the flow chart with dates on it.

- Bill explained us his ideas about the wire stringing. He will use the strong-back that is at IUCF. Lubomir will take care of bringing the strong-back to JLab. The idea is to use tape pads to hold the wires at the right positions before gluing and soldering them. The wire positions will adjusted by hands (or with some tool) using the camera. We discussed once more different options for the tension measurements.

- the templates for the rohacell arcs will be ready next Wednesday. Two students will start cutting the arcs, supervised by Mark. Bill said the most important is to have the I.D. cut correctly. The arcs will be stored in a box and then they will start gluing the rings.

Electronics

- Fernando: CEM was awarded to produce the PCBs. After getting the first article (two of each) on 7/19, the PCBs will be tested by Fernando within two weeks before starting the mass production. In parallel, the first boards will be given to an outside company for stuffing, they will be tested again and then we will continue with the stuffing of all the boards.

- Lubomir looked with the differential probe at the output (with 18m cable) of the new anode and cathode cards. The dynamic range of the anode cards is about 2/3 of the range of the cathode cards; according to Fernando this is normal and comes from the difference in the gains. This explains the cutoff in the fADC spectra discussed before.


Cathode redesign

- Roger is ready with the design, except for a few cosmetic changes. He will send the Gerber files to the company by tomorrow and expects estimations from the company for 70 cathodes by the middle of the next week. At the same time he will start the PR paperwork, so that he can submit it as soon as he gets the quotation from the company.

Full-scale prototype test results

- Lubomir showed several Beni's plots, linked above. Based on high statistics cosmic data, the mean ADC, measuring the total charge from the wires, goes down with the drift time. Same was observed before for the maximum amplitude, using the fADC data. This can be explained by ~0.1% oxygen contamination. Beni also did measurements at different, by 20%, gas flow rates, but there's no visible change in the results.

- To measure the oxygen contamination we need a pump at the end of the oxygen sensor, as discussed last time. The problem is that the pressure there should not be less than 0.5 atm, according to the documentation of the sensor. Beni also confirmed this talking to the company. We will look what are the parameters of the pump that we have. We may need a relieve valve to keep the pressure there above half atm.

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