Difference between revisions of "Minutes-3-1-2012"

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#* Production status
 
#* Production status
 
#* Testing at Blue Crab (Lubomir)
 
#* Testing at Blue Crab (Lubomir)
−
# Oxygen contamination in the first package: monitoring results, possible explanation and options to reduce it  [https://halldweb1.jlab.org/elog-halld/FDC/ FDC ELOG] (Beni, Bill, Lubomir)
+
# Oxygen contamination in the first package: monitoring results, possible explanation and options to reduce it  [https://halldweb.jlab.org/elog-halld/FDC/ FDC ELOG] (Beni, Bill, Lubomir)
 
# Engineering update (Bill)  
 
# Engineering update (Bill)  
 
# Electronics update (Chris)
 
# Electronics update (Chris)
 
# Other
 
# Other
  
−
<!--
 
  
 
= Minutes =
 
= Minutes =
  
−
Participants: Bill, Dave, Nick, Elton, Mark, Simon, Beni, and Lubomir.   
+
Participants: Simon, Nick, Eugene, Beni, Chris, Bill, Dave, and Lubomir.   
  
 
== Production ==
 
== Production ==
  
−
- Dave: Deadened the first wire plane of package 3 with the larger diameter using the procedure with increased current and the same time as for the smaller diameter, but adding extra polishing cycle. Working on four cathodes now and on the last wire frame for the third package. One more cathode to finish the package. There's not much space to start the fourth package. Testing the chambers of the third package will be the bottleneck since it takes time to flush the chambers with gas. We will try to use weekends for that if possible. Third package was started partially end of November, so less than three months ago. Still we need to work on the subsystems for both package 2 and 3.
+
- Dave: Chris will come tomorrow to install the elements on the next wire frame; we decided it will be #23 and will have #13 (with the glued HV caps!) at the top of the package in case we have to fix it. Dave will do the electroplating tomorrow, as well. So, the wire frame and the cathodes for the next cell will be ready by Monday. Working on the rest of the cathodes for package #3 and started working also on the first cathode for package #4.
  
−
- First cell of the third package was assembled yesterday, flushed with gas over night and today we were able to apply HV which by now is already the nominal one. The dark currents are very low. If it holds over the night we will assume that the wire deadening procedure works and we will continue tomorrow with the deadening of the next wire plane. Tomorrow also we will test the first cell and if everything is OK will try to assemble the second cell so that we can use the weekend to flush it.  
+
- Lubomir: first two cells of package #3 were installed, flushed with gas, conditioned and tested without problems within one week (~3 days for each). Yesterday we installed the third cell and started flushing with gas. Today after applying HV we found high dark current between the field and sense wires. We had similar problems before and we knew it is related to the epoxy used to glue the wires. It turned out that this is the first frame on which Casey used a new epoxy batch, both resin and hardener. Same epoxy was used on another three wire frames that will go next in the package. We will stop using this batch till we figure out if this is a problem.
 +
 
 +
== Oxygen contamination in the first package ==
  
−
== First package testing ==
+
- Beni explained what have been tried so far. The assumption is there is trapped air in the volumes between the cathodes and ground plane connected to the main volumes through small openings. The package was turned vertical with the gas supply on the bottom and the exhaust on the top. A pump was installed at the end of the exhaust line through a rotarmeter (to regulate the flow) and oxygen sensor. The Gas flow was increased up to ~450 ccpm.
 +
There was some improvement in the oxygen percentage: from about ~12000 volumes per minute (vpm) to ~8000 vpm within three days of keeping the chamber vertical. Still not sure exactly how to convert vpm to percentage but at the gas supply we have ~200vpm and with the prototype we had ~800vpm.   
  
−
- Beni showed results posted in the new FDC Elog linked above. After all the gas problems have been fixed/identified, now the main concern is the chamber efficiency. The only time we had full efficiency was in cell#3 when it was leaking through the hole in the exhaust tube and was taking most of the gas flaw, but not clear what fraction of the total 200ccpm at that time. There are also two groups of 4 channels not working, but the problem is not in the chamber; Beni will investigate it.
+
- Bill has another explanation: syphoning air through the manifold fittings or the gas inlet at the gas spacers. Bill also started using ANSYS to model these effects. He suggested to measure the oxygen after the supply manifold and in the gauge tube. After the meeting Beni measured both: ~200vpm at one of the output of the supply manifold, and about ~8000vpm at the gauge tube. Therefore if there's syphoning effect it can be at the supply gas inlet in the spacer ring.  
  
−
- Obviously this is a gas problem and we discussed different ways to approach it. Beni: wanted to install the two new mass flow controllers that allow to have 500ccpm each, but before that we will install the oxygen sensor. Lubomir: we have to make sure there are no air bubbles between the cathode and ground planes; for that we will incline the package so that the supply is at the lowest and the exhaust at the highest point. For the electrons to be attached to the oxygen a third molecule is needed, it could be CO2 but water is 10 times more efficient than CO2. Water may come inside from the kapton that may have 1-2% water due to
+
- Eugene estimated: ~10^5 cm^3 chamber volume, if half is trapped air the oxygen in the chamber will be 10^4 cm^3. At 200 cm^3/min flow and 1% oxygen in the exhaust will have 2 cm^3/min oxygen. so it will take ~100 hours to get the oxygen out. Since the oxygen percentage will drop it will take more.
−
to foil aligning procedure. The foils stay in direct contact with water for at least 16 hours. Depending on the results for the oxygen content we will decide if we need moisture measurements (to 0.1% precision).     
+
 
−
+
- Bill suggested using fan pump instead of vacuum one to increase the flow through the chamber. With proper control one can keep the pressure in the chamber independent from the gas flow. Bill and Dave will investigate this option.
 +
    
 
== Engineering ==
 
== Engineering ==
  
−
- Bill showed models (attached above) of the cooling system manifolds and their attachment to the package; four manifolds per package. Discussed what is the best material for the holding brackets. Bill offered two options, aluminum or G10, but prefers aluminum. Elton after checking the radiation lengths (what matters for the photon conversion): G10 is factor of 2 better if sizes are the same. Bill will look for the best solution.    
+
- Bill got permission to do pressure tests of the cooling system in the Hall. Will use first  water then maybe fluorinert.  
  
−
- There was a long discussion how to survey the FDC packages outside and inside the magnet. Bill explained his ideas about the fiducial points. It will be a ball attached to the gusset ring with a post, holder and carbon-fiber rod. It can be surveyed outside of the magnet. For the inside survey we need optical targets. Precision will be about 0.5mm. Beni proposed to use something more rigid than the carbon fiber rods. Elton: if we can't get precision similar to the chamber resolution of 0.2mm then the survey will not help. Bill: this is what we can get with such light frames; due to deformations the positions will be different when inserted in the magnet. Bill wants to design g10 cylinders and rods between the packages firmly attached to the gusset rings so that such deformations are minimal. Thus, even if we don't have very precise positions from the survey we will make sure that the positions of the packages are stable and one can do the alignment with the data.  
+
- Mark borrowed a moisture sensor for a couple of weeks that we will install at the exhaust.
 
      
 
      
 
== Electronics ==
 
== Electronics ==
 
   
 
   
−
- Nick: all the pre-amp cards are assembled and now with Cody.
+
- Grounding: Bill came with an idea how to make the common ground connections at the 6 points around the package with low material: using plastic clamps with Cu tape in between.
−
 
+
−
-->
+

Latest revision as of 17:22, 31 March 2015

March 1, 2012 FDC meeting

Agenda

  1. Production Construction Tracking (Dave)
    • Production status
    • Testing at Blue Crab (Lubomir)
  2. Oxygen contamination in the first package: monitoring results, possible explanation and options to reduce it FDC ELOG (Beni, Bill, Lubomir)
  3. Engineering update (Bill)
  4. Electronics update (Chris)
  5. Other


Minutes

Participants: Simon, Nick, Eugene, Beni, Chris, Bill, Dave, and Lubomir.

Production

- Dave: Chris will come tomorrow to install the elements on the next wire frame; we decided it will be #23 and will have #13 (with the glued HV caps!) at the top of the package in case we have to fix it. Dave will do the electroplating tomorrow, as well. So, the wire frame and the cathodes for the next cell will be ready by Monday. Working on the rest of the cathodes for package #3 and started working also on the first cathode for package #4.

- Lubomir: first two cells of package #3 were installed, flushed with gas, conditioned and tested without problems within one week (~3 days for each). Yesterday we installed the third cell and started flushing with gas. Today after applying HV we found high dark current between the field and sense wires. We had similar problems before and we knew it is related to the epoxy used to glue the wires. It turned out that this is the first frame on which Casey used a new epoxy batch, both resin and hardener. Same epoxy was used on another three wire frames that will go next in the package. We will stop using this batch till we figure out if this is a problem.

Oxygen contamination in the first package

- Beni explained what have been tried so far. The assumption is there is trapped air in the volumes between the cathodes and ground plane connected to the main volumes through small openings. The package was turned vertical with the gas supply on the bottom and the exhaust on the top. A pump was installed at the end of the exhaust line through a rotarmeter (to regulate the flow) and oxygen sensor. The Gas flow was increased up to ~450 ccpm. There was some improvement in the oxygen percentage: from about ~12000 volumes per minute (vpm) to ~8000 vpm within three days of keeping the chamber vertical. Still not sure exactly how to convert vpm to percentage but at the gas supply we have ~200vpm and with the prototype we had ~800vpm.

- Bill has another explanation: syphoning air through the manifold fittings or the gas inlet at the gas spacers. Bill also started using ANSYS to model these effects. He suggested to measure the oxygen after the supply manifold and in the gauge tube. After the meeting Beni measured both: ~200vpm at one of the output of the supply manifold, and about ~8000vpm at the gauge tube. Therefore if there's syphoning effect it can be at the supply gas inlet in the spacer ring.

- Eugene estimated: ~10^5 cm^3 chamber volume, if half is trapped air the oxygen in the chamber will be 10^4 cm^3. At 200 cm^3/min flow and 1% oxygen in the exhaust will have 2 cm^3/min oxygen. so it will take ~100 hours to get the oxygen out. Since the oxygen percentage will drop it will take more.

- Bill suggested using fan pump instead of vacuum one to increase the flow through the chamber. With proper control one can keep the pressure in the chamber independent from the gas flow. Bill and Dave will investigate this option.

Engineering

- Bill got permission to do pressure tests of the cooling system in the Hall. Will use first water then maybe fluorinert.

- Mark borrowed a moisture sensor for a couple of weeks that we will install at the exhaust.

Electronics

- Grounding: Bill came with an idea how to make the common ground connections at the 6 points around the package with low material: using plastic clamps with Cu tape in between.

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