Difference between revisions of "Minutes-3-15-2012"

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#* Production status
 
#* Production status
 
#* Testing at Blue Crab (Lubomir)
 
#* Testing at Blue Crab (Lubomir)
−
# Oxygen contamination in the first package  [https://halldweb1.jlab.org/elog-halld/FDC/ FDC ELOG] (Beni, Bill, Lubomir)
+
# Oxygen contamination in the first package  [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: Simon, Nick, Eugene, Beni, Chris, Bill, Dave, and Lubomir.   
+
Participants: Dave, Bill, John, Nick, Eugene, Beni, Simon, and Lubomir.   
  
 
== Production ==
 
== 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.
+
- Dave for the third package: wire planes #4 and #13 remain to be deadened. The chemical re-crystalized  and has to be reheated. Chris will put the components on #13 on Friday. Mylar will be tensioned on cathode #40 type-2 and we will be done with the parts for the third package. Package four: started working on the first two cathodes type-3, laminating and testing the wire frames. Most likely Anatoly will start working on BCAL lightguides gluing (in couple of weeks?), so we would like him first to replace the HV caps and do the testing on the rest of the wire frames.  
  
−
- 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.
+
- Lubomir: third cell on the third package had to be opened twice to clean a noise place (10-20 kHz high amplitude) on a sense wire; turned out to be a small hair on the back side of the wire. Fourth cell was installed too but not tested yet. As Eugene suggested on the tracking meeting we discussed if we stop the package assembly till we figure out the oxygen issue. Everybody agreed. We will continue mostly with the cathode production and wire frame production, preferably without stringing the wires to avoid damage/cleaning.
 
    
 
    
 
== Oxygen contamination in the first package ==
 
== 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 rotameter (to regulate the flow) and oxygen sensor. The Gas flow was increased up to ~450 ccpm.
+
- Beni showed different results from the FDC ELog about efficiency dependence on the gas flow for three different Ar/CO2 gas mixtures we had recently. The efficiency is between 90-100% with 90/10 at high flow (400-500 scc/min). For 40/60 at 500 scc/min the efficiency is 60-70% but very uniform. Beni studied also the dependence of the oxygen percentage on the flow and differential pressure in the chamber. Actually the two parameters were varied at the same time, but by using a pump to lower the pressure almost to zero Pa, Beni didn't see strong dependence on the pressure. For 500 scc/min and ~150Pa the best value for the oxygen was 6200vpm, while with 300scc/min and ~250Pa oxygen went up to ~8000vpm.
−
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.  
+
- Casey started replacing the plastic rods with aluminum ones on the first package and applying 100 in*oz torque instead of 50; not an easy work since some of the plastic broke. Bill explained that with 50 in*oz two surfaces must be flush when the O-ring has its max compression of 35%. Due to possible deformation this may not be the case and increasing the torque will just make the frames flatter. Higher torque will be applied on the test chamber as well and look at the oxygen percentage.
  
−
- 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/m
+
- Future plans: we will start flushing the second package with a premix 40/60 bottle at Blue Crab and later measure the oxygen there. We discussed again if we can use other gases like He or Ne to test for leakage. If changing the rods doesn't fix the problem we will consider replacing the O-rings. Bill ordered new O-rings: Buna-N (Nitrile) and according to a table where this material is mentioned with a similar name, the oxygen permeability must be an order of magnitude better. First we will change the O-rings in the testing chamber.
−
in 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 ==
 
== Engineering ==
  
−
- Bill got permission to do pressure tests of the cooling system in the Hall. Will use first  water then maybe fluorinert.  
+
- Bill working now on the package connections and cooling system drawings.
 +
 
 +
- We discussed if the Fluorinert will be a problem for our leaky chambers. It is known that very small percentge of Fluorine can cause serious problems in the chamber, but what about Fluorinert? Eugene suggested talking to experts.
  
−
- Mark borrowed a moisture sensor for a couple of weeks that we will install at the exhaust. 
 
−
   
 
 
== Electronics ==
 
== 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.
 
  
−
-->
+
- Nick: 5 additional pre-amp sets (22 each) ready, plus one at Blue Crab, we have the sets needed for the second package.
 +
 
 +
- Nick made the control for the fan pump that is installed now in an Al cylinder that Bill designed for it, ready to be tested on the first package.

Latest revision as of 04:25, 1 April 2015

March 15, 2012 FDC meeting

Agenda

  1. Production Construction Tracking (Dave)
    • Production status
    • Testing at Blue Crab (Lubomir)
  2. Oxygen contamination in the first package FDC ELOG (Beni, Bill, Lubomir)
  3. Engineering update (Bill)
  4. Electronics update (Chris)
  5. Other


Minutes

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

Production

- Dave for the third package: wire planes #4 and #13 remain to be deadened. The chemical re-crystalized and has to be reheated. Chris will put the components on #13 on Friday. Mylar will be tensioned on cathode #40 type-2 and we will be done with the parts for the third package. Package four: started working on the first two cathodes type-3, laminating and testing the wire frames. Most likely Anatoly will start working on BCAL lightguides gluing (in couple of weeks?), so we would like him first to replace the HV caps and do the testing on the rest of the wire frames.

- Lubomir: third cell on the third package had to be opened twice to clean a noise place (10-20 kHz high amplitude) on a sense wire; turned out to be a small hair on the back side of the wire. Fourth cell was installed too but not tested yet. As Eugene suggested on the tracking meeting we discussed if we stop the package assembly till we figure out the oxygen issue. Everybody agreed. We will continue mostly with the cathode production and wire frame production, preferably without stringing the wires to avoid damage/cleaning.

Oxygen contamination in the first package

- Beni showed different results from the FDC ELog about efficiency dependence on the gas flow for three different Ar/CO2 gas mixtures we had recently. The efficiency is between 90-100% with 90/10 at high flow (400-500 scc/min). For 40/60 at 500 scc/min the efficiency is 60-70% but very uniform. Beni studied also the dependence of the oxygen percentage on the flow and differential pressure in the chamber. Actually the two parameters were varied at the same time, but by using a pump to lower the pressure almost to zero Pa, Beni didn't see strong dependence on the pressure. For 500 scc/min and ~150Pa the best value for the oxygen was 6200vpm, while with 300scc/min and ~250Pa oxygen went up to ~8000vpm.

- Casey started replacing the plastic rods with aluminum ones on the first package and applying 100 in*oz torque instead of 50; not an easy work since some of the plastic broke. Bill explained that with 50 in*oz two surfaces must be flush when the O-ring has its max compression of 35%. Due to possible deformation this may not be the case and increasing the torque will just make the frames flatter. Higher torque will be applied on the test chamber as well and look at the oxygen percentage.

- Future plans: we will start flushing the second package with a premix 40/60 bottle at Blue Crab and later measure the oxygen there. We discussed again if we can use other gases like He or Ne to test for leakage. If changing the rods doesn't fix the problem we will consider replacing the O-rings. Bill ordered new O-rings: Buna-N (Nitrile) and according to a table where this material is mentioned with a similar name, the oxygen permeability must be an order of magnitude better. First we will change the O-rings in the testing chamber.

Engineering

- Bill working now on the package connections and cooling system drawings.

- We discussed if the Fluorinert will be a problem for our leaky chambers. It is known that very small percentge of Fluorine can cause serious problems in the chamber, but what about Fluorinert? Eugene suggested talking to experts.

Electronics

- Nick: 5 additional pre-amp sets (22 each) ready, plus one at Blue Crab, we have the sets needed for the second package.

- Nick made the control for the fan pump that is installed now in an Al cylinder that Bill designed for it, ready to be tested on the first package.

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