Difference between revisions of "Minutes-4-12-2012"

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== Results from the oxygen studies ==
 
== Results from the oxygen studies ==
  
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- Lubomir: now performing oxygen measurements at Blue Crab; Brooks gas system with two flow controllers and the oxygen sensor were moved there.
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- Starting from configuration 12 in the table linked above, we are performing oxygen measurements at Blue Crab; Brooks gas system with two flow controllers and the oxygen sensor were moved there. Before looking into the results there was a long discussion about the way the measurements are done. We estimate the relative uncertainties of the measurements to be ~200 ppm, in addition we may have an overall factor of up to 30%. 
  
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- Eugene: what's the acceptable oxygen level; must be <0.05%, but in the prototype we had ~0.1% and was still operational. Assuming we will have ~300ppm per cell at 200cc/min then we will have 1800ppm for the whole package, but if operating at 400cc/min for the whole package it will be 900ppm or 0.09%. However, for this estimation we have to subtract the contribution from the oxygen in the supply gas. More realistic estimation can be done at Blue Crab with the real package.
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- The first production cell with new Viton O-rings was installed and oxygen was measured (it took 4 days) 500-600 ppm at 330 ccpm gas flow and 900-1000 ppm at 220 ccpm. For comparison, before disassembling the four cells there with the original EPDM O-rings had ~7,000 ppm at 330 ccpm gas flow, an improvement of more than a factor of 3, but a factor of ~2 worse than in the testing chamber. There was a significant leak, that later turned out to be caused by a small piece of Kapton tape on the top of the O-ring. Since yesterday, we replaced the top end window and cathode type-3 with a cathode type-1 and Lexan sheet. This is to investigate to role of the flatness and possible frame deformation.  
  
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- Results of the oxygen studies: contamination is an effect of a combination of the O-ring type and the surfaces around the O-ring. When g10 groove coated there was no difference which O-ring used, but with the plastic spacer EPDM showed higher oxygen. Viton and Buna-N showed no difference; Viton was chosen for the production due to reports of outgassing for Buna-N. We want to continue the studies to understand the mechanism of the oxygen permeation, but later when we have time.
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- Due to the difficulties to maintain clean and flat surfaces needed for the Viton O-rings, we started looking again at the possibilities to use EPDM. We installed at Blue Crab second testing place. There we
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- Oxygen sensor system was moved to Blue Crab and the four cells of the package #3 were tested at about the same flow of 200cc/min (measured with rotarmeter): ~7000ppm, which is in agreement with ~10000ppm for the whole package #1. Bill proposed and Beni agreed to move the new gas system (Brooks)
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to Blue Crab to better control the flow, while using the old MKS at JLab.
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== Engineering ==
 
== Engineering ==

Revision as of 17:46, 12 April 2012

April 12, 2012 FDC meeting

Agenda

  1. Production Construction Tracking (Dave)
    • Production status
  2. Results from the oxygen studies (Lubomir)
    • First production cell with Viton O-rings
    • New tests with EPDM
  3. Engineering update (Bill)
  4. Electronics update (Chris)
  5. Other


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