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Message ID: 252     Entry time: Tue Jul 27 14:32:30 2021
Author: Rich Abbott 
Type: Electronics 
Category: Helicoflex Enclosure 
Subject: 105kHz FC Detector 

Luis, Chub, Calum, Jordan, Dean, Rich

Today we filled neon into the new enclosure (Dxxx) that's destined for use with the A+ filter cavity length and alignment detector, plus the new DCPD preamplifiers.  The goal is to do a neon accumulation test over in the 40m lab.

Here is some related information:

  1. The enclosure, lid, Helicoflex gasket, A286 10-32 SHCS bolts (used 20), S5 titanium washers (used 38*), S5 titanium nuts (used 20) were all cleaned and baked in the 40m bake facility by Jordan as an initial condition. * there were two holes where the washer would not fit under the head of the SHCS
  2. We had on hand:
    1. Fresh bottle of neon plus hoses and regulators (loosen the regulator knob for minimum pressure, tighten the knob for more pressure to load)
    2. Torque wrench
    3. Allan adapters for torque wrench to go into SHCS
    4. 3/8 inch spanner to hold nuts
    5. Fresh glove bag
    6. Vacuum pump plus hoses
    7. Kapton tape to seal hose ports
    8. Measuring tape to judge how much volume of neon we used
    9. iPad to take pictures as we went
    10. Big adjustable wrench and allen key to change out regulator on neon bottle
    11. Circuit board to install inside
    12. Ribbon cable to attach the circuit board to the inner wall of the enclosure (need strain relief design to be sure these connectors don't fall off)
  3. Here's what happened:
    1. Luis and Rich staged all the stuff in the clean room in the jitter lab
    2. We put the internal circuit board into the enclosure
    3. We plugged in the ribbon cable but had a bit of difficulty with putting the strain relief screws into the connectors (need a different setup here).  We ended up using some 4-40 screws in the connector on the wall of the enclosure, plus some zip ties to anchor down the connector to the PCB
    4. We didn't have any shorting plugs for the external connectors to avoid ESD damage, so we were careful, but no guarantees.
    5. We placed the gasket in its groove, then placed the lid on top of the enclosure.  Before tightening the bolts at all, we put a rolled up lint free cloth between the lid and the enclosure body so the neon had access to the inside of the enclosure while filling
    6. We put the allen adapters and 3/8 inch wrench into the glove bag
    7. We put the enclosure plus lid and gasket into a glove bag and rolled up as much of the bag as we could while still allowing room to get our hands into the access ports
    8. We added the vacuum hose and neon hose into the ports on the glove bag and taped them closed.
    9. We evacuated the bag with the vacuum pump, and then filled the bag with neon to a bag volume of approximately a 24-inch sphere.
    10. We removed the lint free cloth, then blew more neon into the enclosure to be sure it was filled well.  At this point, we were not thinking that neon was lighter than air.  Our first potential mistake.
    11. We snugged down the bolts and then removed the enclosure from the bag.  
    12. We then went off to lunch (our second mistake) and came back later to do the final torquing.
    13. When we returned, we realized that we now didn't know how much neon may have diffused from the interior of the enclosure, thus the experiment was uncertain.
    14. We proceeded anyway, and found torqued the bolts initially in a star pattern to 30 inch-pounds.
    15. After seven loops, (the second of which we abandoned the star pattern as it was too hard to keep our heads straight) we were at metal to metal on the flange surfaces, and could no longer rotate the bolts at 30 inch pounds.

We are chalking our inconclusive results up to experience, and starting again tomorrow with a fresh gasket.  We will be sure to account for the boyancy of neon in our fill method, and to rig a better way of flushing the interior of the enclosure with neon.

 

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