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 Thu Mar 15 14:25:05 2018, Craig, DailyProgress, Other, Cavity Power fluctuations vs Temp Fluctuations 
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 Thu Mar 15 15:58:02 2018, Craig, DailyProgress, BEAT, Cavity Power fluctuations vs Temp Fluctuations
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Thu Mar 15 18:37:06 2018, Craig, DailyProgress, Other, Cavity Power fluctuations vs Temp Fluctuations
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Thu Mar 15 22:48:21 2018, Craig, DailyProgress, Other, Cavity Power fluctuations vs Temp Fluctuations
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Mon Mar 19 12:10:27 2018, Craig, DailyProgress, Other, Cavity Power fluctuations vs Temp Fluctuations
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Mon Mar 19 13:29:24 2018, awade, DailyProgress, Other, Cavity Power fluctuations vs Temp Fluctuations
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Mon Mar 19 14:22:57 2018, Craig, DailyProgress, Other, Cavity Power fluctuations vs Temp Fluctuations
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Fri Mar 30 20:12:22 2018, awade, DailyProgress, Other, Disabling the air springs on the vac can: Shimming and clamping
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Message ID: 2160
Entry time: Fri Mar 30 20:12:22 2018
In reply to: 2148
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| Author: |
awade |
| Type: |
DailyProgress |
| Category: |
Other |
| Subject: |
Disabling the air springs on the vac can: Shimming and clamping |
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Following up on the airspring issues. Its not clear that suspending our vacuum can on 3 Hz air springs will improving things much in terms of noise hunting for now. As there is a leak and no stable supply of air, the air springs seem more a nuisance for now. They are varying the alignment enough to change the power transmitted and reflected by about 12% (when using the wall supply of air). Rana has suggested that it would be much better to have a really rigid connection to the table.
Craig placed metal shims under each of the four legs of the tank. I have now clamped the tank down very tight using L-shaped pieces (see attachment). I used a T-driver to get the tension nice and tight. Alignment of the cavities will not have changed much as the tank was already resting on the shims.
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Considering I can't even lock the North cavity today because of alignment drift, I'd upgrade this to super high priority.
Looks like you need to connect the air springs via this black tubing, and not the clear 1/4'' tubing. There are 8 of these metal screw clamps on the North side of the table and 5 on the other side. These are surely the cause of leaking, but I don't have any good ideas for how to eliminate them. I'll google around for ways to eliminate this black tubing from the setup so we don't have 13 leaky connections.
At this rate, the cylinder will hit low 100's later this week. This is why I'm disconnecting the air springs and shimming up the vaccan for now.
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I guess going back to the wall supply would be a stupid step backwards. We need to fix this leak, its either in the tubing or the air springs themselves.
Can you check out what the connection to the air springs is and whether this can be connected to the standard clear tubing airlines? We are using the standard 1/4" tubing (see Newport Pneumatic Isolator Accessories). I'm not even sure if they are supposed to be permanently hooked up to air, the Newport air springs seem to have a Schrader valve (cars/bike valve) on the side and the description suggest that they only need to be pumped up and leveled once. They do degrade. If that is the case then we need to assess if these older rubber diaphragms need replacing.
This is moderate priority. Scattering is top of the list.
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We need to return this cylinder when getting a new one. It will need to reach the low 100s, then we hit reorder on N2.
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Ever since I attached the vaccan air springs to the cylinder, it has been rapidly losing air pressure. It is now down to ~1100 psi, where on Thursday it was ~1800 psi. At this rate we will have to order a new cylinder, and figure out how to make the air springs less leaky, as this is affecting our alignment over time.
For now, I'll relock the cavities, replace the shims, and turn off the air springs as they are causing more harm than good. We will rely on the floating table until then.
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