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Entry  Wed Jan 9 20:01:25 2019, Jon, Update, VAC, Second pumpdown completed Screenshot_from_2019-01-09_20-00-39.pngIMG_3088.jpg
    Reply  Thu Jan 10 10:23:46 2019, gautam, Update, VAC, overnight leak rate OvernightLeak.png
       Reply  Sat Feb 2 21:53:24 2019, Koji, Update, VAC, overnight leak rate Screen_Shot_2019-02-02_at_21.49.33.png
          Reply  Sun Feb 3 15:15:21 2019, gautam, Update, VAC, overnight leak rate Jan10_data.pngFeb1_data.png
             Reply  Sun Feb 3 20:52:34 2019, Koji, Update, VAC, overnight leak rate 
                Reply  Mon Feb 4 12:23:24 2019, gautam, Update, VAC, pumpdown 83 - leak tests PD83.png
                   Reply  Tue Feb 5 10:11:30 2019, gautam, Update, VAC, leak tests complete, pumpdown 83 resumed Annuli.pngMainVol.png
                      Reply  Tue Feb 5 19:30:14 2019, gautam, Update, VAC, Main volume at 20 uTorr PD83.png
                         Reply  Thu Feb 7 13:55:25 2019, gautam, Update, VAC, RGA turned on 
                            Reply  Thu Feb 7 19:28:46 2019, gautam, Update, VAC, IFO recovery 
Message ID: 14394     Entry time: Thu Jan 10 10:23:46 2019     In reply to: 14393     Reply to this: 14429
Author: gautam 
Type: Update 
Category: VAC 
Subject: overnight leak rate 

Overnight, the pressure increased from 247 uTorr to 264 uTorr over a period of 30000 seconds. Assuming an IFO volume of 33,000 liters, this corresponds to an average leak rate of ~20 uTorr L / s. It'd be interesting to see how this compares with the spec'd leak rates of the Viton O-ring seals and valves/ outgassing rates. The two channels in the screenshot are monitoring the same pressure from the same sensor, top pane is a digital readout while the bottom is a calibrated analog readout that is subsequently digitized into the CDS system.

Quote:
 

We allowed the pumpdown to continue until reaching 9e-4 torr in the main volume. At this point we valved off the main volume, valved off TP2 and TP3, and then shut down all turbo pumps/dry pumps. We will continue pumping tomorrow under the supervision of an operator. If the system continues to perform problem-free, we will likely leave the turbos pumping on the main volume and annuli after tomorrow.

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