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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: 14434     Entry time: Tue Feb 5 10:11:30 2019     In reply to: 14432     Reply to this: 14436
Author: gautam 
Type: Update 
Category: VAC 
Subject: leak tests complete, pumpdown 83 resumed 

I guess we forgot to close V5, so we were indeed pumping on the ITMY and ETMY annuli, but the other three were isolated suggest a leak rate of ~200-300 mtorr/day, see Attachment #1 (consistent with my earlier post).

As for the main volume - according to CC1, the pressure saturates at ~250 uTorr and is stable, while the Pirani P1a reports ~100x that pressure. I guess the cold-cathode gauge is supposed to be more accurate at low pressures, but how well do we believe the calibration on either gauge? Either ways, based on last night's test (see Attachment #2), we can set an upper limit of 12 mtorr/day. This is 2-3x the number Steve said is normal, but perhaps this is down to the fact that the outgassing from the main volume is higher immediately after a vent and in-chamber work. It is also 5x lower rate of pressure increase than what was observed on Feb 2.

I am resuming the pumping down with the turbo-pumps, let's see how long we take to get down to the nominal operating pressure of 8e-6 torr, it ususally takes ~ 1 week. V1, VASV, VASE and VABS were opened at 1030am PST. Per Chub's request (see #14435), I ran RP1 and RP3 for ~30 seconds, he will check if the oil level has changed.

Quote:
 

Let's leave things in this state overnight - V1 and V5 closed so that neither the main volume nor the annuli are being pumped, and get some baseline numbers for what the outgassing rate is.

Attachment 1: Annuli.png  61 kB  | Hide | Hide all
Annuli.png
Attachment 2: MainVol.png  60 kB  | Hide | Hide all
MainVol.png
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