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Entry  Fri Nov 7 10:52:57 2008, steve, Update, PEM, AC is back on acf.jpgacc_mc1.jpgtest.jpg
    Reply  Fri Nov 7 15:58:10 2008, rana, Update, PEM, AC is back on mc-acc.pdfmc-acc-quad.pdf
       Reply  Mon Nov 10 19:39:40 2008, steve, Update, PEM, thump noise from particle counter partcfm.jpg
          Reply  Tue Nov 12 23:05:06 2013, rana, Update, PEM, thump noise from particle counter 
             Reply  Wed Nov 13 11:30:07 2013, Steve, Update, PEM, particle counter MOVED Met1Moved.JPG
Message ID: 1122     Entry time: Fri Nov 7 15:58:10 2008     In reply to: 1121     Reply to this: 1129  
Author: rana 
Type: Update 
Category: PEM 
Subject: AC is back on 
I'll bet Steve a dollar that it is mechanical. The attached PDF compares all of the accelerometers from right now.

You can see that the RMS in MC2 is way bigger than MC1.

In the second PDF file you can see the time series. I had to play around a lot with DTT to get it to work. The DTT/Foton
combo on Allegra is not stable, so make sure your work early and often.

In the plots shown, I am bandpassing the time series from 600-700 Hz. I found that doing so allowed the burp in MC1 to remain
large and reduce the extraneous fuzz in MC2. As you can see there is no such noise in MC2.

So its a noise around 600-700 Hz that comes on quickly and then shuts off after several seconds. Its also very periodic in that
it comes on around every 20 minutes. Steve also tells me (although he refuses to put in the elog) that it started up around
August 20th (?). I feel like someone in the 40m lab ought to be able to guess what this is at this point.

Please convince Steve to elog his findings about when the noise started.

If one goes out there and stands next to it when the trend predicts its happening it becomes clear what it is.
Attachment 1: mc-acc.pdf  24 kB  | Hide | Hide all
Attachment 2: mc-acc-quad.pdf  135 kB  | Hide | Hide all
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