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Entry  Wed Nov 4 00:10:43 2020, gautam, Update, General, Vent activities today IMG_0184.jpgIMG_0185.jpgIMG_0187.jpgIMG_0207.jpegIMG_0210.jpg
    Reply  Thu Nov 5 22:27:34 2020, gautam, Update, General, Vent activities today 
       Reply  Fri Nov 6 11:36:37 2020, gautam, Update, General, ETMY suspension eigenmodes ETMY_pkFitNaive.pdfETMY.tar.bz2
          Reply  Tue Nov 10 15:13:41 2020, rana, Update, General, ETMY suspension eigenmodes 
             Reply  Thu Nov 12 14:26:35 2020, gautam, Update, General, ETMY suspension eigenmodes ETMY.tar.bz2
       Reply  Sun Nov 8 20:22:35 2020, gautam, Update, General, Vent activities today IFOalignment.png
          Reply  Sun Nov 8 23:24:29 2020, Koji, Update, General, Vent activities today 
          Reply  Mon Nov 9 17:40:17 2020, gautam, Update, General, Pumpdown IMG_8937.jpgpumpdown.png
             Reply  Tue Nov 10 11:31:13 2020, Koji, Update, General, Pumpdown Screen_Shot_2020-11-10_at_11.30.21.png
Message ID: 15673     Entry time: Thu Nov 12 14:26:35 2020     In reply to: 15671
Author: gautam 
Type: Update 
Category: General 
Subject: ETMY suspension eigenmodes 

The results from the ringdown are attached - in summary:

  • The peak positions have shifted <50 mHz from their in-air locations, so that's good I guess
  • The fitted Qs of the POS and SIDE eigenmodes are ~500, but those for PIT and YAW are only ~200
  • The fitting might be sub-optimal due to spurious sideband lobes around the peaks themselves - I didn't go too deep into investigating this, especially since the damping seems to work okay for now
  • There is up to a factor of 5 variation in the response at the eigenfrequencies in the various sensors - this seems rather large
  • The condition number of the matrix that would diagonalize the sensing is a scarcely believable 240, but this is unsurprising given the large variation in the response in the different sensors. Unclear what the implications are - I'm not messing with the input matrix for now
Attachment 1: ETMY.tar.bz2  767 kB
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