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Reports until 18:08, Thursday 19 March 2015
H1 SUS
daniel.hoak@LIGO.ORG - posted 18:08, Thursday 19 March 2015 - last comment - 04:54, Saturday 21 March 2015(17365)
violin modes and damping settings

Slowly, over the past week, I have found a set of filter settings that damp the violin modes.  In the tables below I identify the mode frequencies that are matched to each test mass; the matching was done based on which lines were suppressed or excited using bandpass filters in the L2_DAMP filter banks for each test mass.  I also indicate which filter damps that particular line. 

The filter settings are given at the bottom of each table.  For all the L2_DAMP filter modules, FM1 is the bandpass filter (with +120dB gain in the pass band), FM2 and 3 are phase shifters (+/-60deg respectively), and FM4 is a 100dB gain.  FM1 and FM4 are always on.  FM2 and FM3 are used as indicated.  The gain settings are included in the Guardian - the filters shouldn't change in the locking process, but I haven't updated the safe.snap files for the suspensions!

 

ITMX  
f (Hz) damped using...
500.053 MODE3
500.210 MODE3
501.091 MODE6 (still too high)
501.253 MODE3
501.450 MODE3
502.620 MODE3 (still too high)
502.743 MODE3
   
   
MODE3 0deg, -200
MODE6 -60deg, +400

 

ITMY  
f (Hz) damped using...
501.680 MODE5
501.747 MODE6
503.007 MODE3
504.857 MODE2
   
   
MODE2 0deg, -100
MODE3 +60deg,
MODE5 -60deg
MODE6 +60deg

 

ETMX  
f (Hz) damped using...
504.870 MODE6
505.585 MODE6
505.708 MODE6 (still too high)
505.805 MODE4 (still too high)
506.921 MODE6
507.157 MODE6
507.389 MODE6 (still too high)
   
   
MODE4 -60deg, -300
MODE6 -60deg, +100

 

ETMY  
f (Hz) damped using...
508.008 MODE5
508.145 MODE5
508.204 MODE5
508.219 MODE5 (still too high)
508.583 MODE5
508.659 MODE5
   
1008.49 MODE3
1009.03 MODE3
1009.44 MODE3
1009.49 MODE3
   
~1484.5 MODE6?
   
   
MODE3 +60deg, +100
MODE5 -60deg, -100
MODE6 -60deg, +10k (?)

 

Unaccounted for:  
f (Hz) best guess
501.606 ITMY
501.810 ITMY
503.119  
504.803  
507.192 ETMX
507.991  
508.288 ETMY
508.659 ETMY
   

 

The attached figure compares the noise spectrum from Friday and today.  The first harmonics of the violin modes are now the dominant feature in the spectrum, along with 60Hz and the 2.5kHz BS butterfly mode.

 

Images attached to this report
Comments related to this report
daniel.hoak@LIGO.ORG - 04:54, Saturday 21 March 2015 (17374)

I forgot to note the gains for the ITMY filters.  They are:

MODE2, 0deg, -100
MODE3, +60deg, +200
MODE5, -60deg, +100
MODE6, +60deg, +200
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