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VIS (General)
yoshinori.fujii - 14:31 Wednesday 25 September 2019 (10695) Print this report
GAS filters loops are being reshaped (for my own purpose for now), please do not rm them.

= ITMX and ETMX =

  • I found that the residual motion of the GAS fiters (keystones) looked reatively large and it seemed that reshaping filters would bring me a benefit for my work, then I did and impelemetd to "GAS DAMP" filter bank.
    • The newly made ones are labeled dcdamp_test or dc_test, pelase do not remove them.
    • The most upper stage has dc+damp fiter, and the others have (dc+damp) and dc. This conbination is to be decided. I confirmed that the worked individually at least.
    • The attachments shows the spectra of the GAS motion before and after the reshaping work, there was improvement somehow, to be tuned more though.
    • Figure 1 is about ITMX, Figure 2 is about ETMX suspension.
      • before: labeled (REF*)
      • after: labeled w/o ( )
    • Note that ITMX-BFGAS loop could NOT be closed properly, and I did not used it. It seemed due to a line at high frequency, to be checked.
    • Since I did not finish a long-term stability test, I reset the configuration to the today's starting point. Nothing is changed from before now. To be done for next.
    • note for ITMX, ETMX
    • The data is in: /users/VIS/TypeA/general/LogNotes/20190924/*/
Images attached to this report
Comments to this report:
yoshinori.fujii - 15:53 Thursday 26 September 2019 (10717) Print this report

I re-newed/installed the ITM-GAS filters and then :

  • I did a half-day stability test, and it was confirmed that those filters did not excite resonances (basically of the payload ones) during theat slot.
  • Then I keep those fiters turned on.
  • The attachements shows the residual motion, the dashed ones are the soectra w/ the previous filters and the solid ones are with thees ones.
    • Still a gain-peaking looks to be there and so I should work a bit more.
    • About the 0.2Hz and 0.5Hz peaks, I will want to try to suppress them by using seismometers on the ground since the ground was shakung the suspension at that frequency (Figure 2).
  • If previous config is necessary, please see the Figure 4.
  • A note related to GAS fiters of ITMs:
    • It was know that we had some annoyingly steep lines at 240Hz (and 189Hz, 569Hz, 379Hz ... for ITMX) in the sensor signals.
    • We are believing that they are from the LVDT boards.
    • Since they were annoying, I put notches to the LVDTINF filter bank (even though we still have the ines in the real life) like in Figure 3, the black ones are the ground and the others are the GAS motion.
    • A visible improvememt was found at ETMX and ITMX, but still line(s) at frquency higher than 900Hz looks there at ITMX.
    • This kind of LVDT-boards related issues is to be investigated and debugged....
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yoshinori.fujii - 16:03 Thursday 26 September 2019 (10719) Print this report
  • Now I found that my memory was too weak. I did not have any plots showing that those line was from sensors not the actuators..
  • I will check them tomorrow.
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