Supplementary note

• > Then the VIS team tried to release the tower part, finding that some of the IP LVDT signals are freaky.
  > It was caused by loose connection of in-vac cables. We ended up crimping the D-Sub pins again.
  • We did this work for all the IP-LVDTs (H1/H2/H3), and confirmed that all of them were electrically connected even when we touched the connectors by hand.This isssue went away for ITMY suspension.
• > We decided to forget about putting Y to zero, because we can adjust Yaw with the stepper motor.
  • Just for making sure; because we can adjust "TM-Yaw" with the stepper motor "on F0-GAS for Yaw".
• > The current set points for the IP control are: L = 100, T=200, Y=-710
  > #L=100 and T=200 comes from when Fujii-kun searched for an IP position which makes the BF Yaw transfer function better
  • For L and T, this set point was used since the transfer function of BF-Yaw was optimized at that point so far (klog#9172), however, there is not much reason to stick the IP at this point if the transfer functions are healthy. If healthy TFs are measured at ex. (L, T) = (0, 0), we can change the IP position to the point.
    • The point was totally depended on the BF-Yaw TF, thus we should want to check it with changing IP position to find the sweet point.
  • For Y, this position was decided so that the IP-motor-H2 had some margin. However, after the work, I found that the current margin might not be enough for the pumping-down compensation business, according to a measurement in klog#9732. (see the Figure 1 to 3, more beautiful ones are to be posted.) This confirmation was done by eye at the site during the buisiness and I seemed to find a gap between the limitter and the motor, however, it might not be enough.
    • The current motor set point after the IP centering work was (H1, H2, H3) = (43.0mm, 36.0mm, 43.0mm). The definition is in Figure 4.
    • Thus the Yaw position might be necessary:
      • to change the set point in Yaw so that the IP-motor-H2 has larger mergin.
      • or, to change the motor limmiter position
    • FYI, until quite recently the IP set point was at (L, T, Y) = (100, 200, 0), but it looked that all the IP-slider-motors were at the edge of the motor-range. NOT setting Yaw to zero should save us.
    •  we also confirmed that the accelerometers, 3 of them, became operational successfully, even though we did not check the noise levels in spectra. Still it looked noisy by eye.
• > After releasing the IP, we tried to recover the mirror alignment with OpLev.
  • This was done with F0(Y) motor since the picomotor on the BF for Yaw adjustment was not available.
  • The oplev was back when IP was at (100, 200, -710) and BF-Yaw was at 11350.
  • We decide that we do not tune the BF-LVDT position horizontally at that time since the position was not so close to the secondary coil holders. If the IP position is tuned again, we might have to takecare of this though.
• > Along the way, we found that the weight of the cryo-payload changed from the addition of the wire clamp, causing the change of the GAS DC positions. CRY people adjusted the weight with ballast masses also adjusting pitch. 
  • During this work, we also found that the sensor polarity of the F1- and BF- GAS were NOT collect.. This is to be fixed maybe after the ITMY pumping is finished(?) in order to avoid confusions.
  • We adjusted some amount of masses so that the BF-GAS filter oscillates. A compensation with fishing rods is necessary.
  •  

Attachments.

Only the coeeficient is useful.

Note:

For F0Y, a negative value makes positive yaw direction. The red/blue curve is the results before/after the PEEK part was installed.

Summary of the next steps:

• take care of the IP-H2 motor
• GAS position tuning with the fishing rods.
• conduct the mechanical transfer function measurement and confirm if the suspension is healthy indeed [1]
  • for the template files, see klog#9734.
  • /users/VISsvn/TypeAtower/ITMY/Measurements/TF/template/
  • /users/VISsvn/TypeAtower/ITMY/Measurements/TF/reference/

[1] After the measurement, do the followings:

• Compare the results to the references, i.e., to the simulated ones and previous measurements:
  • Check if a resonant peak and Q-factor at its frequency are as we designed.
  • Check if the dc-gain is comparable with the simulated one, previous or the other suspensions'
  •  
  • NOTE:
  • Especially IP-L, T and BF-Yaw d.o.fs. is necessary to be chacled deeply.
  • Small band-width like 3mHz will be necessary, and smaller excitation amplitude is recommended in that measurement in order NOT to damage the suspensions.