With Hirata-san and Washimi-san.

Pictures at SR3 remedying work after O3.

• Temperature when we began working: 22.9 degrees.
• We put the H1 OSEM flag back onto the IM.
• We removed the ballast mass stacks from the top IM. Amount and location cas be found in this notebook page.
• We prepared two new stacks 38 grams lighter each.
• We put them in their respective places on the IM.
• We released the mirror, RM and IM, in this order.
• We closed the chamber and went for lunch to let the suspension motion damp.
• After lunch the condition of the suspension is as follows:
  • The IM seems to be oscillating freely.
  • BF LVDT: 580 um; the aim is 311 um but the FR is not in midrange yet. See this picture.
  • H1 OSEM is not installed.
  • Vertical OSEMs seem to be out of range.
  • The orientation in of the mirror and IM does not seem to have changed significaly in IM-Y, IM-T, TM-Y and TM-P (TM DoF measured in normalized displacement units). See this picture. 
  • IM-Y and TM-Y changed by small amounts, but this is expected because BF keystone moved up and there is a coupling via cables.
• Then we moved the BF fishing rod to midrange.
  • We need to move it by 225,000 additional steps (575,000 steps in total from upper limit and yesterday we moved it by 350,000 steps).
  • Motor initial: 334,533 steps. (Yesterday's final.)
  • Motor final: 559,533 steps.
  • Final position of BF LVDT: -252 um. See this picture.
  • Vertical OSEMs seem to be in range.
• I calculated that the mass needed to raise the BF keystone to 311 um is 24 grams, 12 grams from each stack. See this notebook page.
• After we removed 12 grams from each stack we realized pitch was disturbed by approximately 600 urad. We recovered the pitch by temporarily putting 4 grams on the -Y side of the IM.

Tomorow we will continue. 

Yesterday I forgot to report that after we removed 12 grams from the IM, the BF LVDT went up to about 308 um. The aim was 311 um, so the adjustment was successful.

With Hirata-san and Washimi-san.

Pictures at SR3 remedying work after O3.

• Temperature 22.9 degrees.
• I removed the 4 grams from the top of the IM on the -Y side.
• We set BF LVDT to zero with coil-magnet actuation.
• We were able to recover the TM-P (per oplev readout in ndu) with -1365 counts of IM-P coil-magnet actuation.
• Now IM-P is  -406 urad (IRM is locked and partially disassembled, therefore, this is a relative measurement useful in this context only).
• I removed the IM-P coil-magnet actuation.
• IM-P them becomes  372 urad (again, this is a relative measurement useful in this context only).
• This means that in our latest ballast mass adjustment we disturbed the pitch by 778 urad (in a previous entry I had written appromately 600 urad).
• I adjusted IM-P with the picomotor:
  • TM-P around zero (per oplev in ndu).
  • IM-P around -409 urad (again, this is a relative measurement useful in this context only).
• This means we don't need to redistribute ballast mass on the IM to modify pitch.
• I removed the coil-magnet actuation in the BF and it went up to 379 um; it's higher than yesterday because the temperature went down (now 22.8 degrees). Nevertheless, the distance from the aim is very small: 379 um - 311 um = 68 um; it requires -1500 counts of actuation to bring it to the aimed position.
• Then we proceeded to reassemble the IRM and release the system: we locked the IM, RM and mirror.
• We softly tightened the ballast masses with an Allen key.
• We measured the position of the shaft of the IM-P picomotor. See the diagram in this notebook page. There will be a separate entry to report the result of this measurement.
• We removed the H1 OSEM flag.
• We put back the front and back panels of the IRM.
• We connected the OSEM and clamped the cable on the front panel.
• We put back the H1 OSEM flag; we set the North out per klog 5035 and notebook notes.
• We released the payload and BF case from the security structure.
• The SF LVDT went up to 1764 um. We will add mass to the BF soon in order to correct this.
• The oplev went out of range, which was expected, lilkely because of the cables.
• IM-P became 1610 urad. (I'm not sure about the reson, but tend to blame coupling via cables.)
• I applied -6100 counts of coil-magnet actuation to bring BF LVDT to zero.
• Measurements of transfer functions in IM-L, T, R, P and Y show a healthy system. I didn't measure IM-V because F0 is locked.
• I removed the coil-magnet actuation in BF, the BF LVDT went up to 300 um (temperature 23.1 degrees with aim 311 um).
• IM-P changed to -1150 urad due to coupling via cables.

The next step woulld be to move IM-P with the picomotor to a suitable value.

Today I moved IM-P to a suitable value using the picomotor:

• I set BF LVDT to zero using -8000 counts of coil-magnet actuation.
• Temperature: 22.9 ºC.
• The aim is the value of IM-P during O3GK: -339 urad (see klog 15928).
• Initial value of IM-P values:
  • Initial: -1631 urad (this value should have been close to -339 urad after releasing the IRM, but apparently we were not not so good in using the oplev as a reference during thre work when IRM was locked.)
  • Final: -335 urad.
  • Difference: +1296 urad.
• According to one of the screenshots of the medm screen reported in klog 15963, the value of IM-P before begining the IM ballast mass adjustment, when BF LVDT was zero, was -336 urad, which is the value I brought it back to today.

Now I can calculate by how much we disturbed IM-P with out work 

• According to to klog 15991, I had moved the IM-P with the picomotor by -778 urad.
• Today I moved it +1296 urad.
• We disturbed IM-P by ( -778 + 1296 ) urad =  518 urad.

I measured transfer functions of the IM (with the exception of IM-V because F0 is locked) and the system looks healthy.