Pictures can be found in the album SR2 Remedying work after O3.

• The temperature was T = 23.1 °C.
• I moved the BF and F1 close to their setpoints at zero using the fishing rods. I read in previous entries that I didn't want to do this before because I didn't want to risk jamming the fishing rod. However, this morning I had forgotten about such a concern and did it. There was no problem.
• With the IP unlocked I moved the FR all the way up. I stoppped moving it right before it reached the physical stop (~ 2 mm or less). At this height I set the limit switch to a suitable position:
  • The limit switch triggers at 1,018,568 steps.
  • The keystone positin here is F0 LVDT = -559 um.
  • I set the software limit to 1,019,000 steps.
• Then I locked the IP and F0 and removed the ballast mass from the keystone top plate. It was 192 grams.
• Without the ballast mass the keystone reached 314 um, which is just 132 um above the target position of 182 um, which is the size of the buoyancy correction.
• This means that, with the current keystone top plate, we would only be able to move the keystone by 132 um above zero, which will be the nominal position.

We require to change the heavy keystone top plate for the lighter kind. 

Pictures can be found in the album SR2 Remedying work after O3.

• This morning the F0 fishing rod was at its upper limit: 1,019,000 steps.
• I moved it all the way down to its lowert limit  watching that the payload didn't touch the security structure underneath each stage.
• I set the lower limit switch in position. Before I could write down the data on the notebook the digital system went down. I'll do it tomorrow.
• I changed the F0 keystone top plate for a lighter one:
  • Ballas mass I removed yesterday (already reported): 192 grams.
  • Mass of the old plate with screws: 809 g + 7.1 g = 816.1 g
  • Mass of the new plate with screws: 385 g + 4.8 g = 389.8 g
  • Ballast mass removed with respect to what we had in O3GK: 389.8 g - 816.1 g - 192 g = -618.3 g.
• Temperature: T= 23.4 °C in the afternoon.

Tomorrow I'll adjust the amount of ballast mass in order to have the keystone in the suitable position per the buoyancy correction.

Pictures can be found in the album SR2 Remedying work after O3.

• I adjusted the postion of the lower limit switch and set a value for the software limit.
• I changed the value for the upper software limit.
• The final parameters are
  • Hardware limit switches trigger at: [ -2,072,149 ; 1,018,568 ] steps
  • Software limits: [ -2,050,000 ; 1,017,000 ] steps
  • F0 LVDT: [ -977 , 929 ] µm.
  • Temperarure: T = 23.2 °C (O3GK temperature was 23.5 °C, klog 15816 ).
  • The mid-point of the FR is -516,500 steps.
• I added 301 grams to the F0 ketstone top plate.
• In such amount of ballast mass, at the FR mid-point, the F0 keystone goes to 120 µm, which is very close to the goal of 182 µm per the buoyancy effect (klog15322).

With Hirata-san.

Related pictures can be found in the album SR2 Remedying work after O3.

• We set the GAS filters in zero and measured the height of the mirror. It is approximately 0.95 mm above the nominal level (Terada-san's mark). This value is consistent with previous measurements.
• We measured the position of Tereda-san's mark with respect to
  • the center of the flange: it is 1 mm above the center, which is fine given the laser level line thickness (approx. 2 mm).
  • the mortar base (floor): 1217.9 mm. The 3D-CAD value is 1217 mm. We used a ruler and the laser level.

With Hirata-san and Washimi-san.

Pictures can be found in the album SR2 Remedying work after O3.

Today we finally lowered the pre-isolator:

• The size and thread of the jacks are M42 and 2 mm respectively.
• We lowered 1 mm, which is a 180° rotation of each jack. The aim was 0.95 mm but, given the measurement uncertainty and the thread size, it was easier just to do 1 mm.
• We did it in steps of 1/8 of a turn, which is 250 um.
• Once we finished lowering it, we measured the height of the mirror again: it is approximately 50 µm above nominal (per Terada-san's mark).
• Later we corrected the tilt of the IP using the jacks (L was -1.3 mm). We moved them by very small amounts such that the height is not expected to be affected. The final position of the IP is:
  • L: 228 um,
  • T: -217 um,
  • Y: 6 urad.
• After this work the setpoint of F0 must be changed to zero.
• Hirata-san assembled the thermistor assembly.

With Hirata-san.

We changed the F0 GAS setpoint to zero, which is where it should be. We updated the SDF.

With Aso-san, Hirata-san and Yano-san.

Summary: we set the mirror height according the new height markings.

Pictures can be found in the album SR2 Remedying work after O3.

Tomaru-san recently made new markings in vacuum chambers and pillars indicating what the suitable height of the mirrors are. These new markings are slightly different to those made  by Terada-san long ago. The work today was to adjust the height of the mirror to the new marking. It happened that now we needed to raise the pre-isolator.

• We opened the top of the chamber, locked the IP and locked F0 very close to zero, which is its nominal position.
• We set the positions of the F1 and BF keystones close to zero using coil-magnet actuation.
  • F1: -2100 counts,
  • BF: -1100 cnt,
  • Temperature: 23.4 degrees.
• We measured the height of the mirror with respect to the new marking: it was 1.6 mm below it.
• We turned off the actuation and raised the pre-isolator by approximately 1.6 mm. The jacks have a M42 X 2 mm, so we moved it by 3 steps of 90 degrees plus one of around 22.5 degrees, which is close to 288 degrees = (1.6mm / 2mm ) X 360 degrees.
• After turning the actuation on in F1 and BF, we measured the height of the mirror again: it was 0.15 mm below the target. We decided this was good enough.
• We then released the F0 and the IP and turned the actuation off in the BF and F1.
• We leveled the IP by moving the jackes slightly until it was close to the setpoint.

With Hirata-san.

We took pictures of the different markings related to the heights of the mirror and vacuum chamber.

Alledgelly, the one we used to adjust the mirror height on the 16th of September 2021, was the marking made by Aso-san with the legend "Expected Mirror Height 2021.9.16 Aso".

With Hirata-san.

Summary: we measured that the mirror is 0.2 below the expected height is the beam, value consistent with previous measurements.

Pictures can be found in the album SR2 Remedying work after O3.

We corroborated that in the previous measurement we used Aso-san's marking of the expected beam height. Today we were not able to use Tomaru-san's becuase he pasted the sticker at the +Y side of the chamber and we need it at the -Y side, where the RM scratch marks are (HR side of the mirror).

• We set the GAS filters to zero using coil-magnet actuation.
• Then we measured that the RM is 0.2 mm below the expected height of the beam. This value is consistent with the one reported in entry 18282, where 0.15 below is reported.