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fabian.arellano - 17:57 Wednesday 21 April 2021 (16529) Print this report
Comment to Setting the mirror to nominal height (16521)

With Hirata-san.

See pictures in album PR3 Remedying Work.

  • We measured the height of the mirror assembly when the SF was at nominal height per the 3D-CAD (65.5 mm from base plate) and the BF was at the setpoint given in the medm screen.
    • The laser level was at the nominal height of the mirror.
    • -Y side picture: approximately 2.7 mm below nominal (by visual inspection with ruler).
    • +Y side picture: approximately 1.7 mm below nominal.
    • Note there is certain amount of roll revealed by the 1 mm difference between the two sides.
  • The mirror has scribe marks on the cylindrical part showing the vertical mid-plane. One of them seemed to be below the laser level by the same amount as the mark in the RM, but it was impossible to check with a ruler. 
  • We also used the vernier calliper the size of the buoyancy correction in the SF by setting the keystone in the positions it was before and after the venting according to entry 16445. We did it because we were not sure whether there had been any problem with the LVDT card. We measured 460 µm and the measured LVDT value was 585 µm, which is close enough taking into account possible errors in measuring with the calliper today.
  • Then we moved the SF keystone up with the fishing rod until the mirror asembly was at the nominal height (see pictures of the day in the album):
    • The fishing rod reached its upper limit. See this picture, which is also attached to this report. This is a very inconvenient situation.
    • Additionally, the keystone has to move even further up in order to take into account the buoyancy correction
    • The temperature now is 24.7 °C, which is very high compared to the O3GK temperature 23.2 °C (entry 15816).

The last item suggests we need to move the fishing rod to mid-range and remove mass from the top of the BF to allow the SF go up to the suitable height. However, in order to assess the situation better we require to have the O3GK temperature. Now it's 1.5 °C higher.

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