This morning, we have moved the IMC cavity axis vertically in translation in order to zero the IMMT trans QPDs.

Consequently, the normalized IMC transmitted light reduced from 1.5 to 1.0.

We will be running the IMC like this until further notice.

[PR2 spot is too low]

Yuta and his company noticed yesterday that the IR beam on the PR2 mirror is too low with respect to the mirror center by a cm or so. We then checked the input optics (i.e., IMMTs) but they seemed fine in the sense that they were within a few 10 urad as seen by the optical lever. So we suspected that something is wrong with the IMC pointing.

[Translating the IMC cavity axis]

Initially both IMMT1 trans QPDs read normalized pitch value of -0.5. Remember that, even though we have two QPDs as IMMT1 trans, they are not separated in the Gouy phase (3688). This means that they carry the identical information about the beam pointing. So it is not easy to tell whether it is a tilt misalignment or that for translation. So for now, we have moved the IMC eigen axis vertically to translate it up. Initially the pitch readout for both QPDs were about -0.5 and now they are almost zero.

To do this movement, we changed the MCe pitch bias slider from -1850 counts to 9781.5 counts.

However, the effect on the PR2 spot position didn't seem to have moved by this action.

Also, remember that the PR2 vertical position is currently not controlled at all (3938). Qualitatively, the miscentering on the PR2 can be explained by this vertical effect.

[k1imcasc is having a Dolphine  issue]

Therefore one can not see the IMMT1 trans signals on this machine. Perhaps it is related to this timing issue (4050). Sad.