anamaria.effler@LIGO.ORG - posted 13:03, Thursday 04 June 2026 - last comment - 13:19, Tuesday 09 June 2026(90485)
ITM reference positions
Before starting the cage baffle install we took a reference of the optical levers (with ISI locked) such that later when we unlock the quad we can tell if there was a significant shift. NB there were small shifts at LLO when we installed these baffles and we are still baffled as to why. Since they attach to the cage, which is connected to the ISI and the ISI gets rebalanced, it's unclear why they'd shift more than some 20-30 urad.
I took one reference pre-vent, circa Nov 28, when we were still locking full ifo. The second reference is recent, at air, with the ISI locked.
| ITMX | pre-vent | vent, pre-work |
| date | Nov 28 '25 | Jun 3 '26 |
| sliders P,Y | -113, 110 | -35, 94 |
| oplev P | 8 | 0 |
| oplev Y | 6 | 0 |
| oplev sum | 3400 | 3200 |
| ITMY | pre-vent | vent, pre-work |
| date | Nov 28 '25 | Jun 2 '26 |
| sliders P,Y | -14, -18 | -90, -16 |
| oplev P | -30 | 0 |
| oplev Y | -15 | 0 |
| oplev sum | 9000 | 9000 |
After the cage baffle installation we freed the two ITMs and recorded again the sliders that would be required to bring the oplev to 0,0. ISIs still locked.
ITMX: -35 P, 94 Y (same as before) data from Jun 9
ITMY: -240 P, -16 Y data from Jun 5
ITMY shifted some in pitch but it is still within range. Assuming that it will shift back going to vacuum as it did above, then we would end up with some -170 in pitch, which is less than half range and fine to work with.