sophie.muusse@LIGO.ORG - posted 12:04, Wednesday 28 January 2026 (88946)
CHETA Update
S. Muusse, M. Todd
Lens realigned on X-arm CHETA table for corrected focal lengths and the beam profiled which had better agreement with the model. ITM beam size from fit are much closer to ideal beamsize on ITM (≈ 52.7mm).
- Model was updated to use measured L1 focal length replacing manufactorer spec which was given for 588nm.
- Lens were repositioned based on the updated model
- Beam was profiled after L2 and used to fit q-parameters (attached). This was completed using a non-linear fit where M2 was fixed to 1
- Modelled beam parameters are just outside of the uncertainty bounds on the fit. We are suspicious of higher order mode contibutions effecting our fit especially in the vertical axis.
- Beam profiler is being shipped to LLO
Fit for profile after L2 vs model
| Fit | Model | |
| w0x,w0y [um] | [970.5 ± 28.7, 940.8 ± 23.3] | [1023.9, 981.71] |
| z0x,z0y [mm] | [-1078.1 ± 32.0, -901.9 ± 22.5] | [1.046 , 0.928 ] |
| qx [mm] | 1.078 ± 32.0 + 0.643 ± 38j | 1.046 + 0.708j |
| qy [mm] | 0.902 ± 22.5 + 0.604 ± 30j | 0.928 + 0.651j |
| Beam radii at ITM [mm] | [54.442, 55.885] | [52.311, 54.385] |
Beam radii at ITM is foudnfrom fit by propagating the fit q to the ITM.
Images attached to this report
