KAGRA Logbook

AOS (Beam Reducing Telescopes)

matteo.leonardi - 19:48 Monday 28 March 2022 (20263)

Alignment of IR QPD on TMSX

[Akutsu, Matteo, Ushiba]

After recovery work of IR Xarm (klog #20265), we went to Xend to center the IR QPD on TMS-X. Note that QPDA1 is currently not aligned so should not be considered. The good one is QPDA2.
The alignment was performed by using the QPD's translation stages.

After alignment of QPD was done, thanks to Ushiba-san, the IR Xarm was better aligned using the dithering system, This allowed for longer lock which allowed a good power spectrum measurement of K1:TMS-X_IR_QPDA2_PIT_OUT_DQ and K1:TMS-X_IR_QPDA2_YAW_OUT_DQ. The spectra can be seen in attached fig1 and are saved in /users/Commissioning/data/AOS/2022/0328/TMS-X_IR_QPDA2.xml

In the spectra are visible several peaks identified as ITMX and ETMX dithering lines and suspension resonances.
In the following table the values of several of them with computed coupling. The PIT2YAW coupling seems to be between 2.3% to 2.5% while the YAW2PIT coupling ranges from 1.8% to 2.7%.

Frequency [Hz]	K1:TMS-X_IR_QPDA2_PIT_OUT_DQ	K1:TMS-X_IR_QPDA2_YAW_OUT_DQ	PIT/YAW (YAW/PIT)
4.1 (ITMX_YAW)	0.00556256	0.240299	0.023 (43.2)
4.6 (ETMX_YAW)	0.00275301	0.11041	0.025 (40.1)
6.1 (ITMX_PIT)	0.11084	0.00269066	41.2 (0.024)
6.6 (ETMX_PIT)	0.102501	0.00186367	55 (0.018)
7.4375	0.0612188	0.00163421	37.5 (0.027)

Images attached to this report

20263_1648462910_TSM-X_IR_QPDA2_(PIT,YAW)_OUT_DQ.png

Comments to this report:

hirose.chiaki - 22:31 Tuesday 27 September 2022 (22221)

Kokeyama-san, Hirose

We checked PIT YAW coupling of IR QPD on TMSX, with ITMX PIT moving 1Hz and placing QPD2 roughly.

ITMX PIT movement was clearly detected from the graphs for both when placed far and near to lens2.→x_far_lens.png, x_near_lens.png
(../../users/Commissioning/data/ASC/2022/TMSX/BeamProfile/20220927/beam_shake_x_{far,near}_lens.xml)

＊＊＊＊＊＊＊

For the QPD installation for the Xarm ASC, we measured beam profile of TMSX IR.

We need to separate two QPDs by more than gouy phase 90 degrees in order to separate DoF (shift and tilt) of ASC,

but it looks like we can separate them (although the distance is far). →TMS_IR_beamprofile_gouy.png

Images attached to this comment

keiko.kokeyama - 10:46 Wednesday 28 September 2022 (22228)

Here are the CCD movies at TMSX when ITMX was shaken at 0.1 Hz. The first movie was taken just after the second lens (RLNS2). The second movie is around the X axis's waist (z~1000, with z=0 at RLNS2). The last movie is at around z=1500. At the far field (z=1500). It shows pitch-and-yaw coupled motion. We'll check if this PY coupling is seen by the QPD at a far field or not. If not, we'll leave the beam as is and install the two QPDs with 90 deg Gouy phase separated, or if two QPD positions with 90 deg Gouy phase separated without PY coupling. We'll investigate the beam more if not.

[Hirose, Kokeyama, Remote Ushiba]

Images attached to this comment

hirose.chiaki - 22:24 Monday 03 October 2022 (22315)

[Terri, Keiko, Chiaki]

We measured the PITYAW coupling at a place near Y waist.

QPD2 position is showen 22310.

result : 20221003_beam_so_far_result.png (../../users/Commissioning/data/ASC/2022/TMSX/BeamProfile/20221003/beam_shake_x_so_far_lens.xml)

This is the result when ITM is moved to 0.1Hz in the PIT direction.

The PITYAW coupling at this location is larger than the results at the previous measurement location.

According to Keiko's last movie(22228), we think it is because the beam is elliptical and an arc.

Images attached to this comment