KAGRA Logbook

VIS (OMM)

yoichi.aso - 15:31 Thursday 14 November 2024 (31633)

OMMT1 recovery work

Takahashi, Tanaka, Uchiyama, Aso

What we did.

Released the OMMT1 IM by benting the rods holding the damping cage.
Checked the OSEMs: not seem to touch anywhere
Checked the beam at the OFI: largely shifted in Yaw.
By rotating the Yaw picomotor of OMMT1, moved the beam spot on the OFI to be centered.
Checked the OMMT2 trans QPD: nearly centered.
Adjusted the OMMT1 picos to center the OMMT2 trans QPD.
The OMC QPDs had beams inside at this point.
Adjusted the OMMT2/OSTM picos to center the OMC QPDs.
Checked the OMMT1 and OSTM damping magnets: fine.
Ran the health check of OMMT1 and OSTM (to be reported separately): fine

Note: we did not remove the black panels because we were able to check OSEMs even with the panel.

Comments to this report:

ryutaro.takahashi - 17:03 Thursday 14 November 2024 (31635)

The attached pictures show releasing the IM. The TFs of H1 and H4 OSEMs show that the mode Qs decreased due to recovered damping. The H3 OSEM went into the range a little. The H2 OSEM has large glitches.

Images attached to this comment

ryutaro.takahashi - 8:12 Saturday 16 November 2024 (31659)

(Log on 14th)

I investigated the glitches (Fig.1) in the H2 OSEM of the OMMT1 suspension. When the D-sub cable was disconnected from the feedthrough, the glitches disappeared. The LED's voltage drop in forward bias decreased.

	7/10	11/14
1-6: PD	0.704V	0.710V
2-7: LED	1.191V	0.954V
3-8: Coil	16.8Ω	16.2Ω

I found the shield lines in the D-sub cables for H2 and H3 disconnected from the satellite box (arrows in Fig.2). Connecting the shield lines reduced the high-frequency noises (Fig.3), but the glitches did not disappear.

Images attached to this comment