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MIF (General)
tomotada.akutsu - 22:13 Tuesday 06 July 2021 (17407) Print this report
Trial of GreenX reflection from Xend Day2 AM: Green reflected from ITMX

Ushiba, Miyo, Akutsu: Continued from 17398.

Abstract

The reflected green beam from ITMX reached the POP table. The GrRFPD and the relevant optics were re-located to bring the green beam to the GrRFPD.

Details

Further more details on how the ITMX suspension was aligned will be reported by Ushiba-kun, so my report is a kind of overall report and on the optics.

After Ushiba-kun succeeded to let the green beam reflected at ITMX get out from the GV window (in-between BS and IXC), the beam happyily came back near the input point at PR2 (Fig. 1), and made a spot near the input aperture of the Faraday isolator (FI) already. So we tele-communicated each other to bring the beam go through the FI. Then I noticed that the beam from the FI missed the first steering mirror. After several consideration, I determined my mind to relocate this steering mirror (1inch), the following lens (1inch), and the GrRFPD.

Then the beam on the GrRFPD was aligned by the steering mirror while looking at the DC signal (Figs. 2 and 3).

Notes

  • During the relocation of the optics, I could not avoid touching the optical fiber several times, unfortunately. Please check the FNC.
  • The beam dump to catch ghost beams from GrRFPD (and some ghost beams from FI itself.. they can be removed by locating an iris diaphragm, maybe) was just tentatively located with its magnet foot. I did not fix it by a proper folk. Sorry.
  • Maybe need to modify the RF phase when the Green cavity will be needed, as I may change the optical axis length to the GrRFPD.
  • There are many unused (? I cannot know, but it seems no green beams were hit) optics and parts. They may be better to be removed for improving noise, if necessary.
  • Maybe a serious problem: the reflected beam from th FI was tilted in pitch. The beam is illuminating the upper side of the 1 inch steering mirror, so I tried to put the 1 inch mirror as close as possible to the FI. This point needs to be revisited.... hope this is not a sad destructive problem.

 

Images attached to this report
Comments to this report:
takafumi.ushiba - 22:48 Tuesday 06 July 2021 (17411) Print this report

Details of our work.

1. Remove the white covers and aluminum foils from PR2 and BS chambers to send the green beam at Xend.
2. See the signal of PDA placed at EXA chamber and confirm the alignment to Xend is good.
3. Enter IXC and align the ITMX YAW inclination by BF picomotors while seeing the reflection beam at the viewport on the gate valve near BS (roughly 20000 steps to -YAW direction).
4. Drive the moving mass on MN for aligning the PIT inclination while seeing the beam at the same viewport (about 50 steps to -PIT direction).
5. Pass the green beam to Akutsu-san and align the POP table.

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