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MIF (General)
masayuki.nakano - 22:35 Wednesday 06 April 2016 (1383) Print this report
OUR IFO CAME BACK!!

[Michimura, Akutsu, Shoda, Enomoto, Miyo, Nakano]

The beam from both end mirrors get back to REFL DC PD!

Luckily we could get IFO situation back within half a day, but it was just a chance. This accident was so serious and we have to consider the counter-plans never to make such mistake again.

Procedure

1. Check spot positions on IMMTs

First of all, we checked the beam position on IMMT1 and IMMT2 to make sure which mirror was misaligned. 400mm flanges of IMMT and IFI chambers were opened, and Akutsu-san checked by sensor card that the beam hit roughly center. The both flange remained open and covered with alminum foil.
 As yesterday's klog, we know the beam doesn't hit the PR2 mirror. So we decided to move the IMMT2 by pico motor.

 2. Aligned the IMMT2

 The IMMT2 was aligned with using PR2 camera as reference. The reference picture is the one of Kokeyama-san posted. The attached picture is the screenshot of the PR2 camera after aligning. We also checked the cameras of EX and EY, and tiny slay light appeared.

 3.aligned the PR3 and EX

 PR3 and EX was aligned with EX-TRANS camera and REFL-DC-PD. The DCPD count from EX was around 1100 after aligning of both mirrors. It was same level as the highest count in previous day, so there would not be any clip after the accidents. At this point, the steering mirror for DCPD was moved because the beam cliped on the mirror. We are not sure that it is because of the accident. The oplev dump was disabled during alignment, so I turned on those of two suspensions.

 4. aligned the BS and EY

BS and EY were aligned as same as PR3 and EY. The DCPD count from EY was around 3100. It is also comparable as past data, even better!
Images attached to this report
Comments to this report:
tomotada.akutsu - 4:12 Thursday 07 April 2016 (1391) Print this report

The remaining concrens around this topic are:

(1) I guess a picomotor driver has been still connected to the IMMT2. It would be better to be removed by certified persons I could point.

(2) The 400-mm flanges at the IMM and IFI chambers has not been closed by vacuum compatible lids; they are now covered by aluminum foils. We need to carefully decide how should we do around here. Keeping the aluminum foil envlosures would be ok but you need to be sure that the O-rings will not come off during the 2nd test run. In my opinion, we can close here by vacuum compatible lids if we can successfully work with each other; the workers around the chamber and the Mozumi control room keep in touch (literally) by phones or something, and check what was/is happening on the optical axis during the closing. If the Mozumi worker would feel something wrong, the worker should stop all the works in the tunnel. In my observation, the researchers misunderstand that they have the right to determine what can be done by them, but now we have "daily commisioning leader" system, so just obey what the leader determines (except for severe accidents; don't forget that every worker in the tunnel is given a right to stop every work if the one feels it would become dangerous).  Without controlling the situation at once by a tetative dictator, this kind of a large equipment cannot be operated well.

----

Another concern that is still not solved is the reason why this mis-alignment had happend. In this time, tuning the picomotors on the IMMT2 resolved this issue, but the modified angle of the tilt of the optical axis is in the order of 1.2 mrad in vertical, which means the IMMT2 would be re-aligned 0.6 mrad in vertical (the angle of optical reflection will make the tilt twice). Could this amount of tilt be realistically achievable by fixing the bellows feet of the IFI chamber? Bluntly put, about 0.7 mm height difference had happened because of the fixing (assuming the diameter of the IFI chamber be 1200 mm). We need to have a concrete and quantitative discussion on this issue.

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