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MIF (General)
kouseki.miyo - 23:38 Thursday 12 October 2017 (3500) Print this report
Reflection beam from PR2 is inclined about 2-30 mrad
Arai, Enomoto, Kaji, Nakano, Izumi, Kokeyama, Miyo

Today, we hit the beam at the center of the PR2 mirror, but we found a problem that pit angle of the reflection beam from PR2 is inclined about 20 mrad against the direction from PR2 to PR3 mirror .
 
[ Reduction of the beam jitter caused by the KOCH filter for the IMMT ]
  • First, we rotate the PR2 mirror -600 mrad gradually using the traverser with python script (/kagra/Dropbox/Persopnal/miyo/script/Traverser/cont_serial.py) by referring [klog:581]. 
  • After that, we saw that the reflection beam from the PR2 is moved from left side of the duct wall to around the left side of PR3 EQ stop flame. It means rotation of the beam was clockwise.
  • We guess that the sign of the rotation defined on this script was the opposite compared with the actual rotation. Was this happened by the script bug? Beam was not a 0th beam? Did we just saw multiple reflection beam in duct? 
  • However, anyway, we could not confirm the position precisely because of the beam jitter.
  • After we covered the flange of the IMMT1,2 chamber with Alumi-foil, RMS of the Oplev signal in each the IMMT1 and IMMT2 was reduced  [immt1.png,immt2.png], and beam jitter at front of the PR2 mirror is quiet effectively! We had a lunch with a happy mood...smiley

 
[ Inclination of the beam from PR2 problem ]
  • After lunch, we found beam from IMMT2 is not in the center of the PR2 mirror, so that, we re-align the IMMT1 and 2 mirror to hit the beam at the center of  PR2 and IMMT2 mirror. 
  • However pit angle of the reflection beam spot from PR2 on the screen which is putted 1m distance from front of the PR2 mirror was differed  about 2-3 cm compared with the incident beam spot from IMMT2 to PR2. it's about 2-30 mrad incination... frown
  • To compensate this beam inclination, we moved the moving mass on the IM of PR2 using picomotor with joystick a lot, but we could not recognize motion as long as we see the reflection beam from PR2 to PR3. Later, Enomoto-kun found that pit was rotated [ pr2impit.png ] .  
  • We asked shoda-san in Mitaka whether we should compensate this inclination using IM picomotor more or not. 
  • We conclude that it was necessary to organize the situation in all participants. Therefore we interrupted work and opened a commissioning meeting. Meeting log is written in japanese [log]
 
Tomorrow,

  • To distinguish whether this problem is caused by the inclination of the PR2 mirror or incident beam from IMMT, we can check the inclination using PR2 oplev for now.yes

 

 

 

 

Comments to this report:
kouseki.miyo - 9:14 Friday 13 October 2017 (3501) Print this report
ayaka.shoda - 11:49 Friday 13 October 2017 (3502) Print this report

Hmmm... it is strange that the Traverser is not working in the right direction.
When we checked the Traverser actuation during the installation, the sign of the actuation direction is as shown in the attached figure.

If we still have problem with the beaming, it would be better to open the tank and check the rotation by eyes.

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