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Entry  Thu Apr 18 02:24:58 2013, Den, Update, ASC, dither alignment of yarm OL.pngdither_yarm.pngYARM_CTRL_DITHER.pdfTRY_DITHER.pdf
    Reply  Fri Apr 19 13:28:39 2013, Den, Update, ASC, dither alignment of yarm 
Message ID: 8465     Entry time: Fri Apr 19 13:28:39 2013     In reply to: 8459
Author: Den 
Type: Update 
Category: ASC 
Subject: dither alignment of yarm 

I've put 4 scripts into ASS directory for YARM alignment. They should be called from !Scripts YARM button on c1ass main medm screen.

Scripts configure the servo to align the cavity and then save computed offsets. If everything goes right, no tuning of the servo is needed.

Call TRANS MON script to monitor YARM transmission, then "ON" script for aligning the cavity, then "SAVE OFFSETS" and "OFF" for turning the servo off.

ON script:

  • sets demodulation gains that I used during OL measuments
  • sets LO oscillator frequency and amplitude for each optic
  • sets demodulation phase rotation
  • sets sensing matrix
  • sets servo gains for each degree of freedom
  • sets up limits for servo outputs
  • gently increases the common gain from 0 to 1

SAVE OFFSETS script:

  • holds servo outputs
  • sets servo common gain to 0 and clears outputs
  • reads old optics DC offsets
  • computes new DC offsets
  • writes new offsets to C1:SUS-OPTIC_ANGLE_OFFSET channel
  • holds off servo outputs

OFF script:

  • sets LO amplitudes to 0
  • blocks servo outputs

Notes:

SAVE OFFSET script writes DC offsets to C1:OPTIC_ANGLE_OFFSET channel, not to _COMM channel!

LIMITS are set to 500 for cavity axis degrees of freedom and to 0.5 for input steering. Usually servo outputs is ~30% if these numbers. But if something goes wrong, check this for saturation.

DC offsets of all 8 degrees of freedom are written one by one but the whole offset of put at the same time. This works fine so far, but we might change it to ezcastep in future.

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