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fabian.arellano - 12:36 Thursday 22 October 2020 (15305) Print this report
Comment to SRM recovery after pump down (8672)

Yesterday 21st of October 2020 I checked the BF condition again.

Some conditions and what I did:

  • Suspension in NEUTRAL mode.
  • Current keystone nominal position 100 um.
  • I moved the keystone down using coil-magnet actuation in the test channel.
  • I measured BF transfer functions in some positions.

What I found, see the picture:

  • When the keystone is at 50 um an oscillation at about 40 mHz appears with a small amplitude.
  • As the kestone keeps going down the oscillation increases.
  • I measured the BF transfer function three times, and the only healthy one is the one with the keystone above 100 um.

What this suggests:

  • The problem doesn't seem to be a hard physical stop. The keystone is always moving.
  • I tend to think a cable pulling is producing coupling with another body.
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