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AdV-FLT (Pre-commissioning)
grimaldi, delaurentis, perreca - 15:49 Thursday 23 September 2021 (53246) Print this report
Recover of GR alignment to the FC

This morning we found the Filter cavity unlocked and strongly misaligned.

When we started the recover procedure and we misaligned the FCEM, we found out that the beam was not in center of FCEB_GR_cam ( Figure 1). In order to recover the position we discharge the correction of the BPC loop using the following procedure:

  1. On AFC_Ctrl we turned off Drift controll and BPC controll pushing OFF on VPM interface
  2. After that we Discharge the Correction pushing Corr Disable on both the controller (Figure 2)
  3. Re-enable the correcion pushing Corr Enable on both the controller
  4. Re-enable both the controller

The beam went back in the standard position on FCEB_GR_CAM Figure 3

After that we moved the FCEM at the same posiotion of the begging of the shift and started the prealignment using FCEM and FCIM


  • Figure 1 Beam position at the FCEB_GR_CAM before
  • Figure 2 Discharge of the BPC correction
  • Figure 3 Beam position at the FCEB_GR_CAM after
  • Figure 4 Trend unlock night (yesterday we left around 1:00 CEST)
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guo, vardaro - 18:56 Thursday 23 September 2021 (53249) Print this report

We checked the data of this night during the misalignment of the cavity. The problem was that the drift control of the FCIM was no more enabled. 

When we tested the drift control for the first time we forgot to save some weight in the configuration file. The process was restarted the 22 september at 10:33 UTC and from this date the drift control at FCIM was open (fig 1). Before this event was ok see fig 2.  We restored it.

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