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dan.chen - 12:42 Friday 04 July 2025 (34460) Print this report
ETMX IP Offload

With Takahumi USHIBA

Purpose and Overview

  • Due to tidal motion, an offset gradually accumulates in the feedback signal applied to the IP (Inverted Pendulum).
  • The purpose of this work was to offload this offset before the IP feedback signal saturates.
  • Because there is LPY coupling, the offloading causes a drift in the PY alignment of ETMX. Therefore, after offloading, the PY alignment was manually adjusted to maximize the green transmission, and the good oplev setpoints were updated accordingly.

Procedure

  1. Request RESET_ASC_FEEDBACK and DOWN to LSC_LOCK
    This was necessary to correct the alignment and set all suspensions to LOCK_ACQUISITION.
  2. Monitoring TM Oplev and Green Transmission
    TM oplev signals and green transmission were monitored during the procedure.
  3. ETMX-IP-ISC2LVDT Filter Bank
    Opened the filter bank of ETMX-IP-ISC2LVDT.
    The objective was to bring the output signal to zero.
    Set the ramp time to 100 seconds.
    Set the gain to 0.
    Waited for 100 seconds.
    Observed that the green transmission decreased (flash level dropped to around 0.4), which was too low for locking.
    Pressed Clear History.
    Restored the ramp time to 3 seconds.
    Restored the gain to 1.
  4. Recovery of Green Transmission by Adjusting TM Oplev Setpoints
    Manually adjusted TM oplev setpoints referencing the green transmission value.
    After adjustment, the green transmission recovered to approximately 0.9.
  5. Updating Good Oplev Setpoints
    Updated oplev setpoints to reflect the adjustments made during this work today:
    Pitch: 37.2 → 39.1
    Yaw: –9.26 → –1.76
  6. Lock Trial
    Performed a lock acquisition trial.
    Successfully achieved lock.
Comments to this report:
dan.chen - 16:17 Friday 11 July 2025 (34525) Print this report

Date: 2025/7/11

I performed this work as a weekly work.

Attached figure is a screen-shot just after the work.

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