Angular Sensing and Control (Oct, 2022)

WFS ports

REFL (17, 45 MHz)

• Optical layout

  • https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=9238

  • Same as O3GK
• PZT1, PZT2, and REFL_WFS picomotors are available to center the beam on REFL_WFS1 and REFL_WFS2

POP (17, 45 MHz)

• Optical layout

  • https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=9623

  • POP WFSs were newly installed after O3GK
• POP-S and POP-P cameras are available

AS (17, 28 MHz)

• Optical layout

  • https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=9817

  • Mostly same as O3GK
• PZT1, PZT2, and AS_WFS picomotors are available to center the beam on AS_WFS1 and AS_WFS2
• AS and OMC_TRANS CCDs are available
• OMC_REFL CCD hasn't been connected

DC QPD ports

TMSY

• TMSY QPD1 and 2 are placed on the TMSY in-air table, with 90 degrees separated in Gouy phase
• QPD1 is used to steer the beam from BS (ASC DOF1 is the TMSY QPD loop feeding back to the BS)
• Beam profile

  • https://klog.icrr.u-tokyo.ac.jp/osl/?r=22479

• No PIT-YAW coupling

  • https://klog.icrr.u-tokyo.ac.jp/osl/?r=22575

TMSX

• There is only one DC QPD installed on the TMSX in-air path. At a random Gouy phase position.
• The beam is NOT centered on the DC QPD when the X-arm is locked, but the X-arm alignment may have changed since then.
• TMSX in-air table power budget

  • https://klog.icrr.u-tokyo.ac.jp/osl/?r=22310

• The in-air beam is extremely astigmatic

  • https://klog.icrr.u-tokyo.ac.jp/osl/?r=22221

• There are strong PIT-YAW coupling depending on the position of the beam

  • https://klog.icrr.u-tokyo.ac.jp/osl/?r=22228

  • Matteo-san's previous measurement did not show a strong coupling. It seems to depend on the position of the DC QPDs.

    • https://klog.icrr.u-tokyo.ac.jp/osl/?r=20263

POP Forward

• There are two DC QPDs on POP Forward, used for the initial alignment

DC PDs

• There are POP_P and POP_S DC PDs on POP.

WFS Commissioning

WFS DC centering

• Open the REFL shutter for REFL WFS
• Beam spots on the quadrant diodes must be centered (DC centering)
  • PZTs and picomotors are available

Single Y arm

• Sensing matrix

  • https://klog.icrr.u-tokyo.ac.jp/osl/?r=22578

• Input matrix

  • https://klog.icrr.u-tokyo.ac.jp/osl/?r=22602

• Loops closed

  • https://klog.icrr.u-tokyo.ac.jp/osl/?r=22671

  • DSOFT is IY, DHARD is EY
• Loops or noise haven't been characterized
• No offsets were necessary on the sensors

Single X arm

PRMI

PRFPMI

DRFPMI

Next Steps

Infrastructure

• Guardian implementation
  • DC centering loops on REFL, POP, and AS
  • Single Y, X arms, and PRMI guardstates for initial alignment
• Add trigger for the main ASC switch (K1:ASC-WFS_GAIN) similarly to the IMC switch (K1:IMC-WFS_GAIN)

Simulation

• Compare the measured sensing matrices against the simulation
  • Koyama-kun's simulation GUI tool is available on the workstations

    • sitemap > Commissioning Top > finesse GUI

Integration

• Implement single-Y, single-X, and PRMI controls for the initial alignment
  • If the alignment is too off, first ADS then WFS control?
• PRFPMI/DRFPMI angular controls
• Noise budget

Known issues

• TMSX PIT-YAW coupling
  • The beam is slightly not centered in yaw on the second lens on the in-air table. Adjusting the beam position on the lens might fix the problem.