Angular Sensing and Control (Oct, 2022)
WFS ports
REFL (17, 45 MHz)
- Optical layout
- PZT1, PZT2, and REFL_WFS picomotors are available to center the beam on REFL_WFS1 and REFL_WFS2
- Phasing is done by Kenta
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
- Phasing is done by Kenta
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
- Phasing is done by Kenta in June
DC QPD ports
TMSX
There is only QPD2 (K1:TMS-X_IR_QPDA2_{PIT,YAW} ) on the TMSX in-air path. At a random Gouy phase position.
- The beam was sent to the QPD2 when the X-arm is locked, but the X-arm alignment may have changed since then.
- TMSX in-air table power budget
- The in-air beam is extremely astigmatic
- There are strong PIT-YAW coupling depending on the position of the beam
- Matteo-san's previous measurement did not show a strong coupling. It seems to depend on the position of the DC QPDs.
- Is the TMSX in-air beam clipped in the TMS in-vac?
TMSY
- TMSY QPD1 and 2 are placed on the TMSY in-air table, with 90 degrees separated in Gouy phase
QPD1 is used to the beam position control feeding back to the BS (K1:ASC-DOF1_{P,Y} )
- Beam profile
- No PIT-YAW coupling
POP Forward
- There are two DC QPDs on POP Forward, used for the initial alignment
K1:ASC-POP_FORWARD_QPDA1_DC_{PIT,YAW}
They can be found on sitemap > ASC overview > All DC QPDs
DC PDs
- There are POP_P and POP_S DC PDs on POP.
K1:LSC-POP_S{P}POL_DC
- Can anyone add them on an MEDM screen somewhere?
WFS Commissioning
WFS DC centering
General
- Beam spots on the quadrant diodes must be centered (DC centering)
- If the beam is off from the WFSs, use the picomotors first because the PZT ranges are not large
K1:ASC-DC{5,6,7}_{P,Y} are to be used for the WFS DC centering loops
REFL
- Open the REFL shutter first for REFL WFS
K1:ASC-DC5_{P,Y} are used for the DC centering controls
- FM filters:
- Gains: null (gain of 0) and Gain(UGF40)
- LPF: p1 (pole at 1 Hz)
- Integrator: p0:z1 (pole at 0 Hz, zero at 1 Hz) - turn this on after the LPF
- FM filters:
POP
- DC control loop not implemented yet
AS
- DC control loop not implemented yet
Single Y arm
- Sensing matrix
- Input matrix
- Output matrix
K1:ASC-DSOFT_{P,Y} to IY
K1:ASC-DHARD_{P,Y} to EY
- Loops closed
- 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
- Koyama-kun's simulation GUI tool is available on the workstations
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.