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Message ID: 9685     Entry time: Mon Mar 3 17:35:10 2014
Author: Koji 
Type: Update 
Category: LSC 
Subject: Various demod phase measurement 

I wanted to check how the refl signals looked like.
I decided to measure the demod phase where PRCL and MICH appear, one by one.

The method I used is to actuate PRCL or MICH at a fixed frequency and rotate the demod phase such that
the signal at the actuating frequency disappears.

For the PRCL actuation, PRM was actuated by the lock-in oscillator with the amplitude of 100cnt.
For MICH, the ITMX and ITMY was actuate at the amplitude of 1000cnt and 1015cnt respectively.

The script I used was something like this

ezcaread C1:LSC-REFL11_PHASE_R
ezcaservo -r C1:CAL-SENSMAT_CARM_REFL11_Q_I_OUTPUT C1:LSC-REFL11_PHASE_R -g 100 -t 60
ezcaread C1:LSC-REFL11_PHASE_R

"11" should be changed according to the PD you want to test.
"Q" should be changed to "I" depending on form which quadrature you want to eliminate the signal

The option "-g" specifies the servo gain. This specifies which slope (up or down) of the sinusoidal curve the signal is locked.
Therefore, it is important to flip the signal angle 180degree if a negative gain is used.


Note: Original phase settings before touching them

REFL11  - 19.2
REFL33   135.4
REFL55    48.0
RELF165 -118.5

 

Here in the measurement PRMI was locked with AS55Q (MICH) and REFL55I (PRCL)


Without no serious reason I injected a peak at 503.1Hz. This peak is not notched out by the servo. There may have been
some residual effect of the feedback loops.

PRCL: By elliminating the peak from the Q quadrature, we optimize the I phase for PRCL.

REFL11,   minimize PRCL in "Q", gain, -1, -19.3659 deg
REFL33,   minimize PRCL in "Q", gain, -1, 132.813 deg
REFL55,   minimize PRCL in "Q", gain, -1, 20.9747 deg
REFL165, minimize PRCL in "Q", gain, -1, -119.004 deg

MICH: By elliminating the peak from the I quadrature, we optimize the Q phase for MICH.
If PRCL and MICH appears at the same phase, the resulting angles shows an identical number.

REFL11,   minimize PRCL in "I", gain, -1, -28.4526 deg
REFL33,   minimize PRCL in "I", gain, -1, 65.9148 deg
REFL55,   minimize PRCL in "I", gain, -1, 12.4051 deg
REFL165, minimize PRCL in "I", gain, -0.1, -143.75 deg


Then, the signal frequency was changed to 675Hz where the notch filters in the servo is active.

PRCL: By elliminating the peak from the Q quadrature, we optimize the I phase for PRCL.

REFL11,   minimize PRCL in "Q", gain, 1, -19.5224 deg
REFL33,   minimize PRCL in "Q", gain, -1, 135.868 deg
REFL55,   minimize PRCL in "Q", gain, 1, 48.5716 deg
REFL165, minimize PRCL in "Q", gain, 1, -122.398 deg

MICH: By elliminating the peak from the I quadrature, we optimize the Q phase for MICH.
If PRCL and MICH appears at the same phase, the resulting angles shows an identical number.

REFL11,   minimize PRCL in "I", gain, -10, -73.7153 deg
REFL33,   minimize PRCL in "I", gain, -10, 135.5 deg
REFL55,   minimize PRCL in "I", gain, 10, -2.55868 deg
REFL165, minimize PRCL in "I", gain, -5, -156.135 deg


 

 

This is just a test of the REFL channels for the arms signals. ETMX or ETMY were actuated.

YARM

REFL11, minimize ETMY in "Q", gain 100 => C1:LSC-REFL11_PHASE_R = 145.694
REFL55, minimize ETMY in "Q", gain 100 => C1:LSC-REFL11_PHASE_R = -60.1512

XARM

REFL11, minimize ETMX in "Q", gain 100 => C1:LSC-REFL11_PHASE_R = 142.365
REFL55, minimize ETMX in "Q", gain 100 => C1:LSC-REFL55_PHASE_R = -68.6521

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