The WFS demod phases were adjusted this afternoon. The WFS loops were successfully closed.

This was needed because the RF phase rotated for some reason a week ago (see alog 7181).

The new demod settings :

H1:IMC-WFS_A_SEG1_PHASE_R = -90
H1:IMC-WFS_A_SEG2_PHASE_R = -17
H1:IMC-WFS_A_SEG3_PHASE_R = -27
H1:IMC-WFS_A_SEG4_PHASE_R = 22
 

H1:IMC-WFS_B_SEG1_PHASE_R = 15
H1:IMC-WFS_B_SEG2_PHASE_R = -34
H1:IMC-WFS_B_SEG3_PHASE_R = 28.5
H1:IMC-WFS_B_SEG4_PHASE_R = -81

The adjustment :

As usual I hooked up a function generator to EXC_A of the IMC servo board at the floor to excite the longitudinal signal. I set it to be 6 Hz and 4 Vp-p. I had to put such a big signal because the IMC locking loop had a big gain at around this frequency. Looking at diaggui I rotated the demod phases so that a peak at the excitation frequency in the Q signals becomes as small as possible. Roughly speaking all of them needed to be rotated by 95 degrees. This is consistent with what I saw in the length signal (see alog 7181). By the way I took a look at the length demod signal and confirmed that the RF phase stayed the same.

Notes on the control loops :

I enabled FM1, which is a 10 dB flat gain, in all six degrees of freedom. These are the ones we disabled in order to empirically avoid an oscillation at around 0.1 Hz when we were adjusting the demod phase on July 18th (which was not alogged unfortunately). A current screenshot of the IMC WFS control is attached. Besides the demod phases and FM1, everything stays the same. After all these settings I ran /opt/rtcds/userapps/release/ioo/h1/scripts/imc/mcwfsrelieve to offload the control signals to the static offset in H1IMC-MCX_PIT where X can be 1, 2 or 3.