Shoshana, Arnaud
wp 13430
CRS laser was turned back on. HOQI signals are alive, and CRS is still ringing down at 25mHz (fig 1)
Some convention we implementend :
1) hoqi photodiode signals calibrated in mW with calibration gain (see below) and filter was added to FM1 of the HOQI{1,2}_{SIN,COS,MCOS} filterbanks. A minus sign was added to have positive power at the output of the hoqi filterbanks (fig 2)
[1] PD sensitivity
[2] Transimpendance Amplfier Gain
[3] 16 bit ADC
2) hoqi distance was calibrated as per section 2 in the assembly procedure such that a positive hoqi distance signal corresponds to the retroreflector on the CRS moving away from the sensor. For this, we had to add a -1 gain in the HOQI{1,2}_DIST filterbank (fig 3)
The next two conventions not yet implemented are to match the sign of the CRS with the CPS and get the CRS tilt signal calibrated in nrad (at the CRSINF filterbank)
- urad to nrad calibration was added in the CRSINF_RY filterbank (fig1) so the CRS signal in the HAM3-ISI model is in the same units as the CPS
- The sensor inversion filter was turned on in the CRSRY_THETA filterbank (fig2)
- ISI-CRS damping with the ISI in the isolated state was commissioned and damping is working (fig3, fig4)
- For this we use the RY BLND7 path, with the same CPS/GS13 blnd copied from the BLND4 path, adding the CRS damping (commissioned in alog 90937) in parallel, which acts the same as sending the damping control signal to the error point of the loop.
- The damping took about 30 minutes to get to sub urad of tilt at the 25mHz resonance
- After damping, a first spectra of the HOQIs and CRS tilt was measured, see the pdf attached
- the HOQI noise reaches sub pm/sqrt(Hz) above 10Hz
- the CRS tilt spectrum matches the GS13 tilt between 0.1-1Hz, and the sum channel is below 1e-10rad/sqrt(Hz) above 0.1Hz. The CRS signal shown here is taken after sensor inversion
- another long spectrum is running overnight
- The CRS is moving relative to the frame at a rate of about ~6urad/hour. This drift has been observed previously during pump down.
