TFs between 1)vertical seismic and beat, 2) v seismic and ACAV feedback, and 3) v_seismic and TTFSS feedback are measured. The contribution from vertical seismic to beat signal is mostly from ACAV.
==Setup==
I used frequency response measurement (FFT1/FFT2) to measure frequency response [dB], phase [dB], and coherence between.
- vertical seismic and beat, -> D/A
- Actuator point for ACAV loop -> C/A
- Fast Actuator point, RCAV loop ->B/A (I used a T connector to pull the signal from feedback to NPRO)
The calibration for beat signal[D] is 7kHz/V, for ACAV actuator point [C] is 7kHz/V, for RCAV fast actuator [B] is 3.07 MHz/V, for accelerometer [A] is 1023mV/g (psl:716)
==result==
1)calibrated signal, in the unit of Frequency noise in beat/ acceleration [Hz/ (m/s^2) ]
fig1: calibrated frequency response, with 250 vector avg.
==comments==
The plots show that the seismic contribution in the beat is mostly coupled through ACAV. RCAV is not sensitive to seismic at all, since the coherence is almost zero. We have to open the chamber and fix the ACAV's support. |