[This entry is being fixed, it's not done yet]
I measured the TF between accelerometer/seismometer and shadow sensing signal. To see if we can measure any resonance peaks of the suspension or not.
The result does not look clear, except a peak at 22 Hz.
The frequency range for accelerometer is 0.1 Hz -1kHz, so we can measure the seismic up to high frequency
1) noise from shadow sensing: FFT of the signal from RFPD. No driving force on the table.
I sent the HeNe beam along the cavity axis. The spring surrounded the cavity blocked part of the beam when
the cavity moves, so the power falling on the PD changes.
Unfortunately, the measurement will include all kinds of motion, vertical/horizontal translational motion, pitch/ yaw, roll, but this was the best I can setup
without opening the vacuum chamber.
2) TF between ref) acceleration in vertical direction, resp) shadow sensing tech. When the table is driven by the PZT, integration cycle= 75. settling cycle = 10, and not driven.
I'll try to measure the TF between seismic and beat directly.