[Kamiizumi, Aoumi, YamaT]
 

Abstract

This is series work of
klog#24725 (IY), klog#24726 (IX), klog#24919 (EY), klog#25011 (EX),
klog#24916 (BS),
klog#25009 (PR2), and klog#25886 (PR3).
We measured DAC noise of TM and IM coil out for SR3.
One and two stages of dewhitening filter are enough in order to avoid DAC noise limit for TM and IM stage, respectively.
 
 

Details

Differences from measurements in the case of Type-A
Measurement procedure is based on klog#24725 (IY).
Different points from Type-A case are that a satellite box is used also for TM and satellite boxes are installed mini rack far from DGS rack at 2nd floor of clean booth.
So we measured noise level of TM coil out at a monitor port of satellite box (this is same configuration as IM and MN of Type-A).
And also 30m cable is used to pick up the coil out at ADC in the DGS rack.
(According to the measured ASD, there seems to be no problem related to a cable oscillation due to long cable.)

Measurement results
For TM (Fig.1-4), though I failed on saving file for the case of coil out measurement without dewhitening filter stages,
we can see the removal of peaks around 130Hz, 260Hz, structure around 650Hz, etc. on the noise at AI output by enabling 1 dewhitening filter stage.
And also there is no improvement by 2nd and 3rd stages of dewhitening filter.

Also for IMV (Fig.5-7) and IMH (Fig.8-10), peaks around 130Hz, 260Hz, structure around 650Hz etc can be seen on AI output.
They are removed by enabling two stages of dewhitening filters (for IM, two dewhitening filters always turned ON during lock acq).
We cannot see the improvement by enabling three stages of dewhitening filters.
So two stages of dewhitening filter seems to be enough as current nominal configuration.