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EleonoraCapocasa - 18:43, Tuesday 10 July 2018 (875)Get code to link to this report
Rampeauto noise reduction

[Eleonora, Matteo B.]

We have measured the rampeuto PZT output noise by connecting the PZT output to the spectrum analyzer. It is about 2 uV/sqrt(Hz) at low frequency and it starts to decrease above 5 kHz, as can be seen from pic 1 (blue curve) 

We also observed with the oscilloscope that there is an offset of -10mV. (pic 2).

In order to reduce the rampeauto output noise, following the advice of Pierre, we have disconnected the ramp input (which normaly is not used for suspended cavities). (pic 3) 

The output noise has been reduced by a factor 3 and now  it is about 800 nV/sqrt(Hz),  below 5 kHz.  (see pic. 1 and 4)

In pic 5,  we have compared the rampeauto noise (actuation noise)  with the free running laser noise and found that it becomes dominant above 2 kHz.

For the conversion to Hz we used a piezo gain of 2 MHz/V, as measeured in entry  #859.

The next step is to re-measure the phase noise, as done in entry #863, with this new configuration.

Images attached to this report
875_20180710112527_pl1.png 875_20180710112640_offset.jpg 875_20180710113359_ramp.jpg 875_20180710114558_plot2.png 875_20180710114606_plcf3.png
Comments related to this report
YuhangZhao - 11:37, Friday 13 July 2018 (883)

We compare the green error signal spectrum before and after the disconnection of Ramp injection point in the circuit. We can see the noise level is reduced by a factor up to 3 from 2kHz.