Today the TCS ISS box was modified, the resulting transfer function was measured, and we began to set up the box in the experiment.

Setup:

I used LISO to design two additional op amp stages and soldered in the necessary components. I attached the updated pdf for the schematic.

TF Measurements:

The transfer function for the four total op amp stages is shown below:

The transfer functions for the two individually added stages are shown below:

Thankfully all of the measured transfer functions seem to match up nicely with those generated with LISO.

The transfer function for the entire box (not just filter stages) is:

So, there isn't really much else contributing to the transfer function than the four filter stages.

Implementation of ISS Box:

We then proceeded to hook up the box to suppress RCAV RIN. The eaom was used as the actuator, and we used to pd's as in loop and out of loop sensors. We found out that the input signal to the ISS box needs to be AC coupled, which the pd signal is not. As a quick fix, we used an SR560 set to AC coupling between the pd signal measuring intensity noise and the servo. A more carefully constructed component will have to added in order to fix this, so ill have to think about this. 

The following plot shows the results for the free intensity noise vs the suppressed intensity noise:

The suppression was just a quick check. There might be an issue with using the SR560.

The gain for the whole loop is plotted below against the calculated open loop gain [(free noise / suppressed noise) -1]: