We set up Viton Pads under HAM3-ISI balancing masses. The size of those pads is the same as the size of LLO's. However we set those pads under 1/2 the mass LLO uses, in order to rise the corner frequency of the mass+Viton stack.
Comparison before/after is attached.
The Viton Pads improve the 310Hz peak in V efficiently, by a factor > 5 without any drawback to it. Results are satisfying enough for now. We may try other configurations next time the chamber is open.
This Viton Pads Efficiency Test was plotted in the cartesian basis. Results are attached.
Best improvements can be seen along RX and RY, in the 310Hz region. Suspension modes can be seen there and they are known to be coupling with the ISI.
Plots show that the Viton Pads we used helped limiting the impact of SUS/SEI couplings, on the ISI's Transfer Functions.
Having those viton pads should also facilitate the design of control loops, and eventually allow pushing the performance a bit further, as more gain margin will be available.