Ikenoue-san, Simon

After trying many different possible configurations of magnets on the damper, I found that with the current two dampers on the NAB placing big Nd-magnets (2x2cm) in the most densest way (in alternating polarization) is most effective in terms of the Q factor.
We measured then the damping of all modes by using laser-displacement sensors attached to the NAB and an optical lever. In order to do that, I excited the NAB suspension in certain directions (like in yaw, vertical, roll, and transvers) so that the specific eigenmodes of the suspension are actuated.
After each measurement using the displacement sensors, we used Uraguchi-san's python script to calculate the fft-spectrum of each time-signal.

We did this measurements for two different distances of the magnets to the damper plates. The nominal distance of the magnets to the plates is ~5mm, but for a more effective damping, we put some washers between the damper-magnet holder and the damper-suspension to decrease the distance by 1mm.
Note: the magnets itself have ~1mm smaller thickness than designed. Therefore, for the nominal distance, we already had to put washers in place! That is why in the attached figures "-1mm distance" refers to the nominal position and "-2mm distance" refers to the closer state.

I did the analysis of the outcome of our measurements in terms of the damping afterwards (the results are attached to this report)

• For "yaw" excitations, I fitted only the longitudinal placed displacement-sensor's and OpLev's result
• For "vertical" excitations, I only present the vertical placed displacement-sensor's result
• Also, we were using two vertical sensors on both sides of the baffle in order to distinguish the pure vertical mode from the roll mode
• Below there is a table summarizing the Q-factors for the two different cases and all found eigenmodes
  Please note that we could not accomplish some of the measurements because of the lack of time. Also, you may find that the damping values in the attached figures are sometimes varying depending of the amount of other modes and their strength (a.k.a. amplitude). Therefore in the table, I used only the damping values from those measurements where the respective mode is the strongest.