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AOS (Baffles & Beam dumps)
simon.zeidler - 8:19 Wednesday 28 February 2018 (4293) Print this report
Damping of the WAB (first part)

Akutsu, Simon

We have successfully replaced the temporary installed breadboard with an adapter board to host the PS, although we had some trouble in the beginning with stain on the board due to a mistake happen during washing (see klog entry 4292).

Anyway, we did some more coil-injection measurements with the photosensors in all three directions (X, Y, Z). I show here the (digitally) lowpass-filtered signal (comb and butterworth @ 60Hz) as we are interested mainly in the swing-modes of the baffle in which are around 1Hz.
In picture 1, the outcome of these measurements for a time before replacing the board is shown. It is the time-signal for switching the coil magnet on and off after some time. As can be seen, the baffle is clearly responding to the coil's magnetic field, and in all three DoF, we can find a dominating mode around roughly 1Hz. But also some modes atop the dominating mode.
This phenomenom is partly visible also in the spectra (picture 2). Here, the mentioned mode around 1Hz but also some modes around 2Hz, and especially strong modes around 3.2Hz 5.5Hz seem to be present (the latter only for Y and X channels). Unfortunately, the frequency resolution is more or less limited to 0.05Hz, also as the relaxing time for the baffle is not long enough.
Also containing in the picture, are reference spectra of the same channels from today around 5 pm (at that time we already replaced the board). Interestingly, at around 1.1Hz, there seems to be another mode which is especially strong for the X-channel (and also visible when the baffle is not actuated), while the main actuated mode is mainly at around 0.8 - 0.9 Hz. Thus, the impression is that the strong mode around 1Hz for the actuated baffle is actually a double mode.

In picture 3, the response to the magnetic actuation after the installation of the adapter board is shown. The response is as clear as before, only the signals are now much closer to each other. Also, we put a longer time-gap between switching the coil-magnet on and off. The effect of this can be seen in the corresponding spectra (picture 4). The 2Hz mode is now much better visible and appears clearly for Y an Z channel too. In addition to that, we see a small mode at around 2.5Hz for the X channel which was not visible before. Other than that, there is not so much difference to the spectra before.

Images attached to this report
Comments to this report:
tomotada.akutsu - 9:16 Wednesday 28 February 2018 (4294) Print this report

Well, with the current alignment of the photosensor heads, I think the enlightened marked boxes should have relatively strong correlations. Let's check them later. The broken heart-marked boxes will also have some correlations, as the reflector cube is not attached to the rotation center of the WAB.

  X Y Z
Pitch broken heart enlightened enlightened
Yaw   broken heart  
Roll enlightened    

By the way, the signal names are collected? I remembered some channels have wrong name assigns.

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