The results can be seen in JGWDoc15370.
Injection : 80 - 100 Hz vibration
Results :
Page 1-4 : Four placed on the upper part of the OMC chamber. (Fig.1. showed the Page 1 of JGWDoc15370)
As you can see, there are two peaks in OMC LSC control signals 82.5 Hz and 93 Hz.
The amplitude of two peaks have position dependence.
+Y side : both peaks
-Y side : 82.5 Hz peak
+x side : 93 Hz peak
Page 5-6 : On the feed through flange
When we measured those two positions, the accelerometer was placed on the floor.
Similar two peaks detected, the trend is also similar (-Y side 82.5 Hz, +X side 93 Hz)
So, the vibration may not go inside the chamber through the cables and feed through flange.
Page 7-10 : On the (bellows) leg of OMC chamber (or optical table)
The effect of vibration from legs is relatively smaller than upper part injection.
Page 11 : On the bellows between OMC and OMMT chamber.
Very large effect can be detected, and the tendency is different form other results.
We need more investigation.
Conclusion :
Actually, there are response function and this response function is position dependence.
(92 Hz > 91.1 Hz > 90.8 Hz > 89.6 Hz > 89 Hz)
We performed the tapping test at various places around OMC area.
The detail is placed in JGWDoc15370.
1. Bottom side of OMC chamber
As you can see, there are some excess in the spectrum of geophone inside the vacuum, but it seemed not critical vibration.
Beam duct tapping between OMC and OMM chamber is larger.
(But I couldn't control the tapping power)
2. OMC chamber +Y side
We performed the various placed at the +Y side of the OMC chamber, the vibration would be larger.
3. White structure for the vacuum pumps
Surprisingly, we can see the excess of spectrum when we tapped the white structure for the vacuum pump.
4. Cable floor
When we tapped the cable on the floor, some excess can be seen.
Also, we performed the tapping test at various places with checking the spectrum, but we could not find the critical point at this time.
Thanks, I shold have joined the session. By the way, in your slide, the height of "Side middle +Y righ" is around the laser beam height??
It might be interesting to take some transfer function from the injection point to the geohpone.
Yes.
One of the main motivation of today work is to find the good position for measuring the transfer function, (maybe because the transfer function is position dependence)
And from the experiment of today work, multiple eye is necessary.