[Hirata-san, Koz]
We calibrated the SR3 top filter (F0). We hoped the resonant frequency would become ~0.2 Hz when we hung the standard filter. So we tried to find the best compression value which satisfies the above requirement. But we failed.
Result:
The more we press blades, the lower the frequency is.
On the other hand, the more we press them, the lower the load capacity is.
From today's work, we know that the weight of all components from TM to SF (including the flying saucer and the rod between SF and PI) is 255.4 kg but this value doesn't include the weight of cables. So we estimate the real weight becomes around 256-257 kg.
So from this graph, the resonant frequency becomes ~0.6 Hz at best. See picture No.1.
Solution:
1.
To change the copper boards (on top the SF) to aluminium boards. See picture No.3. This eliminates ~6 kg.
2.
To order thinner copper boards. We change the thickness 8 mm to 4 mm and this eliminates ~5 kg.
3.
To combine thick aluminium boards and thin copper boards.
For example, if aluminium is 5.5 mm and copper is 2.5 mm, we can eliminate ~4 kg.
4.
The final idea is to not install one copper board.
Now we have three boards and they are 10.592 kg in total (without screws) on top.
This idea eliminates ~3.7 kg.
Ideas 1, 2 and 3 will take several weeks to install because we would need to order new ones.
We will discuss with Aso-san, Takahashi-san and Mark.
Data:
I uploaded these data to KAGRA dropbox (home/Subsystems/VIS/TypeB/SR3 calibration/F0 calibration).
