KAGRA Logbook

[Uchiyama, Ushiba, YokozaWashimi]

We performed the tapping test for the center area.
The detail of the results would be reported later.

1. Tapping teat IYC BF area again.
We confirmed the similar result (L direction around the BF filter) by tapping test by Uchiyama-san
When we tapped using the hollow of the hand (Tenohira), the excitation at lower frequency (<30 Hz) became larger (hollow tapping includes the lower frequency injection)
We also used the shaker to inject the single frequency.
The brief summary for the IYC tapping test was following;
(1) Tapping test at lower frequency may affect the IP
(2) When we performed the single frequency injection using shaker, both IP and BF can be seen in certain frequency.
- We can inject the 30 Hz shaker injection and we can see the signal in IP L(2 order larger than floor) and BF
- 13.5 Hz signal can be seen BF
- Even when we turned off the shaker excitation, but put the shaker on the bellows by Uchiyama-san, we can see the 13.5 Hz signal in BF
- When we leave the shaker from bellows, 13.5 Hz peak may be disappeared (but the fluctuation of the spectrum was large)
- No coherence between the excitation channel and DARM
- No significant signal in DARM
- When we performed the shaker injection test from side flange (-X side), the vibrated signal in IP became much smaller when performed the shaker injection at -Y side.
(3) We concluded that the when we tapped the bellows near the BF, the vibration affect to the IP and non-linear coupling happened in DARM
(4) This is Yokozawa's feeling, we don't need to treat it before O4b, but we need several investigation toward the O5

2. Tapping test around the Gave Valve between IYC and BS
We performed several tapping test and shaker injection test aroudn GV between IYC and BS.
By checking the IFO signals by Ushiba-san, he said the large signal can be seen in PRCL err signal and Geophone at BS.
We also concluded that the low frequency of the vibration near the BS may affect the IP of the BS and non-linear coupling happened in DARM
We need the swept sine injection using the shaker which was placed the IYC site of the GV by checking the existence of the critical frequency before starting the cooling down.

3. Tapping test SR2 - OMC
We can find some excess when tapping the SR2, SR3 and SRM, but the we cannot see the excess around 100 Hz.

4. Tapping test OMC
When we touched the OMMT2 and OMC chamber, large excess were detected in 80 Hz and 100 Hz.
From the Ushiba-san's comment, the large peak of 92 Hz was appeared in OMC LSC err(about 3 order higher than background), and sideband of the 8 Hz may be appeared.
For evaluating around the the OMC, tapping test would be too large and we need the additional shaker and acoustic injection test for evaluating the noise budget

5. We will continue the tapping test IMC - PR2 tomorrow for detail
- We can see that the amplitude of the 127 Hz became larger when we tapped around the IFI chamber (REFL viewport, chamber, chamber legs and so on)
- From the check of the tapping by Ushiba-san, the vibration from the ground can excess the larger amplitude to 127 Hz
- So we will put the large shaker and seismometer near the IFI chamber and shaker injection measurement would be performed(and measured the TF from ground motion to DARM)
- Larger excess can be found when we tapped the beam duct between PR2 and PR3, we need to check with IFO signals

Option:
Ushiba-san and Uchiyama-san took the photo at the POP table and REFL table, the pictures would be uploaded later.