Reports 1-1 of 1 Clear search Modify search
PEM (Center)
takaaki.yokozawa - 6:30 Tuesday 14 February 2023 (23950) Print this report
Installed the accelerometer near the vacuum pumps
To check the effect of vibration from TMP, I installed the four accelerometers(TEAC706) near the vacuum pump.

15 : near the OMC
K1:PEM-PORTABLE_OMC_BOOTH_OMC_BNC4_OUT_DQ

2 : near the PR2 and POP table
K1:PEM-PORTABLE_BS_BOOTH_POP_BNC3_OUT_DQ

12 : near the SR2 and POS table (picture is wrong...)
K1:PEM-PORTABLE_BS_BOOTH_POS_BNC3_OUT_DQ

4 : between BS and IYC
K1:PEM-PORTABLE_BS_BOOTH_BS_BNC3_OUT_DQ

Images attached to this report
Comments to this report:
takaaki.yokozawa - 8:42 Tuesday 14 February 2023 (23951) Print this report
There were only a few lines which have some coherence, but we couldn't find the main contribution to high frequency.
Images attached to this comment
takaaki.yokozawa - 10:27 Tuesday 14 February 2023 (23952) Print this report
According to klog13881 (Shaker injection to OMC chamber during at 2020) we compared the spectrum between current one and previous one.
The shape seems similar, so if we can reduce the vibration around OMC chamber (turn off pumps and FFUs and so on), we may reduce the noise, I think.

The figure is placed in
https://dac.icrr.u-tokyo.ac.jp/KAGRA/DAWG/Detchar/klog/klog23952
tomotada.akutsu - 13:17 Tuesday 14 February 2023 (23954) Print this report

Thanks. If you can overplot (calibrate it) this on the noise budget on the link in 23945, it would be very more helpful. ok, it is already kinda overplotted, thanks! It seems most of the structures that are not coherent with beam jitter or CARM ones (see 23903) could be explained. Anyway, if they are actually there, considering the coupling path, the meaning is headich to me. As detailed around 22942, we know already some weak points in terms of scattered light in the OMC chamber.

  1. Do the shaker injection now to identify the kinda transfer function from the shaking to DARM.
  2. Leave acceleromter to see if it is coherent with DARM
  3. If it would be the case, open the OMC chamber...
tatsuki.washimi - 13:36 Tuesday 14 February 2023 (23955) Print this report
shinji.miyoki - 19:30 Tuesday 14 February 2023 (23959) Print this report

The following are the vibration sources around OMC

  • SR-C Daikin cooler set on the floor without a rubber-like vibration absorber
    • We can stop this and reoperate the BS-C cooler near the SR2 tank that is set on the vibration dumper, to keep the total cooling power.
    • During O3GK, this BS-C cooler is the only Daikin cooler that was operated to keep the temp in the corner station. This situation could be realized at that time because all TMPs that are more heat generators were off in the corner station. 
  • TMP and its scroll pump.
    • Especially, the scroll pump is also set on the floor directly. No vibration absorbers.
  • FFUs around AS table.
    • According to my memory, a small amount of FFUs' influence is not so remarkable. However, a better sensitivity in the future might see it.
takaaki.yokozawa - 6:58 Friday 17 February 2023 (24003) Print this report
I investigated the coherence between ACC on the OMC leg and ACCs near the vacuu pumps.

From this result, the coherence up to SR2 area is small, but at OMC area is large.
If we can stop the TMP at OMC and SRM, the ground motion would be smaller, I think.
Images attached to this comment
takaaki.yokozawa - 7:34 Friday 17 February 2023 (24005) Print this report
I focused three acceleromters(OMC beamduct, chamber and leg) and frequency between 80 and 100 Hz.
If we put the shaker near the OMC beamduct, we can evaluate the transfer function more.

Anyway, there are some peaks near the 86, 88.15, 92.5 and 99.3 Hz with lower coherence.
Images attached to this comment
shinji.miyoki - 18:13 Saturday 18 February 2023 (24027) Print this report

If the scattered light is one of the noise sources, the noise in the sensitivity curve using obtained by only one of two PDs for the DC readout can be different because I think it is rare that the scattered light affects completely in the same manner on each PD. If there is no difference in the noise performance of the sensitivity, the possibility of scattered light can be small at the present noise level.

tomotada.akutsu - 20:37 Saturday 18 February 2023 (24029) Print this report

Good point... but if the scattered light might not matter, and the OMC suspension matters, we may actually need to modify it from now...

Search Help
×

Warning

×