Agenda/Minutes

CRY+VIS Interface Meeting

Date: 2021/6/18 13:00-

Participants:

IX: H4 geophone was replaced. Top chamber was closed again.
IY: Schedule: Rough alignment of TM?
EX: Adjustment of Yaw FR and IP tuning was finished. Broken cable was recovered. Top chamber was closed.
- Broken cable
EY: Assembly of payload is on going. Status of mirror cleaning?

14:00-

Participants:

This is generated by python script in /users/Miyo/dropbox/Script/scrapping/main.py.

Tuned the F0 in IY.
Adjusted the yaw FR in EX. Tuned the IP. The H4 geophone was put on the IP. Repaired some in-vacuum cables.
Closed the top chambers in IX and EX.

There were three switches that didn't seem to be working. Hirata-san fixed them and we checked them with the multimeter. They are working now

We measured IP TF on Monday:
- The resonant frequencies in L and T looked low enough (63 and 55 mHz) so we didn't adjust the ballast masses.
- The coherence wasn't bad but not excelent either; the frequency resolution was 10 mHz.
Terrence measured TFs again with a better frequency resolution and found that L and T are highly coupled.

[Terrence]

Fabian locked the SRM IP so I can measure the LVDT sensor noises.
I measured the geophone readouts as well when the IP is unlocked. The suspension is quiet enough so these can be used as sensor noise estimates. [notebook sneak peek]
I then measured transfer functions and cross-transfer functions.
- cross-coupling is confusing. Explain with figure: klog 17137
- I reverted the sensing matrix and the actuation matrix using Mark's old matrix, which is derived from geometry.
- Cross-coupling is still confusing between L and T. But at least I can decouple L2Y, T2Y, Y2L and Y2T.
- I suspect the lowest frequency modes are L-T coupled. I am pretty sure L and T sensors are not 100% coupled as suggested in the figures.
- I compared the L and T readout with seismic noise in the x-arm and y-arm direction and L has minimal coherence with x-arm while T has minimal coherence with y-arm.
- Peaks are too close :*(.
Some opinion about the RT-model
- LVDTALIGN and ACCALIGN matrices are great for sensor diagonalization.
- Why don't add something like COILALIGN (for actuation)?

We revisited the BS IP to check stability and values of resonance frequencies.

When we adjusted the ballast mass before the temperature 22.7 degrees, this week was 23.5 degrees; O3GK temperature is 23 degrees.
I moved the IP close to the setpoints using the horizontal fishing rods: it looked unstable, it began moving by small amount but it suddendly moved a lot (e.g. from -1.5 mm to 1.5 mm). With some care I was able to move it at the setpoint and measured TFs, the resonant frequencies were 43 and 86 mHz for L and T respectively.
We removed 4.5 kg and and the frequencies changed to 93 and 70 mHz for L and T respectively.
With the same amount of mass we tested different distributions to check whether we can reduce the assymetry between the resonant frequencies in L and T:
- See klog.
- The assymetry remains around 25 mHz: one is typically around 65 mHz and the other one around 90 mHz.
- Becuase of temperature changes one might be too low and the other too high.
- L and T seem strongly coupled.
I wonder how to proceed: during installation we were not able to distribute the masses evenly around the circumference becuase the magic wand (yet to be conforimed with a kalog entry).

Milestone

2021/03/29 updated

The week from 6/21

The week from 6/28