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tomotada.akutsu - 22:20 Thursday 26 August 2021 (18027) Print this report
MCi and MCo pitch strange behavior; the suspension repsonse

Ushiba, YamaT, Akutsu


Comparing the measured suspension responses of MCo used in the acceptancce check the other day and the rececnt one, we found a big differenec of the pitch repsonse! Seems severe, and needs inspection!!


In the mid-night, we tried to play with the IMC ASC. Firstly, we enjoyed looking at the input and output signals from some filters while engaging the ASC loops one by one ... but immediately we found a strange behavior of the MCi pitch by comparing with the MCo pitch; seems the actuator gains are too much (~20 times) different. It would be too much. So we looked for the past result in the acceptance check the other day (Fig. 1), and compared it with the recent one (Fig. 2). As you can see, apparently the MCo pitch repsonses have differed much! So strange...


  • Hmm, rather, maybe the fact would be, MCi response has been too low from the first???
  • Yaw seems not changed. So simple coil failuers would not explain the things well....
  • Any other?


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takafumi.ushiba - 23:04 Thursday 26 August 2021 (18029) Print this report

During the work, we found the strange(?) calibration-factor unbalance of MCI and MCE OpLevs (see attached).
The difference between PIT and YAW calibration factors are about 20 and 3, respectively.

If the beam profile is not so eliptic, the calibration factors should be almost same for both PIT and YAW because the incident angle is small for MCI and MCE.
It would be necessary to check the beam pofile of both OpLevs.

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takaaki.yokozawa - 10:46 Saturday 28 August 2021 (18051) Print this report
Now I am collecting the information about IMC oplevs.
As written in,
We have to confirm all calibration factors.
takaaki.yokozawa - 11:30 Saturday 28 August 2021 (18052) Print this report
Collect the information about IMC oplevs.

L=860 [mm] (klog3157)
alpha=0.23 [deg]
measure_Pit=2.31 [count/mm]
measure_Yaw=-2.10 [count/mm]

Calibrated_Pit=283.4 [urad/cnt]
Calibrated_Yaw=-250.6 [urad/cnt]

(medm calibration factor 28th Aug.)
Calibrated_Pit=13.953 [urad/cnt]
Calibrated_Yaw=-276.560 [urad/cnt]

(Calibration factor before O3GK)
Calibrated_Pit=312 [urad/cnt]
Calibrated_Yaw=286 [urad/cnt]

L=850 [mm] (klog3157)
alpha=17.8 [deg]
measure_Pit=1.71 [count/mm]
measure_Yaw=-1.52 [count/mm]

Calibrated_Pit=85.0 [urad/cnt]
Calibrated_Yaw=-95.6 [urad/cnt]

(medm calibration factor 28th Aug.)
Calibrated_Pit=584.795 [urad/cnt]
Calibrated_Yaw=-657.890 [urad/cnt]

(Calibration factor before O3GK)
Calibrated_Pit=102 [urad/cnt]
Calibrated_Yaw=97 [urad/cnt]

L=950 [mm] (klog3157)
alpha=36.5 [deg]
measure_Pit=4.59 [count/mm]
measure_Yaw=-4.84 [count/mm]

Calibrated_Pit=134.6 [urad/cnt]
Calibrated_Yaw=-121.5 [urad/cnt]

(medm calibration factor 28th Aug.)
Calibrated_Pit=33.947 [urad/cnt]
Calibrated_Yaw=-108.760 [urad/cnt]

(Calibration factor before O3GK)
Calibrated_Pit=145 [urad/cnt]
Calibrated_Yaw=145 [urad/cnt]
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takaaki.yokozawa - 8:30 Thursday 23 September 2021 (18338) Print this report
Hirose-san noticed the difference between her and my calculation.
After my check, I found mis-programming and correct calibration factor is

PIT_i=251.688326 [urad/cnt]
YAW_i=-276.854928 [urad/cnt]
PIT_o=90.323135 [urad/cnt]
YAW_o=-96.749226 [urad/cnt]
PIT_e=142.644487 [urad/cnt]
YAW_e=-108.742932 [urad/cnt]

And from klog3175, the alpha value of MCi oplev was 0.23 deg., but is it too small?
We will check by CAD
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