[Sheila, Jenne]
These are numbers pulled from our dP/dTheta measurements from last night (mentioned in alog 27235). I have gotten the numbers into RIN/theta, since we want to know how much the power fluctuates for a given angular motion of an optic. The short summary is that the Yarm optics affect the power fluctuation much more significantly than the Xarm optics do, and that the ETMs affect the power more than the ITMs.
Sum up of 2W results:
| RIN_POP / theta_ITMX | 0.79 e4 |
| RIN_POP / theta_ITMY | 2.9 e4 |
| RIN_POP / theta_ETMX | 2.4 e4 |
| RIN_POP / theta_ETMY | 4.25 e4 |
We'd like to remeasure these values at different powers - hopefully they're constant. Of course, these are relative power fluctuations versus angle, so the overall force on the optics will be increasing as we increase the power.
The following table with more detailed results has a crazy-town amount of information, some of which I'm not totally sure what to do with yet. The difficulty is that since we have ASC loops running, when we dither one test mass, all 4 test masses move. So. Here's the gory detail. All dithers were at 0.51 Hz in pitch to the L2 stage of the test masses. Start times are UTC of 17 May 2016. The values in the table below are at our 0.51 Hz dither freq. The numbers in the summary table above are the RIN of POP_A_LF versus the angular motion of the optic we were driving at the time.
| drive optic | start time | drive amplitude [cts] | ITMX oplev [urad] | ITMY oplev [urad] | ETMX oplev [urad] | ETMY oplev [urad] | TRX RIN | TRY RIN | POP_A_LF RIN | RIN_POP / theta_driveOptic | drive optic |
| ITMY | 05:21:54 | 500 | 0.03 | 0.23 | 0.03 | 0.13 | 7.1 e-3 | 1.3 e-2 | 6.7 e-3 | 2.9 e4 | ITMY |
| ITMX | 05:27:53 | 500 | 0.24 | 0.01 | 0.14 | 0.02 | 4.4 e-3 | 8.0 e-3 | 1.9 e-3 | 0.79 e4 | ITMX |
| ETMX | 05:33:54 | 300 | 0.12 | 0.01 | 0.11 | 0.02 | 5.5 e-3 | 1.2 e-2 | 2.7 e-3 | 2.4 e4 | ETMX |
| ETMY | 05:38:13 | 300 | 0.01 | 0.1 | 0.03 | 0.08 | 2.4 e-3 | 1.2 e-2 | 3.4 e-3 | 4.25 e4 | ETMY |
These numbers already seem very large to me. Did you happen to measure the phase relation as well? Also is this measurement with a maximum power recycling gain (i.e. >40)?
Jenne provided me with the phase measurement data and diaggui templates. Here are a summary of the phase of the transfer functions between various optics to various channels. All the quantities are in unit of [deg].
to
ITMX oplev
to
ITMY oplev
to
ETMX oplev
to
ETMY oplev
to
TRX B
to
TRY B
to
POP A
I need some time to digest this result.
In addition, the power recycling seems to have been suboptimal. According to POP A, the recycling gain was estimated to be 34 while an average of the TR signals tell that it was 37. For the record, the highest recycling gain we achieved was about 41.