NaokiAritomi - 23:50, Friday 01 November 2019 (1797)
Locking accuracy with good IR alignment
First I checked IR alignment and found that IR TEM00 transmission was small. So I tweaked steering mirrors for IR injection and could recover the good alignment. Mode matching is around 95%.
| Mode | IR transmission |
| TEM00 | 385 |
| pitch | 110 |
| IG20 | - |
| offset | 94 |
Then we measured locking accuracy again as entry 1769.
Calibration:
peak-peak voltage of error signal: 266 mV
peak-peak time difference of error signal: 114 ms
slope = peak-peak voltage of error signal/peak-peak time difference of error signal = 266 mV/114 ms = 2.33 V/s
AOM scan frequency: 500 mHz
AOM deviation: 1 kHz
AOM scan speed for green: AOM deviation/AOM scan frequency = 2 kHz/s
AOM scan speed for IR: 2 kHz/s /2 = 1 kHz/s
Calibration factor:
AOM scan speed (Hz/s)/(2*slope(V/s)) = 1000(Hz/s)/(2*2.33(V/s)) = 215 Hz/V
Attached picture shows IR error signal. Locking accuracy is 4.4 Hz which corresponds to 4.7 pm. 1.3 Hz out of 4.4 Hz is coming from 600 Hz turbo pump and 1 Hz out of 4.4 Hz is coming from 9 Hz input mirror pitch (entry 1795). If we remove the 9 Hz and 600 Hz peak, we will have 2.1 Hz of locking accuracy and squeezing degradation will be much less.
Images attached to this report
