stefan.ballmer@LIGO.ORG - posted 18:40, Sunday 02 August 2015 - last comment - 18:50, Sunday 02 August 2015(20147)
Broadband frequency noise injection
Evan, Stefan, We set up a function generator to get a 3kHz-30kHz broadband frequency noise injection. Details: - Function generator, set on 'noise' - Followed by an SR560 (AC, band-passed between 3kHz and 30kHz, gain 1) - This drives drive a noise floor of about 22uVrms/rtHz at 10kHz. - We hooked this up the the CM board input 2 (note to self - need to reconnect SUM_B for the IFO to re-lock). - Next we turned on the CM board input 2 with -20dB gain: this should add about 2.2uVrms/rtHz at 10kHz. Attached is a plot of REFL_9 and OMC_DCPD_A, with annotated features at the carrier 10 and carrier 20 modes. We left this excitation on for the thermal run tonight.
Images attached to this report
Comments related to this report
Here are updated numbers for higher order arm resonances: f1=9100230Hz (verified) f2=5*f1 Arm length: L=3994.47 (same used for x and y) RoC: ETMX: 2241.54m ITMX: 1939.3m ETMY: 2238.9m ITMY: 1939.39m XARM: Resonance condition: fres = FSR * (q + (l+m+1)*fTM/FSR) Free Spectral Range (FSR) : 37.5259 kHz Transverse Mode Spacing (fTM): 32.4296 kHz f1 sideband: q=243 l+m=0 Freq. diff. = 18.5727 kHz q=242 l+m=0 Freq. from antiresonant = 0.190312 kHz q=242 l+m=1 Freq. diff. = 13.4763 kHz q=241 l+m=1 Freq. from antiresonant = 5.28668 kHz q=241 l+m=2 Freq. diff. = 8.37992 kHz q=-243 l+m=0 Freq. diff. = 18.5727 kHz q=-243 l+m=0 Freq. from antiresonant = 0.190312 kHz q=-243 l+m=1 Freq. diff. = 13.8569 kHz q=-244 l+m=1 Freq. from antiresonant = 4.90605 kHz q=-244 l+m=2 Freq. diff. = 8.76055 kHz f2 sideband: q=1213 l+m=0 Freq. diff. = 17.8114 kHz q=1212 l+m=0 Freq. from antiresonant = 0.95156 kHz q=1212 l+m=1 Freq. diff. = 12.715 kHz q=1211 l+m=1 Freq. from antiresonant = 6.04793 kHz q=1211 l+m=2 Freq. diff. = 7.61868 kHz q=-1213 l+m=0 Freq. diff. = 17.8114 kHz q=-1213 l+m=0 Freq. from antiresonant = 0.95156 kHz q=-1213 l+m=1 Freq. diff. = 14.6182 kHz q=-1214 l+m=1 Freq. from antiresonant = 4.14481 kHz q=-1214 l+m=2 Freq. diff. = 9.5218 kHz Carrier: l+m=1 Freq. diff. = 5096.3661 Hz l+m=2 Freq. diff. = 10192.7323 Hz YARM: Checking accidental sideband resonances in the arm cavities: Resonance condition: fres = FSR * (q + (l+m+1)*fTM/FSR) Free Spectral Range (FSR) : 37.5259 kHz Transverse Mode Spacing (fTM): 32.4638 kHz f1 sideband: q=243 l+m=0 Freq. diff. = 18.5727 kHz q=242 l+m=0 Freq. from antiresonant = 0.190312 kHz q=242 l+m=1 Freq. diff. = 13.5105 kHz q=241 l+m=1 Freq. from antiresonant = 5.25248 kHz q=241 l+m=2 Freq. diff. = 8.44832 kHz q=-243 l+m=0 Freq. diff. = 18.5727 kHz q=-243 l+m=0 Freq. from antiresonant = 0.190312 kHz q=-243 l+m=1 Freq. diff. = 13.8911 kHz q=-244 l+m=1 Freq. from antiresonant = 4.87185 kHz q=-244 l+m=2 Freq. diff. = 8.82895 kHz f2 sideband: q=1213 l+m=0 Freq. diff. = 17.8114 kHz q=1212 l+m=0 Freq. from antiresonant = 0.95156 kHz q=1212 l+m=1 Freq. diff. = 12.7492 kHz q=1211 l+m=1 Freq. from antiresonant = 6.01373 kHz q=1211 l+m=2 Freq. diff. = 7.68708 kHz q=-1213 l+m=0 Freq. diff. = 17.8114 kHz q=-1213 l+m=0 Freq. from antiresonant = 0.95156 kHz q=-1213 l+m=1 Freq. diff. = 14.6524 kHz q=-1214 l+m=1 Freq. from antiresonant = 4.11061 kHz q=-1214 l+m=2 Freq. diff. = 9.5902 kHz Carrier: l+m=1 Freq. diff. = 5062.1663Hz l+m=2 Freq. diff. = 10124.3327Hz