Frequency Noise in Virgo
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Transcript of Frequency Noise in Virgo
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Frequency Noise in Virgoby Matt Evans
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The ActorsNoise SourcesInput Mode Cleaner length noiseSensing noise on IMC lockFrequency ServoServo topologyGain limitationsSensing noisesCoupling to the Dark FringeCommon Mode Rejection RatioFluctuations
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Sources: IMC Length ExcitationInjection bench alignment sensor noise below 15HzSeismic excitationbetween 15 and 20Hzalso possibly higher problem with suspension?Actuator noiseIB coil-driver/DAC noiseMode cleaner end mirror DAC noise
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Sources: Seismic Excitation
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Sources: IB transfer functionDihedron resonace at 80Hz
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Sources: Actuator NoiseDihedron resonace at 80HzCouples also through offsets (FmodErr)
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Frequency ServoFast Loop 250kHzSSFS 25kHzMC path100Hz
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Servo: Fast LoopNoise properties not known
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Servo: SSFS
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Servo: SSFS
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Servo: MC path
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Coupling to the Dark FringeLine match at 444 and 1111HzModulation spreads line powerThe coupling fluctuates quickly Coherent analysis is difficultNoise projection is approximate
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Coupling to the Dark FringeB1 Shot NoiseB5 Shot NoiseLine matchFeature matchALL VERY ROUGH!!!
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Left to be DoneTune SSFSIncrease gain between 1 and 5kHzImprove phase margin by removing unnecessary delay in cables, OpAmps, ...Understand fast loop noiseElectronicsScattering on external benchND filters, clippingOther ideas?Stabilize coupling (alignment?)