Calibration/validation of the AS_Q_FAST channels

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Calibration/validation of the AS_Q_FAST channels Rick Savage - LHO Stefanos Giampanis – Univ. Rochester ( Daniel Sigg – LHO )

description

Calibration/validation of the AS_Q_FAST channels. Rick Savage - LHO Stefanos Giampanis – Univ. Rochester ( Daniel Sigg – LHO ). High frequency length response. 1FSR. 2FSR. Length response TF detail. DC. 1FSR. 1% error at 1 kHz. 12% error at 10 kHz. - PowerPoint PPT Presentation

Transcript of Calibration/validation of the AS_Q_FAST channels

Page 1: Calibration/validation of the AS_Q_FAST  channels

Calibration/validation of the AS_Q_FAST channels

Rick Savage - LHO

Stefanos Giampanis – Univ. Rochester

( Daniel Sigg – LHO )

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High frequency length response

1FSR 2FSR

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Length response TF detail

DC

1FSR

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Comparison with single pole approximation

1% error at 1 kHz

12% error at 10 kHz

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“FAST” channels

All three interferometers have FAST (262 kHz) data acquisition systems generating AS_Q_FAST signals with 100 kHz bandwidths

The signals are also digitally heterodyned at 1024 Hz and 37.504 kHz and downsampled to 2048 Hz to generate the 0FSR and 1FSR channels» AS_Q_0FSR.mag AS_Q_1FSR.mag

» AS_Q_0FSR.phs AS_Q_1FSR.phs

» AS_Q_0FSR.real AS_Q_1FSR.real

» AS_Q_0FSR.img AS_Q_1FSR.img

At LHO the full 262 kHz AS_Q_FAST channels are written to the frames. Not yet implemented at LLO.

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AS signal flow

AS_Q path

Whitening filter

ICS 130 ADC (262 kHz)

Monitor outputs a b a b a b a b

AS portphotodetectors

DAQ channels AS_Q_FAST and 0FSR and 1FSR channels

AS1 demod AS2 demod AS3 demod AS4 demod

AS_Q_FAST path

Pentium front-end processor (e.g. h1adcufast)

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Hardware – AS demod end

ASnoutputs

ASn-monoutputs(x 2 gain)

whitening filters for ICS 130

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Hardware – ADC end

ICS 130 – 8 channelsrunning at 262,144 Hz

Pentek code generates the AS_Q_FAST and hetrodyned channels

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Whitening filter transfer function

100

101

102

103

104

105

-20

-10

0

10

20

30

40

50

Freqency (Hz)

Mag

nitu

de (

dB)

H1 AS_Q_FAST whitening board transfer function

100

101

102

103

104

105

-200

-100

0

100

200

Freqency (Hz)

Phas

e (

deg

.)

gain of 0.2, four zeros at 20 Hz, four poles at 100 Hz, poles at 150 kHz and 300 kHz

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ASPD summation for AS_Q and AS_Q_FAST

» Similar calculation done in adcufast

» Presently, startup.cmd must be updated manually every time medm settings are changed

» LLO adjusts ASPD matrix coefficients for each lock stretch

» Working toward reading epics settings on the fly.

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AS_Q : AS_Q_FAST comparison

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AS_Q_FAST signals during full ifo. lock

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0FSR signals

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1FSR signals

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Calibration options

Drive test mass at 37.5 kHz» Attempted during Oct. 2005

– Factor of five larger value than expected– Electronics not designed to be driven at this frequency– Uncertainty in force/displacement too high

Photon calibrator» Now driving at ~ 1600 Hz

– To resolve peak in ASD factor at the level of a factor of a few above the background requires hundreds of seconds of integration

– At 37.5 kHz one data point would require ~ one year integration time

Thermally-excited TM internal mode vibrations» Modeling (and more thought) required

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“Blind” extrapolation of low-freq. calibration

Use cal line at ~1150 Hz Replace cavity pole approximation with length

response given by HL(f) Extrapolate to 100 kHz without HF measurement

» Analytic model used to date for single FP cavity - probably gets differential mode right , but not leakage of common mode effects into AS port – doesn’t model noise floor.

» Use full interferometer model such as Finesse to study noise couplings at high frequencies.

Effort underway to implement “blind” calibration