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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 ). High frequency length response. 1FSR. 2FSR. Length response TF detail. DC. 1FSR. 1% error at 1 kHz. 12% error at 10 kHz.

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Calibration/validation of the AS_Q_FAST channels

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

  2. High frequency length response 1FSR 2FSR LIGO-G060106-00-W March 2006 LSC meeting - LHO

  3. Length response TF detail DC 1FSR LIGO-G060106-00-W March 2006 LSC meeting - LHO

  4. 1% error at 1 kHz 12% error at 10 kHz Comparison with single pole approximation LIGO-G060106-00-W March 2006 LSC meeting - LHO

  5. “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. LIGO-G060106-00-W March 2006 LSC meeting - LHO

  6. AS_Q path AS port photodetectors AS1 demod AS2 demod AS3 demod AS4 demod Monitor outputs a b a b a b a b Whitening filter AS_Q_FAST path ICS 130 ADC (262 kHz) Pentium front-end processor (e.g. h1adcufast) DAQ channels AS_Q_FAST and 0FSR and 1FSR channels AS signal flow LIGO-G060106-00-W March 2006 LSC meeting - LHO

  7. Hardware – AS demod end ASnoutputs ASn-monoutputs(x 2 gain) whitening filters for ICS 130 LIGO-G060106-00-W March 2006 LSC meeting - LHO

  8. Hardware – ADC end ICS 130 – 8 channelsrunning at 262,144 Hz Pentek code generates the AS_Q_FAST and hetrodyned channels LIGO-G060106-00-W March 2006 LSC meeting - LHO

  9. Whitening filter transfer function LIGO-G060106-00-W March 2006 LSC meeting - LHO

  10. 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. LIGO-G060106-00-W March 2006 LSC meeting - LHO

  11. AS_Q : AS_Q_FAST comparison LIGO-G060106-00-W March 2006 LSC meeting - LHO

  12. AS_Q_FAST signals during full ifo. lock LIGO-G060106-00-W March 2006 LSC meeting - LHO

  13. 0FSR signals LIGO-G060106-00-W March 2006 LSC meeting - LHO

  14. 1FSR signals LIGO-G060106-00-W March 2006 LSC meeting - LHO

  15. 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 LIGO-G060106-00-W March 2006 LSC meeting - LHO

  16. “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 LIGO-G060106-00-W March 2006 LSC meeting - LHO

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