HACR at Virgo: implementation and results Gabriele Vajente 12 th ILIAS WG1 meeting Geneva, March 29...

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HACR at Virgo: implementation and results Gabriele Vajente 12 th ILIAS WG1 meeting Geneva, March 29 th -30 th 2007

Transcript of HACR at Virgo: implementation and results Gabriele Vajente 12 th ILIAS WG1 meeting Geneva, March 29...

Page 1: HACR at Virgo: implementation and results Gabriele Vajente 12 th ILIAS WG1 meeting Geneva, March 29 th -30 th 2007.

HACR at Virgo: implementation and results

Gabriele Vajente

12th ILIAS WG1 meeting

Geneva, March 29th -30th 2007

Page 2: HACR at Virgo: implementation and results Gabriele Vajente 12 th ILIAS WG1 meeting Geneva, March 29 th -30 th 2007.

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Summary

HACR algorithm

Implementation at Virgo

Some results from WSR9

Page 3: HACR at Virgo: implementation and results Gabriele Vajente 12 th ILIAS WG1 meeting Geneva, March 29 th -30 th 2007.

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HACR algorithm

Based on HACR developed at GEO60

Search for transients in time-frequency domainTimes and frequencies with an excess of power with respect to the mean

Page 4: HACR at Virgo: implementation and results Gabriele Vajente 12 th ILIAS WG1 meeting Geneva, March 29 th -30 th 2007.

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How HACR works

Compute short FFTs (50 ms) of a signal without averages

Frequency resolution about 40 Hz

Create a time – frequency map of the signal

),( ftF

Simulated data, white noise plus sine-gaussian

Zoom around one transient

Page 5: HACR at Virgo: implementation and results Gabriele Vajente 12 th ILIAS WG1 meeting Geneva, March 29 th -30 th 2007.

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How HACR works

Compute an averaged spectrum over time

Using a decay average with time constant of about 10 s

Compute also the standard deviation over time for each frequency

),()( ftFfM

22 )(),()( fMftFf

),()( ftFfM

Page 6: HACR at Virgo: implementation and results Gabriele Vajente 12 th ILIAS WG1 meeting Geneva, March 29 th -30 th 2007.

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How HACR works

Compute the deviation of the point from the mean

This gives an indication of how much each point deviates from the mean statistics of the spectrum(significance of the bin)

)(

)(),(),(

2

2

f

fMftFftS

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How HACR works

Trigger if the significance is above a given threshold THIGH

Build up a cluster by searching neighboring points with significance above a lower threshold TLOW

For each cluster computeMean time and frequency (weighted average with power)Time and frequency widthMaximum and mean significanceSNR as square root of power in the cluster divided by power in the mean spectrum Number of points

Points above THIGHPoints above TLOW

CLUSTER

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Implementation at VirgoProgram written in C using FFTW and Virgo frame interfaceRunning online since a couple of weeksSome performances

10 hours of data, analyzing 11 channelstook 3.3 hours Analysis of one frame, one 20kHz channel, estimated with profiler 14 ms of machine timeLimited mainly by data access

Output sent to MySQL databaseAlso: number of cluster per second and max snr for each second sent to main data stream

Page 9: HACR at Virgo: implementation and results Gabriele Vajente 12 th ILIAS WG1 meeting Geneva, March 29 th -30 th 2007.

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Report generator

Simple script written in Perl and OctaveQuery the database, perform basics analysis and produce plots

Time, frequency, SNR distributionTime – freuency – SNR mapsCorrelogramsCoincidences between pairs of channels

Examples at http://wwwcascina.virgo.infn.it/MonitoringWeb/HACR/

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Time – Frequency – SNR map

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Distributions

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Correlograms

WSR7 WSR9

During WSR7 strong 600mHz excitation of BS transversal motion

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Coincidences phase - quadrature

Coincidence between phase and quadrature of dark fringe signal

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Coicidences both frequency and time

20 % of all glitches are coincident both in time and frequency

dt < 0.1s df < 100 Hz

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Coincidences both time and frequency

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Conclusions

HACR is working well at Virgo

Still some tuning needed for the reports

Soon the report generator will run automatically (once every 8 hours)

HACR can give lots of information on the quality of data

Vetoes?