Michigan Group NSF Proposal - 12/6/02

R. Gustafson, K. Riles - University of Michigan

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LIGO-G020XXX-00-Z

Michigan Group NSF Proposal

Richard Gustafson, Keith Riles

University of Michigan

LIGO Program Advisory Committee Meeting

Livingston, Louisiana

December 5-6, 2002

Michigan Group NSF Proposal - 12/6/02

R. Gustafson, K. Riles - University of Michigan

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LIGO-G020XXX-00-Z

• Detector Characterization» Leadership

» Organization of LSC participation in data runs

» Online, real-time diagnostic & characterization software

» Noise and pathology investigation

• Search for Periodic Sources of Gravitational Waves» Active contributors to Periodic Upper Limits Group (PULG)

» Focussed on “unbiased” (less sensitive) search over entire sky

» Identification of instrumental lines with frequency modulations

Overview of Activities

Michigan Group NSF Proposal - 12/6/02

R. Gustafson, K. Riles - University of Michigan

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LIGO-G020XXX-00-Z

• Commissioning & Detector Advancement» Instrumental diagnostics» RF & digitization noise investigations» Alternative servo control error signals for robust diagnostics / locking

• Advanced LIGO » Servo controls development

Michigan Group Members

• Ph.D.’s: Richard Gustafson, Keith Riles• Graduate student: Dave Chin• Undergraduate: Michael La Marca• Programmer / future

Graduate Student: Vladimir Dergachev

Overview of Activities

Michigan Group NSF Proposal - 12/6/02

R. Gustafson, K. Riles - University of Michigan

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LIGO-G020XXX-00-Z

LSC Detector Characterization Working Group (Chair: K. Riles, Lab Liaison: D. Sigg – LHO)

Working Group Functions:• Provide online, real-time diagnostics in control room• Record instrumental/environmental transients and performance trends• Investigations of noise sources and pathologies in data runs• Calibration and data quality information for data runs• Data set reduction• Staffing of scientific monitoring shifts during data runs

Miscellaneous related administrative duties (Riles)• Meetings (organizing, hosting, writing minutes), liaison to other

groups, reporting to NSF panels, author on analysis white paper

Detector Characterization

Michigan Group NSF Proposal - 12/6/02

R. Gustafson, K. Riles - University of Michigan

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LIGO-G020XXX-00-Z

Detector Characterization

Data Run Activities (organized by Riles)

• Staffing of scientific monitoring shifts in data runs:» Monitoring of data – Detecting pathologies» Decisions on running mode & control parameter adjustments» Sample S1 “scimon” shift list

• Investigations:» Typically ~dozen teams formed for each run (E2-E7, S1)» Sample topics of study: calibration, data quality, lock losses,

glitches, inter-channel correlations,bilinear noise, data set reduction, timing precision, line noise, signal injection,

» Investigation reports given at regular DetChar telecons & at bi-annual LSC meetings

Michigan Group NSF Proposal - 12/6/02

R. Gustafson, K. Riles - University of Michigan

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LIGO-G020XXX-00-Z

Detector CharacterizationDirect Michigan participation in data run investigations

(Chin, Dergachev, Gustafson, Riles)

Past:• Led Lock Loss Team for E2, E3, E4, E5 runs

» Identified saturations & other pathologies» Quantified severity of LLO seismic noise (see figure)

• Provided data quality info for E2-E7 runs• Contributor to S1 Data Quality Team• Wrote offline trend viewer with remote access to site data

Future:• Spectral distortion (monitoring)• Servo instabilities / drifts (modelling)

• Upgrade trend viewer as site bandwidth increases

Michigan Group NSF Proposal - 12/6/02

R. Gustafson, K. Riles - University of Michigan

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LIGO-G020XXX-00-Z

Seismic Impact at LLO in E4

Seismic noise over the 3-day run

Resulting lock livetime fraction

Michigan Group NSF Proposal - 12/6/02

R. Gustafson, K. Riles - University of Michigan

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LIGO-G020XXX-00-Z

Detector Characterization

Michigan Contributions to Online Diagnostics(Chin, Riles)

Operational State Conditions:• General-purpose interferometer state conditions used by many

online Data Monitoring Tool (DMT) programs • Supports arbitrary, run-time Boolean combinations of conditions

LockLoss Monitoring Program (DMT)• Provides graphic display of interferometer state vector history,

cumulative livetime, database triggers, permanent record of all lock transitions

• Mature program – essential in data runs

Michigan Group NSF Proposal - 12/6/02

R. Gustafson, K. Riles - University of Michigan

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LIGO-G020XXX-00-Z

Detector Characterization

Michigan Contributions to Online Diagnostics (cont.)

ServoMon Monitoring Program (DMT)• Monitors sudden increases in spectral noise (violin modes, gain

peaking, etc.) with alarms, database triggers, trends• Useful now but needs refinement• Planned enhancement:

GW servo modelling with spectral prediction

Michigan Group NSF Proposal - 12/6/02

R. Gustafson, K. Riles - University of Michigan

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LIGO-G020XXX-00-Z

Search for CW Sources

The Michigan group analysis focus is the search for Continuous Wave (CW) Sources of Gravitational Waves

(Chin, Dergachev, Gustafson, Riles)

• Now contributing members of PULG

• Prior to PULG formation wrote general-purpose antenna pattern analysis code for LIGO Analysis Library (LAL) under aegis of A.S.I.S. W.G. Code now used by several analysis groups

• Have only recently begun intensive work on CW analysis

Ph.D. dissertation topic for Chin

Michigan Group NSF Proposal - 12/6/02

R. Gustafson, K. Riles - University of Michigan

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LIGO-G020XXX-00-Z

Search for CW SourcesMost promising periodic source: Rotating Neutron Stars (e.g., pulsar)

But radiation requires an asymmetry or perturbation:

• Equatorial ellipticity (e.g., – mm-high “mountain”): h α εequat

• Poloidal ellipticity (natural) + wobble angle: h α εpol x Θwobble

(precession due to different L and Ω axes)

Serious technical difficulty: Doppler frequency shifts (see figure)» Frequency modulation from earth’s rotation (v/c ~ 10-6)» Frequency modulation from earth’s orbital motion (v/c ~ 10-4)

Additional, related complications:» Daily amplitude modulation of antenna pattern (sensitivity)» Spin-down of source» Orbital motion of sources in binary systems

Michigan Group NSF Proposal - 12/6/02

R. Gustafson, K. Riles - University of Michigan

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LIGO-G020XXX-00-Z

Search for CW Sources

Modulations / drifts complicate analysis enormously:» Simple Fourier transform

inadequate

» Every sky direction requires different demodulation

All-sky survey at full sensitivity is formidable computing challenge

Standard deviation in f/f (x106) vs RA & declination (S1 data run)

Michigan Group NSF Proposal - 12/6/02

R. Gustafson, K. Riles - University of Michigan

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LIGO-G020XXX-00-Z

Search for CW Sources

Michigan focus – “Unbiased” all-sky search for CW flux:(based on incoherent averaging, i.e., less sensitive approach)

First iteration – Brute force:• Measure power in selected bins of averaged periodograms• Bins defined by source parameters (f, RA, ) • Estimate noise level & statistics from neighboring bins• Set upper limit on quasi-sinusoidal signal on top of

empirically determined noise• Scale upper limit by antenna pattern correction• Quasi-analytic method, anchored in Monte Carlo simulation

Michigan Group NSF Proposal - 12/6/02

R. Gustafson, K. Riles - University of Michigan

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LIGO-G020XXX-00-Z

Search for CW Sources

Disadvantages of brute-force approach:• Intrinsic sensitivity suffers; depends on sky direction• Detector non-stationarity especially harmful to sensitivity

Advantages:• Computationally tractable• Robust against uncertainties in source parameters

First look at S1 data:• Highly non-stationary (see figures)• Exploring data segment vetoes and reweighting schemes• Focussing on “playground frequency band” near 660 Hz

Michigan Group NSF Proposal - 12/6/02

R. Gustafson, K. Riles - University of Michigan

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LIGO-G020XXX-00-Z

Search for CW SourcesStatistical measures of noise in narrow band for >600 2048-second DFT’s (LLO data from

S1)

Plotted vs time during run: Ordered by least variance

Michigan Group NSF Proposal - 12/6/02

R. Gustafson, K. Riles - University of Michigan

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LIGO-G020XXX-00-Z

Search for CW Sources

Diminishing returns on total variance after ~100 DFT’s

Michigan Group NSF Proposal - 12/6/02

R. Gustafson, K. Riles - University of Michigan

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LIGO-G020XXX-00-Z

Search for CW Sources

Immediate plan:• Complete present brute-force analysis with only modest refinements• Aim: Inclusion in first upper limits publication on periodic sources

Longer term:• More sophisticated, time-dependent search over frequency bins

(similar to “stack-slide” method of Brady et al.)• Inclusion of varying source parameters, including binary orbital motion• Explore more exotic “periodic glitch” sources

Michigan Group NSF Proposal - 12/6/02

R. Gustafson, K. Riles - University of Michigan

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LIGO-G020XXX-00-Z

Commissioning & Detector Advancement

We’ve worked with LHO staff and CIT/MIT commissioners to• Bring interferometers into operation• Reduce noise• Evolve the operations procedures• Understand operational reality• Develop new ideas

Michigan Group NSF Proposal - 12/6/02

R. Gustafson, K. Riles - University of Michigan

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LIGO-G020XXX-00-Z

Commissioning & Detector Advancement

Some Michigan contributions:• 2Ώ scheme of monitoring recycling cavity sideband (SB) buildup

(with W. Kells from the 40-Meter experience)• 2Ώ demod hardware for deriving SB power signal for lock acquisition • Assistance in evolving the lock acquisition with M. Evans & other IFO

scientists• Identification / fix of gross RF leakage contamination problem• Identification / fix of gross 60 Hz ground noise problem• Invention of AM-based l+ / l- servo scheme: (more later)

» Used on fully recycled 40 Meter» Tested on 2-km IFO power recycled cavity – Full lock expected soon

• Found new clean way to derive AM second SB for AM servo @ 40 MHz

Michigan Group NSF Proposal - 12/6/02

R. Gustafson, K. Riles - University of Michigan

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LIGO-G020XXX-00-Z

Commissioning & Detector Advancement

Some Michigan contributions: (continued)• Early study of Pentec ADC/DAC problems:

» Gross phase noise massive down conversion» Programming subtleties

• Temperature trouble elucidated: Pentiums shut down when too hot (!)• “Hop test” for alignment

» Reflected beam spot must not hop when arm on/off» Devised at 40 meter

Michigan Group NSF Proposal - 12/6/02

R. Gustafson, K. Riles - University of Michigan

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LIGO-G020XXX-00-Z

The AM Servo for l+, l- Degrees of Freedom

Standard LIGO length error signals derived by comparing phase shift of carrier in a cavity with RF sidebands (Pound-Drever-Hall). One serves as local oscillator for the other.

Works well in arms, but in recycled Michelson cavity the carrier signal info contains arm errors in addition to local cavity error.

Hierarchical servos make a miracle happen, but lock acquisition challenging and fragile

We asked:

Why not add a 2nd virgin (non-resonant, non-phase-shifted) SB

to beat against the first for l+, l- servos?

Michigan Group NSF Proposal - 12/6/02

R. Gustafson, K. Riles - University of Michigan

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LIGO-G020XXX-00-Z

The AM Servo for l+, l- Degrees of Freedom

Used at the 40 Meter:• Quick, long, robust locks

Have started on the LHO 2-km:• Power recycled Michelson (no arms) works robustly• Full lock to be attempted soon• Expect quick, robust locking• Noise character unknown – will be measured

Michigan Group NSF Proposal - 12/6/02

R. Gustafson, K. Riles - University of Michigan

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LIGO-G020XXX-00-Z

Future Commissioning: More of the Above

Help drive IFO’s from 10-17 m/Hz1/2 to 10-19 m/Hz1/2

It’s getting harder to improve!

Many proposal bullets well underway (by us and other IFO scientists)

Study the DAC/ADC noise with new digital suspension controllers Explore issues at –60 db below 1 bit; relevant to CW search

Devise on-line monitors of digital aspects of servo noise

Explore alignment/clipping of the output beams and devise diagnostics short of opening / resurveying (work in progress)

Michigan Group NSF Proposal - 12/6/02

R. Gustafson, K. Riles - University of Michigan

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LIGO-G020XXX-00-Z

Future Commissioning

Demonstrate Full Lock of LHO Interferometers with AM l+ l- servo• Expect immediate lock acquisition• Noise issues not so clear

Develop compound alignment knobs; rotate “aligned” arm about a point “Software knobs”

Pursue more subtle forms of 60 Hz and its harmonics

Michigan Group NSF Proposal - 12/6/02

R. Gustafson, K. Riles - University of Michigan

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LIGO-G020XXX-00-Z

Advanced LIGO – New Servo Schema: Dither Lock

We propose to explore dither modulation of arms and cavities, effected by driving a test mass mirror at a resonant frequency, e.g., N x 15 kHz

We locked a 40-meter arm by dither lock (low frequency)

15 kHz x 4 = 50 kHz might be far enough out of LIGO ban to operate

Advantages:• Handles any power level• Allows independent error signals for different cavities• Possibly no Schnupp asymmetry operation better contrast• Noise issues to be explored

Michigan Group NSF Proposal - 12/6/02

R. Gustafson, K. Riles - University of Michigan

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LIGO-G020XXX-00-Z

SummaryGroup is active:• Detector characterization• Search for periodic sources• Commissioning• IFO servo control development

Have voted with our feet to make LIGO succeed:• Committed to success of instrument• Carrying out astrophysical analysis

Have made good use of resources – including undergraduates

Michigan Group NSF Proposal - 12/6/02

R. Gustafson, K. Riles - University of Michigan

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LIGO-G020XXX-00-Z

Summary

Request: • Continued funding• PLUS postdoc and 2nd graduate student

Plan:• Station postdoc and student at Hanford• Find gravity waves !