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Michigan Group NSF Proposal - 12/6/02
R. Gustafson, K. Riles - University of Michigan
1
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
2
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
3
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
9
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
12
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
13
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
14
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
15
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
16
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
17
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
18
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
19
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
20
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
21
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
22
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
23
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
24
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
25
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
26
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 !