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Status of Detector Commissioning

LSC Meeting, March 2001

Nergis MavalvalaCalifornia Institute of Technology

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Promises at Aug 00 LSC meeting

Power recycled Michelson locks Carrier or sideband resonance

Arm cavity locks Feedback to ITM or ETM

…get both locking at same time…

…add second arm cavity…

…full interferometer!

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Livingston overview: what’s new

Installation/alignment of remaining in-vacuum components – Nov. 2000

Beam sighted down arm cavities – Jan. 2001 Within < 3 rad of optic centers

Some realignment of input optics beam required

4 km arm cavity (longest ever!) locked – Feb. 2001

Full interferometer locking underway

Learning about differences in seismic environment between both sites

E3: first ‘coincidence’ run – Mar. 2001 LLO X arm cavity locked for ~ 80%

PEM channels acquired at both observatories

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Hanford overview: what’s new

Initial full ifo locking – Oct. 2000Intentionally reduced buildup

E2: recombined interferometer – Nov. 2000

Full ifo locking with no intentional loss – Jan. 2001Carrier power recycling gain: 15

Hour long lock stretches

Sensitivity spectra noisy as expected

Noise reduction studiesSensing noise

PSL/IO frequency noise

Electronics noise (low input power, less filtering)

Olympia earthquake – Feb. 2001Damage to magnets on several suspended optics

Under repairs

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Interferometer Locking: lock acquisition

Masterminded by Matt Evans (CIT grad student). His reward: PhD thesis

Acquisition C code named for him: “Matt’s code”

Basic problem Sensing matrix goes through singularity as both arm cavities start building

up power

Solution implemented Judicious use of light power levels to estimate when matrix determinant too

small; turn of controller till dofs coast through singularity

LSC digital controls made it possible “Matt’s code” interfaced with “Rolf’s code”

All testing of actual C code was done using E2E model of full ifo Angular fluctuations not included had to rethink use of signals a few times

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Length Sensing Matrix: very near resonance

AS_Q: DARM

REFL_I: CARM, PRC

REFL_Q: MICH

PO_I: CARM, PRC

PO_Q: MICH

Phase modulated light: C and SB

Reflection and Pick-off I phase signals both dominated by CARM (~100x), but with different amounts of PRC

=> Matrix can be inverted!

Reflection and Pick-off Q phase signals are clean MICH signals, but ~100x smaller than corresponding I phase signals

Phase must be set accurately

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Lock acquisition:the problem

Sensor signals, S, are related to degrees of freedom, D, via the optical gain matrix, Ĝ Ĝ depends on buildup of fields in the ifo, i.e. Ĝ(t)

Ĝ must be invertible, i.e. det(Ĝ) 0

Lock acquisition sequence: states

State 2

State 3State 4

Sideband resonance in arm cavity in State 2/3 kills lock

Change in optical gain

Matrix for separating CARM, PRC goes through singularity

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Lock Acquisition Programa.k.a. Matt’s code

DC and 2fSB

Use DC power signals (total power) as well as 2fSB demodulated signals (sideband power) to determine state and optical gain

Use measured optical gains in easily locked states (2 and 3) to estimate gain matrix in State 4

Determine occurrence of matrix singularity and turn off control of PRC dof in a carefully tuned window around that zero crossing

DC

DC

DC

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Matt’s Code in Action

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Full Interferometer Locking

S. Whitcomb

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From “first lock” to stable high buildup lock

Optical lever damping for angular dof on several optics Mitigate 1.06 m light coupling problem

Improved signal-to-noise on critical light power signals (dynamic range)

Wavefront sensor on antisymmetric port ETM angles differentially

Detour to run recombined configuration First look at ‘differential mode’

E2: >90% duty cycle for lock

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Displacement Sensitivity

M. Landry

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What’s next?Near future

LHO 2km Repairs – expect to re-commission in 05/01

Improvements – new 1.06 m insensitive OSEMs

LHO 4km Expect to begin commissioning in 05/01

LLO 4km Characterize environmental noise better

Proceed with full interferometer locking

Identify in-vacuum problems that must be fixed in next vent

Vent coordinated with installation/repair effort at LHO