LIGO-G010075-00-D 1 Status of Detector Commissioning LSC Meeting, March 2001 Nergis Mavalvala...
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Transcript of LIGO-G010075-00-D 1 Status of Detector Commissioning LSC Meeting, March 2001 Nergis Mavalvala...
1LIGO-G010075-00-D
Status of Detector Commissioning
LSC Meeting, March 2001
Nergis MavalvalaCalifornia Institute of Technology
2LIGO-G010075-00-D
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!
3LIGO-G010075-00-D
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
4LIGO-G010075-00-D
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
5LIGO-G010075-00-D
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
6LIGO-G010075-00-D
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
7LIGO-G010075-00-D
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
8LIGO-G010075-00-D
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
9LIGO-G010075-00-D
Matt’s Code in Action
10LIGO-G010075-00-D
Full Interferometer Locking
S. Whitcomb
11LIGO-G010075-00-D
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
12LIGO-G010075-00-D
Displacement Sensitivity
M. Landry
13LIGO-G010075-00-D
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