LASER INTERFEROMETER GRAVITATIONAL-WAVE OBSERVATORY
-LIGOCALIFORNIA INSTITUTE OF TECHNOLOGY
MASSACHUSETTS INSTITUTE OF TECHNOLOGY
Annual Report
AdL progress and plans; LASTI progress and
plans
California Institute of Technology
LIGO Project – MS 51-33
Pasadena CA 91125
Phone (626) 395-2129
Fax (626) 304-9834
E-mail: mailto:info@ligo.caltech.edu
Massachusetts Institute of Technology
LIGO Project – MS 20B-145
Cambridge, MA 01239
Phone (617) 253-4824
Fax (617) 253-7014
E-mail: mailto:info@ligo.mit.edu
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A.
PROJECT SUMMARY
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B.
TABLE OF CONTENTS
A.
B.
C.
PROJECT SUMMARY .............................................................................................. 3
TABLE OF CONTENTS ............................................................................................ 4
PROJECT DESCRIPTION ......................................................................................... 5
C.1. Work Accomplished During FY 2003 ...............Error! Bookmark not defined.
C.1.1.
LIGO Hanford Observatory .......................Error! Bookmark not defined.
C.1.2.
LIGO Livingston Observatory ...................Error! Bookmark not defined.
C.1.3.
Educational Outreach .................................Error! Bookmark not defined.
C.1.4.
Safety .........................................................Error! Bookmark not defined.
C.1.5.
Technical and Engineering Support ...........Error! Bookmark not defined.
C.1.6.
Detector Support ........................................Error! Bookmark not defined.
C.1.7.
Data and Computing Group .......................Error! Bookmark not defined.
C.1.8.
Campus Research Facilities .......................Error! Bookmark not defined.
C.1.9.
Advanced R&D ........................................................................................... 6
C.1.10. LIGO Scientific Collaboration (LSC) ........Error! Bookmark not defined.
C.1.11. Astrophysics and Data Analysis ................Error! Bookmark not defined.
C.1.12. Actual Costs, Staffing, Organization .........Error! Bookmark not defined.
C.2. Work Planned for FY 2004 ............................................................................... 15
C.2.1.
Operations ..................................................Error! Bookmark not defined.
C.2.2.
Detector Commissioning Goals .................Error! Bookmark not defined.
C.2.3.
Modeling and Simulation ...........................Error! Bookmark not defined.
C.2.4.
LIGO Data Analysis System (LDAS)........Error! Bookmark not defined.
C.2.5.
Information Technology Support Group ...Error! Bookmark not defined.
C.2.6.
Campus Research Facilities ...................................................................... 15
C.2.7.
Advanced R&D ......................................................................................... 15
C.2.8.
LIGO Scientific Collaboration ...................Error! Bookmark not defined.
C.2.9.
Astrophysics and Data Analysis ................Error! Bookmark not defined.
C.2.10. FY 2004 Meetings......................................Error! Bookmark not defined.
D. References ..................................................................Error! Bookmark not defined.
F. PROPOSAL BUDGET JUSTIFICATION ................Error! Bookmark not defined.
F.1. Summary ............................................................Error! Bookmark not defined.
F.2. MIT Funding ......................................................Error! Bookmark not defined.
F.3. Proposal Budgets ...............................................Error! Bookmark not defined.
F.3.1.
Line A—Senior Personnel .........................Error! Bookmark not defined.
F.3.2.
Line B—Salaries and Wages .....................Error! Bookmark not defined.
F.3.3.
Line C—Fringe Benefits ............................Error! Bookmark not defined.
F.3.4.
Line D—Equipment ...................................Error! Bookmark not defined.
F.3.5.
Line F—Participant Costs ..........................Error! Bookmark not defined.
F.3.6.
Line G5—Other Direct Costs, Subawards .Error! Bookmark not defined.
F.3.7.
Line G6—Other Direct Costs, Other (GRA Benefits, Subcontracts) Error!
Bookmark not defined.
F.3.8.
Line I—Indirect Costs................................Error! Bookmark not defined.
Appendix A. ...................................................................................................................... 17
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Appendix B. ...................................................................................................................... 18
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C.
PROJECT DESCRIPTION
C.1.1.1.
MIT Facilities (LASTI)
The goal of the MIT LASTI facility is to support the development and testing of a range of LIGO
subsystems and components at full scale in an environment that is as close to that found at the
observatories as possible. The present principal use of this facility is for the testing of the
External Pre-Isolator (EPI) system currently being implemented at the LIGO Livingston
Observatory to alleviate the problems caused by excessive seismic noise due to logging in the
area.
The development of the EPI has been the focus of the LASTI group for the last two years. This
year’s efforts have been devoted to learning optimal methods for the control of the system. In
addition to this a considerable amount of LASTI manpower has been spent on transferring the
lessons learned at LASTI during the EPI tests to the local staff at Livingston Observatory. This
significantly contributed to the efficient implementation of the system at the LIGO Livingston
Observatory. This has involved many of the LASTI personnel spending considerable time
amounts of time at the site.
The LASTI personnel also contributed to the design, installation and commissioning of a
Thermal Compensation System (TCS). This system has been incorporated into the LIGO
Hanford 4km detector. The TCS allows distortions in the transmission profile of the Input Test
Masses (ITMs) caused by excessive 1.064 um power absorption to be corrected.
The 10 Watt PSL system at LASTI was used in the development of new frequency stabilization
and intensity stabilization servos that will be implemented at the sites sometime before the S4
science run.
In the Advanced LIGO system it will be necessary to mount geophones and photo-detectors on
the seismic isolation platforms within the high vacuum envelope. Obviously these components
will need to be ultra-high vacuum compatible. With this in mind we designed and build a
vacuum compatible geophone. This consisted of placing a regular geophone inside a stainless
steel vacuum vessel that was filled with a neon buffer gas. The outside of these containers is ultra
high vacuum compatible and the neon buffer gas enables the detection of any significant leaks.
These vacuum compatible geophones are now routinely used inside the LASTI vacuum system.
With the completion of the HEPI testing of LASTI we are now able to use the HEPI system as a
tool. This will be utilized later in 2004 when we will characterize a prototype triple suspension in
one of our vacuum chambers. The HEPI system will then be used as a shake table to study the
dynamics of the triple under the effects of ground excitation. In addition to this installation and
alignment procedures will be learned that will reduce the installation time for Advanced LIGO at
the sites.
.
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C.1.2.
Advanced R&D
This year we initiated or continued a broad range of research to support the development of
advanced detectors. This effort is very strongly collaborative, and the research highlights
described below are often the result of collaborations with other institutions in the LIGO
Scientific Collaboration (LSC). The results confirm the basic Advanced LIGO Design, and have
allowed us to further refine and detail the subsystem designs.
C.1.2.1.
Systems and Interferometer Sensing and Control
The Systems group supported the development of more detailed requirements for a number of
subsystems, including the Core Optics, Suspensions, and Isolation subsystems. The detailed
optical layout of the interferometer has proceeded as a tool to ensure interface compatibility and
to establish ‘footprints’ and allowed volumes for in-vacuum subsystems.
The Interferometer Sensing and Control subsystem met a milestone in selecting a DC readout for
the gravitational wave signal rather than the traditional modulation-demodulation system. This
was enabled by a quantum-mechanical analysis (REF
http://www.ligo.caltech.edu/docs/P/P020034-00.pdf) of the readout indicating that this system
will deliver the best sensitivity, and associcated work showing that this is also the easiest to
implement.
C.1.2.2.
Seismic Isolation
The seismic isolation team continued to focus on pre-isolator research for Initial LIGO. As
reported above, the development of this element of Advanced LIGO was accelerated to be
applied to reduce the excess seismic noise at the Livingston Observatory. In addition to
supporting the fabrication and installation of the pre-isolator at the observatory, the prototype
and first-article units at the MIT LASTI testbed were exploited to characterize the mechanical
system, develop and test servo control laws, and to write software routines for the operation, test,
and safety aspects of the real-time controllers. Sample performance at an intermediate state of
commissioning is shown in Figure X, showing the fulfillment of the basic requirements of a
factor of 10 suppression in the critical region between 1-3 Hz. Innovative work in adaptive feedforward schemes have been shown to give superior performance to traditional fixed-gain
systems, and may be integrated into the Observatory controls when ready.
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Figure 1: Performance of HEPI external pre-isolator in commissioning at the MIT LASTI
facility.
The seismic isolation Technology Demonstrator, designed by the LSU-Stanford-LIGO team,
fabricated by the LIGO Laboratory, and installed in the Stanford Engineering Test Facility, has
delivered valuable results. A photograph of the installed system is shown in Figure X. It has
allowed detailed requirements on geometry and dynamics to be delivered to the designers of the
final prototypes, and control topologies have been tested to optimize the performance for the
sensors and actuators in the system. Some early results are shown in Figure X; each stage will
supply roughly a factor of 30 suppression over a frequency range from ~2 - ~20 Hz, which with
the external pre-isolator and suspension meets the requirement for suppression of seismic motion
for Advanced LIGO.
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Figure 2: Figure 5. Picture of the Advanced LIGO seismic isolation technology
demonstrator two-stage active platform inside the vacuum tank. The two stages are
structurally interleaved to correctly position the centers of gravity. One of the 3 STS-2
seismometers mounted on the first stage, and one of the Geotech GS-13 geophones mounted
on stage two are indicated. The overall width is approximately 1.5 m. Masses simulating
the load of the suspension system can be seen on the optics table which is part of stage two
of the platform.
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Figure 3: Measurements from the technology demonstrator prototype active isolation
platform at Stanford, indicating the desired suppression of a factor of 30 in one axis of one
stage. The heavy black curve shows the displacement noise level on the ground in a
horizontal direction and the dotted curve the residual noise on stage 1 of the platform. The
blend frequency used for these measurements was 0.5 Hz. The feature seen at around 25
Hz is believed to be a resonance of the current support structure.
.Based on the encouraging results and detailed information from these prototypes, a contract has
been let with ASI for the design of the Advanced LIGO seismic isolation in-vacuum platform, as
well as for the fabrication of a test-mass version of the isolator. The delivery date for this isolator
is November 2004, when it will be installed at the MIT LASTI facility for standalone testing and
subsequent integration with a test-mass suspension.
C.1.2.3.
Suspensions
The suspension design for Advanced LIGO is based on developments by the Glasgow UK GEO
group for the GEO 600 detector, and the effort remains a close collaboration of scientists from
Glasgow, Stanford, and the LIGO Laboratory. Two suspension designs received considerable
attention this year. The triple pendulum prototype suspension for auxiliary optics was
characterized, and models refined to correctly reflect experimental measurements. The modes of
the system were damped, and various actuator and control loops were developed. The suspension
was sent from Caltech, where it had been fabricated and assembled, to MIT, where it was
installed in the MIT LASTI testbed. This allowed exercise of installation tooling and procedures,
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and precision mechanical alignment with the metrology tools used for initial LIGO. It is
undergoing further characterization at MIT, using the HEPI system there as a ‘shake table’ for
measurement of transfer functions.
Work continued in Glasgow, Stanford, and Caltech on the test-mass quadruple suspension
design. Fabrication techniques for the fused-silica suspension ribbons and attachments were
refined in Glasgow, and detailed designs and finite-element models were pursued at Caltech. An
overall sketch from this on-going design effort, and a solid-model rendering, are shown in Figure
X.
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Figure 4: Schematic diagram of quadruple pendulum suspension system for Advanced LIGO. A face view of the main chain is
shown on the left, and in the middle is shown a side view with main and reaction chains visible. On the right is a conceptual
design for the supporting structure which is approximately 2 m in height, and whose top surface would be rigidly attached to the
optics table. This structure would support elements of the sensor and actuators for local control, and earthquake stops to restrict
motion of the masses and support them in the event of a wire or ribbon failure.
C.1.2.4.
Optics
The requirements and conceptual design for the optics subsystem were documented and brought
to a successful Design Requirements Review in January 2004. Requirements for both the
baseline sapphire substrate material and the fused silica alternative were addressed.
Considerable effort has gone into the background research and fact-gathering for the selection of
the substrate for continued development. Studies pursued by the Glasgow-Stanford-LIGO team
include polishing, annealing (to address mechanical loss in fused silica and optical loss in
sapphire), mechanical loss (‘Q’) measurements, scatter characterization, as well as thermal
modeling. Direct measurement of thermal noise was performed in the TNI (see below). A
recommendation to the LIGO Laboratory Directorate and LSC for the choice of substrate is
planned to take place this year to support the further development of suspensions in the US and
UK.
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The Thermal Noise Interferometer (TNI) research at Caltech produced several very interesting
results this year. This special-purpose interferometer is designed to demonstrate our
understanding of thermal noise in substrates and coatings by magnifying the effects (using small
optical spot sized on the substrates) and suppressing other noise sources (with a short baseline
and common-mode seismic excitation).
In the first result, fused silica substrates with typical optical coatings were used. After
considerable effort to reduce spurious electronic noise sources, a region of noise which appears
to be limited only by thermal noise from ~500 Hz to ~10 kHz was exposed (see Figure X). A
model for the substrate and coating thermal noise is effectively in agreement with the observed
form and level of noise using model values consistent with other measurements. This confirms,
and extends to lower more interesting noise levels, an earlier measurement by our Japanese
TAMA colleagues (Numata, et al., PRL 91 (26), 260602 (Dec. 31, 2003)), and gives us
considerable comfort that our independent measurements of mechanical losses in coatings can be
used to predict thermal noise levels in interferometers, both initial and Advanced.
Figure 5: Thermal Noise Interferometer results, indicating that the thermal noise level in
fused silica substrates with conventional optical coatings behaves as anticipated. The
coating mechanical loss from this experiment is ~1.5x10^-4.
In the second result, the fused silica substrates were removed and replaced with sapphire
substrates. For this substrate, the thermal expansion and contraction due to thermal fluctuations
in the substrate are expected to dominate in the gravitational wave band. Using materials
parameters measured in earlier work at MIT and elsewhere, the observed level agrees quite well
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with the observed level. Again, this gives us confirmation of a central element in the noise
budget of Advanced LIGO and allows us to move forward with our substrate recommendation
with confidence.
Figure 6: Thermal Noise Interferometer results with sapphire substrates. The
thermoelastic noise is seen, consistent with models, between ~500 Hz and ~10 kHz.
C.1.2.5.
Optical Coatings
Both the (familiar) optical losses but also the mechanical loss in optical coatings are important
to the performance to Advanced LIGO. The challenge for Advanced LIGO lies in achieving the
required low mechanical loss that is needed to control the thermal noise perceived by the
interferometer. We have put into place contracts with two state-of-the-art coating firms (VIRGO
SMA, Lyon, France; CSIRO, Sydney, Australia) to help us understand the sources of loss and to
develop low mechanical loss coatings. Along with our LSC Collaborators (Stanford and
Glasgow), we have a combination of academic and practical expertise to address the questions.
This year trial coatings were made by both coating firms to establish a baseline, and some doping
and annealing processes were explored. To date the losses have been reduced by small
increments, but in a way consistent with the theories of losses in the Tantala, and are
encouraging for further reductions.
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C.1.2.6.
Pre-stabilized Laser and Input Optics
The baseline approach to producing the Advanced LIGO laser met an important milestone at the
development lab in the Max Planck AEI Hannover (Germany). This end-pumped Nd:YAG rod
laser, set up as a free-running butterfly cavity, produced 213 W with an M^2 of 1.15. This meets
the requirements for power, and may have met the beam quality requirement as well (this must
await single-mode operation). Work continued on alternative designs at Stanford and Adelaide.
Within the LIGO Laboratory, progress was made on setting the performance requirements for the
laser, and refining the intensity stabilization. Final measurements were made on the prototype
setup at MIT for developing this control system, and a student completed his thesis on the topic
(Jameson Rollins). The result, shown in Figure X, indicates that the requirement is met for
frequencies above 40 Hz. The limit to the performance is thought to be residual beam jitter due
to the air path for the laser beam; the design (and the next stage of prototyping) calls for an allin-vacuum sensing system which will sidestep this difficulty.
Figure 7: Performance of the prototype Advanced LIGO Intensity stabilization system. The
red curve indicates the performance to date; the black curve represents the requirement.
The Input Optics are the responsibility of the University of Florida for Advanced LIGO (as they
were for initial LIGO). Development of high-power Faraday Isolators and Modulators have been
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a focus for them. The LIGO Lab’s participation is at the LIGO Livingston Laboratory, where
postdocs shared with Florida have set up a high-power testing laboratory. We have been
searching for a vendor of a 100W class laser for ‘stress testing’ of the components, and have
recently taken delivery of a fiber laser (from IPG Photonics) which is just now undergoing
characterization and qualification.
C.1.2.7.
Thermal Compensation
The lens formed in the substrates due to the absorption of the laser light in the substrate make the
interferometer optical system sensitive to the power level. We wish to have a system which can
work at all power levels, and so will apply complementary heat to the substrates to bring the
curvature to the correct value for all input powers. For Advanced LIGO, most of the recent work
has been in the modeling of the system, using both the mode-based MELODY model (developed
by our Stanford collaborators) and the FFT-based Huygens propagation numerical code
(developed at MIT for initial LIGO and now exercised at Caltech). As reported elsewhere, the
basic ideas of thermal compensation have been applied to initial LIGO, and the Advanced LIGO
team has been central in that application. Not surprisingly, the creative process and testing in situ
have helped the Advanced LIGO design progress as well .Interface issues with the Core Optics
and the Suspensions teams have been resolved, with simplification of the overall interferometer
design.
C.2. Work Planned for FY 2004
C.2.1.
Campus Research Facilities
C.2.1.1.
MIT Facilities (LASTI)
In the winter of 2004 we will take delivery of the first prototype of the Advanced LIGO Seismic
Isolation system for a BSC chamber. The first part of next year will be spent learning how install
and optimally control this system. It is also planned that a prototype of the Advanced LIGO quad
pendulum design will also be delivered. This quad pendulum design is the planned suspension
for the core optics. This will enable us to demonstrate for the first time in LIGO the cartridge
installation technique. It is thought that this technique will help to minimize the downtime
between initial LIGO and Advanced LIGO. In addition to this we will be able to check for
unforeseen interactions between the Advanced LIGO Seismic Isolation and Suspension systems.
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C.2.2.
Advanced R&D
The R&D program will continue to focus on the Advanced LIGO subsystems, the establishment
of detailed requirements, and the preliminary design phases. Significant activities planned for
FY2005 include the following:

Seismic Isolation: Stanford Engineering Test Facility (ETF) testing will be further
exploited. A set of software for the control systems and the supervisory control will be
delivered for system testing at MIT LASTI. The test-mass (‘BSC’) in-vacuum prototype
will be installed at LASTI and commissioned.

Suspensions: The UK team, working with the LIGO team, will complete the design for
the test mass suspension. The first ‘controls’ quadruple suspension will be built at
Caltech and delivered to LASTI. It will be integrated with the seismic isolation prototype,
and the combined system characterized.

Optics: The full-size substrates to be used in LASTI system testing will complete their
pathfinder process: they will be polished and coated, and prepared for attachment to the
suspension. Tests of thermal compensation in a suspended cavity, performed at the
Australian Gingin facility in collaboration with LIGO, will be completed. Design and
prototyping of the Input Optics (in collaboration with the University of Florida), and the
Auxiliary Optics, will continue.

Lasers: The formal requirements review and documentation for the complete PreStabilized Laser will be completed, and prototyping of the system will continue at the
University of Hannover.

Systems: We will continue to refine the baseline optical layout and interface
documentation. The end-to-end simulation tool, developed for Initial LIGO, will be used
to simulate locking of the complete Advanced LIGO and to study the consequences of the
stored power in the optical cavities and their influence on the longitudinal and angular
controls.
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Appendix A.
Anticipated, Near-Term, Major LIGO Procurements
This list summarizes our current estimates concerning the size and scheduling of near-term
significant LIGO procurements and whether or not NSF review and approval will be required.
Where the fund source is FY 2003, these are procurements in process under the funding already
approved by the Cooperative Agreement.
TBD FOR ADL
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Appendix B.
MIT Proposal Budget for FY 2004 Participation in LIGO
The original signed MIT Proposal including budget allocations is retained on file at Caltech.
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