Laser Interferomter Gravitational-Wave Observatory

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LIGO Undergraduate Research Projects -- 2002

For more information on the projects below, contact the appropriate mentor (email addresses and other contact information can be found on the LIGO Roster).

LIGO's Thermal Noise Interferometer: Calibration and Electronic Noise Reduction
Kyle Barbary
Mentor: Eric Black

The Thermal Noise Interferometer (TNI) at Caltech is devoted to the measurement and characterization of thermal noise in mirrors designed for use in LIGO (Laser Interferometer Gravitational Wave Observatory). Here, I address two problems in the TNI that have limited the accuracy of noise measurements. First, recent measurements have shown that electronic noise is at least an order of magnitude too high for us to see thermal noise. To remedy this, I designed and built low-noise filter/amplifiers and low-noise summing junctions. Their input referred noise of approximately 25 nV/vHz represents a 40 dB reduction in electronic noise level. Second, in order to measure noise levels, the TNI must be accurately calibrated. Calibration in the TNI is accomplished using a broadband phase modulator. Accurate calibration is dependent upon how well the transfer function of the phase modulator is known. The response of a broadband phase modulator was characterized in the frequency region between 50 Hz to 100 kHz. This data will be used to calibrate the TNI.


Considerations on Dual-Recycled Gravitational Wave Interferometers: Alignment of mirrors by wavefront sensing, investigation of quantum noise in signal-recycled interferometers and experimental characterization of a suspended mass mode cleaner
Markus Kenna (King's College, Cambridge Univ.)
Mentor: Alan Weinstein

In the context of Caltech's 40m prototype for Advanced LIGO, we investigate various issues related to what is arguably the most challenging task in designing a gravitational wave interferometer, which must be able to detect strains of the order of 10-21, namely to keep noise from all conceivable sources to an absolute minimum.

In order to sense small angular misalignments of the optics and correct for it via a feedback loop, a wavefront sensing scheme has to be implemented. We show that for the Advanced LIGO optical configuration two pairs of resonant sidebands (with only one of them resonant in the signal recycling cavity) allow us to discriminate between misalignments in different mirrors, and calculate the applicable wavefront sensing matrix relating the individual angular degrees of freedom to the signals at various output ports and at different demodulation frequencies.

Building on recent work on quantum nondemolition due to dynamical radiation pressure - shot noise correlations caused by the signal-recycling mirror, we outline the derivation of the quantum noise spectrum for Advanced LIGO-like interferometers. Paying special attention to include unavoidable optical losses and use realistic parameters we show that Advanced LIGO interferometers can indeed beat the na´ve quantum limit over a limited frequency range, provided thermal noise can be sufficiently reduced.

In the final part of the paper we describe a series of experiments with the newly installed suspended mass input mode cleaner at the 40m prototype interferometer, aimed at quantifying its efficiency in terms of higher order mode rejection, frequency stabilization and reduction in beam jitter.


Characterization and Commissioning of Digital Suspensions for the 40m Mode Cleaner
Ilya Berdnikov (Cornell University)
Mentor: Aan Weinstein

The 40m LIGO prototype at Caltech has recently acquired a new input modecleaner, an optical system, which serves to stabilize the input laser beam in frequency, position, angle and transverse profile before it enters into the arms of the Michelson interferometer. A core component of the mode cleaner is three suspended optics, each controlled by a separate digital suspension controller. The goal of this summer was to characterize and commission these controllers. I measured noise characteristics and transfer functions of the controllers, diagonalized them to maximally decouple the optics' degrees of freedom, and calibrated the motion of the mirrors.


Mapping of Synthetic Sapphire Optical Absorption at 1064nm
Robert Dan Berry
Mentor: Joseph Kovalik

The properties of synthetic sapphire (Al2O3) make its use in precision optical applications attractive, but its absorption properties are not sufficiently characterized. The focus of this experiment is the measurement of optical absorption at 1064 nm. This is accomplished by photothermal deflection spectroscopy. The sample is then translated in order to map the absorption through the crystal. These measurements will be useful in improving synthetic sapphire production for reduction of the absorption of 1064 nm radiation.


Characterising the Length Sensing and Control System of the Mode Cleaner in the LIGO 40m lab
David Bonfield
Mentor: Alan Weinstein

The LIGO project aims to build the world's first large (km) scale detectors of gravitational waves. The 40m lab is designed to prototype a number of systems to be used in Advanced LIGO, the second generation of LIGO interferometers, and is being upgraded with a 13 meter mode cleaner cavity to produce a highly stable laser beam. I have characterized the components of the systems that control the length of the cavity and stabilize the laser frequency. I hope to be able to choose gains to provide a stable feedback loop and confirm that the residual frequency noise in the laser meets the design requirement (which is 10-4 Hz per root Hz at 100Hz, decreasing with frequency).


Detector Sensitivity Investigation at the Thermal Noise Interferometer
Adam Bushmaker
Mentor: Eric Black

In mechanical experiments, the Quality factor Q and the level of thermal noise present are related through the fluctuation dissipation theorem. However, this relationship has never been tested in the low noise range of gravitational wave detectors, and subsequently, must be examined and understood. Using the finite element analysis program Algor, I modeled the resonant frequencies of fused silica and sapphire mirrors. Also, I measured the Q factors in the actual mirrors by observing the ring down times for several resonant modes. This data will be used in future thermal noise models and calculations.


Study of the Maximum Likelihood Estimator for Amplitude and Phase Modulated Gravitational Wave Signals
Patrick B. Cameron
Mentor: Gregory Mendell

We present analysis of test data for continuous, periodic gravitational wave signals from pulsars in LIGO detectors. We analyze the amplitude and phase modulation of the signals due to the motion of the Earth and natural frequency evolution of the neutron star source. This includes the development and testing of software to simulate periodic signals. We study the signal detection via the maximum likelihood principle. Additionally, we review the relevant statistics of signal detection as they apply to the Maximum Likelihood Estimator proposed by Jaranowski, Krolak, and Schutz (gr-qc/9804014). We verify the derived probability distributions for well-understood Gaussian random noise by Monte Carlo techniques. We then go on to examine how the distribution changes in the presence of a signal, and more complicated sources of noise, including nonstationary effects and nongaussian tails.


The Effects of Gravity Gradient Noises on Gravitational Wave Detection in the LIGO Livingston Observatory
Kwun Hung Cheung
Mentor: Mark Coles

Gravity gradients provide noises to interferometric gravitational wave detection. The gravity gradient noise is a limit on the sensitivity of the interferometer. In order to determine the gravity gradients in the region, ground motions are measured by seismometers installed into an array of eighteen bunkers. Then the ground motions data are collected, analyzed and implemented in determining gravitational waves.

Sixteen of the bunkers are arranged into two concentric squares with eight bunkers on each square, and three bunkers on each side of the squares. The edges of the squares run either from north to south or from east to west. The remaining two bunkers are located at the north and the east of the larger square in the array. The seismometers are all aligned with the north-south line and placed horizontally, and they are all ready to detect ground motions in three dimensions. The arrangement allows the determination of the strength as well as the direction of ground motion. The ground motion data can then be used to reproduce the ground waves passing by. Then gravitational gradients upon the array can be calculated and used in determining the noises of the interferometer.


Noise Characterization in the LIGO Livingston 4-km Interferometer
Raghuveer Dodda
Mentor: Sanichiro Yoshida

This project aims to characterize the motion of the Mode Matching Telescope Mirror-3 (MMT3) at LIGO, Livingston. The characterization process involved 3 major steps:

  • Construction of a simulation model (using e2e) of MMT3 that takes in as input the realistic ground noise and outputs the motion of the mirror with respect to the ground.
  • Creating a method to monitor the HAM table motion using the optics on the table
  • Measuring ground noise in the LVEA so that the ground noise at the HAM1 table on which MMT3 is placed, can be known.
The observations and conclusions from the above mentioned study are presented here.


Analysis of rapidly cooled refractory metals using x-ray diffraction
Brian Emmerson
Mentor: Riccardo DeSalvo

As part of our study to reduce thermal noise in LIGO mirror suspensions, we are investigating the mechanical and thermal properties of amorphous alloys made from refractory metals. The composition under investigation, glassy (Mo0.6Ru0.4)1-xBx, is produced in a two-piston apparatus (splat quencher). Owing to the mechanics of the machine, samples thus produced are only partially amorphous. It is therefore necessary to have reliable techniques for isolating amorphous regions of sample on which diagnostic measurements can be performed. Ultimately, we want to select specific samples for use in a flexible mirror suspension, so the techniques employed should neither damage sample shape nor induce phase transitions (from amorphous to crystalline states). Using x-ray diffraction, I am developing a quantitative, non-destructive technique to determine the ratio of crystalline to amorphous material present in samples produced by rapid quenching. This technique will be used by the LIGO group in the continued investigation of these and other alloys.


Late-Time Decay of Scalar Fields in Black Hole Spacetimes
Adrienne L. Erickcek
Mentor: Mark Scheel

When a black hole forms, any deviations from the Kerr-Newman geometry are radiated away as gravitational waves. This gravitational wave emission may be modeled by tracking the evolution of a massless scalar field in a single black hole spacetime. Initially, the amplitude of a scalar perturbation falls off exponentially, but at late times, scattering off the black hole's gravitational potential well results in a power-law decay. For a Schwarzschild black hole background and an initial scalar perturbation proportional to Ylm, the scalar field decreases as t-(2l+3) at late times t. Due to the absence of spherical symmetry, the corresponding power law for rotating black holes is expected to be more complicated, but there is some disagreement as to its precise form. Furthermore, some numerical results appear to conflict with all current analytical predictions.

Using a three-dimensional spectral code, we have numerically tracked the evolution of a scalar-field perturbation on a stationary black hole background. For a Schwarzschild background, our simulations exhibit the expected power-law decay. We then investigate scalar perturbations on rotating black hole backgrounds. Finally, we extend our simulations to include self-gravitating scalar fields.


Dumbbell-shaped Fused Silica Fibers
Lisa Fukui
Mentor: Phil Willems

In a dumbbell-shaped fused silica fiber, the radius of the top and bottom are optimized for minimal thermal noise, and the radius of the middle part is thinner in order to lower the vertical bounce frequency. These fibers may be used to suspend the mirrors in the interferometers for the LIGO project. I have developed a method to make dumbbell-shaped fibers using an automated fiber-pulling lathe. I have used a vise to bend the dumbbell-shaped fibers to test their strength at random points in the fiber. These fibers seem to be strong enough to suspend the mirrors in advanced LIGO.


An Improved Template Matching Algorithm for LIGO
Akash Kansagra
Mentors: Szabolcs Marka and John Zweizig

The current method of identifying gravitational wave signals in the data from the Laser Interferometer Gravitational Wave Observatory (LIGO) is to compute the inner product of the incoming data with predetermined gravitational waveforms. Although conceptually simple, the technique identifies far too many candidate signals, due largely to momentary spike in the data. A more rigorous method of identifying true signals is to compute a gamma2 fit to the data. A new matching algorithm has recently been implemented which utilizes this fitting technique to identify gravity wave signals. In addition to reducing the numbers of false gravitational wave candidates, the algorithm provides estimates of the signal parameters, such as the masses of the astrophysical objects that created the disturbance. However, the highly complex topology of the gamma2 surface complicates the search for a global minimum. The mechanics and function of this new data-fitting algorithm, along with possible improvements in the minimization technique, will be discussed in detail.


Detector Sensitivity Investigations at the Thermal Noise Interferometer
Fumiko Kawazoe
Mentor: Eric Black

LIGO's Thermal Noise Interferometer (TNI) is a test-bet interferometer designed to study thermal noise at levels low enough to be relevant for gravitational-wave detection. To find thermal noise in the TNI's sensitivity curve we need to identify as many noise sources in the instrument as possible. To do that we need to measure each noise separately and compare them with the total noise curve. Since what we want to know is the equivalent length noise, each measured noise should be expressed in terms of an equivalent displacement.

The TNI currently has the best displacement sensitivity of any operating interferometer. In this talk I will describe this instrument, and I will consider the contributions for each of the currently identified noise sources.


Three Input Matching/Driving Systems for Electro-Optic Modulators
Lucas Koerner
Mentors: Richard Gustafson and Paul Schwinberg

LIGO interferometers use three consecutive Electro-Optic Modulators, EOMs, each of which introduce radio frequency sidebands onto the 1064nm wavelength laser beam. Electro-Optic Modulators result in decreased laser power and increased optical distortion. Our purpose is to develop a radio frequency drive system so that a single broadband EOM can place all three pairs of sidebands (26.7 MHz, 29.5 MHz, and 68.8 MHz) onto the laser light. Using circuit-modeling software and building test circuits for analysis with a Network Analyzer, we have developed a tunable LC circuit with voltage step-up factors of 12, 9, and 4 at 29.5 MHz, 26.7 MHz, and 68.8 MHz, respectively. We have shown the circuit to be effective by driving a broadband EOM, modulating a laser beam, and quantifying the sidebands placed onto the laser light with an Optical Spectrum Analyzer.


X-Ray Micro-densitometry of Amorphous MoRuB for LIGO Flex-Joint Mirror Suspensions
Eric Adam Kort
Mentor: Riccardo DeSalvo

For Advanced LIGO, suspension thermal noise has become a limitation in the resolution of the interferometer, hindering our ability to detect gravity waves. The initial solution, fused silica fibers, has many inherent problems that are difficult to overcome. The most important problem is oxidation, which weakens the fiber and lowers the quality factor, reducing the advantages of using fused silica as suspensions. These problems with fused silica are the incentive for researching amorphous metals as an alternative material for mirror suspensions. Amorphous MoRuB samples are currently being made and tested for use as flex joints for mirror suspensions. Through x-ray imaging of the samples with a diagnostic medical x-ray unit, digitizing the images using a scanner, and then analyzing the results in Matlab, we developed a process that certifies a sample as being uniform (same thickness throughout and free of any holes/cracks) and therefore suitable for testing and, ultimately, for use as a flex-joint suspension.


BEAM Centering on the LIGO test masses
Nathan Kurz
Mentor: Michael Landry, Fred Raab, Daniel Sigg

An algorithm was devised for finding the deviation of the 1064 nm laser from the center of the test masses in the LIGO interferometers. Poor centering is a potential source of displacement noise. It leads to light from the Gaussian tails of the beam profile spilling into the beam tube as stray light. Additionally, poor centering allows for radiation pressure-induced noise. The beam must be centered on the face of the optic to within a tolerance of 1mm to keep these noise sources down to an acceptable level. Using images of the test masses and MATLAB code, the center of the optic and the deviation of the center of the beam from that point were calculated from the apparent positions of the four Optical Shadow Sensors and Magnetic Actuators.


Characterization of (Mo0.6Ru0.4)1-xBx Alloy for Use in Developing Suspensions for Gravitational Wave Detectors
Maddalena Mantovani
Mentor: Riccardo De Salvo

Mirror suspension noise is one of the biggest factors limiting the sensitivity of current gravitational wave detectors. This problem can possibly be overcome by using amorphous metals for making the suspensions. The most promising composition available seems to be (Mo0.6Ru0.4)1-xBx alloy, which due to its superior physical properties can help reduce the suspension thermal noise. We investigate these physical properties for the amorphous regime (x = 12 to x=24) by altering the boron atomic percentage in the material. My work involves the production of the alloy itself and particularly the investigation of temperature dependence of its properties such as the brittleness and hardness. These results will help determine the most appropriate composition to be used for the suspensions.


Advanced LIGO Suspension Research
Daniel Mason
Mentor: Calum Torrie and Janeen Romie

The suspension system for the main mirrors for Advanced LIGO, the planned upgrade to LIGO, are based on the triple pendulum design developed for GEO 600, the German/UK interferometric gravitational wave detector. The project studied several enhancements for a second-generation pendulum prototype. These included investigating the phenomenon of cold-welding and modeling the bending of components under load using finite element analysis and algebraic calculation methods. Many types of spring wire were tested for their physical properties and new methods were explored for clamping them. The breakthroughs made here will shave years off the LIGO timetable and lead ultimately to the indisputable evidence of the existence of gravitational waves.


Non-Gaussian Noise in the Thermal Noise Interferometer
Sharon Meidt
Mentor: Eric Black

Almost all interferometric gravitational wave observatories focus on eliminating Gaussian noise from the system. Real materials within the system, however, exhibit non-Gaussian behavior, similar to an actual gravitational wave signal. Non-Gaussian noise typically appears as a 'ping' or 'pop' which excites resonances and harmonics in the suspension wires and arm cavity mirrors within the interferometers themselves. I designed and implemented a data acquisition system to study non-Gaussian noise in LIGO's Thermal Noise Interferometer (TNI). The software I have written reads data from the north and south arm cavities through a data acquisition board, calculates a histogram of the amplitudes of a time series signal from each cavity and plots a histogram. Candidate non-Gaussian noise signals appear as outliers on a histogram of Gaussian probability distribution. An analysis of non-Gaussian noise in the TNI will be presented along with a discussion of the difficulties with, and solutions for, locking the instrument.


Fused Silica Suspension Research
Corinne M. Lamb
Mentor: Phil Willems

The proposed use of fused silica fibers in Advanced LIGO suspension systems is based on the low mechanical dissipation, or high quality factor of this material. Previous and detailed measurements of the quality factor have revealed deviations from expected values. A possible stress dependence of the quality factor is analyzed using a 3 pendulum system composed entirely of fused silica. The large upper and lower masses isolate the motions of a central mass which are excited using an electrostatic drive and observed by means of a laser beam and photodetector system. There are six total modes which will be measured: vertical bounce, pendulum, torsional, violin, and two rotational modes. An alteration of the lower mass will allow for direct comparison of quality factor measurements of fused silica fibers under varied stress.


Photothermal Deflection in a Synthetic Sapphire Crystal
George Noid
Mentor: Joseph Kovalik

In the study of optical systems a useful test is the study of laser deflection due to the intersection of two beams. Researchers can use the process known as photothermal deflection spectroscopy, PDS, to non-destructively probe both the surface and the interior of an optical material, such as a synthetic sapphire crystal (Al2O3). PDS utilizes a temperature gradient caused by a powerful pump laser in order to create a thermal lens. Position sensing photo-diodes then detect the deflected probe laser. We hope to observe the deflection through a cross-section of a single crystal by translating the intersection of the lasers. From that data the properties of a crystal, specifically possible impurities, will be localized. The techniques therein devised can then be applied to sample a variety of crystals. PDS may be preferred over chemical methods because it leaves the sample undamaged. Sapphire of the purity and size required for advanced LIGO test masses are difficult to synthesize and hence unlikely to be subjected to highly sensitive but destructive analysis.


An Improved Actuator for Earth-Tide Compensation
Heather Partner
Mentors: Rick Savage, Paul Schwinberg

Tidal stretching of the earth changes the lengths of the arms of the LIGO interferometers by hundreds of microns during peak periods. We compensate for the common-mode component of this tidal effect by adjusting the frequency of the laser, which is controlled by changing the temperature of the optical cavity to which the laser frequency is locked. The configuration presently in use regulates the temperature of the reference cavity by controlling the temperature of the walls of the vacuum chamber which houses it; the improved design utilizes a temperature-regulated shroud that surrounds the cavity inside the vacuum and is controlled by a temperature stabilization servo. The design, fabrication, assembly, installation, and testing of the improved apparatus are discussed, including the configuration of the in-vacuum shroud assembly and the electronics and modeling of the tidal compensation servo. Based on measurements of the improved tidal actuator prototype we characterize the system and assess the suitability of the improved design for implementation in the LIGO interferometers.


Seismic Surveys to Determine the Spectrum of Gravity Gradient Noise in LIGO
William M. Quarles
Mentor: Mark Coles

Seismic waves can cause time-dependent fluctuations in the mass distribution of earth near a test mass in a gravitational-wave interferometer. Even if the test masses are fully isolated from the mechanical waves, this results in a gravitational field that has non-negligible time, space, and frequency dependencies. An array of 20 Guralp CMG-40T seismometers was distributed over a field near the LIGO Livingston Observatory (LLO). High spatial resolution analysis of the local seismic activity is being performed with the data from these seismometers to infer the spectrum of this gravity gradient noise that would be observed in an advanced LIGO interferometer in that area. Different methods of retrieving data were investigated, including USB, IEEE 1394, and SCSI on a laptop computer using RedHat Linux 7.3. The full model involves analyzing the effects of Rayleigh waves, and we expect to get results with an accuracy of one part in 100. A simplified model that merely focuses on the frequency-dependent velocities of the seismometers was also developed. The data is being analyzed using scripts developed in MATLAB. Data acquisition and analysis is ongoing. The seismology equipment was lent to the LIGO Project by the courtesy of the PASSCAL Instrument Center, IRIS Consortium.


Topics in Data Analysis from Gravitational Wave Interferometers, Including a Cross Correlation Statistic to Identify Co-incident Bursts in LIGO
Surjeet Rajendran
Mentor: Alan Weinstein

LIGO (Laser Interferometer Gravitational wave Observatory) seeks to open a new avenue to explore the universe by detecting gravitational radiation from extra-terrestrial sources. Gravitational waves from astrophysical sources can be broadly classified into four categories: bursts, chirps, periodic waves and stochastic waves. Bursts are emissions from localized sources in the sky whose precise waveforms are difficult to predict in advance, so that matched filtering techniques are not useful. The classical methodology adopted to detect bursts is to identify peaks of excess power in the sensitive frequency bands of the data stream and then localize the analysis around these peaks in order to rule out the possibility of the burst being the result of noise. This paper explores the possibility of using the coherence function (between the gravitational wave streams) as a statistic to further analyze the burst peaks. The paper also seeks to identify the optimal value of the coherence function statistic, which minimizes the fake rate of detection while maintaining an acceptable level of efficiency of detection. This paper also seeks to quantitatively verify claims that the laser frequency noise and spacecraft displacement noise of the proposed LISA mission are suppressed using different combinations of measured quantities in time-delay interferometry.


Measurement of the laser beam profile for the 40-Meter Prototype Interferometer Gravitational Wave Detector
Aya Sekido
Mentors: Alan Weinstein, Osamu Miyakawa

A laser Interferometer is used for the gravitational wave detectors. The TEM00 mode, which is a basic mode of the laser, is needed for a cavity in the interferometer. Mode cleaner is a kind of Fabry-Perot cavity, which resonates for the TEM00 Mode and transmits it. Therefore, mode cleaner needs a proper mode matching and we have to measure the profile of the beam. For this purpose, the BeamScan Analyzer of Photonics was used. For preparation of the measurement of profile, we investigated reliability of the BeamScan Analyzer. The error of 1 time measurement was quite big. We found the average was useful to make error small. And we examined the beam width dependence on the laser power. We found the BeamScan Analyzer should be used with proper laser power.

We concluded that this BeamScan has a good performance for our requirement. We finished preparation for the measurement of the beam profile.


Classification of Physical Characteristics of (Mo0.6Ru0.4)1-x Bx in the amorphous regime
Barbara Simoni
Mentor: Riccardo De Salvo

The structure and properties of several new metallic glasses based on refractory transition metals have been systematically investigated as a function of their composition in the past. We are proposing such an amorphous metal, (Mo0.6Ru0.4)1-x Bx, as a possible solution for making mirror suspensions for gravitational wave detectors to reduce one of the major noise sources in these detectors, the suspension thermal noise. My work deals with the study of physical properties of (Mo0.6Ru0.4)1-x Bx, within the amorphous phase (x=12 to x=24), so as to help determine the best possible composition which can be used for producing low thermal noise suspensions. This project involves the production of the alloy with varying boron atomic percentages and not only characterizes the Tg (Glass transition temperature), Tm (melting temperature) for these compositions but also classifies the trend of other physical properties such as heat conductivity, heat capacity etc.


Metal Creep Measurement in Gravitational Wave Detectors
Rosalia Stellacci
Mentor: Riccardo De Salvo

Mirrors for gravitational interferometer experiment must be isolated from seismic motion. Soft suspensions can be used for vertical isolation using highly stressed materials. Since stress produces creep which can generate noise, it is necessary to select materials and treatments for the suspensions. Eight metal springs have been prepared and loaded, a multichannel LVDT readout system has been designed and connected, data acquisition and data analysis software has been written. Results: the system has been left in data acquisition mode to collect the data. The data have been analyzed to obtain the creep behavior.


Characterization of LIGO LSC Electronics
Andrea J. Smith
Mentor: Matthew Evans

The main objective of this project is to set up a system of web pages that detail the noise properties of the analog filters in the LSC sensing and actuation chains. These filters process the photodiode signal before it is converted to digital, and currently their properties are not documented in an accessible form. My goal is to build a site that is straightforward to access and contains all the relevant information.

To start, I will build a series of template web pages to contain the necessary information, and will index the collection in several ways so a user can look up the desired board by serial number, type, or location. After building the site, I will travel to the LIGO Hanford Observatory and take the measurements to flesh out the web site with measured data. Upon returning I will process the data and update the site.

I plan to create a working catalog of specifications that is easy to access and up-to-date. I hope in the future that the site can be expanded to include not just the noise properties of each board, but a complete set of all the specific information that any LIGO staff might need.


Investigating stress/strain behaviour of amorphous metallic alloys proposed for suspensions in gravitational waves detectors
Stefano Tirelli
Mentor: Riccardo DeSalvo

To evaluate the suitability of MoRuB alloys for mirror suspensions in LIGO and other interferometers for gravitational waves detection, we need to study the properties of these materials under stress. The composition of the alloys range from 15 to 20 atomic percent of Boron, while Molybdenum and Ruthenium are in a ratio of 0.6 and 0.4 to the remaining mass. Tests are performed with a mechanical stress frame, using a specially designed micro-LVDT for measuring strain and a Wheatstone bridge-based load cell for stress measurement. Observing the sample and applying different loads, it is possible to evaluate Young modulus, Poisson's ratio, and crack propagation. Due to the glassicity of these metallic alloys, it will be possible to observe shear bands that cause plastic deformation that eventually rupture the material. Here the experimental apparatus is presented, together with some of the first measurements obtained with a low-resolution stress gauge.


Advanced LIGO Suspension Research
John Veitch
Mentors: Calum Torrie, Janeen Romie

The suspension system for the main mirrors for Advanced LIGO, the planned upgrade to LIGO, are based on the triple pendulum design developed for GEO 600, the German/UK interferometric gravitational wave detector. This project analyzed several aspects of these suspensions, including measuring the physical properties of the suspension wire, setting up a prototype crossed-blade pendulum, and measuring its frequencies with comparisons to calculated results. Also, the effects of creep on the suspension system were investigated and techniques were developed to adjust the cantilever blades. The information gathered in this project will aid the construction of the next stage of LIGO detectors.


Characterization of Glitches in LHO Interferometers
Aaron Virshup
Mentors: Michael Landry, Daniel Sigg, and Fred Raab

Glitches (short, fast jumps in a signal) in LIGO data channels reduce the detector $B'7 (Bs sensitivity to gravitational radiation. My SURF project was an investigation of glitches in the interferometer in order to find and eliminate their sources. Analysis focused on establishing correlations between a glitch in a certain channel and anomalous behaviors in other channels. The correlated behaviors were then separated into causes and effects of the glitch. Presented here are characterizations of several common glitches.


Angular and Frequency Response of Gravitational Wave Interferometers at Higher Frequencies
Andrew H. Weber
Mentor: Andri Gretarsson

The sensitivity of LIGO and similar ground based gravitational wave interferometers are bounded at lower frequencies by seismic noise. For larger interferometers, sensitivities at higher frequencies are reduced as the disturbance period approaches twice the round trip time for light in the cavity. This, combined with noise, provides a notch in the strain sensitivity curve where observation of gravitational signals would be most likely (between 0.1 and 1 kHz for LIGO 4 km IFO). However, when the frequency of the disturbance is near the round trip frequency or frt, sensitivity is restored (~37.5 kHz for LIGO 4 km IFO). This analysis investigates the angular and frequency response of a single Fabry-Perot cavity then generalizes the results to describe two-arm interferometers. It was found that simple mirror displacements at frequencies of frt yielded sensitivities equal to those at lower frequencies. When a gravitational wave with frequency frt is considered, the response acquires an angular dependence different than that from lower band gravitational waves. Later work should average the sensitivities at frt over all angles to obtain a mean sensitivity curve for gravitational wave interferometers.


Non-linear Thermoelastic Damping in a Fused Silica Suspension
Jaap Weel
Mentor: Phil Willems

In interferometric gravitational wave detectors, thermal motion in optics suspension wires causes noise. A major thermal noise source is dissipation of energy due to irreversible heat flow in a bending material, known as thermoelastic damping. This damping may be cancelled out in certain fibers by non-linear thermoelastic damping, which is due to the temperature dependence of the material's Young's modulus. In order to show the existence of this effect, we investigate a fused silica suspension in which it should significantly lower dissipation.


ALADDIN: A Computer Application for the Analysis of Data Received from the LIGO Observation Channels
Ryan Williams
Mentors: Szabolcs Marka and John Zweizig

The focus of my SURF has been to create a computer application that uses a graphical user interface to display data from the Laser Interferometer Gravitational Wave Observatory (LIGO). The program pulls data from existing observation channels that monitor environmental conditions inside and outside of the interferometer, and displays it in a variety of user-specified formats, including one-, two-, and three dimensional histograms, amplitude vs. time plots, and frequency spectrums. Additional functionality is currently being developed for the purpose of filtering out known noise sources from the data streams.

ALADDIN is an acronym for ALADDIN Looks At Data Distributions Interferometrists Need. It is written in C++, and utilizes the ROOT object oriented data analysis framework.

Updated on November 5, 2002