SURF Project Proposals 2015 ____________________________________________________ At LIGO Livingston (Louisiana) ____________________________________________________ ____________________________________________________ Scatter Coupling Studies Mentors: Anamaria Effler, Valera Frolov (LLO) The sensitive LIGO detector is susceptible to scatter noise due to stray beams which scatter inside the vacuum system and then recombine with the main beam of the interferometer. We would like to survey possible scatter sources and account for their contributions to detector noise. For example, using acoustic or low frequency injections at various detector locations. This project will require the student to learn about light scatter mechanisms, data analysis (in Matlab or Python) and some basic mechanics and electronics. ____________________________________________________ Homodyne Detector Characterization Mentors: Ryan DeRosa, Valera Frolov (LLO) Currently the Advanced LIGO interferometers read out the gravitational wave data stream, as well as control the differential arm length, using a self-homodyne detection scheme. A static offset in the differential arm length provides a local oscillator field at the antisymmetric port which interferes with the small variations which could be gravitational waves. A potential improvement would be to switch to a balanced homodyne detection configuration, interfering the light exiting the antisymmetric port of the interferometer with a local oscillator field picked off from filtered light on the bright side of the main beamsplitter. Another beamsplitter at the detection port combines the signal and local oscillator fields, with two photodiodes to sense each output field, together feeding a current subtracting electrical amplifier. This photodiode/amplifier assembly is the homodyne detector, which comes with its own noises. The performance and characterization of a homodyne detector, potentially for use in an experiment on the main interferometer, could be investigated by the student. ____________________________________________________ At LIGO Hanford (Washington) ____________________________________________________ ____________________________________________________ Optimization of lock acquisition in a suspended dual-recycled Michelson interferometer Mentor: Kiwamu Izumi (LHO) The Dual-Recycled Michelson Interferometer (DRMI) is a modern interferometer configuration used in the large-scale gravitational-wave interferometers such as advanced LIGO. It offers a way to mitigate some thermal issues and therefore advantageous. However, on the other hand, the DRMI adds complexity to lock acquisition which is a process to bring all the optical length degrees of freedom to the operating point by controlling the distance between the mirrors. In particular, lock acquisition of the suspended DRMI in advanced LIGO has been known to be nontrivial because (1) the mirror distances are seismically excited in an unpredictable way and (2) the length signals are highly nonlinear and cross-coupled. In this project, we will explore a possible parameter space using numerical simulations under realistic constraints to study possible optimizations. ____________________________________________________ Physical Environment Investigations Mentor: Robert Schofield (LHO) Advanced LIGO will detect gravitational wave radiation by measuring test mass motions of as little as 1e-20 m/sqrt(Hz). It is important to keep motions resulting from environmental signals, such as acoustic vibrations and ambient magnetic fields from overwhelming the motions produced by astrophysical signals, and of course it is important to be able to distinguish between the two. The student will join the group responsible for the system of environmental monitors (seismometers, accelerometers, microphones, radio receivers, magnetometers, etc.) used for this purpose. The student will be involved in setting up some of these monitors (most are already installed), trouble shooting, repairing, and calibrating them, and updating the web page that previous students have made (pem.ligo.org). In addition the student will be involved in injecting environmental signals to study how the signals couple into the detector, and in attempts to reduce the level of coupling if necessary. ____________________________________________________ Cavity alignment using fringe scanning Mentors: Michael Landry, Keita Kawabe (LHO) LIGO employs 4 km long arm cavities which need to be aligned, before they can be locked on a TEM00 mode. Once the cavity is locked, alignment signals can be derived from wavefront sensors which measure the TEM01 mode content. However, the alignment state is not always good enough for locking on TEM00. A free swinging cavity shows flashes when higher order modes become resonant. The goal of this project is to derive the alignment state from scanning the cavity length and observing the power build-up of the laser light. By making small changes to the mirror orientation, the TEM00 mode can be optimized iteratively. ____________________________________________________ Carrier Independent IFO Cavity Control Scheme Mentors: Dick Gustafson (LHO) We will analyze, build and demonstrate, characterize, a Sideband on Sideband Variant ( carrier independent ) of the Pound Drever Hall scheme for controlling an IFO Cavity. Features very robust control of the Michelson Cavities in LIGO like interferometers especially in Lock Aquisition. Optical lab work involved. Cavity: fsr < ~ 50 MHz, ie > 6 m round trip… and laser; 2 RF gens, Faraday isolator, a bunch of optics; vacuum? on a 12' optical table. Perhaps explore possibility of use in ALIGO. ____________________________________________________ Warble Frequency FFT extension Mentors: Dick Gustafson (LHO) Explore practical efficient Fast Fourier Transform (FFT) extension based schemes for detecting ie, analyzing frequency warbling signals (detecting phase modulated sine waves slowly phase modulated by “sine waves” ). This is relevant to detection of Pulsar Gravity Wave signals ( ~ 100 to 1000 Hz ) from binary Pulsar systems. Think doppler and phase shifted signal untangling to map warbling signals into one “effectiveFFT” frequency bin; best for noise. The one dimensional FFT search becomes a 3 dimensional search problem: two frequency (pulsar, orbit ) and one modulation index ( = freq swing ). Mostly analysis and MATLAB based simulations, demonstrations. ____________________________________________________ Caltech Experimental Projects ____________________________________________________ ____________________________________________________ Experimental study of crackling noise as micro-mechanics of flow Mentors: Xiaoyue Ni For an in-depth investigation of macroscopic mechanical behavior of materials, the micro physics provides important fundaments. In the study of mechanical noises for advanced LIGO suspension system, understanding the micro-structural dynamics will serve as the building blocks of the crackling noise phenomena. In crystalline metal, dislocation motion can generate strain noises when subjected to fast-changing stress, even before yielding. In the so-called “elastic” regime, the relationship between a varying external load and the strain respond is still vague. A micro-mechanical experiment is being carried out to probe the materials internal dynamics when a stress modulation is applied. The candidate will contribute to preparing samples, running the tests, and improving the experiment. She/He will learn the basics of nano-mechanics of materials, including how to make nano-pillars for uniaxial compression test, the nano-indenting methodology, and the dynamic mechanical analysis. ____________________________________________________ Crackling noise in mechanical systems Mentors: Gabriele Vajente, Rana Adhikari Elastic materials such a metals are described with very good accuracy with linear models. However, material defects can introduce non linear behavior that can be the source of excess noise. One important case is the displacement noise generated by the motion of crystal dislocations (crackling) which can be triggered by the external stress applied to the material. A low frequency variation of the stress can modulate the noise level at much higher frequencies. Such effect may be relevant in the suspension system for the advanced gravitational wave detectors being built. A dedicated experiment to try to measure this crackling noise is being built, based on a seismically isolated in-vacuum laser interferometer. The successful candidate will contribute to the assembly and tuning of the suspension system and of the laser control. She/he will learn how to use digital feed-back controls and interferometry, which are the basis of the present gravitational wave detector operations. ____________________________________________________ Tilt-free seismometer Mentors: Kate Dooley, Rana Adhikari The LIGO interferometers are very sensitive to ground motion and many steps are taken to isolate the mirrors from the ground both passively and actively. One approach to correct for seismic-induced mirror motion is to measure the ground acceleration using seismometers and feed-forward the information to actuators on the mirrors. This has proven to be a very effective technique in increasing the detector's duty cycle and reducing glitches in the data. However, the extent of its effectiveness is limited. At low frequencies, the seismometers cannot distinguish between linear acceleration of the ground and tilt of the ground. When used, this seismometer data injects unwanted tilt noise to the mirror positions. The student will help with the design, construction and testing of a prototype seismometer which is inherently insensitive to ground tilt. Skills in Matlab or python, mechanics, electronics and laser optics would be helpful, but are not required. ____________________________________________________ Investigation of thermal noise in thin silicon structures Mentors: Zach Korth, Nic Smith, Rana Adhikari The next generation of gravitational wave detectors will use silicon test masses and suspensions. In order to inform this future suspension design, an experiment is underway at Caltech to directly measure the thermal noise in thin silicon structures. In practice, thermal noise in thin systems is dominated by contributions from lossy surface layers. Therefore, the primary goal of this experiment will be to characterize the losses attributable to these surface effects. For this project, the student will investigate losses in prototype structures using a ringdown measurement technique, as well as assist in the construction and initial operation of the optical cavity frequency beat setup that will be used for the eventual direct thermal noise measurement. ____________________________________________________ Investigation of excess noise in high-current photodetection Mentors: Eric Gustafson, Zach Korth, Rana Adhikari Excess noise arising from non-idealities in semiconductor photodiodes currently imposes a limit to how much optical power can be sensed on a single photocell. In the absence of such noise—and below the saturation point—higher detected power allows for higher-SNR measurements with respect to photon shot noise, which sets a fundamental limit. In order to meet its stringent intensity stabilization requirements, Advanced LIGO uses a complicated array of eight photodiodes to detect enough total power. For many reasons, it would be much easier to use fewer. For this project, we will study a family of wide-area (3 mm) InGaAs photodiodes that shows some promise of exhibiting lower excess noise than previously shown. The student will work with a custom balanced photodetection setup to measure the performance of these diodes. ____________________________________________________ Adaptive feedforward seismic noise cancellation at the 40m interferometer Mentors: Eric Quintero, Koji Arai, Rana Adhikari LIGO detectors are extremely sensitive to low frequency seismic motion. At the 40m Prototype Interferometer, we will test new adaptive noise cancellation techniques to reduce seismic noise in the detectors. This technology will be applied to the Advanced LIGO detectors to improve low frequency sensitivity to astrophysical events, and progress made on seismic cancellation will be used to adaptively reduce other noise sources, including audio and magnetic noise. The student will deploy IIR wiener filtering techniques to reduce noise in the 40m interferometer. General laboratory skills, with an emphasis on computing and filtering algorithms are recommended. ____________________________________________________ Hysteresis of mirror suspensions at the 40m interferometer Mentors: Eric Quintero, Rana Adhikari LIGO operates a prototype laser interferometer with 40 meter long arms at Caltech that is being used to explore new sensing and control techniques for the Advanced LIGO interferometers. This project concerns performance of mirror suspension systems the 40m prototype. The student will perform hysteresis measurements on the suspension system, and will compare the results with mechanical simulations. This project will involve learning skills in building, characterizing, and modeling of mechanical systems. General laboratory skills including electronics and computing are recommended. ____________________________________________________ Quantization noise reduction in the LIGO digital control systems Mentors: Christopher Wipf, Jameson Graef Rollins Advanced LIGO implements hundreds of control loops using digital signal processing techniques. These controllers are known to inject noise due to round-off error as signals are IIR filtered, and converted to and from the digital domain. In this project, we will investigate the origins of this quantization noise, and identify methods of optimizing the controllers to mitigate it. ____________________________________________________ Detector characterization of a laserinterferometer gravitational wave detector Mentors: Koji Arai, Maximiliano Isi ____________________________________________________ At LIGO Caltech Data Analysis / Astrophysics ____________________________________________________ ____________________________________________________ Detector Characterization for Advanced LIGO Mentors: Jonah Kanner and Alan Weinstein The Advanced LIGO detectors are expected to reach an unprecedented level of sensitivity, and make gravitational wave observations possible for the first time. Historically, searches for transient gravitational waves have often been limited not by steady detector noise, but rather by noise transients, known as ěglitchesî. Understanding glitches and their sources in an important activity of the collaboration, and one that requires both knowledge of modern software tools and understanding of the LIGO instrument. For this project, a student will study the rates and characteristics of classes of glitches in the Advanced LIGO detector. Through conversations with experts and careful analysis, we will attempt to identify the sources of these glitches, with an eye toward removing them from the data. The student will gain experience with various software tools in a Linux environment, signal processing, and the LIGO instrument. This is a great opportunity to learn both about the astrophysics of gravitational waves as well as the tools we use to find them. ____________________________________________________ Detecting gravitational waves from unmodeled sources Mentors: Jonah Kanner, Alan Weinstein Transient gravitational waves may come from a number of sources in the universe, including supernovae, merging compact objects, and soft gamma-ray repeaters. Sources where the gravitational waveform is unkown or uncertain may be the most difficult to detect, since instrumental artifacts (known as glitches) in LIGO data may be confused with astrophysical signals. This is a “needle in a haystack” problem, since glitches are very common. Currently, we are testing a new algorithm that attempts to address this issue (See http://arxiv.org/abs/1410.3835). The “BayesWave” pipeline uses modern data analysis techniques to separate signals from glitches. In this project, we will test the BayesWave pipeline to measure its performance identifying astrophysical signals in noisy data. In order to collect high statistics performance data, we will utilize the LIGO computing cluster to run hundreds of processes in parallel. If the algorithm is shown to be successful, it will be used to search for gravitational waves in the upcoming Advanced LIGO observations, which are expected to begin sometime this year. In addition to experience with gravitational-wave astrophysics, this project will develop experience and skills in the Python programming language, statistical analysis, high throughput computing, and the Linux/Unix environment. ____________________________________________________ Testing the strong field dynamics of general relativity using compact binary systems Mentors: Maximiliano Isi, Tjonnie Li, Yanbei Chen Collisions of stellar mass compact objects, such as neutron stars or black holes, are among the most promising sources of gravitational waves for Advanced LIGO. These systems have strong gravitational fields and are highly relativistic, making them excellent laboratories for testing the strong field dynamics of general relativity. In this project, we explore the ability of Advanced LIGO to constrain alternative theories of general relativity. In particular, we simulate gravitational wave signals from various alternative theories, and quantify the sensitivity of Advanced LIGO to these deviations from general relativity. For this project, experience with computer programming and Unix-like environments is highly recommended. Moreover, some understanding of general relativity and statistics is preferred. In turn, students will learn about the generation of gravitational waves by compact binary systems, alternative theories of general relativity, and advanced statistical tools to extract information from tiny signals buried deep in the noise. ____________________________________________________ Searching for gravitational waves from the coalescence of high mass black hole binaries. Mentors: Surabhi Sachdev, Tjonnie Li, Kent Blackburn and Alan Weinstein We aim to detect gravitational wave signals from the coalescence (inspiral, merger and final black hole ringown) of compact binary systems (neutron stars and/or black holes) with data from the advanced detectors (LIGO, Virgo, KAGRA). The merger signal from the coalescence of Low-mass systems (binary neutron stars) tends to lie above the LIGO frequency band; only the inspiral phase is detectable. For higher mass systems (involving black holes, each of mass greater than 5 solar masses), the merger and final ringdown are also detectable. We search for these signals using analysis pipelines which filter all the data, identify “triggers” of interest, form coincident triggers between multiple detectors in the network, and attempt to optimally separate signal from detector background noise fluctuations. The size of these noise fluctuations in the advanced detectors is currently unknown. We use simulated signal injections to evaluate the sensitivity of the search pipeline. The analysis pipeline has numerous parameters that can be tuned to improve the sensitivity. In this project, we will run high-statistics simulations to evaluate the search sensitivity as the analysis parameters are tuned, to arrive at optimal settings under different anticipated noise fluctuation conditions. This project will develop experience and skills in statistical analysis, high throughput computing and the Linux/Unix environment. The student will learn about the physics and astrophysics of compact binary coalescence, and gain experience with modern analysis techniques with large data samples. ____________________________________________________ Inferring the nuclear-matter equation of state using mergers of neutron stars Mentors: Tjonnie Li, Alan Weinstein Neutron stars are remnants of stellar explosions that occur when a massive star has burned all of its fuel. These stars contain matter which are several times denser than atomic nuclei. Consequently, neutron stars exhibit a range of astonishing physical properties. When two neutron stars collide a copious amount of gravitational waves is emitted. These gravitational waves encode information about the core of neutron stars, which will give us insight into the nuclear-matter equation of state. In this project, we explore the ability of Advanced LIGO to infer the nuclear-matter equation of state. For this project, experience with computer programming and Unix-like environments is highly recommended. In turn, students will learn about the generation of gravitational waves by merging neutorn stars and advanced statistical tools to extract information from tiny signals buried deep in the noise. ____________________________________________________ Cosmography & Black Hole Spectroscopy by Coherent Synthesis of the Terrestrial / Space GW Antennae Network Mentors: Tom Callister, Curt Cutler, Rana Adhikari A series of low-cost alternatives to the LISA / DECIGO / BBO missions have been proposed to a subset of the scientific missions for a subset of the cost. We will explore the UNOGO mission: a ~100 km Michelson interferometer in space utilizing squeezed light to reduce the quantum noise. Combining the simulated data streams of UNOGO with the earth based detectors of 2020: LIGO, Virgo, & KAGRA will allow for an unprecedented angular resolution and capability of testing for violations of Einsteinian gravity. Knowledge of signal processing, Fourier techniques, basic astronomy, and Python programming would be very useful. ____________________________________________________ At Caltech TAPIR ____________________________________________________ ____________________________________________________ R-Process Nucleosynthesis Sensitivity to Neutrino Luminosity Mentors: Hannalore Gerling-Dunsmore and Luke Roberts During neutron star-neutron star (NS-NS) mergers, a significant quantity of material is ejected from the system. This material is neutron rich, and as it decompresses, heavy nuclei form via rapid neutron capture (the r-process). In older models of NS-NS merger nucleosynthesis, it was assumed the initial neutron to proton ratio entirely dictated the resulting heavy nuclei. However, it is now understood that weak interactions (i.e., beta decay) have time to change the neutron to proton ratio in the ejecta, and thus change the resultant heavy nuclei. We aim to study the effects of neutrino luminosity on r-process nucleosyntheis. We will use the nuclear reaction network code SkyNet to see how varying neutrino luminosity in the ejecta of NS-NS mergers changes the heavy nuclei produced. Decays of the heavy nuclei produced in the ejecta can power electromagnetic (EM) transients that peak approximately a week after the NS-NS merger itself. This project will allow us to better constrain the properties of these EM transients that may be associated with LIGO detections of NS-NS merger gravitational wave signals. Additionally, this study will put further constraints on the contribution of NS-NS merger ejecta to galactic chemical evolution. ____________________________________________________ Numerical simulations of black-hole binaries Mentors: Mark Scheel Numerical models of gravitational-wave sources are important both for improving detection algorithms for LIGO, and for understanding and interpreting future LIGO detections. In this project, we will use the parallel computer code “SpEC” to solve Einstein's equations for colliding black holes and to compute the resulting waveforms. In particular we will concentrate on cases (such as large-kick configurations) where small changes in initial parameters (masses and spins of the black holes) might lead to large differences in the waveforms. The waveforms will be used as part of an ongoing effort to produce a fast, accurate model for black-hole binary waveforms for use with LIGO. This project will develop experience and skills in high-performance parallel computing, the C++ programming language, and the Linux/Unix programming environment. The student will learn about numerical methods, black hole physics, and phenomenology of black-hole binaries. ____________________________________________________ Multi-carrier optimization of future laser gravitational-wave detectors Mentor: Yanbei Chen Abstract: In this project, we start off from two opposite approaches toward the suppression of gravitational-wave detectors' quantum noise. In one approach, two carriers were proposed to create a specific kind of optical spring called negative optical inertia. It effectively reduces the inertial mass of the test mirrors, suppressing thus quantum noise in low-frequency band. The price for this, however, is radically increased quantum noise in higher frequency band. In another approach, the so-called antisymmetric carriers pairs, high frequency sensitivity was improved by arranging two carrier fields that have their optical springs completely cancel each other. We propose to carry out a numerical optimization to combine these two approaches — toward a broadband improvement.