Bulletin of the American Physical Society
77th Annual Meeting of the Southeastern Section of the APS
Volume 55, Number 10
Wednesday–Saturday, October 20–23, 2010; Baton Rouge, Louisiana
Session CC: Gravitation: LIGO and LISA |
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Chair: Soren Sorensen, University of Tennessee Room: Nicholson Hall 118 |
Thursday, October 21, 2010 10:45AM - 10:57AM |
CC.00001: Developing LIGO Detector Characterization Tools and Methods Cesar Costa Laser Interferometric Gravitational-Wave Observatory (LIGO) has been in constant process of improvement to achieve its main goal: the detection of gravitational waves (GWs). For the current science run (S6), improved control systems have been installed in order to increase the instrument sensitivity. The LIGO Detector Characterization (DetChar) Group works to understand how such devices and environmental sources could affect the GW channel, specially when they contaminate measurements by introducing spurious signals. To decrease false alarm rates DetChar monitors several auxiliary channels in order to diagnose environmental and instrumental glitches which can produce GW signal-like events. This improves the data quality for GW searches, and also informs commissioners about instrumental issues. This talk describes the methodology that we have been applying to LIGO Detector Characterization, specially glitch hunting and monitoring tools. [Preview Abstract] |
Thursday, October 21, 2010 10:57AM - 11:09AM |
CC.00002: Global Noise Subtraction in LIGO Interferometers Ryan DeRosa In order to provide local seismic isolation and reduce the feedback control signals in the 4 km LIGO detectors an active feed forward system has been in use since 2004. As a modification to this scheme a network of seismometers has been used to create global feed forward signals, resulting in increased seismic isolation below 3 Hz. This additional isolation has provided increased duty cycle and sensitivity. The force applied to each optic to maintain cavity resonance has also been reduced, producing less transient noise in the data stream. [Preview Abstract] |
Thursday, October 21, 2010 11:09AM - 11:21AM |
CC.00003: Data quality and vetoes in searches for gravitational waves in LIGO data Jacob Slutsky Searches for gravitational waves with LIGO are hindered by the presence of transient detector noises not of astrophysical origin. Interferometric gravitational wave detectors are sensitive to a wide variety of these transients, originating both within the detector and from the surrounding environment. The LIGO-Virgo Collaboration has identified a variety of data quality issues that induce false alarms in searches for compact binary coalescences in LIGO data. We define time intervals effected by these artifacts, and use them as vetoes. These vetoes reduce the false coincidence rate of the searches. [Preview Abstract] |
Thursday, October 21, 2010 11:21AM - 11:33AM |
CC.00004: Adding an astrophysically motivated detection confidence test, Effective Distance Ratio, to our standard confidence tests for Inspiral Candidate Events Cristina Torres In order to detect gravitational-wave signals from compact binary inspiral systems in the data from the LIGO detectors the LSC-Virgo Compact Binary Coalescence (CBC) group has developed an analysis method based on optimal matched filtering. In order to confirm the possible discovery of gravitational waves, the CBC group has developed a detection checklist intended to validate the statistically significant candidate events produced by the CBC analysis. This checklist is a series of additional tests under active development for integration into our search infrastructure, or a set of ``final'' quantitative checks geared to corroborating a detection or to identifying a false alarm. We practice this checklist with the loudest candidates found (even if not statistically significant) and with simulated signals. As part of this talk we will present an evolving checklist test, the Effective Distance Ratio, and discuss this tests potential for candidate validation because of simple astrophysical basis. In addition to presenting this test, we will review the standard inspiral candidate validation methodology giving context about where our new confidence test fits into the inspiral search hierarchy. [Preview Abstract] |
Thursday, October 21, 2010 11:33AM - 11:45AM |
CC.00005: Laser Communication for LISA Kendall Ackley, Dylan Sweeney, Guido Mueller The Laser Interferometer Space Antenna (LISA) is a joint mission between NASA and ESA to detect gravitational wave radiation between 0.1 and 1 Hz by measuring phase fluctuations of laser heterodyne signals. The phase of the signals must be measured to microradian accuracy. For LISA to be successful the distance between the spacecraft (SC) must be measured to meter precision and the clock signals on each SC must be recorded. These functions will be accomplished using the laser links between the SC. Pseudo random noise (PRN) codes will be modulated onto the light and used to measure the light travel delay between the SC. The clock signals on each SC will be frequency up-converted to GHz frequencies, modulated onto the laser links, and sent to the other SC where it will be recorded and used in post-processing to cancel the clock noise. We have tested components of these systems such as frequency up-converters, electro-optic modulators, and photodetectors, as well as the systems themselves to see if they are capable of meeting their performance requirements for LISA. We will discuss the work being completed at UF. This work is supported by NASA Grant NNX09AF99G. [Preview Abstract] |
Thursday, October 21, 2010 11:45AM - 11:57AM |
CC.00006: Heterodyne Stabilization for the Laser Interferometer Space Antenna (LISA) Johannes Eichholz, Steven Hochman, Alix Preston, Guido Mueller LISA is a joint NASA/ESA space mission to detect gravitational waves from 0.1 mHz to 1 Hz generated e.g. by super-massive black hole mergers. Three spacecraft move in a triangular constellation on a heliocentric orbit. Their distances are monitored interferometrically with laser links. LISA detects fluctuations of the 5 million km arm lengths on a picometer scale. The requirement for the frequency stability of the lasers is $141~\mathrm{Hz}/\sqrt{\mathrm{Hz}}$. I will present a new stabilization scheme based on heterodyne interferometry. It requires less components than the currently envisioned Pound Drever Hall technique and can easily be integrated into LISA's interferometry measurement system. The two lasers of each spacecraft are injected into the same optical cavity. Near resonance, the phase of the reflected light is sensitive to frequency fluctuations. The second, off-resonant beam can be used to lock the primary laser to the cavity resonance. I will discuss this technique and present experimental results. This work is supported by NASA Contract \#00078244 and NASA Grant NNX08AG75G. [Preview Abstract] |
Thursday, October 21, 2010 11:57AM - 12:09PM |
CC.00007: Development and Analysis of Micro-cycle Phase Measurements for LISA Darsa Donelan, Shawn Mitryk, Syed Reza, Jose Sanjuan, Guido Mueller The Laser Interferometer Space Antenna (LISA) project is a space-based gravitational wave (GW) interferometer designed to measure gravitational radiation in the frequency range from 0.1 mHz to 1 Hz. One-way laser phase measurements between the individual spacecraft in the LISA constellation are used to reconstruct an equal-arm interferometer, cancel the laser phase noise, and extract the gravitational wave information. The 2-20 MHz-frequency laser beat signals must be measured with a sensitivity of 1 ucycle/sqrt(Hz) in order to cancel the laser noise and~accurately reconstruct the GW signal. The beat signal phase is measured with a phasemeter. In this presentation, the performance of our phasemeter and its limiting noise sources will be discussed. Methods of mitigating the phase noise, including the application of a post-processing calibration technique and active temperature stabilization, are considered and investigated for their applicability and usefulness to the LISA mission This work is supported by NASA grant NNX08AG75G. [Preview Abstract] |
Thursday, October 21, 2010 12:09PM - 12:21PM |
CC.00008: Investigations on a LISA Telescope Spacer Aaron Spector, Josep Sanjuan, Alix Preston The Laser Interferometer Space Antenna (LISA) is a space-based mission designed to observe gravitational waves from 0.1 mHz to 1 Hz. Using a triangular constellation of three spacecraft separated by 5x10$^{6}$ km, LISA will be able to detect the length changes between the spacecraft induced by gravitational waves. These length changes can be detected with pm/rtHz sensitivity using laser interferometry. Each spacecraft must contain two telescopes that can transmit and receive light between spacecraft. To expand and collimate the beam, a two-mirror system was designed with a primary and secondary mirror separated by a spacer. The noise requirements for LISA demand that the telescope spacer must be extremely stable. Two designs, on-axis and off-axis, are being considered for the telescope spacer. Various materials are also being examined. An on-axis silicon carbide telescope test structure was built to assess the stability of this configuration. A Michelson Interferometer was used to monitor length changes of the test structure while being cooled to space-like temperatures. Stability measurements are currently being made by locking the telescope laser to a cavity mounted on the test structure and then the beat note between the telescope laser and another cavity-locked laser is observed. A beat note between another laser locked to the Doppler-free spectral lines of iodine and the telescope laser will be used to determine the long term stability of the test structure. [Preview Abstract] |
Thursday, October 21, 2010 12:21PM - 12:33PM |
CC.00009: The effective source approach to the self-force problem Peter Diener Extreme Mass Ratio In-spirals of compact objects into super massive black holes are expected to be a very important source of gravitational waves for LISA. Perturbation techniques have traditionally been employed Here the small compact object is treated as a point particle moving on a perturbed geodesic in an exact black hole spacetime. Gravitational waves are emitted due to the particle motion which are then back scattered off the curvature of the background space-time and interact with the particle itself at a later point in the orbit: The so called self-force problem. Traditionally, to solve this problem, the field equations have been evolved with a singular delta-source, yielding a singular field at the location of the particle. To calculate the self-force the singular field then has to be carefully subtracted. I will present results for the calculation of the self-force for a scalar point charge moving in circular orbits around a non-rotating black hole using a new technique where the singularity of the point particle is subtracted from the source before the evolution is done, resulting in a regular field at the particle location from which the self-force can easily be calculated. [Preview Abstract] |
Thursday, October 21, 2010 12:33PM - 12:45PM |
CC.00010: A new look at Gravity Waves Richard Kriske The author has previously proposed that perhaps there needs to be a look at the CMBR as being a measure of curvature. It seems that a valid theory of curved space in a four dimensional space time would allow the Red Shift to occur due to the changing orientation of the time dimension that would slowly point more and more away from any observer at any point until like the Earth's horizon in two curved space dimensions to point away from the observer and give the sharp cut off of the Horizon. A three curved space dimensional cut off would result in the appearace of increasing velocity as the distance from the observer increases and this without the Big-Bang theory. What would one observe for Gravitational waves on this surface? The three space dimensions would wiggle and the time dimension (which is not curved) would move to stay perpendicular to this motion, giving odd accelerations and I predict a different Microwave signal. Perhaps a nonuniformity in the Back Ground radiation that would shift over time. [Preview Abstract] |
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