Bulletin of the American Physical Society
APS April Meeting 2017
Volume 62, Number 1
Saturday–Tuesday, January 28–31, 2017; Washington, DC
Session Y8: Achieving Optimal Sensitivity with LIGO and other High-frequency Gravitational-wave Detectors |
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Sponsoring Units: DGRAV Chair: Marco Cavaglia, University of Mississippi Room: Delaware B |
Tuesday, January 31, 2017 1:30PM - 1:42PM |
Y8.00001: Parametric instability in the high power era of Advanced LIGO Terra Hardwick, Carl Blair, Ross Kennedy, Matthew Evans, Peter Fritschel After the first direct detections of gravitational waves, Advanced LIGO aims to increase its detection rate during the upcoming science runs through a series of detector improvements, including increased optical power. Higher circulating power increases the likelihood for three-mode parametric instabilities (PIs), in which mechanical modes of the mirrors scatter light into higher-order optical modes in the cavity and the resulting optical modes reinforce the mechanical modes via radiation pressure. Currently, LIGO uses two PI mitigation methods: thermal tuning to change the cavity $g$-factor and effectively decrease the frequency overlap between mechanical and optical modes, and active damping of mechanical modes with electrostatic actuation. While the combined methods provide stability at the current operating power, there is evidence that these will be insufficient for the next planned power increase; future suppression methods including acoustic mode dampers and dynamic $g$-factor modulation are discussed. [Preview Abstract] |
Tuesday, January 31, 2017 1:42PM - 1:54PM |
Y8.00002: Cavity alignment using fringe scanning Laura Paulina Sinkunaite, Keita Kawabe, Michael Landry LIGO employs two 4-km long Fabry–Pérot arm cavities, which need to be aligned in order for an interferometer to be locked on a TEM00 mode. Once the cavity is locked, alignment signals can be derived from wave-front sensors which measure the TEM01 mode content. However, the alignment state is not always good enough for locking on TEM00. Even when this is the case, the alignment can be evaluated using a free swinging cavity, that shows flashes when higher-order modes become resonant. By moving test masses, small changes are made to the mirror orientation, and hence the TEM00 mode can be optimized iteratively. Currently, this is a manual procedure, and thus it is very time-consuming. Therefore, this project is aimed to study another possible way to lock the cavity on the TEM00 mode. Misalignment information can also be extracted from the power of the higher-order modes transmitted through the cavity. This talk will present an algorithm for this alternative and faster way to derive the alignment state of the arm cavities. [Preview Abstract] |
Tuesday, January 31, 2017 1:54PM - 2:06PM |
Y8.00003: RF Jitter Modulation Alignment Sensing L. F. Ortega, P. Fulda, M. Diaz-Ortiz, G. Perez Sanchez, G. Ciani, D. Voss, G. Mueller, D. B. Tanner We will present the numerical and experimental results of a new alignment sensing scheme which can reduce the complexity of alignment sensing systems currently used, while maintaining the same shot noise limited sensitivity. This scheme relies on the ability of electro-optic beam deflectors to create angular modulation sidebands in radio frequency, and needs only a single-element photodiode and IQ demodulation to generate error signals for tilt and translation degrees of freedom in one dimension. It distances itself from current techniques by eliminating the need for beam centering servo systems, quadrant photodetectors and Gouy phase telescopes. RF Jitter alignment sensing can be used to reduce the complexity in the alignment systems of many laser optical experiments, including LIGO and the ALPS experiment. [Preview Abstract] |
Tuesday, January 31, 2017 2:06PM - 2:18PM |
Y8.00004: Dealing with Instrumental Lines in Searches for Continuous Gravitational Waves in LIGO Data Orion Sauter Although the first observing run of Advanced LIGO (O1) gave us two definitive detections of gravitational waves from binary black hole mergers, searches for a continuous-wave (CW) source are computationally very demanding and still ongoing. CW sources are expected to be much weaker, requiring integration of the signal for several months. PowerFlux is one analysis pipeline designed for such searches; in following up outliers, the program uses a loosely coherent algorithm to improve the signal-to-noise ratio and to separate astrophysical signals from instrumental artifacts. Unfortunately, the O1 data has many sharp spectral artifacts (lines) that create spurious outliers in the low-frequency region, 20-135 Hz. The effects of these lines on the PowerFlux analysis will be discussed, along with methods used to mitigate those effects, including a line-cleaning process. Prospects for contending with instrumental line effects in the second observing run (O2) will also be presented. [Preview Abstract] |
Tuesday, January 31, 2017 2:18PM - 2:30PM |
Y8.00005: Spectral comb mitigation to improve continuous-wave search sensitivity in Advanced LIGO Ansel Neunzert Searches for continuous gravitational waves, such as those emitted by rapidly spinning non-axisymmetric neutron stars, are degraded by the presence of narrow noise "lines" in detector data. These lines either reduce the spectral band available for analysis (if identified as noise and removed) or cause spurious outliers (if unidentified). Many belong to larger structures known as combs: series of evenly-spaced lines which appear across wide frequency ranges. This talk will focus on the challenges of comb identification and mitigation. I will discuss tools and methods for comb analysis, and case studies of comb mitigation at the LIGO Hanford detector site. [Preview Abstract] |
Tuesday, January 31, 2017 2:30PM - 2:42PM |
Y8.00006: Modeling Thermal Noise From Crystalline Coatings For Gravitational-Wave Detectors Nicholas Demos, Geoffrey Lovelace In 2015, Advanced LIGO made the first direct detection of gravitational waves. The sensitivity of current and future ground-based gravitational-wave detectors is limited by thermal noise in each detector’s test mass substrate and coating. This noise can be modeled using the fluctuation-dissipation theorem, which relates thermal noise to an auxiliary elastic problem. I will present results from a new code that numerically models thermal noise for different crystalline mirror coatings. The thermal noise in crystalline mirror coatings could be significantly lower but is challenging to model analytically. The code uses a finite element method with adaptive mesh refinement to model the auxiliary elastic problem which is then related to thermal noise. Specifically, I will show results for a crystal coating on an amorphous substrate of varying sizes and elastic properties. This and future work will help develop the next generation of ground-based gravitational-wave detectors. [Preview Abstract] |
Tuesday, January 31, 2017 2:42PM - 2:54PM |
Y8.00007: Wave Detection Beyond the Standard Quantum Limit via EPR Entanglement YIQIU MA, Haixing Miao, Belinda Pang, Matthew Evans, Chunnong Zhao, Jan Harms, Roman Schnabel, Yanbei Chen The Standard Quantum Limit in continuous monitoring of a system is given by the trade-off of shot noise and back-action noise. In gravitational-wave detectors, such as Advanced LIGO, both contributions can simultaneously be squeezed in a broad frequency band by injecting a spectrum of squeezed vacuum states with a frequency-dependent squeeze angle. This approach requires setting up an additional long base-line, low-loss filter cavity in a vacuum system at the detector's site. Here, we show that the need for such a filter cavity can be eliminated, by exploiting EPR-entangled signal and idler beams. By harnessing their mutual quantum correlations and the difference in the way each beam propagates in the interferometer, we can engineer the input signal beam to have the appropriate frequency dependent conditional squeezing once the out-going idler beam is detected. Our proposal is appropriate for all future gravitational-wave detectors for achieving sensitivities beyond the Standard Quantum Limit. [Preview Abstract] |
Tuesday, January 31, 2017 2:54PM - 3:06PM |
Y8.00008: Gravitational wave radiation by LIGO-type detectors and its reciprocity relation with the detector's fundamental quantum limited sensitivity Belinda Pang, Yiqiu Ma, Haixing Miao, Yanbei Chen We relate the radiation of gravitational waves (GW) by a light interferometer with cavity arms (such as LIGO) to its quantum limited sensitivity as a detector of GW's, thereby demonstrating a reciprocity relation between the interferometer's function as a detector and emitter. We derive the pairwise interactions among the cavity optical field, the cavity end mirror, and the gravitational perturbation from the action principle. We quantize these degrees of freedom to calculate the GW's generated by a quantum object. We find that the rate of gravitational wave generation is related to the so-called quantum Cramer Rao bound of the detector, which is a general result from linear measurement theory that gives the fundamental limit to a detector's sensitivity. We show that increasing the maximal sensitivity for the interferometer also increases its GW radiation. This finding may point towards a new paradigm for improving detector sensitivity by maximizing GW radiator. [Preview Abstract] |
Tuesday, January 31, 2017 3:06PM - 3:18PM |
Y8.00009: Accumulative coupling between magnetized tenuous plasma and gravitational waves Fan Zhang This talk presents solutions to the plasma waves induced by a plane gravitational wave (GW) train travelling through a region of strongly magnetized plasma. The computations constitute a very preliminary feasibility study for a possible ultra-high frequency gravitational wave detector, meant to take advantage of the observation that the plasma current is proportional to the GW amplitude, and not its square. [Preview Abstract] |
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