Bulletin of the American Physical Society
78th Annual Meeting of the Southeastern Section of the APS
Volume 56, Number 9
Wednesday–Saturday, October 19–22, 2011; Roanoke, Virginia
Session HA: Gravitation |
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Chair: George Siopsis, University of Tennessee Room: Crystal Ballroom A |
Friday, October 21, 2011 10:45AM - 10:57AM |
HA.00001: LISA: the space-based gravitational wave observatory Josep Sanjuan The Laser Interferometer Space Antenna (LISA) is a space-based gravitational wave (GW) observatory with the primary scientific goal of detecting and observing GW from astronomical sources in the milli-Hertz range. Such observations will provide a new way to explore the Universe and they will bring new rich information about its structure and evolution. However, GWs signals are very weak and thus very precise and low-noise measurements are required. GWs are detected by measuring the relative change in distance between free falling proof masses inside widely separated spacecraft. These changes are measured with pico-meter sensitivity by means of laser interferometry. I will give an overview of the LISA mission and a summary of the research done at the University of Florida. [Preview Abstract] |
Friday, October 21, 2011 10:57AM - 11:09AM |
HA.00002: Ring Heater for Advanced LIGO Eric Deleeuw, Giacomo Ciani, Guido Mueller The Laser Interferometer Gravitational-wave Observatory (LIGO) is currently being upgraded to Advanced LIGO. One of the main changes is the increase in input laser power from 30W to 165W. In Advanced LIGO up to 600kW laser power will circulate inside the interferometer. Some of the power will be absorbed by the LIGO test masses, creating a thermal gradient that will deform them changing the spatial mode of the laser field inside the interferometer. Radiative ring-shaped heaters will be installed close to the test masses to provide additional heat to counteract this effect and minimize the deformation. In this talk we will present the proposed University of Florida ring heater design, and measurements of the thermal profile homogeneity to be compared with initial requirements. In addition, we present initial results of outgassing measurements to qualify our ring heater for use in the LIGO vacuum system. [Preview Abstract] |
Friday, October 21, 2011 11:09AM - 11:21AM |
HA.00003: Laser frequency stabilization Darsa Donelan, Guido Mueller, James Thorpe, Jeffrey Livas Laser ranging and interferometry are essential technologies allowing for many astounding new space-based missions such as the Laser Interferometer Space Antenna (LISA) to measure gravitational radiation emitted from distant super massive black hole mergers or distributed aperture telescopes with unprecedented angular resolution in the NIR or visible regime. The requirements on laser frequency noise depend on the residual motion and the distances between the spacecraft forming the interferometer. The intrinsic frequency stability of commercial lasers is several orders of magnitude above these requirements. Therefore, it is necessary for lasers to be stabilized to an ultrastable frequency reference so that they can be used to sense and control distances between spacecraft. Various optical frequency references and frequency stabilization schemes are considered and investigated for the applicability and usefulness for space-based interferometry missions. [Preview Abstract] |
Friday, October 21, 2011 11:21AM - 11:33AM |
HA.00004: High Speed Alignment Control of an Optical Resonator Daniel Amariutei Laser interferometric gravitational wave detectors are by far the most sensitive interferometer in the world. They require exquisite control over all degrees of freedom of the optical components comprising the main detector but also over all degrees of freedom of the used laser beam. One of the most critical degrees of freedom is the propagation direction and beam location of the input beam when it enters the interferometer. Any variations in these two parameters will couple to static misalignments inside the interferometer and will generate spurious signals, which can easily limit the sensitivity of gravitational wave detectors such as Advanced LIGO. This has long been recognized and has led to alignment sensing and control systems, which use piezo mounted mirrors to control the alignment of the laser beam. The disadvantage of these systems is their low bandwidth and intrinsic noise. We have are in the process of characterizing actuators which use the electro-optical effect to steer the laser beam. These systems have a significantly higher bandwidth and don't require any moving parts which usually means much higher reliability. We report on the performance of these devices. [Preview Abstract] |
Friday, October 21, 2011 11:33AM - 11:45AM |
HA.00005: Orbits and Scaling for an Isotropic Metric Joseph Rudmin Scaling of physical quantities shows the symmetries of an isotropic metric. For example, invariance of Planck's constant under gravitational scaling provides consistency of general relativity with quantum mechanics. Invariance of charge and electric field strength provide consistency with electromagnetism. Transitivity of scaling eliminates the traditional need for a globally preferred reference frame. Rather, diagonalization of the metric yields local rest frames. Conventional application of the Einstein Equation has inconsistencies and contradictions, such as gravitational fields without energy, objects crossing event-horizons, objects exceeding the speed of light, and inconsistency in scaling the speed of light and its factors. An isotropic metric resolves such problems by attributing energy to the gravitational field, in the energy-momentum tensor of the Einstein Equation. Scattering, orbital period, and precession offer ways to distinguish an isotropic from a Schwarzschild metric. [Preview Abstract] |
Friday, October 21, 2011 11:45AM - 11:57AM |
HA.00006: Telescope Spacer Design Investigations Danila Korytov, Josep Sanjuan, Guido Mueller, Jeffrey Livas, Alix Preston, Petar Arsenovic, Ruven Spannagel Space-based interferometric gravitational wave observatories will measure changes in the distance between free falling proof masses inside widely separated spacecraft with pm sensitivity. These observatories~will use fast telescopes to exchange laser beams. These telescopes are part of the probed optical distances and any length change in the gravitational wave band between secondary and primary can limit the sensitivity of the observatories. Furthermore, the large distance between and space constrains on the spacecraft require to use very fast telescopes with f-numbers approaching unity. These telescopes are very sensitive against any absolute length change which would reduce interferometer visibility and, ultimately, sensitivity. Our group has assembled a Silicon Carbide test structure and investigated its dimensional stability in the 10$^{-4}$ to 1Hz frequency band at different operating temperatures. We also measured the overall length change and started investigating asymmetric length changes during cool down which would lead to misalignments in the telescope [Preview Abstract] |
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