The second generation of LIGO detectors has finished construction and the commissioning effort is pushing the instruments towards their designed sensitivity. Around the world similar undertakings are ...underway, and soon a global network capable of astrophysical observation will be operational. The first sentences are being written in an important chapter of terrestrial gravitational wave detection, an entire century after the theoretical foundations of general relativity were laid, and after decades of calculation, design, proposals, plans, and laboratory work.In order to make sensitive measurements, the detector must be well isolated from the vibrations of the ground, and much of this thesis describes the effectiveness of active control platforms used to mitigate the transmission of seismic motions to the test masses. This work was performed both during the last science run of the first generation LIGO detector and as part of the commissioning of the second generation instrument.
This dissertation connects Hollywood "integration films" of the 1950s to the modern civil rights movement and to "liberal" racial ideologies. We use the historiography of Foucault to exhume ...correspondences between political and popular representations of racial-national identity and of integration, following changes in the formation of ideas empowering racial liberalism. We place film interactively alongside Supreme Court rulings and Congressional debates around race integration, contemporaneously published works of history and sociology, and the "memory" of slavery and Reconstruction as displayed in the wider culture. In films centering a protagonist who is racially or culturally "mixed," we examine a change in discourse surrounding racial integration. In the early fifties—from the social problem film such as No Way Out (1950) to the pro-Indian western such as Broken Arrow (1950) and Broken Lance (1954)—motion pictures employ a framework of the melting pot, or cultural assimilation, to represent integration. This signifies national support for racial progress yet also, by using terms of "culture" to repress terms of "class," suggests widespread resistance to imagining and ensuring needed change in the racial-social structure of society. In the later fifties, a different logic—based on cultural pluralism—represents integration, often in films making miscegenation or racial mixing problematic. Movies such as The Searchers (1956) and Imitation of Life (1959) construct an imagined "right" to protect white status as a "culture," or "racial cultural" boundaries that would oppose our political knowledge of race and class struggle. Further, we connect seminal liberal representations of race in the fifties to ideological positions today that efface the persistence of segregation—or that would represent poverty but do not advance a social remedy for it. This dissertation would challenge liberalism to speak not just for passive racial "progress," for "rationalism" and for the individual, but moreover for the rights of the poor and working class to equal social resources, rights that interact with and would advance racial equality.
The second generation of LIGO detectors has finished construction and the commissioning effort is pushing the instruments towards their designed sensitivity. Around the world similar undertakings are ...underway, and soon a global network capable of astrophysical observation will be operational. The first sentences are being written in an important chapter of terrestrial gravitational wave detection, an entire century after the theoretical foundations of general relativity were laid, and after decades of calculation, design, proposals, plans, and laboratory work.
In order to make sensitive measurements, the detector must be well isolated from the vibrations of the ground, and much of this thesis describes the effectiveness of active control platforms used to mitigate the transmission of seismic motions to the test masses. This work was performed both during the last science run of the first generation LIGO detector and as part of the commissioning of the second generation instrument.
The first terrestrial gravitational wave interferometers have dramatically underscored the scientific value of observing the Universe through an entirely different window, and of folding this new ...channel of information with traditional astronomical data for a multimessenger view. The Laser Interferometer Space Antenna (LISA) will broaden the reach of gravitational wave astronomy by conducting the first survey of the millihertz gravitational wave sky, detecting tens of thousands of individual astrophysical sources ranging from white-dwarf binaries in our own galaxy to mergers of massive black holes at redshifts extending beyond the epoch of reionization. These observations will inform - and transform - our understanding of the end state of stellar evolution, massive black hole birth, and the co-evolution of galaxies and black holes through cosmic time. LISA also has the potential to detect gravitational wave emission from elusive astrophysical sources such as intermediate-mass black holes as well as exotic cosmological sources such as inflationary fields and cosmic string cusps.
Interferometric gravitational wave detectors operate with high optical power in their arms in order to achieve high shot-noise limited strain sensitivity. A significant limitation to increasing the ...optical power is the phenomenon of three-mode parametric instabilities, in which the laser field in the arm cavities is scattered into higher order optical modes by acoustic modes of the cavity mirrors. The optical modes can further drive the acoustic modes via radiation pressure, potentially producing an exponential buildup. One proposed technique to stabilize parametric instability is active damping of acoustic modes. We report here the first demonstration of damping a parametrically unstable mode using active feedback forces on the cavity mirror. A 15,538 Hz mode that grew exponentially with a time constant of 182 sec was damped using electro-static actuation, with a resulting decay time constant of 23 sec. An average control force of 0.03 nNrms was required to maintain the acoustic mode at its minimum amplitude.
The Advanced LIGO gravitational wave detectors are nearing their design sensitivity and should begin taking meaningful astrophysical data in the fall of 2015. These resonant optical interferometers ...will have unprecedented sensitivity to the strains caused by passing gravitational waves. The input optics play a significant part in allowing these devices to reach such sensitivities. Residing between the pre-stabilized laser and the main interferometer, the input optics is tasked with preparing the laser beam for interferometry at the sub-attometer level while operating at continuous wave input power levels ranging from 100 mW to 150 W. These extreme operating conditions required every major component to be custom designed. These designs draw heavily on the experience and understanding gained during the operation of Initial LIGO and Enhanced LIGO. In this article we report on how the components of the input optics were designed to meet their stringent requirements and present measurements showing how well they have lived up to their design.
PDF
