1,309 research outputs found
Angular instability due to radiation pressure in the LIGO gravitational-wave detector
We observed the effect of radiation pressure on the angular sensing and control system of the Laser Interferometer Gravitational-Wave Observatory (LIGO) interferometer’s core optics at LIGO Hanford Observatory. This is the first measurement of this effect in a complete gravitational-wave interferometer. Only one of the two angular modes survives with feedback control, because the other mode is suppressed when the control gain is sufficiently large. We developed a mathematical model to understand the physics of the system. This model matches well with the dynamics that we observe
Readout and Control of a Power-recycled Interferometric Gravitational-wave Antenna
Interferometric gravitational wave antennas are based on Michelson
interferometers whose sensitivity to small differential length changes has been
enhanced by adding multiple coupled optical resonators. The use of optical
cavities is essential for reaching the required sensitivity, but sets
challenges for the control system which must maintain the cavities near
resonance. The goal for the strain sensitivity of the Laser Interferometer
Gravitational-wave Observatory (LIGO) is 10^-21 rms, integrated over a 100 Hz
bandwidth centered at 150 Hz. We present the major design features of the LIGO
length and frequency sensing and control system which will hold the
differential length to within 5 10^-14 m of the operating point. We also
highlight the restrictions imposed by couplings of noise into the gravitational
wave readout signal and the required immunity against them.Comment: Presentation at ICALEPCS 2001, San Jose, November 2001, (WECT003), 3
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Sexualmedizinische Behandlungsfälle – Entwicklungen 1980 – 1990 – 2004
Sexual dysfunctions can adversely affect men's and women's satisfaction with life over a prolonged period. Besides sexual medicine services in primary medical care, in Switzerland there exist specialized consultation services at University Hospitals. The assessment of the case histories of three years (1980, 1990, and 2004) of the Sexual Medicine Consultation Service at Zurich University Hospital provided the following results: the most common disorders are lack/loss of libido in women and erectile dysfunction in men. Treatment options for sexual disorders have become more differentiated in recent years. The collaboration between the doctors making the referral and the sexual medicine specialists improved markedly between 1980 and 2004. After a diagnostic assessment and a primary treatment in the specialized consultation service, many patients are referred back to the referring doctors for further treatment. Basic and further training in sexual medicine ought to be intensified and improved
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HOLDUP MEASUREMENTS FOR VISUAL EXAMINATION GLOVEBOXES AT THE SAVANNAH RIVER SITE
Visual Examination (VE) gloveboxes are used at the Savannah River Site (SRS) to remediate transuranic waste (TRU) drums. Noncompliant items are removed before the drums undergo further characterization in preparation for shipment to the Waste Isolation Pilot Plant (WIPP). Maintaining the flow of drums through the remediation process is critical to the program's seven-days-per-week operation. Conservative assumptions are used to ensure that glovebox contamination from this continual operation is below acceptable limits. Holdup measurements are performed in order to confirm that these assumptions are conservative. High Cs-137 backgrounds in the VE glovebox areas preclude the use of a sodium iodide spectrometer, so a high-purity germanium (HPGe) detector, having superior resolution, is used. Plutonium-239 is usually the nuclide of interest; however, Pu-241, Np-237 (including its daughter Pa-233) and Pu-238 (if detected) are typically assayed. Cs-137 and Co-60 may also be detected but are not reported since they do not contribute to the Pu-239 Fissile Gram Equivalent or Pu-239 Equivalent Curies. HEPA filters, drums and waste boxes are also assayed by the same methodology. If--for example--the HEPA is contained in a stainless steel housing, attenuation corrections must be applied for both the filter and the housing. Dimensions, detector locations, materials and densities are provided as inputs to Ortec's ISOTOPIC software to estimate attenuation and geometry corrections for the measurement positions. This paper discusses the methodology, results and limitations of these measurements for different VE glovebox configurations
Journal of African Christian Biography: v. 4, no. 2
A publication of the Dictionary of African Christian Biography with U.S. offices located at the Center for Global Christianity and Mission at Boston University. This issue focuses on: 1. Tributes to Lamin Sanneh by friends, family, colleagues, scholars, a Bible translator, and an editor. 2. Biographies by Lamin Sanneh in the DACB. 3. A selected bibliography by Lamin Sanneh, compiled by B. Restrick. 4. Book Notes, compiled by B. Restric
Adaptive thermal compensation of test masses in advanced LIGO
As the first generation of laser interferometric gravitational wave detectors
near operation, research and development has begun on increasing the
instrument's sensitivity while utilizing the existing infrastructure. In the
Laser Interferometer Gravitational Wave Observatory (LIGO), significant
improvements are being planned for installation in ~2007, increasing strain
sensitivity through improved suspensions and test mass substrates, active
seismic isolation, and higher input laser power. Even with the highest quality
optics available today, however, finite absorption of laser power within
transmissive optics, coupled with the tremendous amount of optical power
circulating in various parts of the interferometer, result in critical
wavefront deformations which would cripple the performance of the instrument.
Discussed is a method of active wavefront correction via direct thermal
actuation on optical elements of the interferometer. A simple nichrome heating
element suspended off the face of an affected optic will, through radiative
heating, remove the gross axisymmetric part of the original thermal distortion.
A scanning heating laser will then be used to remove any remaining
non-axisymmetric wavefront distortion, generated by inhomogeneities in the
substrate's absorption, thermal conductivity, etc. A proof-of-principle
experiment has been constructed at MIT, selected data of which are presented.Comment: 11 pages, 7 figures, submitted to Classical and Quantum Gravit
Hadronic Atoms and Effective Interactions
We examine the problem of hadronic atom energy shifts using the technique of
effective interactions and demonstrate equivalence with the conventional
quantum mechanical approach.Comment: 22 page latex file with 2 figure
Benefits of Artificially Generated Gravity Gradients for Interferometric Gravitational-Wave Detectors
We present an approach to experimentally evaluate gravity gradient noise, a
potentially limiting noise source in advanced interferometric gravitational
wave (GW) detectors. In addition, the method can be used to provide sub-percent
calibration in phase and amplitude of modern interferometric GW detectors.
Knowledge of calibration to such certainties shall enhance the scientific
output of the instruments in case of an eventual detection of GWs. The method
relies on a rotating symmetrical two-body mass, a Dynamic gravity Field
Generator (DFG). The placement of the DFG in the proximity of one of the
interferometer's suspended test masses generates a change in the local
gravitational field detectable with current interferometric GW detectors.Comment: 16 pages, 4 figure
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