The Advanced LIGO Photon Calibrators

The two interferometers of the Laser Interferometry Gravitaional-wave Observatory (LIGO) recently detected gravitational waves from the mergers of binary black hole systems. Accurate calibration of the output of these detectors was crucial for the observation of these events, and the extraction of parameters of the sources. The principal tools used to calibrate the responses of the second-generation (Advanced) LIGO detectors to gravitational waves are systems based on radiation pressure and referred to as Photon Calibrators. These systems, which were completely redesigned for Advanced LIGO, include several significant upgrades that enable them to meet the calibration requirements of second-generation gravitational wave detectors in the new era of gravitational-wave astronomy. We report on the design, implementation, and operation of these Advanced LIGO Photon Calibrators that are currently providing fiducial displacements on the order of $10^{-18}$ m/$\sqrt{\textrm{Hz}}$ with accuracy and precision of better than 1 %.Comment: 14 pages, 19 figure

Swept frequency eddy current (SFEC) measurements of Inconel 718 as a function of microstructure and residual stress

The goal of this thesis was to determine the dependency of swept frequency eddy current (SFEC) measurements on the microstructure of the Ni-based alloy, Inconel 718 as a function of heat treatment and shot peening. This involved extensive characterization of the sample using SEM and TEM coupled with measurements and analysis of the eddy current response of the various sample conditions using SFEC data. Specific objectives included determining the eddy current response at varying depths within the sample, and this was accomplished by taking SFEC measurements in frequencies ranging from 100 kHz to 50 MHz. Conductivity profile fitting of the resulting SFEC signals was obtained by considering influencing factors (such as surface damage). The problems associated with surface roughness and near surface damage produced by shot peening were overcome by using an inversion model. Differences in signal were seen as a result of precipitation produced by heat treatment and by residual stresses induced due to the shot peening. Hardness of the material, which is related both to precipitation and shot peening, was seen to correlate with the measured SFEC signal. Surface stress measurement was carried out using XRD giving stress in the near surface regions, but not included in the calculations due to shallow depth information provided by the technique compared to SFEC. By comparing theoretical SFEC signal computed using the microstructural values (precipitate fraction) and experimental SFEC data, dependency of the SFEC signals on microstructure and residual stress was obtained

Sliding Vane Pump Shaft Structural Response and Intermittent Failure Investigation

The objectives of this study were to examine the structural response of a swept vane pump shaft subject to normal operational loading and use the results obtained from laboratory experimentation and numerical simulations to determine possible root cause pertaining to intermittent structural failure. Microscopic and SEM photographs were taken to examine the effects of the seal drive pin press fit operation on the pump shaft. Dynamic measurements of the pump discharge and pump chamber pressure were acquired at a high sample rate to study the pressures the pump shaft would be subjected to. Dynamic strain measurements of the pump shaft during the operation of the pump were also gathered through the use of telemetry data acquisition hard. Numerical simulation models involving both elastic and plastic deformations were created to simulate the press fit operation, the dynamic strain measurement experiments, and to examine the total stress when all applicable loads and interferences were applied. Research concluded that the interference fit between the seal drive pin and the pump shaft resulted in an appreciable amount of plastic deformation pertaining to the pump shaft and also resulted in levels of stress that were approaching the endurance limit of the material. Subsequent numerical simulation models that included all applicable loads and interference fits revealed stress levels that exceeded the endurance limit of the material. However, all experimentation and numerical simulation models were conducted on geometry at the nominal design dimensions. Tolerance analysis revealed a wide range of interference between the seal drive pin and the shaft, which would result in dramatic changes in the amount of plastic deformation and the magnitudes of the surrounding stresses. The press fit operation was perceived as being a major source of variability, which would contribute to the overall intermittent nature of the pump shaft failures. In addition, results stemming from the pump discharge/pump chamber pressure testing and the dynamic strain measurement experimentation revealed the presence of liquid compression, which serve to increase the levels of stress and reduce the overall serviceable life of the pump shaft.Mechanical & Aerospace Engineerin

Computational fluid mixing

Computational fluid dynamics (CFD) is an extremely powerful tool for solving problems associated with flow, mixing, heat and mass transfer and chemical reaction. Although the equations of motion for fluid flow were established in the first half of the nineteenth century (e.g. Navier, 1822; Stokes, 1845), it was not until the arrival of digital computers in the 1960s and 1970s that it became feasible to perform numerical simulations of complex engineering flows. In these early days, CFD was a very much a research tool and most of the early work was aimed at developing numerical methods, solution algorithms and Reynolds-averaged turbulence models. However, in the 1980s, the first commercial codes emerged — e.g. PHOENICS, FLUENT, FIDAP, Star-CD, FLOW3D (which later became CFX) — providing general purpose software packages for both academic and industry users. The aerospace and automotive industries were amongst the first to embrace the use of CFD in engineering design, but from the 1990s onwards commercial codes have found widespread applications, for example in: biomedical engineering, environmental and atmospheric modelling, meteorology, chemical reaction engineering and more recently in the food and beverage industries. This chapter will focus on mixing vessel applications for the last two of these industry sectors, where CFD is increasingly used to provide process understanding and semi-quantitative analysis. In their review, Norton and Sun (2006) presented a graph showing the very significant increase in the number of peer-reviewed papers related to CFD applications to food process engineering. Figure 0.1 is an updated version of this graph, containing more recent data and showing that the number of papers that specifically analyse food mixing operations using CFD is still relatively small. In contrast, there are a vast numbers of papers on CFD simulation of (i) other food process operations, (e.g. drying, sterilisation, thermal treatment and extrusion, many of which are described by Sun (2007)) and (ii) more conventional mixing operations in the chemicals and specialty product industries (see for example, Marshall and Bakker (2004)). This chapter will outline the background knowledge required for CFD studies, present some examples of CFD modelling of mixing vessel flows and finally will discuss the current difficulties in applying this approach to food mixing processes

Aeronautical Engineering: A continuing bibliography, supplement 120

This bibliography contains abstracts for 297 reports, articles, and other documents introduced into the NASA scientific and technical information system in February 1980