655 research outputs found
Interview with Ronald W. P. Drever
No full textAn interview in five sessions, January through June, 1997, with Ronald W. P. Drever, professor of physics (now emeritus) in the Division of Physics, Mathematics, and Astronomy. Dr. Drever graduated with first honors from the University of Glasgow in 1953 and received his PhD there in 1958. He moved from Glasgow to Caltech in 1977 to help establish the gravitational-wave project later known as LIGO (Laser Interferometry Gravitational-Wave Observatory)—first as a visiting associate, then a half-time professor (1979-1984), becoming full-time in 1984.
He discusses his postdoctoral work at Glasgow on the anisotropy of inertia; a fellowship at Harvard with R. V. Pound measuring gravitational redshift; and collaboration with John Jelley of Harwell looking for radio and light pulses from supernovae and the Crab pulsar.
Recalls his interest in Joseph Weber’s experiments to detect gravitational waves and his own bar-detector work at Glasgow; his switch to interferometers; his “friendly rivalry” with the gravitational-wave group at the Max Planck Institute in Munich; his adaptation of Fabry-Perot cavities vs. the delay-line technique of MIT’s Rainer Weiss. Recalls his collaboration with John Hall, of JILA, in Boulder, CO. Discusses his recruitment to Caltech by Kip S. Thorne; designing Caltech’s 40-meter prototype interferometer; his various innovations; his disagreements with Weiss, Thorne, and particularly Robbie [Rochus E.] Vogt, LIGO director 1987-1994; his July 1992 dismissal from LIGO; his grievance hearing before Caltech’s Academic Freedom & Tenure Committee, and its eventual outcome.
The interview concludes with comments on his current research and on the prospects for LIGO and allied gravity-wave projects
Planar-Waveguide External Cavity Laser Stabilization for an Optical Link with 1E-19 Frequency Stability
No full textWe stabilized the frequency of a compact planar-waveguide external cavity laser (ECL) on a Fabry-P\'erot cavity (FPC) through a Pound-Drever-Hall scheme. The residual frequency stability of the ECL is 1E-14, comparable to the stability achievable with a fiber laser (FL) locked to a FPC through the same scheme. We set up an optical link of 100 km, based on fiber spools, that reaches 1E-19 relative stability, and we show that its performances using the ECL or FL are comparable. Thus ECLs could serve as an excellent replacement for FLs in optical links where cost-effectiveness and robustness are important consideration
Laser interferometer gravitational radiation detectors
No full textSome techniques proposed or currently under development for detection of gravitational radiation by laser interferometers are reviewed, with particular emphasis on experiments covering the lower frequencies potentially accessible to ground based instruments
Mission Concept Study for Sagittarius: A Spaceborn Astronomical Gravity-Wave Interferometer
No full textLaser-frequency locking techniques for high-sensitivity strain measurements by high-birefringence fiber Bragg gratings and resonators
No full textA new approach to simultaneously interrogate orthogonal axes of single Fiber-
Bragg-Gratings (FBGs) and FBG-FabryPerot resonator sensors fabricated in
linearly highly birefringent (HiBi) fibre is presented. Novel interrogation
techniquesof single Fiber-Bragg-Gratings (FBGs) and FBG-resonator sensors are
presented. For a single FBG, we combined alaser-modulation technique to an
electronic feedback loop that keeps the source always frequency locked to one
peak ofthe sensor's reflected spectrum. Two different lasers, with orthogonally-
polarized states, were adopted to monitorsimultaneously both the "fast" and
"slow" FBG peaks. The corresponding correction signals from the servo-loop
outputscan be interpreted as strain or temperature induced on the FBG. Detection
limits ranging from 1 nε/√Hz to 100 nε/√Hz,for axial dynamic and static
deformations, respectively, and of 0.025 °C/√Hz for temperature variations, are
expected. Asimilar approach was developed for sub-pϵ resolution interrogation of
an optical resonator made of a high-reflectivityFBG-pair, using the Pound-
Drever-Hall (PDH) stabilizat
Injection-locked single-frequency laser with an output power of 220 W
No full textA solid-state laser system for the next generation of gravitational wave detectors with an output power of 220 W at the wavelength of 1064 nm is presented. Single-frequency operation of the laser was achieved by injection-locking of a high-power ring oscillator to an amplified non-planar ring oscillator (NPRO) following the Pound–Drever–Hall scheme. The high-power stage which features four longitudinally pumped Nd:YAG laser crystals as active media in a ring resonator configuration was designed for reliable long term operation. Using a non-confocal ring cavity to filter the output beam, a pure TEM00 mode with 168 W output power was obtained
RESTART Extended Follow Up Dataset
No full textAnalysis dataset used for the RESTART extended follow up results paper in 2021 (doi:10.1001/jamaneurol.2021.2956).
This dataset contains the data dictionary and statistical analysis plan form the RESTART extended follow up. It also contains the Data sharing description and Request form that should be used to obtain a copy of the data.
Additional information about the data (trial protocol, annotated CRFs) can be found with the RESTART main results dataset ( https://doi.org/10.1016/S0140-6736(19)30840-2 ).SOP, Data dictionary, request form, data sharing process.
Annotated CRFs are available via RESTART trail main results dataset
Isotropy of inertia: A sensitive early experimental test
No full textAn experimental test for anisotropy of inertia performed by a nuclear freeprecession experiment is described. The precession was observed in the Earth's magnetic field, in a countryside location in the open air. The experiment was exceptionally sensitive, and slightly unusual in other ways. Some of the background and other aspects are briefly discussed
Gravitational Wave Astronomy
No full textThis introductory review deals particularly with experimental techniques
used in searches for gravitational radiation, and prospects for developing
gravitational wave detectors of very much higher sensitivity. Some of the
factors which may limit the sensitivity of various types of detectors are
discussed, and future possibilities assessed
Upper limit to anisotropy of inertial mass from nuclear resonance
No full textIt has been pointed out by Bondi (1962) and Cocooni and Salpeter (1958) that if inertial mass is taken to arise from gravitational interaction with distant matter one would expect the concentration of matter near the centre of our town Galaxy to cause some anisotropy of inertia at the
earth. The anisotropy might be as large as one part in 10^7; and Cocconi and Saltepeter suggested that it could be detected from the shifts in atomic energy levels which might result in a single-electron atom in a magnetic
field parallel to the direction of the centre of the Galaxy they find that the energy of a P_(a/2) state with magnetic quantum number m_i = ± 1/2 would be altered by an amount T.ΔM/5M, where T is the mean kinetic energy of the electron and ΔM/M is the fractional difference between the inertial
masses of a body (the electron) for accelerations parallel to the direction of the centre of the Galaxy, and perpendicular to it. A p_(3/2) state foe which m_i = ± 3/2 would show an energy shift of equal magnitude in the opposite direction. If the magnetic field is perpendicular to the direction of the centre of the Galaxy then both these energy shifts would be reversed
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