K-Electron-Capture-to-Positron-Emission Ratio in the Decays of ^(15)O and ^(19)Ne

The K/β^+ ratio in the decays of ^(19)Ne and ^(15)O have been measured as (9.6 ± 0.3) × 10^(-4) and (10.7 ± 0.6) × 10^(-4), respectively. A gas-flow proportional counter, operating in anticoincidence with the surrounding plastic scintillator, was used. Theoretical K/β^+ ratios for ^(19)Ne and ^(15)O were computed, using exchange-overlap corrections calculated by Vatai and, separately, exchange corrections extrapolated from the results of Bahcall for 14 ≤ Z ≤ 37. The experimental results were found to be in better agreement with Vatai's calculations

Measurement of Tritium as Water Vapor

When Geiger or proportional counters are used for the assay of tritiated water, the sample is usually converted into hydrogen or methane which is included in the counter filling. Measurement of the sample itself as water vapor would appear to be a more direct method which avoids possible uncertainties in the chemical conversion, and this technique has been used recently [1,2]. It will be shown, however, that although counters containing water vapor may have satisfactory characteristics, adsorption effects can introduce large errors

Analysis of a four-mirror cavity enhanced Michelson interferometer

We investigate the shot noise limited sensitivity of a four-mirror cavity enhanced Michelson interferometer. The intention of this interferometer topology is the reduction of thermal lensing and the impact of the interferometers contrast although transmissive optics are used with high circulating powers. The analytical expressions describing the light fields and the frequency response are derived. Although the parameter space has 11 dimensions, a detailed analysis of the resonance feature gives boundary conditions allowing systematic parameter studies

Measurements of mechanical Q in levitated paramagnetic crystals

Thermal noise from test masses, arising both from internal noise in the test mass material and from losses in the suspension wires and their attachments, is a significant factor limiting sensitivity of interferometric gravity-wave detectors. To investigate ways of reducing these noise sources we are using magnetic levitation in place of suspension wires. A search for high-Q crystals with magnetic properties allowing tests in moderate field strengths has led us to paramagnetic crystals, and we report preliminary results with small levitated samples of Gadolinium Gallium Garnet (GGG) and Terbium Gallium Garnet (TGG). The technique seems the first to allow Q measurements with no mechanical contact, and may facilitate work aimed at reducing thermal noise

Passive and active seismic isolation for gravitational radiation detectors and other instruments

Some new passive and active methods for reducing the effects of seismic disturbances on suspended masses are described, with special reference to gravitational radiation detectors in which differential horizontal motions of two or more suspended test masses are monitored. In these methods it is important to be able to determine horizontal seismic accelerations independent of tilts of the ground. Measurement of changes in inclination of the suspension wire of a test mass, relative to a direction defined by a reference arm of long period of oscillation, makes it possible to carry this out over the frequency range of interest for earth-based gravitational radiation detectors. The signal obtained can then be used to compensate for the effects of seismic disturbances on the test mass if necessary. Alternatively the signal corresponding to horizontal acceleration can be used to move the point from which the test mass is suspended in such a way as to reduce the effect of the seismic disturbance and also damp pendulum motions of the suspended test mass. Experimental work with an active anti-seismic system of this type is described

Laser interferometer gravitational radiation detectors

Some 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

Gravitational Wave Astronomy

This 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

Spectroscopy of the 1S0−3P0^1S_0-{}^3P_0 Clock Transition of 87^{87}Sr in an Optical Lattice

We report on the spectroscopy of the $5s^2 {}^1S_0 (F=9/2) \to 5s5p {}^3P_0 (F=9/2)$ clock transition of ${}^{87}{\rm Sr}$ atoms (natural linewidth of 1 mHz) trapped in a one-dimensional optical lattice. Recoilless transitions with a linewidth of 0.7 kHz as well as the vibrational structure of the lattice potential were observed. By investigating the wavelength dependence of the carrier linewidth, we determined the magic wavelength, where the light shift in the clock transition vanishes, to be $813.5\pm0.9$ nm.Comment: 4 pages, 4 figures, submitted to Phys. Rev. Lett. (09/May/2003