1,329 research outputs found
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
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
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
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
Effect of Hydrostatic Compression on the Energy of the 14.4-kev Gamma Ray from Fe^(57) in Iron
The energy of the recoil-free fraction of they rays emitted by nuclei bound in solids1 has been found to be affected by temperature and by electronic configuration. The latter effect has been named the "isomeric" shift. Compression of a
solid should influence the energy through both of these mechanisms. We have measured the effect of hydrostatic compression at 295°K on the energy hν of the recoil-free 14.4-kev γ rays emitted by 0.1-μsec Fe^(57) bound in metallic iron
Homodyne locking of a squeezer
We report on the successful implementation of a new approach to locking the
frequencies of an OPO-based squeezed-vacuum source and its driving laser. The
technique allows the simultaneous measurement of the phase-shifts induced by a
cavity, which may be used for the purposes of frequency-locking, as well as the
simultaneous measurement of the sub-quantum-noise-limited (sub-QNL) phase
quadrature output of the OPO. The homodyne locking technique is cheap, easy to
implement and has the distinct advantage that subsequent homodyne measurements
are automatically phase-locked. The homodyne locking technique is also unique
in that it is a sub-QNL frequency discriminator.Comment: Accepted to Optics Letter
Spectroscopy of the Clock Transition of Sr in an Optical Lattice
We report on the spectroscopy of the clock transition of 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 nm.Comment: 4 pages, 4 figures, submitted to Phys. Rev. Lett. (09/May/2003
Isolation of gravitational waves from displacement noise and utility of a time-delay device
Interferometers with kilometer-scale arms have been built for
gravitational-wave detections on the ground; ones with much longer arms are
being planned for space-based detection. One fundamental motivation for long
baseline interferometry is from displacement noise. In general, the longer the
arm length L, the larger the motion the gravitational-wave induces on the test
masses, until L becomes comparable to the gravitational wavelength. Recently,
schemes have been invented, in which displacement noises can be evaded by
employing differences between the influence of test-mass motions and that of
gravitational waves on light propagation. However, in these schemes, such
differences only becomes significant when L approaches the gravitational
wavelength, and shot-noise limited sensitivity becomes worse than that of
conventional configurations by a factor of at least (f L/c)^(-2), for f<c/L.
Such a factor, although can be overcome theoretically by employing high optical
powers, makes these schemes quite impractical. In this paper, we explore the
use of time delay in displacement-noise-free interferometers, which can improve
their shot-noise-limited sensitivity at low frequencies, to a factor of (f
L/c)^(-1) of the shot-noise-limited sensitivity of conventional configurations.Comment: 10 pages, 12 figures, a proceeding for the Spanish Relativity Meeting
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