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LENS: A new pulsed neutron source for research and education
No full textA new pulsed neutron source is under construction at the Indiana University Cyclotron Facility (IUCF). Neutrons are produced via ( p, n) reactions by a low-energy proton beam incident on a thin beryllium target. The source is tightly coupled to a cold methane moderator held at a temperature of 20 K or below. The resulting time-averaged cold neutron flux is expected to be comparable to that of the Intense Pulsed Neutron Source (IPNS) facility at Argonne National Laboratory. The initial experimental suite will include instrumentation for small angle neutron scattering ( SANS), moderator studies, radiography, and zero-field spin-echo SANS
Design and performance of laser-pumped Cs-magnetometers for the planned UCN EDM experiment at PSI
No full textWe designed laser-pumped cesium vapor magnetometers in the M-x configuration for the control and stabilization of magnetic field fluctuations and gradients in a new experiment searching for a permanent electric dipole moment of the neutron. The intrinsic sensitivity of the device was determined to be 30 fT in a measurement bandwidth of 1 Hz, limited by laser noise. In the shot noise limit the magnetometer can reach a sensitivity of 7 fT for 1 s integration time. Test measurements of the stability of a 2 T magnetic field in a threefold magnetic shield have revealed fluctuations on the order of 200 fT to 300 fT with integration times in the range of 2 s to 100 s. Those fluctuations were traced back to the stability of the power supply used to generate the magnetic field. The laser-pumped magnetometer fulfills the requirements set by the planned neutron electric dipole moment experiment
A survey of tables of probability distributions
No full textThis article is a survey of the tables of probability distributions published about or after the publication in 1964 of the Handbook of Mathematical Functions, edited by Abramowitz and Stegun
Measurement of workability of fresh concrete using a mixing truck
No full textThe main objective of this study is to evaluate the workability of fresh portland cement concrete while it is still in the mixing truck by determining fundamental rheological parameters ( plastic viscosity and yield stress). Nine concrete mixtures with different values of yield stress and plastic viscosity were tested in a concrete truck. The measurements made with the truck were based on the typical method of determining the flow behavior in a traditional fluid rheometer; that is, the shear rate in the mixing truck was swept from high to low by varying the rotation speed of the drum. The results of these experiments are discussed and compared with data provided by the ICAR rheometer, a portable rheometer designed for measuring concrete rheology. The test results indicate that the mixing truck equipment is sufficiently sensitive to detect differences in yield stress, slump, and plastic viscosity. However, the plastic viscosity determined by the truck measurement did not correlate with plastic viscosity as measured by the ICAR rheometer, while the yield stress determined by the truck measurement did correlate well with the measured slump and the ICAR rheometer results. Suggestions are given on how to improve the mixing truck for better use as a rheometer
Measurement of parity violation in np capture: the NPDGamma experiment
No full textThe NPDGamma experiment will measure the parity-violating directional gamma ray asymmetry A(gamma) in the reaction (n) over right arrow + p --> d + gamma. Ultimately, this will constitute the first measurement in the neutron-proton system that is sensitive enough to challenge modern theories of nuclear parity violation, providing a theoretically clean determination of the weak pion-nucleon coupling. A new beamline at the Los Alamos Neutron Science Center (LANSCE) delivers pulsed cold neutrons to the apparatus, where they are polarized by transmission through a large volume polarized He-3 spin filter and captured in a liquid para-hydrogen target. The 2.2 MeV gamma rays from the capture reaction are detected in an array of CsI(Tl) scintillators read out by vacuum photodiodes operated in current mode. We will complete commissioning of the apparatus and carry out a first measurement at LANSCE in 2004-05, which would provide a statistics-limited result for A gamma accurate to a standard uncertainty of +/- 5 x 10(-8) level or better, improving on existing measurements in the neutron-proton system by a factor of 4. Plans to move the experiment to a reactor facility, where the greater flux would enable us to make a measurement with a standard uncertainty of +/- 1 x 10(-8), are actively being pursued for the longer term
A silicon UCN detector with large area and with analysis of UCN polarization
No full textA silicon ultracold neutron (UCN) detector with an area of 45 cm(2) and with a (LiF)-Li-6 converter is developed at St. Petersburg Nuclear Physics Institute (PNPI). The spectral efficiency of the silicon UCN detector was measured by means of a gravitational spectrometer at Institut Max von Laue - Paul Langevin ( ILL). The sandwich-type detector from two silicon plates with a (LiF)-Li-6 converter placed between them was also studied. Using this type of technology the UCN detector with analysis of polarization was developed and tested. The analyzing power of this detector assembly reaches up 75 % for the main part of UCN spectrum. This UCN detector with analysis of UCN polarization can be used in the new electric dipole moment (EDM) spectrometer
Papers and posters presented at the April 2004 International Conference on Precision Measurements with Slow Neutrons at the National Institute of Standards and Technology - Preface
No full textProposed measurement of the beta-neutrino correlation in neutron decay
No full textCurrently, the beta-neutrino asymmetry has the largest uncertainty (4%) of the neutron decay angular correlations. Without requiring polarimetry, this decay parameter can be used to measure lambda(g(a)/g(v)), test Cabibbo-Kobayashi-Maskawa (CKM) unitarity, limit scalar and tensor currents, and search for Charged Vector Current (CVC) violation. We propose to measure the beta-neutrino asymmetry coeffcient, a, using time-of-flight for the recoil protons. We hope to achieve a systematic uncertainty of sigma(a)/a approximate to 1.0%. After tests at Indiana University's Low Energy Neutron Source (LENS), the apparatus will be moved to the National Institute of Standards and Technology (NIST) where the measurement can achieve a statistical uncertainty of 1% to 2% in about 200 beam days
Radiative neutron beta-decay in effective field theory
No full textWe consider radiative beta-decay of the neutron in heavy baryon chiral perturbation theory. Nucleon-structure effects not encoded in the weak coupling constants g(A) and g(V) are determined at next-to-leading order in the chiral expansion, and enter at the 0( 0.5%)-level, making a sensitive test of the Dirac structure of the weak currents possible
Investigation of solid D-2 for UCN sources
No full textSolid deuterium (sD(2)) will be used for the production of ultra-cold neutrons (UCN) in a new generation of UCN sources. Scattering cross sections of UCN in sD2 determine the source yield but until now have not been investigated. We report first results from transmission and scattering experiments with cold, very cold and ultra-cold neutrons on sD2 along with light transmission and Raman scattering studies showing the influence of the sD2 crystal properties