Search results for "small-angle"

A Ramsey apparatus for the measurement of the incoherent neutron scattering length of the deuteron

2008

Abstract A Ramsey apparatus for cold, polarised neutrons is described, which enables us to measure neutron precession angles with an absolute accuracy of about 1 ∘ . This is necessary to perform a planned high-accuracy measurement of the incoherent neutron scattering length b i , d of the deuteron. The performance of the apparatus is demonstrated in systematic stability measurements as well as in two selected examples using samples containing polarised nuclear spins.

Angular and polarization dependence of Compton scattering from in the Δ-resonance region

1998

Abstract Using linearly polarized tagged photons from coherent bremsstrahlung, differential cross sections and beam asymmetries for Compton scattering by 4 He have been measured at MAMI in the energy interval between 150 MeV and 500 MeV for scattering angles of θ γ lab =37°, 93° and 137°, thus largely increasing the available data base. Improved calculations in terms of the Δ -hole model completely fail to describe the data at large scattering angles. The same proved to be true for a schematic model, even after taking into account properties of nuclear photo-absorption in very detail.

Angular distribution of scattered electrons associated with collimated bremsstrahlung and the tagging technique

2009

Abstract We investigate the angular correlation between a bremsstrahlung photon and its corresponding post-bremsstrahlung electron within the context of a magnetic tagging spectrometer with the aim of improving the instrument's efficiency. Our results are given in terms of angular distributions of the post-bremsstrahlung electron associated with photons that pass through a circular collimator centered in the forward direction. We start from the fully differential Bethe–Heitler (first Born approximation) cross-section, including the Moliere screening correction, which is then integrated over the photon azimuthal angle and over the photon polar angle defined by the collimator. These integrati…

Small angle scattering from oriented latent nuclear tracks

1984

Abstract Using X-ray and neutron small-angle scattering we studied the defects in mica created by irradiation with uranium ions delivered from the UNILAC accelerator at GSI (Darmstadt, Germany). The defects are regions of reduced density and are best described as cylinders with Gaussian radial density distribution. Scaling laws are given for the time development and the energy dependence of the track parameters.

Comment on “Comparison of Polarization Observables in Electron Scattering from the Proton and Deuteron”

1998

Small Angle Neutron Scattering from Systems of Interacting Particles. Modelling High Density Micellar Fluids

1992

The need for analytical solutions of the scattering equation for complex situations (polydisperse samples, scattering from non centrosymmetrical particles, etc.) has somehow escaped the attention of the workers in the Small Angle Scattering field, although it is clear that, at the level of sophistication today available for the experiments, a more rigorous approach is necessary. For quite a few years our group has been actively engaged in SANS research and has occasionally devoted its attention to develop alternative ways of data analysis based on more rigorous solutions of the scattering equation.

Simbol-X Mirror Module Thermal Shields: II-Small Angle X-Ray Scattering Measurements

2009

The formation flight configuration of the Simbol-X mission implies that the X-ray mirror module will be open to Space on both ends. In order to reduce the power required to maintain the thermal stability and, therefore, the high angular resolution of the shell optics, a thin foil thermal shield will cover the mirror module. Different options are presently being studied for the foil material of these shields. We report results of an experimental investigation conducted to verify that the scattering of X-rays, by interaction with the thin foil material of the thermal shield, will not significantly affect the performances of the telescope.

Inelastic neutron scattering by coupled rotational and translational modes in KCN

1980

The TA [100] phonon branch of the molecular crystal KCN was studied by inelastic neutron scattering in the cubic phase. In addition the distribution of the quasielastic scattered neutrons was investigated. The results are analysed by assuming a coupling of the phonon modes to the rotational degrees of freedom of the CN-dumb-bells which are regarded as a system of interacting quadrupoles. A good description of the present results and also of the existing ultrasonic and Brillouin data is achieved by a simple model which uses a single collective rotational mode of finite excitation energy and line width.

Elastic constants in RbI, determined by inelastic neutron scattering

1978

Long-wavelength acoustic phonons have been studied in the whole (100)-plane of RbI at 295 K by means of inelastic neutron scattering. The raw data have been corrected for resolution effects taking into account the curvature of the dispersion surface and variations of the mode eigenvectors. The shifts of the neutron groups due to these resolution effects are discussed in detail. The analysis of the experimental results gives for the zero sound elastic constantsc11=28.15±0.5,c12=3.7±0.5 andc44=2.85±0.1 1010 dyn/cm2. A comparison with first sound elastic constants taken from ultrasonic measurements yields significant differences between the high and low frequency elastic constantsc11 andc″=(c1…

Mode-coupling crossover in viscous toluene revealed by neutron and light scattering

1998

The dynamics of supercooled toluene, studied in a GHz-THz range by incoherent neutron and depolarized light scattering, is found to be in full accord with mode coupling predictions. Around the susceptibility minimum, neutron spectra are wavenumber independent and proportional to light scattering data; the fast β-relaxation scaling law applies; amplitude and frequency diverge with power laws that extrapolate towards a crossover temperature Tc K.