Wavefront errors in a two-beam interferometer

This paper deals with the impact of wavefront errors, due to the optical aberrations of a two-beam interferometer, on the period of the travelling fringe observed by integrating the interference pattern. A Monte Carlo simulation of the interferometer operation showed that the fringe-period estimate is unbiased if evaluated on the basis of the angular spectrum of the beam entering the interferometer, but the wavefront errors increase the uncertainty

Forward scattering in two-beam laser interferometry

A fractional error as large as 25 pm mm(-1) at the zero optical-path difference has been observed in an optical interferometer measuring the displacement of an x-ray interferometer used to determine the lattice parameter of silicon. Detailed investigations have brought to light that the error was caused by light forward-scattered from the beam feeding the interferometer. This paper reports on the impact of forward-scattered light on the accuracy of two-beam optical interferometry applied to length metrology, and supplies a model capable of explaining the observed error

Historical road system and farmhouses in Apulia

Human settlements often originate from the presence of such natural sustaining water bodies as springs, rivers, or rather from the proximity of relevant infrastructure (roads, harbours, etc.). Rural residential buildings, however, are generally closely linked to the cultivated fields of a farm. A significant example of rural buildings, that particularly identifies some national or regional areas, is that of the Apulian farmhouses known as “masserie”, which are considered as an important cultural heritage in the rural territories of that region. These buildings, featuring relevant architectural and landscape characteristics, encompass several functions within them and often host more than one family living there permanently. Territorial distribution of rural buildings and farmhouses in Apulia is diversified and, in general and as already stated, it can depend on the close relationship between the building and its adjacent agricultural lot. Moreover, in the case of the Apulian farmhouses, owing to their specific role in overseeing the territory and asserting land tenure rights, this distribution may have “genetic” origins influenced by other elements, too. The efforts of the present work regarding this issue are to investigate the existing relationships between the Apulian farmhouses system and the “historical” roads already existing when they were built (XII-XIX centuries). Particularly, the study proved if there are any correlations among the Roman roads, the sheep’s paths (tratturi) crossing the Apulia region and the farmhouses, both from the point of view of the distance from the roads and the importance of the individual farmhouses. Using GIS software and overlay mapping procedures it was possible to quantify the amount of farmhouses and their concentration within the catchment areas of the aforementioned historical roads, while through historical and territorial in-depth analysis those elements characterizing the most interesting farmhouses from the historical and architectural point of view were identified. The research provided interesting information on the existing relations between historical roads and farmhouses, leading to further considerations on the possibility to enhance some of these monuments, located in rural areas, through the promotion of the “integrated” asset represented by the historical road system, with particular reference to the sheep’s paths (tratturi)

Direct calorimetric measurements of isothermal entropy change on single crystal W-type hexaferrites at the spin reorientation transition

We report on the magnetic field induced isothermal entropy change, \Delta s(Ha, T), of W-type ferrite with CoZn substitution. Entropy measurements are performed by direct calorimetry. Single crystals of the composition BaCo$_0.62$Zn$_1.38$Fe$_16$O$_27$, prepared by the flux method, are measured at different fixed temperatures under an applied field perpendicular and parallel to the c axis. At 296 K one deduces a value of K$_1$ = 8.7 \times 10^{4} J m$^-3$ for the first anisotropy constant, which is in good agreement with the literature. The spin reorientation transition temperature is estimated to take place between 200 and 220 K

Defocused travelling fringes in a scanning triple-Laue X-ray interferometry setup

open3noThe measurement of the silicon lattice parameter by a separate-crystal triple-Laue X-ray interferometer is a key step for the realization of the kilogram by counting atoms. Since the measurement accuracy is approaching nine significant digits, a reliable model of the interferometer operation is required to quantify or exclude systematic errors. This paper investigates both analytically and experimentally the effect of the defocus (the difference between the splitter-to-mirror and analyser-to-mirror distances) on the phase of the interference fringes and the measurement of the lattice parameter.openSasso, C P; Mana, G; Massa, ESasso, C P; Mana, G; Massa,

A Three-Dimensional Code for Muon Propagation through the Rock: MUSIC

We present a new three-dimensional Monte-Carlo code MUSIC (MUon SImulation Code) for muon propagation through the rock. All processes of muon interaction with matter with high energy loss (including the knock-on electron production) are treated as stochastic processes. The angular deviation and lateral displacement of muons due to multiple scattering, as well as bremsstrahlung, pair production and inelastic scattering are taken into account. The code has been applied to obtain the energy distribution and angular and lateral deviations of single muons at different depths underground. The muon multiplicity distributions obtained with MUSIC and CORSIKA (Extensive Air Shower simulation code) are also presented. We discuss the systematic uncertainties of the results due to different muon bremsstrahlung cross-sections.Comment: 24 pages, 11 Postscript figures, LaTeX, to be published in Astroparticle Physic