Neutralization of keV Ne and Ar ions during grazing scattering from an Al(1 1 1) surface

Charge fractions after scattering of Ne⁺ ions, Ne⁰ atoms and Ar⁺ ions with keV energies under a grazing angle of incidence from an atomically clean and flat Al(1 1 1) surface are studied. For incoming Ne⁺ ions we observe defined ion fractions in the scattered beams, whereas for incident Ne⁰ atoms ion fractions are more than one order of magnitude smaller. This experimental result provides clear evidence for a survival of Ne⁺ ions over the whole scattering event. From the dependence of ion fractions on the perpendicular energy component we derive neutralization rates as function of distance from the surface. These rates compare well with recent theoretical calculations for the system He⁺–Al(1 1 1). For incident Ar⁺ ions no survival of ions is found and upper limits for the survival probability and lower limits for the neutralization rate are determined.     

An experimental evaluation of spatial distribution for deeply penetrating protons in carbon material

The peak profile of the 4.8-MeV resonance by the ¹²C(p,p)¹²C reaction in backscattering geometry has been analyzed to examine two kinds of stragglings of proton, i.e. the depth straggling in the incoming path and the energy loss straggling in the outgoing path. The analysis, which is combined with existing theoretical treatments for the stopping process and the energy loss straggling, has made it possible to deduce the penetration depth and its spread at the resonance position in carbon materials. The present method, as a new tool for direct inspection of ion beams inside target material, is explained in detail.     

A compact photon-correlation spectrometer for research and education

A compact photon-correlation spectrometer for basic and applied research in physics, chemistry, biology, medicine, engineering, and environmental technology as well as for educational laboratory courses in these subjects has been developed. The instrumental setup enables one to make absolute measurements of the sizes of particles suspended in liquids in the range from 0.001 to 5 μm. The measurements are fast, lasting usually from seconds to several minutes. Real-time size monitoring, such as of kinetic aggregation processes, is also possible. The optical arrangement of the spectrometer even makes it possible to measure light scattering in opaque systems which are characterized by strong light absorption. The quantity of the sample to be studied can be quite small, starting from 0.01 cm³. The system includes specially designed software for performing data interpretation and for implementing fitting procedures, for exchange of data with other programs, and for automation of measurements of long duration or of sequences of measurements. Measurements verifying the accuracy of the system are presented for latex suspensions, for aniline dye dissolved in water, and for dilute solutions of polystyrene in toluene.     

Influence of hemicellulose aggregate and gel layer formation on flux and retention during nanofiltration of alkaline solutions

Nanofiltration of process liquors from viscose-type textile fibre production was investigated using a laboratoryscale crossflow test apparatus. Feed solutions contained about 200 g/l sodium hydroxide and a high concentration of hemicellulose as a contaminant originating from the raw material wood. The effects of various pretreatments and the addition of reagents on flux, retention and irreversible fouling were studied. Reagent addition affected the solution state of hemicellulose thus purposely provoking aggregate formation. Dynamic light scattering and turbidity measurements were used to track the evolution of hemicellulose aggregates. Aggregation generally coincided with distinct flux decline during nanofiltration thus indicating that this phenomenon may result in the build-up of gel layers at the membrane surface. Partial neutralisation with sulfuric acid caused extremely severe fouling, whereas methanol addition had a minor effect. The impact of heat treatment and oxidative degradation of hemicellulose on nanofiltration performance was attributed to changes in molar mass distribution.     

Role of adsorbed iodine into poly(vinyl alcohol) films drawn in KI/I2 solution

We have investigated the microstructure of the poly(vinyl alcohol) (PVA) films using small- and wide-angle X-ray scattering (SAXS and WAXS, respectively) techniques. The samples were uniaxially drawn in water or KI/I₂ aqueous solution and then dried in an air-oven at 333 K for 1 h prior to SAXS and WAXS measurements. It was found that for the films drawn in KI/I₂ solution PVA chains in the microfibrillar structure are more extended upon the film drawing compared to the case of the films drawn in pure water, which is resulted from the correlation function analysis on the SAXS data. Adsorbed iodines into the film were anticipated to act as junction points between the microfibrils via the formation of the PVA-iodine complexes.     

Determination of the parameters of circuit models of resistive microwave structures

New methods of determining the parameters of circuit models of resistive microwave structures are considered, based on a measurement of the wave scattering parameters of the contact device, consisting of coaxial-stripline transitions, a stripline transmission line and the structure analyzed. Results which demonstrate the high efficiency of the proposed methods of solving the problem are presented. __________ Translated from Izmeritel'naya Tekhnika, No. 8, pp. 51–55, August, 2008.     

Diffuse scattering in the cesium pyrochlore CsTi0.5W1.5O6

The structure of the defect pyrochlore CsTi_0.5W_1.5O₆ has been investigated using electron, synchrotron X-ray and neutron diffraction methods. The material is cubic a = 10.2773 Å with displacive disorder of the Cs cations along the 〈1 1 1〉 direction. The local structure, revealed by the diffuse structure in the electron diffraction patterns shows there is correlated displacement of the heavy Cs atoms along the 〈1 1 0〉 directions. The thermal expansion of the material is also described.     

Apatite crystal in hard tissue of conodont fossils

The present study was aimed at examining the nature of apatite crystal in the tooth apparatus of a conodont fossil using transmission electron microscopy (TEM), scanning electron microscopy (SEM), laser Raman microprobe spectrometry and electron-probe microanalysis (EPMA). The hard tissue of the condont consisted of 2 layers and the organization varied with the size of the crystal. Higher magnification showed that the crystals were observed in the lattice of (100) and the central dark lines were not present. Ca, P, and F were detected in the crystal using EPMA. Our results indicate that the apatite crystal in conodont fossils is not hydroxyapatite but fluorapatite.     

Neutron collimator with rectangular beam profile

Several Soller slit-type neutron collimators which give rectangular profiles of transmission as a function of angular divergence have been constructed. The collimators accept a beam of realistic dimensions – greater than 12×22 mm² in all cases. The blades of the collimators are 280 μm thick wafers of single-crystal silicon each coated with a Ni–Gd–Ni multilayer on one side. Tests at a neutron wavelength of 7.5 Å confirm that the transmission profiles are rectangular. Tests at a wavelength of 4.2 Å show that two such collimators rocked against each other give dramatically enhanced transmission and resolution by comparison with conventional collimators. This is the first such demonstration of increased counting rates in a scan on an instrument from rectangular profile collimators, an effect expected but not produced for over 40 years.