Diffusion of linear alkanes in 5A zeolite crystals has been studied by several different experime... more Diffusion of linear alkanes in 5A zeolite crystals has been studied by several different experimental techniques. In the range C3–C8 the diffusivity decreases regularly with carbon number (with a corresponding increase in activation energy) and there is good agreement between ZLC values and the data provided by the “microscopic” techniques (PFG NMR and Quasi-Elastic Neutron Scattering). At higher carbon numbers
A new ultra-high-resolution neutron spin-echo spectrometer at the ILL, Grenoble, extends the time... more A new ultra-high-resolution neutron spin-echo spectrometer at the ILL, Grenoble, extends the time range for measurements of the intermediate scattering function S(q,t) far beyond what has previously been possible. This new dynamic range approaching the microsecond opens up the possibility for exploring dynamic phenomena which have been previously unobservable. The various design ideas for the three operational modes (standard, neutron
The single-chain and collective motions of polymer chains in melts are directly observable by neu... more The single-chain and collective motions of polymer chains in melts are directly observable by neutron spin-echo spectroscopy (NSE). This method has both the necessary spatial resolution (10Å 500Å) as well as the adapted time domain from fractions of a ns to several 100ns. ...
ABSTRACTThe phase separation behaviour and the dynamics of concentration fluctuations of binary l... more ABSTRACTThe phase separation behaviour and the dynamics of concentration fluctuations of binary liquid mixtures are strongly influenced by confinement effects. We have investigated this confinement effect for the binary system isobutyric acid iBA + D2O imbibed into a mesoporous silica glass (CPG-10). The dynamics of the mixture are studied in the one-phase region as well as in the phase-separated state by means of neutron spin echo spectroscopy (NSE). Moreover, the averaged structures of the liquid are explored by means of small angle neutron scattering (SANS) leading to a length scale 4 < ξ < 9 nm for the fluctuations. The associated effective diffusion coefficient Deff as obtained for NSE is found to decrease with temperature ny nearly one order of magnitude in the temperature range from 75°C to 25°C.
In this paper I will try to present some recent results on less usual subjects, which I believe a... more In this paper I will try to present some recent results on less usual subjects, which I believe are forward pointing to fields which might develop faster as new sources/instruments become available. The first deals with an assembly of spherical microemulsions which under certain conditions self-organize themselves into a cubic phase. Applying contrast variation and covering the large dynamical range
The density correlation function F(q,t) of the two similar substituted aromatic liquids, Toluene ... more The density correlation function F(q,t) of the two similar substituted aromatic liquids, Toluene and m-Toluidine, is studied by coherent neutron spin-echo and time-of-flight scattering for wave vectors q around the maximum q_max of the total static structure factor S_m(q) in the supercooled i.e. high density state far away from the normal fluid state. The wave-vector dependence of the mean structural
We report a neutron spin echo (NSE) and dynamic light scattering (DLS) study of droplet dynamics ... more We report a neutron spin echo (NSE) and dynamic light scattering (DLS) study of droplet dynamics in a microemulsion at high droplet packing fraction (Φdroplet∼62%). NSE measurements in range qr⪢1 allow to investigate the short-range Brownian motion of droplets trapped within the cages formed by their nearest neighbors. For a particular scattering contrast, NSE also reveals, for q values around
We have investigated flux lines in low-and high-T c superconductors using unpolarized and polariz... more We have investigated flux lines in low-and high-T c superconductors using unpolarized and polarized neutron techniques. In high-T c materials, we observe transitions from triangular to square flux line lattices (FLLs) which probably represent the effects of d-wave pairing. In ...
This paper describes the design and experimental tests of a novel neutron spin analyzer optimized... more This paper describes the design and experimental tests of a novel neutron spin analyzer optimized for wide angle spin echo spectrometers. The new design is based on nonremanent magnetic supermirrors, which are magnetized by vertical magnetic fields created by NdFeB high field permanent magnets. The solution presented here gives stable performance at moderate costs in contrast to designs invoking remanent supermirrors. In the experimental part of this paper we demonstrate that the new design performs well in terms of polarization, transmission, and that high quality neutron spin echo spectra can be measured.
Diffusion of linear alkanes in 5A zeolite crystals has been studied by several different experime... more Diffusion of linear alkanes in 5A zeolite crystals has been studied by several different experimental techniques. In the range C3–C8 the diffusivity decreases regularly with carbon number (with a corresponding increase in activation energy) and there is good agreement between ZLC values and the data provided by the “microscopic” techniques (PFG NMR and Quasi-Elastic Neutron Scattering). At higher carbon numbers
A new ultra-high-resolution neutron spin-echo spectrometer at the ILL, Grenoble, extends the time... more A new ultra-high-resolution neutron spin-echo spectrometer at the ILL, Grenoble, extends the time range for measurements of the intermediate scattering function S(q,t) far beyond what has previously been possible. This new dynamic range approaching the microsecond opens up the possibility for exploring dynamic phenomena which have been previously unobservable. The various design ideas for the three operational modes (standard, neutron
The single-chain and collective motions of polymer chains in melts are directly observable by neu... more The single-chain and collective motions of polymer chains in melts are directly observable by neutron spin-echo spectroscopy (NSE). This method has both the necessary spatial resolution (10Å 500Å) as well as the adapted time domain from fractions of a ns to several 100ns. ...
ABSTRACTThe phase separation behaviour and the dynamics of concentration fluctuations of binary l... more ABSTRACTThe phase separation behaviour and the dynamics of concentration fluctuations of binary liquid mixtures are strongly influenced by confinement effects. We have investigated this confinement effect for the binary system isobutyric acid iBA + D2O imbibed into a mesoporous silica glass (CPG-10). The dynamics of the mixture are studied in the one-phase region as well as in the phase-separated state by means of neutron spin echo spectroscopy (NSE). Moreover, the averaged structures of the liquid are explored by means of small angle neutron scattering (SANS) leading to a length scale 4 < ξ < 9 nm for the fluctuations. The associated effective diffusion coefficient Deff as obtained for NSE is found to decrease with temperature ny nearly one order of magnitude in the temperature range from 75°C to 25°C.
In this paper I will try to present some recent results on less usual subjects, which I believe a... more In this paper I will try to present some recent results on less usual subjects, which I believe are forward pointing to fields which might develop faster as new sources/instruments become available. The first deals with an assembly of spherical microemulsions which under certain conditions self-organize themselves into a cubic phase. Applying contrast variation and covering the large dynamical range
The density correlation function F(q,t) of the two similar substituted aromatic liquids, Toluene ... more The density correlation function F(q,t) of the two similar substituted aromatic liquids, Toluene and m-Toluidine, is studied by coherent neutron spin-echo and time-of-flight scattering for wave vectors q around the maximum q_max of the total static structure factor S_m(q) in the supercooled i.e. high density state far away from the normal fluid state. The wave-vector dependence of the mean structural
We report a neutron spin echo (NSE) and dynamic light scattering (DLS) study of droplet dynamics ... more We report a neutron spin echo (NSE) and dynamic light scattering (DLS) study of droplet dynamics in a microemulsion at high droplet packing fraction (Φdroplet∼62%). NSE measurements in range qr⪢1 allow to investigate the short-range Brownian motion of droplets trapped within the cages formed by their nearest neighbors. For a particular scattering contrast, NSE also reveals, for q values around
We have investigated flux lines in low-and high-T c superconductors using unpolarized and polariz... more We have investigated flux lines in low-and high-T c superconductors using unpolarized and polarized neutron techniques. In high-T c materials, we observe transitions from triangular to square flux line lattices (FLLs) which probably represent the effects of d-wave pairing. In ...
This paper describes the design and experimental tests of a novel neutron spin analyzer optimized... more This paper describes the design and experimental tests of a novel neutron spin analyzer optimized for wide angle spin echo spectrometers. The new design is based on nonremanent magnetic supermirrors, which are magnetized by vertical magnetic fields created by NdFeB high field permanent magnets. The solution presented here gives stable performance at moderate costs in contrast to designs invoking remanent supermirrors. In the experimental part of this paper we demonstrate that the new design performs well in terms of polarization, transmission, and that high quality neutron spin echo spectra can be measured.
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Papers by Bela Farago