Time dependent neutron optics ? Quantum mechanical effects on beam chopping and a new type of high resolution neutron spectrometer (FOTOF)

Gähler, R.; Golub, R.

doi:10.1007/bf01470206

Cited by 63 publications

(25 citation statements)

References 7 publications

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“…A number of non-stationary phenomena in neutron optics have already been analyzed theoretically [1][2][3][4][5][6][7][8][9] and verified experimentally [10][11][12][13][14][15]. Impressive results were also obtained in atomic optics [16,17].…”

Section: Introductionmentioning

confidence: 91%

Diffraction of ultracold neutrons on a moving grating and neutron focusing in time

Balashov

Bondarenko

Frank

et al. 2004

Physica B: Condensed Matter

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Section: Introductionmentioning

confidence: 91%

Diffraction of ultracold neutrons on a moving grating and neutron focusing in time

Balashov

Bondarenko

Frank

et al. 2004

Physica B: Condensed Matter

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“…In a second type of experiment, the time-resolved SANS response to periodic perturbation from a sine-wave modulation of the external magnetic field was analyzed. Two techniques for investigations of oscillating processes by means of SANS have been compared: 12 a direct stroboscopic mode, which uses a continuous neutron flux, and a new pulsed time-resolved technique, TISANE, proposed by Gähler and Golub, 13 which allows the time resolution to be extended to submillisecond range.…”

Section: Introductionmentioning

confidence: 99%

Low-temperature dynamics of magnetic colloids studied by time-resolved small-angle neutron scattering

et al. 2008

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The dynamics of ordering and relaxation processes in magnetic colloids has been studied by means of stroboscopic small angle neutron scattering techniques in an oscillating magnetic field. Surfactant stabilized ferrofluids ͑FFs͒ of Fe 3 O 4 and Co nanoparticles have been investigated as a function of temperature and frequency and compared to a solid Cu alloy with 0.8 vol % Co precipitates. This technique allowed elucidating the dynamical nature of the locally ordered domains in both ferrofluids as "living objects" becoming arrested below the freezing temperature of the solvent. The time-dependent intensities have been analyzed in terms of Langevin statistics including dynamical interparticle structure factors, which scale with the square of the Langevin function. The local ordering is mainly determined by the effective dipole-dipole interaction, which is enhanced by the partial alignment of the particle moments in an external magnetic field. Starting from the frozen state, the amount of freely rotating particle moments increases continuously with increasing temperature. The dynamical structure factors describing the hexagonal ͑Fe 3 O 4 -FF͒ or chainlike ͑Co-FF͒ ordering reach a maximum around the melting temperature. The alignment of particle moments along the applied field is governed by the fast Brownian rotation of individual nanoparticles and small aggregates, while the magnetic relaxation of longer dipolar chains and local hexagonal domains is much slower. In contrast, no field-induced interparticle correlations occur in the diluted solid CuCo alloy where the moment relaxation is purely of fast Néel type, which-due to a low anisotropy constant-follows the oscillating field at all temperatures.

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“…In order to study the dynamics of reversal and reordering of the particle moments, a periodic sine-wave modulation of the magnetic field was applied to the sample and combined with new time-resolved SANS techniques. Here we present the setup and advantages of two techniques for investigation of oscillating processes by means of SANS: a direct stroboscopic mode using a continuous neutron flux is compared to a pulsed time-resolved technique TISANE 4 based on the FOTOF technique 5 .…”

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confidence: 99%

Dynamics of Field-Induced Ordering in Magnetic Colloids Studied by New Time-Resolved Small-Angle Neutron-Scattering Techniques

et al. 2006

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The reversal of magnetic moments of nanoparticles in concentrated Co-ferrofluids was monitored in an oscillating magnetic field by new time-resolved stroboscopic small-angle neutron-scattering techniques. Time resolution in the µs range was achieved by using a pulsed beam technique, TISANE, while in continuous mode resolution was limited by the wavelength spread to about 1ms. The frequency dependence of anisotropic scattering patterns has been modeled using Langevin dynamics. The dynamics follows a two step mechanism:Field induced ordering is governed by fast Brownian rotation of nanoparticles with a characteristic time of about 160 µs. Magnetic relaxation of locally ordered domains of about 100 nm in size takes place within a few seconds by Brownian rotation or by Néel type rotation of magnetic moments.

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Time dependent neutron optics ? Quantum mechanical effects on beam chopping and a new type of high resolution neutron spectrometer (FOTOF)

Cited by 63 publications

References 7 publications

Diffraction of ultracold neutrons on a moving grating and neutron focusing in time

Diffraction of ultracold neutrons on a moving grating and neutron focusing in time

Low-temperature dynamics of magnetic colloids studied by time-resolved small-angle neutron scattering

Dynamics of Field-Induced Ordering in Magnetic Colloids Studied by New Time-Resolved Small-Angle Neutron-Scattering Techniques

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