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We report on first experimental tests of a neutron magnetic spin resonator at a very cold neutron beam port of the high flux reactor at the ILL Grenoble. When placed between two supermirror neutron polarizers and operated in a pulsed traveling-wave mode it allows to decouple its time- and wavelength-resolution and can therefore be used simultaneously as electronically tunable monochromator and fast beam chopper. As a first ‘real’ scientific application we intend its implementation in the PERC (p roton and e lectron r adiation c hannel) project related to high-precision experiments in neutron beta decay.

We present a novel type of spatial magnetic neutron spin resonator whose time and wavelength resolution can be de- coupled from each other by means of a travelling wave mode of operation. Combined with a pair of highly efficient polarisers such a device could act simultaneously as monochromator and chopper, able to produce short neutron pulses, whose wavelength, spectral width and duration could be varied almost instantaneously by purely electronic means with- out any mechanical modification of the experimental setup. To demonstrate the practical feasibility of this technique we have designed and built a first prototype resonator consisting of ten individually switchable modules which allows to produce neutron pulses in the microsecond regime. It was installed at a polarised 2.6 A neutron beamline at the 250 kW TRIGA research reactor of the Vienna University of Technology where it could deliver pulses of 55 μs duration, which is about three times less than the passage time of the neutrons through the resonator itself. In order to further improve the achievable wavelength resolution to about 3% a second prototype resonator, consisting of 48 individual modules with optimised field homogeneity and enlarged beam cross-section of 6 × 6 cm2 was developed. We present the results of first measurements which demonstrate the successful operation of this device.

The neutron-induced fission cross section of Np237 was experimentally determined at the high-resolution and high-intensity facility n-TOF, at CERN, in the energy range 100 keV to 9 MeV, using the U235(n,f) and U238(n,f) cross section standards below and above 2 MeV, respectively. A fast ionization chamber was used in order to detect the fission fragments from the reactions and the targets were characterized as far as their mass and homogeneity are concerned by means of α spectroscopy and Rutherford backscattering spectroscopy respectively. Theoretical calculations within the Hauser-Feshbach formalism have been performed, employing the empire code, and the model parameters were tuned in order to successfully reproduce the experimental fission cross-sectional data and simultaneously all the competing reaction channels.

The U-238 fission cross section is an international standard beyond 2 MeV where the fission plateau starts. However, due to its importance in fission reactors, this cross-section should be very accurately known also in the threshold region below 2 MeV. The U-238 fission cross section has been measured relative to the U-235 fission cross section at CERN - n_TOF with different detection systems. These datasets have been collected and suitably combined to increase the counting statistics in the threshold region from about 300 keV up to 3 MeV. The results are compared with other experimental data, evaluated libraries, and the IAEA standards.

The uncertainty principle generally prohibits determination of certain pairs of quantum mechanical observables with arbitrary precision and forms the basis of indeterminacy in quantum mechanics. It was Heisenberg who used the famous gamma-ray microscope thought experiment to illustrate this indeterminacy. A lower bound was set for the product of the measurement error of an observable and the disturbance caused by the measurement. Later on, the uncertainty relation was reformulated in terms of standard deviations, which focuses solely on indeterminacy of predictions and neglects unavoidable recoil in measuring devices. A correct formulation of the error-disturbance relation, taking recoil into account, is essential for a deeper understanding of the uncertainty principle. However, the validity of Heisenberg's original error-disturbance uncertainty relation is justifed only under limited circumstances. Another error-disturbance relation, derived by rigorous and general theoretical treatments of quantum measurements, is supposed to be universally valid. Here, we report a neutron optical experiment that records the error of a spin-component measurement as well as the disturbance caused on another spin-component measurement. The results confirm that both error and disturbance completely obey the new, more general relation but violate the old one in a wide range of an experimental parameter., 11 pages, 5 figures, Nature Physics (in press)

Instead of using the phase grating concept for dark field imaging, macroscopic scattering grids were employed at the ANTARES neutron imaging facility. Two Cadmium grids with a 1 mm gap and 1.2 mm bar were adjusted in a distance of only a few cm in order to block the direct beam. Thus, by placing the samples between these two grids only neutrons that were scattered at the samples were transmitted. A linear motion of the coupled grids allowed scanning across the samples and obtaining complete scattering projections, which delivered surprisingly sharp images. The geometric relation between grids permits determination of the transmitted scattering angles.

We present the use of helium-3 spin filters for polarized neutron imaging of magnetic phenomena. These polarization devices allow improvements in both spatial (factor of 2–3) and temporal (factor of ∼5) resolution compared with previously used solid-state benders. This set-up has been used to visualize small-scale magnetic features in an Fe 65.7 Co 18 Si 0.8 B 15.5 foil with a thickness of 21–22 μm and a saturation magnetization of 1.7 T, and trapped magnetic flux in a superconducting lead cylinder.

In this document, we present the nal result obtained at the n TOF experiment for the neutron- induced ssion cross section of the 237Np, from the ssion threshold up to 1 GeV. The method applied to get this result is brie y discussed. n TOF data are compared to the last experimental measurements using other TOF facilities or the surrogate method, reported experiments performed with monoenergetic sources and the FISCAL systematic, including a discussion about the existing discrepancies.

It is well known that upon passage through a spatially alternating transverse magnetic field, produced by a meander-shaped conducting foil, in its rest frame each neutron creates its individual frequency which depends on its velocity and the period of the meander. A resonant spin flip process takes place, if this frequency equals the Larmor frequency determined by a homogeneous vertical field. Clearly, this effect can be used to monochromatise a polarised neutron beam. Here we propose a novel design of such a magnetic resonator consisting of a sequence of separate compact modules, which provide high homogeneity of the transversal field oscillations and allow rapid beam chopping since they meet the specifications of fast electronic switching. The wavelength resolution of this resonator device can be changed in an instant and likewise an arbitrary amplitude modulation of the transversal field can be established, which is required for an efficient suppression of subsidiary maxima of the wavelength-dependent spin flip probability.

The PERC (Proton Electron Radiation Channel) project searches for new physics beyond the Standard Model of particle physics via the beta-decay of free neutrons. This high precision measurement demands perfect knowledge of the key beam parameters, i.e. wavelength distribution, degree of polarisation and time structure. Therefore, we propose a novel design of a spatial magnetic spin resonator, allowing precise velocity selection as well as the accurate definition of the beam's time structure by purely tuning electronic parameters.

Non-local correlations between subsystems sufficiently separated in spacetime have been extensively discussed in the light of the Einstein, Podolsky and Rosen (EPR) paradox, together with Bell's inequality. Within quantum terminology, such a non-locality can be interpreted as a consequence of the entanglement of subsystems. A more general concept, i.e., quantum contextuality, compared to non-locality, can be introduced to describe other striking phenomena predicted by quantum theory. As examples of quantum contextuality, we report several neutron interferometer experiments: a violation of a Bell-like inequality, a Kochen–Specker-like phenomenon, a quantum state tomography. Entanglement is achieved not between the particles, but between the degrees of freedom of a single-particle. Furthermore, an experiment dealing with triple entanglement is presented.

We present a neutron polarimetric experiment where two kinds of spinor precessions are observed: one is induced by different total energy of neutrons (zero-field precession) and the other is induced by a stationary guide field (Larmor precession). A characteristic of the former is the dependence of the energy-difference, which is in practice tuned by the frequency of the interacting oscillating magnetic field. In contrast the latter completely depends on the strength of the guide field, namely Larmor frequency. Our neutron-polarimetric experiment exhibits individual tuning as well as specific properties of each spinor precession, which assures the use of both spin precessions for multi-entangled spinor manipulation., 12 pages, 4 figures

Even in an idealised case conventional methods of neutron polarisation inevitably loose at least 50% of the intensity by removing one spin state from the incident beam. We demonstrate, however, that it should be possible to polarise a pulsed beam of slow neutrons without loosing any particle. This so-called “Dynamical Neutron Polarisation” (DNP) method is based upon acceleration and deceleration, respectively, of the two neutron spin states during passage through an NMR-like arrangement of crossed static and radio-frequency magnetic fields, followed by spin-dependent spin rotation in a homogeneous precession field. Precise ramping of the strength of this precession field synchronously with a time modulated π / 2 -spin turn device at the exit position allows to stop precession for all neutron wavelengths exactly at the moment where both spin states are aligned parallel, albeit on the cost of a tiny energy difference between them. We present a theoretical description of DNP which is essentially based upon a semi-classical spin-rotation formalism and present a typical result of a thorough investigation of the performance of such a non-conventional polariser with respect to a manifold of instrumental parameters.

Perfect crystal neutron interferometry may be applied in the tomographic study of magnetic structures in ferromagnetic solids. As a result of such investigations one can expect a complete 3D representation of the magnetisation distribution inside the sample. While the concept is comparable to absorption and phase contrast tomography, the tensorial technique involves 3D polarisation control and specific reconstruction algorithms due to path-ordering effects contained in the measured projections. We present the current status of related methodical development and outline the experimental and technical requirements essential for the application of this method. A 2D reconstruction example is given for a standardised simulated test sample using a reconstruction algorithm based on elimination of path-ordering effects by measurements at different neutron velocities.

The beta-decay of Re-187 (t(1/2) = 42.3 Gyr) represents a suited cosmo-chronometer for the age of the r-process abundances, since the radiogenic part of the daughter isotope (OS)-O-187 is defined by the difference between the solar Os-187 abundance and s-process contribution to Os-187. The latter component can be determined via the s-process systematics based on the stellar neutron capture cross sections of Os-186 and Os-187. The laboratory cross section of Os-187 requires a significant correction for the effect of the low-lying excited state at 9.75 keV, which is strongly populated under stellar conditions. This theoretical correction can be improved by an experimental cross section for inelastic scattering to the 9.75 keV state. High resolution time-of-flight measurements of (n, gamma) cross sections of (OS)-O-186,187,188 from I eV to I MeV at CERN n-TOF facility are reported. The inferred stellar cross sections differ from previously recommended values. In addition, the inelastic scattering cross section has been measured at 30 keV neutron energy via time-of-flight at the Karlsruhe 3.7 MV Van de Graaff. The implications of these results for the Re/Os clock are discussed. (c) 2007 Elsevier B.V. All rights reserved. ispartof: Progress in Particle and Nuclear Physics vol:59 issue:1 pages:165-173 ispartof: location:ITALY, Erice status: published

The $^{235}$U neutron-induced cross section is widely used as reference cross section for measuring other fission cross sections, but in the resonance region it is not considered as an IAEA standard because of the scarce experimental data covering the full region. In this work, we deal with a new analysis of the experimental data obtained with a detection setup based on parallel plate ionization chambers (PPACs) at the CERN n_TOF facility in the range from 1 eV to 10 keV. The relative cross section has been normalised to the IAEA value in the region between 7.8 and 11 eV, which is claimed as well-known. Comparison with the ENDF/B-VII evaluation and the IAEA reference file from 100 eV to 10 keV are provided.

Non-local correlations between sufficiently separated subsystems have been extensively discussed. Such a non-locality can be interpreted as a consequence of the correlation between commuting observables. A more general concept, i.e., contextuality, compared to non-locality can be introduced to describe striking phenomena predicted by quantum theory. As the first example, we report a neutron interferometer experiment, where the spin and the path degrees of freedom are used to exhibit the clear violation of a Bell-like inequality. Other aspects of the quantum contextuality is presented, e.g., a flavor of Kochen–Specker-like contradiction in neutron optical experiments, in addition to the quantum state tomography of the Bell-states which are used in the experiments.

We have measured the non-cyclic geometric phase acquired during a unitary SU(2) evolution of a neutron spinor wave function for the mixed state case. The data is in good agreement with theory, verifying the predicted values for the mixed state geometric phase.

Improved knowledge of the real part of the neutron scattering length of 3He is important for further development of nuclear few-body theory, as well as for a thorough understanding of neutron scattering off quantum liquids. The real part of the bound incoherent neutron scattering length b i' has recently been measured directly with an experimental uncertainty of better than 1% by means of spin echo spectrometry. The uncertainty of the more fundamental bound multiplet scattering lengths b ±' is thus limited by today's 1.2% uncertainty of the spin-independent coherent part b c'. Employing the skew-symmetric perfect crystal Si-interferometer at the S18 experimental site at ILL, Grenoble, we have re-measured the real part of the bound coherent neutron scattering length b c' of 3He. Our result b c' = 6.010(21)fm exhibits a significant deviation compared to the latest accepted value b c' = 5.74(7)fm (H. Kaiser, H. Rauch, G. Badurek, W. Bauspiess, U. Bonse, Z. Phys. A 291, 231 (1979)). Including the known value of the incoherent neutron scattering length, we obtain new values for the real parts of the free singlet and triplet scattering lengths, a -' = 7.573(30)fm and a +' = 3.480(18)fm. Our result contravenes by more than 7 standard deviations the measurement of the same physical quantity that has recently been performed by a group at NIST in a very similar experiment (P.R. Huffman, D.L. Jacobson, K. Schoen, M. Arif, T.C. Black, W.M. Snow, S.A. Werner, Phys. Rev. C 70, 014004 (2004)) which yielded b c' = 5.853(7)fm.

We have measured the Pancharatnam relative phase for spin- 1 / 2 states. In a neutron polarimetry experiment the minima and maxima of intensity modulations, giving the Pancharatnam phase, were determined. We also considered general SU ( 2 ) evolution for mixed states. The results are in good agreement with theory.

We present an extension to a recently introduced method for the tomographic investigation of magnetic domain structures in ferromagnetic solids which is based on a combination of neutron interferometry and neutron depolarization concepts. Methodical development of the reconstruction algorithm yields significant improvement compared to previous versions. This is expressed by fast convergence and by doubling the maximum computable pixel size from 1.7 μ m before to at least 4 μ m , which is an important step towards actual experimental realization of this novel tomographic method. Furthermore, it is demonstrated that our algorithm converges even when, as in a real experiment, the measured values of the observables are subject to statistical fluctuations.

We report a single-neutron optical experiment to demonstrate the violation of a Bell-like inequality. Entanglement is achieved between the degrees of freedom for a single particle. The total wave function of the neutron is described in a tensor product Hilbert space. A Bell-like inequality is derived not by a non-locality but by a contextuality. Joint measurements of the spinor and the path properties lead to the violation of a Bell-like inequality. Manipulation of the wavefunction in one Hilbert space influences the result of the measurement in the other Hilbert space.

The layout of the planned 1 MW /10 Hz spallation neutron source AUSTRON and the performance of its instruments is discussed. Due to its low pulse rate an UCN factory seems feasible which exceeds existing facilities by 3 orders of magnitude.

An appropriate formalism is developed which describes the effect of simultaneous occurrence of nuclear and magnetic interaction caused by an arbitrary structure of sequential magnetic domains on the emerging intensity and polarization.

A neutron interferometer experiment which clearly demonstrates the violation of a Bell-like inequality is reported. Entanglement is achieved not between particles, but between the degrees of freedom, in this case, for a single particle. The total wave function of spin-1/2 neutron is described in a tensor product Hilbert space. Appropriate combinations of the direction of spin analysis and the position of the phase shifter allow experimental verification of the violation of a Bell-like inequality. Manipulation of the wave function in one Hilbert space influences the result of the measurement in the other Hilbert space: manipulation without touch! The violation of the Bell-like inequality is discussed in terms of quantum contextuality and an entanglement-induced correlation.

The accuracy of the pulse height weighting technique for the determination of neutron capture cross-sections is investigated. The technique is applied to measurements performed with C6D6 liquid scintillation detectors of two different types using capture samples of various dimensions. The data for well-known (n, gamma) resonances are analyzed using weighting functions obtained from Monte Carlo simulations of the experimental set-up. Several causes of systematic deviation are identified and their effect is quantified. In all the cases measured the reaction yield agrees with the standard value within 2%. (C) 2003 Elsevier B.V. All rights reserved. Nuclear Instruments & Methods in Physics Research Section a-Accelerators Spectrometers Detectors and Associated Equipment

Non-local correlations between spatially separated systems have been extensively discussed in the context of the Einstein, Podolsky and Rosen (EPR) paradox1 and Bell's inequalities2. Many proposals and experiments designed to test hidden variable theories and the violation of Bell's inequalities have been reported3,4,5,6,7; usually, these involve correlated photons, although recently an experiment was performed with 9Be+ ions8. Nevertheless, it is of considerable interest to show that such correlations (arising from quantum mechanical entanglement) are not simply a peculiarity of photons. Here we measure correlations between two degrees of freedom (comprising spatial and spin components) of single neutrons; this removes the need for a source of entangled neutron pairs, which would present a considerable technical challenge. A Bell-like inequality is introduced to clarify the correlations that can arise between observables of otherwise independent degrees of freedom. We demonstrate the violation of this Bell-like inequality: our measured value is 2.051 ± 0.019, clearly above the value of 2 predicted by classical hidden variable theories9,10,11,12.

It is demonstrated that a magnetic neutron spin resonator placed between a pair of high-quality polarizers and driven in a ‘travelling-wave’ mode of operation allows to produce neutron pulses whose spectral distribution and temporal width can be varied over a broad range just by purely electronic means.

We propose a new method of investigating domain structures in ferromagnetic solids which combines neutron depolarization concepts with perfect crystal neutron interferometry.

The concept of a Hamiltonian-independent geometric phase which depends only on the path of the evolution in parameter space is well established in a broad spectrum of physical phenomena. Recently it has been extended to the so-called `off-diagonal' geometric phase, which is associated with the off-diagonal matrix elements of the evolution. Here we present a polarized neutron interferometer experiment which for the first time allows an explicit observation and quantitative determination of off-diagonal geometric phase shifts: Final counts with and without polarization analysis enable us to observe simultaneously the off-diagonal and diagonal geometric phases in two detectors. We have quantitatively measured the off-diagonal geometric phase for noncyclic evolutions, confirming the theoretical predictions. We discuss the significance of our experiment in terms of geometric phases (both diagonal and off-diagonal) and in terms of the quantum erasing phenomenon.

We report an interferometric experiment with spin-1/2 neutrons to demonstrate the violation of a Bell-like inequality. The total wave function of neutrons is described by a tensor product Hilbert space. Appropriate combinations of the direction of the spin analysis and the position of the phase shifter allow to demonstrate the violation of the Bell-like inequality. The discussions are presented on the violation of the Bell-like inequality in terms of quantum contextuality and an entanglement-induced correlation in our experiment.

The concept of a Hamiltonian-independent geometric phase which depends only on the path of the evolution in parameter space is well established in a broad spectrum of physical phenomena. Recently it has been extended to the so-called ‘off-diagonal’ geometric phase, which is associated with the off-diagonal matrix elements of the evolution. Here we present a polarized neutron interferometer experiment which for the first time allows an explicit observation and quantitative determination of off-diagonal geometric phase shifts.

We report on the first experimental separation of geometric and dynamical phases, as well as explicit verification of Pauli anticommutation.

Background: The design of new nuclear reactors and transmutation devices requires to reduce the present neutron cross section uncertainties of minor actinides. Purpose: Improvement of the 243Am(n,? ) cross section uncertainty. Method: The 243Am(n,? ) cross section has been measured at the n_TOF facility at CERN with a BaF2 total absorption calorimeter, in the energy range between 0.7 eV and 2.5 keV. Results: The 243Am(n,? ) cross section has been successfully measured in the mentioned energy range. The resolved resonance region has been extended from 250 eV up to 400 eV. In the unresolved resonance region our results are compatible with one of the two incompatible capture data sets available below 2.5 keV. The data available in EXFOR and in the literature have been used to perform a simple analysis above 2.5 keV. Conclusions: The results of this measurement contribute to reduce the 243Am(n,? ) cross section uncertainty and suggest that this cross section is underestimated up to 25% in the neutron energy range between 50 eV and a few keV in the present evaluated data libraries.

The neutron-induced fission cross section of U234 has been measured at the CERN n-TOF facility relative to the standard fission cross section of U235 from 20 keV to 1.4 MeV and of U238 from 1.4 to 200 MeV. A fast ionization chamber (FIC) was used as a fission fragment detector with a detection efficiency of no less than 97%. The high instantaneous flux and the low background characterizing the n-TOF facility resulted in wide-energy-range data (0.02 to 200 MeV), with high energy resolution, high statistics, and systematic uncertainties bellow 3%. Previous investigations around the energy of the fission threshold revealed structures attributed to β-vibrational levels, which have been confirmed by the present measurements. Theoretical calculations have been performed, employing the talys code with model parameters tuned to fairly reproduce the experimental data. © 2014 American Physical Society.

We present the analysis of the resolved resonance region for the 234U(n,f) cross section data measured at the CERN n TOF facility. The resonance parameters in the energy range from 1 eV to 1500 eV have been obtained with the SAMMY code by using as initial parameters for the fit the resonance parameters of the JENDL-3.3 evaluation. In addition, the statistical analysis has been accomplished, partly with the SAMDIST code, in order to study the level spacing and the Mehta-Dyson correlation.

See paper for full list of authors; International audience; The (n, α) reaction in the radioactive 59Ni is of relevance in nuclear astrophysics as 59Ni can be considered as the first branching point in the astrophysical s-process. Its relevance in nuclear technology is especially related to material embrittlement in stainless steel. However, there is a discrepancy between available experimental data and the evaluated nuclear data files for this reaction. At the n_TOF facility at CERN, a dedicated system based on sCVD diamond diodes was set up to measure the 59Ni(n, α)56Fe cross section. The results of this measurement, with special emphasis on the dominant resonance at 203 eV, are presented here.

According to Bell’s theorem, every theory based on local realism is at variance with certain predictions of quantum mechanics. A theory that maintains realism but abandons reliance on locality, which has been proposed by Leggett, is incompatible with experimentally observable quantum correlations. In our experiment correlation measurements of spin-energy entangled single-neutrons violate a Leggett-type inequality by more than 7.6 standard deviations. The experimental data falsify the contextual realistic model and are fully in favor of quantum mechanics.

Spin-dependent bi-refringence of neutrons upon passage through the air gap of a prismatically shaped permanent magnet yoke is used to split a thermal neutron beam in two polarized sub-beams with slightly different directions. This method is ideal to polarize the neutrons within perfect crystal interferometers without loss of intensity. Using a sequential arrangement of two such prisms a splitting larger than twice the rocking-curve width of a perfect crystal Mach–Zehnder-type neutron interferometer has been achieved, yielding a beam polarization of about 97%.

Highly non-classical states are produced in polarized neutron spin precession experiments due to the coherent superposition of spin-up and spin-down states. These states are described within the Wigner function formalism and the measured momentum modulation in a neutron spin precession experiment is taken as a sign of such non-classical states.

We present a neutron polarimetric experiment clearly demarcating geometric and dynamical phases. Here a relative rotation between two identical π spin flippers produces a pure geometric phase and their relative translation yields a pure dynamical phase. The experiment agrees with theory to within about 1%.

An interference experiment with polarized neutrons is proposed to check the duality relation between the fringe visibility and the which-way information for massive fermions with macroscopic spatial separation of the interfering sub-beams. The connection between polarization-sensitive post-selection of sub-ensembles and the concept of quantum erasure is discussed. This neutron experiment will supplement those recently performed with photons and atoms.

The perfect crystal interferometer instrument S18 at the Institute Laue-Langevin (ILL) in Grenoble has been upgraded to allow more advanced neutron optics experiments for fundamental, nuclear and condensed matter physics. The new supermirror guide together with the multipurpose monochromator provides considerably higher intensities in a wide wavelength region. The optimal use of neutrons is obtained by a nondispersive arrangement of the monochromator and the interferometer crystals. This also allows to obtain completely polarised beams using permanent magnetic prism deflection. An additional third analyzer axis permits novel postselection experiments concerning momentum distribution and polarisation analysis of the interfering beams. Several types of large perfect crystal interferometers are available for different applications. The system can be configured as an advanced high-resolution Bonse–Hart small angle scattering camera. The results of various test measurements concerning intensities, interference contrast, long-term stability, the accessible wavelength range and the basic features as a SANS camera will be presented. Various proposals for experiments will be discussed as well.

Dynamic Neutron Polarization (DNP) is a concept which allows to achieve complete polarization of slow neutrons, virtually without any loss of intensity. There the neutrons pass through a combination of a static and a rotating magnetic field in resonance, like in a standard NMR apparatus. Depending on their initial spin state, they end up with different kinetic energies and therefore different velocity. In a succeeding magnetic precession field this distinction causes a different total precession angle. Tuning the field strength can lead to a final state where two original anti-parallel spin states are aligned parallel and hence to polarization. The goal of this work is to describe the quantum mechanical aspects of DNP and to work out the differences to the semi-classical treatment. We show by quantum mechanical means, that the concept works and DNP is feasible, indeed. Therefore, we have to take a closer look to the behavior of neutron wave functions in magnetic fields. In the first Section we consider a monochromatic continuous beam. The more realistic case of a pulsed, polychromatic beam requires a time-dependent field configuration and will be treated in the second Section. In particular the spatial separation of the spin up- and down-states is considered, because it causes an effect of polarization damping so that one cannot achieve a fully polarized final state. This effect is not predicted by the semi-classical treatment of DNP. However, this reduction of polarization is very small and can be neglected in realistic DNP-setups.

In the dynamical neutron polarization (DNP) concept there are mainly two magnetic fields which are used for the energy splitting and the subsequent L armor rotation of the spins, resulting in the alignment of the polarization vector for two partial ensembles with initially opposite spin directions. We present a new approach to the DNP field setup problem, based upon a semi-classical spin rotation formalism, which reveals a manifold of possible field time dependencies for the case of pulsed polychromatic beams and includes and extends the hitherto known solutions. The non-unique relation between the energy splitting and the spin precession field and their “effective” counterparts is discussed.

The development of techniques to determine the magnetic structure of ferromagnetic materials is still an issue for basic research. We present in this contribution methods for tomographic reconstruction of magnetic domains in bulk material by means of polarized neutrons. The effect of magnetic fields on the neutron wave function while traversing a ferromagnetic sample is described by means of path ordered integrals. Such integrals may be determined experimentally in neutron depolarization or neutron interferometer measurements. Application of inverse Radon transformation used in standard tomography does not yield acceptable results for large rotation angles of the neutron polarization vector, due to path-ordering effects. Recently we have developed algorithms which take these effects specifically into account. The best reconstruction results were so far obtained by a modified algebraic reconstruction technique. We present the quality of reconstruction results for a simulated ferromagnetic test sample. These methods are particularly attractive since they result in a direct 3D visualization of the spatial magnetization distribution in bulk material.

‘Dynamical Neutron Polarization’ contrary to all other known techniques offers the possibility to polarize a beam of thermal or cold neutrons without loosing, at least in principle, any of the incident particles. The basic theoretical concept of this unique method based upon spin rotation formalism is presented. Taking into account various technical details and aspects, we have checked its actual feasibility by extensive Monte Carlo simulations under conditions as close to reality as possible.