[en] The use of drilling and coring methods that minimize the disturbance of formation rock and core has permitted field calibration of neutron-moisture tools in relatively large diameter cased and uncased boreholes at Yucca Mountain, Nevada. For 5.5-inch diameter cased holes, there was reasonable agreement between a field calibration in alluvium-colluvium and a laboratory calibration in a chamber containing silica sand. There was little difference between moisture-content profiles obtained in a neutron-access hole with a hand-held neutron-moisture meter and an automated borehole-logging tool using laboratory-generated calibration curves. Field calibrations utilizing linear regression analyses and as many as 119 data pairs show a good correlation between neutron-moisture counts and volumetric water content for sections of uncased 6-inch diameter boreholes in nonwelded and bedded tuff. Regression coefficients ranged from 0.80 to 0.94. There were only small differences between calibration curves in 4.25- and 6-inch uncased sections of boreholes. Results of analyzing field calibration data to determine the effects of formation density on calibration curves were inconclusive. Further experimental and theoretical work is outlined

[en] Recent progress in the various fields related to the project will be described. On the one hand, the development of suitable and reliable filter cells is a crucial task. Especially further decrease of the wall relaxation rate continues to be important. Therefore, we embarked on coatings made out of Cs suboxides, in particular, Cs₇O, and compared such cells in an elementary neutron experiment with those simply coated with Cs. To enable wide-angle applications of the ³He neutron spin filter technique, like reflectometry or small angle scattering, the cell design has been modified in order to get access to scattering angles up to 18 deg. A new type of transportation unit, well adapted to the requirements of those cells, has been constructed and tested. On the other hand, the construction of a filling station to supply filter cells is indispensable. Although a ³He polarization degree of 80% during optical pumping had been achieved reliably, further improvements for a novel optical pumping cell has been evaluated prepared and tested. Moreover, progress in the compressor completion is discussed. To integrate it, the rebuilding of the filling station for a flow-through type of operation has been evaluated and afterwards the construction of certain parts upgraded, allowing determination of the polarization in each of the four optical pumping cells which will be part of the filling station in the future

[en] We investigated the magnetic properties of thin Cr (110) layers in a (110)-oriented V/Cr multilayer consisting of 30-nm-thick Cr layers and 5-nm-thick V layers. The performed neutron-diffraction experiments reveal the existence of the commensurate antiferromagnetic structure in the Cr layers in a temperature range from 2 K to 300 K. At 2 K only a minor contribution of the incommensurate spin-density wave can be observed. (orig.)

[en] The neutron diffraction experiments have been successfully performed in the whole field region of the field-induced ordered phase in the singlet-ground state magnet CsFeCl₃ for the first time. The field dependence of neutron magnetic reflection have clearly demonstrated that the field induced order is described by the order parameter < S_x>. The magnetic ordering is discussed in the context of a Bose-Einstein condensation of magnetic excitations

[en] Complete text of publication follows. Complete text of publication follows. Measurements on the re-entrant spin glass system FeNiMn by full 3D neutron depolarization analysis (3D NDA) and neutron small angle scattering (SANS) are presented. Both methods were used to investigate the size of the mesoscopic ferromagnetic clusters (20 nm up to 1 mm) in the re-entrant spin glass phase in (Fe₆₅Ni₃₅)_1-xMn_x [1] (x ≤ 0.14). Additionally the macroscopic magnetization of the samples was measured simultaneously by the rotation of the polarization vector of the transmitted neutron beam. Zero field cooled and field cooled samples were used to identify the strongly and the weakly irreversible phase in the re-entrant state. The strength of the applied field during cooling down and the cooling rate strongly influence the size of the mesoscopic clusters. The measurements were carried out at the research reactor FRI at GKSS in Geesthacht and at the reactor BMR2 at HMI in Berlin. (author)

[en] Short communication

[en] The magnetic phase diagram of the superconductor ErNi₂B₂C (T_c=11 K and T_N=6 K) has been studied by neutron diffraction as a function of temperature and magnetic field applied along the symmetry directions [0 1 0], [1 1 0] and [0 0 1] of the tetragonal crystal structure. A series of commensurate magnetic structures, consistent with a transversely polarized spin-density wave with modulation vectors Q=n/ma^*(0.55≤n/m<0.60) and the spins along b^*, have been observed. The experimental data are compared with the results of a mean-field model that has been established from an analysis of bulk magnetization and zero-field neutron diffraction data. The model accounts for most of the observed features but fails to explain the occurrence of a small component Q_δ∼-0.005b^* observed close to H_c2 when the field is applied along [1 1 0]

[en] We present neutron elastic scattering results at high magnetic fields for Mg-doped CuGeO₃. For low magnesium concentrations, where a spin-Peierls phase is present, we find an enhancement of the long range antiferromagnetic order in the structural incommensurate phase induced by a high magnetic field. In the incommensurate phase, the Neel temperature increases with field leading to a gain in the magnetic Bragg peak intensity at low temperatures. We also find that the magnetic Bragg peaks remain commensurate even though the structure is incommensurate at high magnetic fields due to the formation of solitons. We interpret these results in terms of the solitons formed at high-magnetic fields effectively acting as doped impurities. Our results point to a strongly disordered ground state with the antiferromagnetic order localized around impurity sites. (author)

[en] Two kinds of experiments are presented in this paper: In the first lead alloy foams were generated in a furnace by expanding a foamable precursor material containing metal and a blowing agent. Vertical columns of liquid metal foam were scanned with a beam of neutrons while recording the time-dependent local neutron transmission. The resulting transmission profiles reflect the kinetics of material redistribution in liquid metallic foams under the influence of gravity (drainage). In the second experiment pre-fabricated solid lead foams were re-melted in a furnace. Neutron transmission profiles were also obtained in these experiments. Results of each type of experiment are presented and compared with theoretical predictions for the density profile of aqueous foams. (orig.)

[en] We investigated the magnetic properties of thin Cr(110) layers in a (110)-oriented Fe/Cr multilayer consisting of 26-nm-thick Cr layers and 1.2-nm-thick Fe layers that were grown epitaxially on a V(110) single crystal. Neutron-diffraction data reveal that the commensurate spin-density wave of the Cr layers is stable up to a temperature of 520 K. In the temperature range from 225 K to 175 K we observe a phase transition to the incommensurate spin-density wave. Measurements on the Cr{111} reflections show that the Fe/Cr multilayer is in a multidomain state with the Cr polarization being parallel to [100], [010], or [001]. The domains do not have equal probability. They are observed with a probability of 41%, 41%, and 18%, respectively. That means that there is a probability of 90% for the Cr polarization being perpendicular to the Fe magnetization that has its easy axis along [001]