Applying the method of beta -radiation detected nuclear magnetic resonance/relaxation ( beta -NMR) to 8Li nuclei in 7Li3N single crystals comprehensive information on static and dynamic properties was obtained. Below T approximately=200 K the electric field gradients (EFG) at the two inequivalent Li lattice sites (Li(1), Li(2)) were determined. The spin-lattice relaxation (SLR) behavior above T approximately=300 K and the 8Li NMR signals in the extreme narrowing regime (T>or=500 K) could be attributed to interlayer diffusion involving Li+ jumps between Li(1) and Li(2) lattice sites ((1 to or from 2) jumps). In the temperature range 200 K
Dedicated to Professor Werner Müller-Warmuth on the occasion of his 65th birthdayInvestigations of Li diffusion in stage-1 and stage-2 Li graphite intercalation compounds with neutron time-of-flight and backscattering techniques and ^-radiation detected nuclear magnetic resonance/relaxation (/J-NMR) with the nucleus 8Li(T1/2 = 0.8 s) are reviewed and compared. De pending on temperature, the spin-lattice relaxation-rate T{1 of 8Li is governed by different pro cesses. Above 300 K, T f1 (T) shows maxima induced by long-range Li+ diffusion. Jump correlation times are estimated. Inspection of the B field dependence of T f1 revealed two-dimensional diffusion behaviour. The neutron spectra showed a quasielastic line broadening above 500 K, which was used to obtain diffusion coefficients and to trace jump vectors of the in-plane motion. The diffusion parameters observed with both techniques are compared, and differences that show up are dis cussed. In addition, the low-temperature spin-lattice relaxation rates, being due to coupling to conduction electrons, are used to explore electronic properties.
The new neutron guide laboratory ELLA at the Jülich research reactor started its full operation at the beginning of this year. The guide system supplies 10 instruments with cold neutrons from the rebuilt hydrogen cold source. We present a description of the technical layout of the guide system. In order to achieve a larger solid angle, the guides were covered with isotopically pure 68Ni. The obtained neutron fluxes will be quoted. In addition, special beam forming devices were installed, namely a neutron guide junction at the entrance of the guide system, a multislit-bender with a radius of curvature of only 57 m, which achieves a large beam separation, and conical focusing neutron guides with supermirror layers to increase the flux at the sample position.
1_ INTRODUCTIONA guide halls for cold neutrons has been built at the research reactor FRJ -2 of the Kernforschungsanlage (KFA) Jülich during 1983 to 1987 and taken into operation. The new hall replaces a former smaller laboratory2, which has been working since 1970. The FRJ -2 is a heavy water reactor (DIDO) with a power of 23 MW and a peak thermal neutron flux at the beam hole noses of about 1.5 1014 n/cm2s. Together with the guide hall and the neutron guide system, the old hydrogen cold source with a thermosyphon system was rebuilt.3 At the position of the hydrogen vessel of the cold source, the thermal flux is approximately 1.0 1014 n/cm2s.4 Between the cold source and the neutron guide system, a helium cooled bismuth filter was installed in order to reduce the background radiation of fast neutrons and gamma rays. The filter is necessary and has been maintained because it allows the installation of straight guides and the adaption of the time -of-flight spectrometer (TOF) inside the reactor hall FRJ -2.The neutron guide system6 starts inside the beam hole in the reactor shielding. The cold neutron flux close to the guide entrance was measured to be 2.0 109 n/cm2s. Altogether 10 neutron instruments6 are connected to the neutron guide system in the guide hall, 4 of them being at end positions.In the following we present the basic parameters for the layout together with details of the technical realization of the guide system as well as special neutron beam forming devices, for instance a neutron guide junction, a neutron guide with a high curvature (bender) and a conical focusing neutron guide for flux enhancement.
ABSTRACTThe new neutron guide laboratory F.I J A at the Jiilich research reactor started its full operation at the beginning of this year. The guide system supplies 10 instruments with cold neutrons from the rebuilt hydrogen cold source. We present a description of the technical layout of the guide system. In order to achieve a larger solid angle, the guides were covered with isotopically pure 58Ni. The obtained neutron fluxes will be quoted. In addition, special beam forming devices were installed, namely a neutron guide junction at the entrance of the guide system, a multislit-bender with a radius of curvature of only 57 m, which achieves a large ...
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