Journal of Neutron Research

Grigoriev, S.V.; Klimko, S.A.; Kopitsa, G.P.; Runov, V.V.

doi: 10.1080/10238169908200233pmid: N/A

Spatial spin-resonance for the monochromatization or spectrum shaping of polarized neutrons is investigated in a system of mutually perpendicular magnetic fields: a constant guiding magnetic field and a static periodic magnetic field whose spatial periodicity is modulated. It is shown that the period modulation of the spatially alternating field as well as the modulation of the guiding magnetic field allows a change in the resonator line-width over a wide range. The harmonic approach to the modulation of an effective magnetic field is considered in a reference frame connected with the neutron. A comparative analysis as well as computer simulation are performed for the spectra obtained by means of different modulation methods.

Pusztai, L.; Mcgreevy, R.L.

doi: 10.1080/10238169908200234pmid: N/A

MCGR (Monte Carlo determination of G(r)) is an inverse method for determining the pair correlation function from the structure factor. In this paper we describe the algorithm in detail, including recent developments such as the possible application of coordination constraints, Gaussian smoothing of peak shapes and the ability to subtract a (quadratic) polynomial background. We will illustrate how these have important practical implications for the way that experiments can be performed. Examples of the applications of MCGR to liquids/glasses and crystalline materials will be given.

Welp, K.A.; Co, C.C.; Wool, R.P.

doi: 10.1080/10238169908200235pmid: N/A

Specular reflectivity is a powerful technique for determining composition depth profiles. In general, extraction of profiles from reflectivity data requires model fitting, the inverse scattering problem. Fitting software exists to calculate reflectivity from profiles, but typically the profiles used are constructed from independent layers. Profiles based on mathematical functions are often more useful, but require interdependent layers, typically not allowed, or requiring source code modification. A new reflectivity fitting package, SERF (Spreadsheet Environment Reflectivity Fitting), is demonstrated, which uses a spreadsheet as the host environment for calculation and data plotting. SERF simplifies the insertion of function-dependent profiles using interdependent layers. SERF uses additional spreadsheet features to improve reflectivity fitting, including reduced command structure via automatic recalculation and easier evaluation of fit quality via simultaneous display of graphical and numerical information. Examples of SERF and Internet download information are presented. Function-dependent profiles and reduced fitting time with SERF extends the reflectivity technique.

Rekveldt, M.TH.; Kraan, W.H.

doi: 10.1080/10238169908200236pmid: N/A

A new high-resolution diffraction method is introduced without the confinement of using a highly collimated beam, necessary in conventional high-resolution diffraction. Larmor precession of a polarised neutron beam is used to label each neutron of the incident and scattered neutron beam with its wavelength and scattering angle. Giving the Larmor precession device front and back faces inclined over an angle adjusted to the scattering angle used, the wavelength–transmission angle relation of the Larmor precession matches precisely with the wavelength–scattering angle relation of the scattering vector. In this way the Larmor precession phases of different momentum transfers and thus the scattering vectors, can be measured with extremely high resolution. It should be possible to measure lattice constants with relative accuracy of better than 10−5, while using a low resolution beam, which means an effective intensity gain of orders of magnitude. Applications of this method are discussed.

Arai, M.; Kiyanagi, Y.; Watanabe, N.; Takagi, R.; Shibazaki, H.; Numajiri, M.; Itoh, S.; Otomo, T.; Furusaka, M.; Inamura, Y.; Ogawa, Y.; Suda, Y.; Satoh, S.

doi: 10.1080/10238169908200237pmid: