Dependence of the ratio between magnetic and nuclear small angle neutron scattering on the size of the heterogeneities M. Groûe a , A. Gokhman b , J. B ohmert a, * a Institut f ur Sicherheitsforschung, Forschungszentrum Rossendorf, Abt. Material- u. Komponentensicherheit, P.O. Box 510 119, D-01314 Dresden, Germany b South Ukrainian Pedagogical University, Staroporto Frankovskay 26, 270020 Odessa, Ukraine Received 13 July 1999 Abstract The ratio between magnetic and nuclear small angle neutron scattering (SANS) can provide additional information about the composition and structure of the scattering inhomogeneities. The method fails if the material system does not meet the two-phase approach. In this case, the ratio can more generally be de®ned and related to the dependence of the scattering particle size by using the indirect transformation method. The method is derived and applied to model systems with two types of non-magnetic spheric inhomogeneities in a ferromagnetic matrix. Ó 2000 Elsevier Science B.V. All rights reserved. Keywords: Analysis of materials; Neutron scattering; Radiation damage; Reactor pressure vessel steel By studying the dierence between the magnetic and the nuclear small angle neutron scattering (SANS) contrast in systems containing ferromag- netic and non-ferromagnetic components, addi- tional information about the composition and the structure of the scattering inhomogeneities can be gained. This method was applied to recognize the nature of irradiation defects in reactor pressure vessel (RPV) steels [1±4]. The system is character- ized by a ferromagnetic iron matrix with embed- ded precipitates. The type of these precipitates is not known, usually these precipitates are assumed to be non-ferromagnetic. Under these circum- stances the measured dierential scattering cross section dRQ=dX measured is the sum of the dier- ential cross section of the magnetic scattering dRQ=dX mag and of the nuclear scattering dRQ=dX nuc , dRQ dX   measured  dRQ dX   nuc  dRQ dX   mag : 1 For the two-phase-approach (homogeneous matrix with one type of diluted inhomogeneities) Nuclear Instruments and Methods in Physics Research B 160 (2000) 515±520 www.elsevier.nl/locate/nimb * Corresponding author. Tel.: +49-351-260-3186; fax: +49- 351-260-2205. E-mail address: j.boehmert@fz-rossendorf.de (J. Bo È hmert). 0168-583X/00/$ - see front matter Ó 2000 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 8 - 5 8 3 X ( 9 9 ) 0 0 6 2 5 - 4