Advanced neutron diffraction techniques for strain measurements in polycrystalline materials

Abstract

Three unique high resolution experimental arrangements for nondestructive strain measurements which are based on neutron Bragg diffraction optics with cylindrically bent perfect crystals are reviewed. Using focusing in momentum and real space thgfe techgiques yield Ad/d (d-lattice spacing) resolution of 10-10-and considerably higher luminosity in comparison with the current dedicated instruments. They permit measurements not only macrostrain components resulting in angular shifts of diffraction peaks but also of microstrains by means of profilebroadening analysis.

Neutron imaging with bent perfect crystals. I. Imaging conditions

“…The optimal setting for this special con®guration [relation (14) of S AE aroun et al (1994)] can be derived from the general relations (28), (30) and (31) (see Appendix A4). The same arrangement has been used in diffraction strain measurements (Mikula et al, 1993(Mikula et al, , 1995. The relations derived here are also valid for that case.…”

“…Applications have been developed with bent perfect crystals in fully asymmetric diffraction geometry: two-bentcrystal small-angle neutron scattering (SANS) with PSD analysis Strunz et al, 1997) and highresolution strain measurements (Mikula et al, 1993(Mikula et al, , 1995. Analyzers with asymmetric re¯ection (not necessarily full) were found to be of interest for inelastic scattering with PSD analysis (Stoica, Popovici, Yelon & Berliner, 2000).…”

The crystal neutron diffractometer resolution function, spatial effects included

“…Another approach is to improve the instrumental performance by using focusing effects. The ®rst attempts were those of a Czech group (Mikula et al, 1990(Mikula et al, , 1992(Mikula et al, , 1993(Mikula et al, , 1994(Mikula et al, , 19961997a,b;Wagner et al, 1994;Kulda et al, 1994;Vrana et al, 1994;Saroun & Kulda, 1997), but important achievements were obtained at PTB Braunschweig, at ILL Grenoble, and by the Missouri group, especially after Dr Popovici joined it , 1995Yelon et al, 1998). Recently, a new concept of high-resolution crystal neutron diffractometry has been developed (Popovici et al, 1987Ionita et al, 1999), offering a viable alternative to the conventional high-resolution con®gurations (Hewat, 1975).…”

High-resolution diffraction using Larmor precession and multiple narrow beams defined by multislits

“…15 That this diffraction field is rather important may be concluded from the great interest there has been in improved diffraction techniques in order to obtain better results. [16][17][18][19][20][21][22][23] In conventional neutron diffraction the resolution of the lattice parameters obtained is strongly determined by the angular resolution of the various parts of the beam. The necessity to use collimated beams means decreasing intensity by increasing collimation.…”