ISO/TS 21432:2005 pdf download.Non-destructive testing -Standard test method for determining residual stresses by neutron diffraction.
5.5 Neutron diffractometers
A monochromatic instrument typically used for strain measurement at a steady state source is shown schematically in Figure 2. The polychromatic neutron beam is fIrst monochromated to a chosen wavelength by diffraction from a suitable rnonodiromator. This monochromatic beam is then given spatial definition by the use of appropflate beam defining optics to produce a bean, of controlled dimen&ons, This beam is then diffracted from the specimen and captured by a neutron detector. An example of a diffraction peak from a monochromatic mstrument is shown In Figure 3.
At TOF-diffractometers typically used at pulsed sources, each pulse provides a diffraction profile across a large range of lattice spacings, A typical TOF-diffractometer used for strain measurement in two directions simultaneously at a pulsed source is shown in Figure 4. As a fixed scattering angle is used, most instruments at spallation sources use radial (focussing) collwnation. This allows neutrons to be detected over a wider solid angle than would be possible using a slit yet ensuring that most of the detected neutrons come from a defined gauge volume (see 6.5). The signals from the individual elements of the detector array are combined taking into account their different angular positions. Two or more detectors with radial collimators can be used to enable more than one () (strain) direction to be measured simultaneously. A typical diffraction pattern from such an instrument Is shown In Figure 5 whIch also shows the result of a Rietveld profile refinement where a crystallographic model of the structure Is fined to the diffraction data using a least squares analysis (see 6.3.2).
A monochromatic instrument typically used for strain measurement at a steady state source is shown schematically in Figure 2. The polychromatic neutron beam is fIrst monochromated to a chosen wavelength by diffraction from a suitable rnonodiromator. This monochromatic beam is then given spatial definition by the use of appropflate beam defining optics to produce a bean, of controlled dimen&ons, This beam is then diffracted from the specimen and captured by a neutron detector. An example of a diffraction peak from a monochromatic mstrument is shown In Figure 3.
At TOF-diffractometers typically used at pulsed sources, each pulse provides a diffraction profile across a large range of lattice spacings, A typical TOF-diffractometer used for strain measurement in two directions simultaneously at a pulsed source is shown in Figure 4. As a fixed scattering angle is used, most instruments at spallation sources use radial (focussing) collwnation. This allows neutrons to be detected over a wider solid angle than would be possible using a slit yet ensuring that most of the detected neutrons come from a defined gauge volume (see 6.5). The signals from the individual elements of the detector array are combined taking into account their different angular positions. Two or more detectors with radial collimators can be used to enable more than one () (strain) direction to be measured simultaneously. A typical diffraction pattern from such an instrument Is shown In Figure 5 whIch also shows the result of a Rietveld profile refinement where a crystallographic model of the structure Is fined to the diffraction data using a least squares analysis (see 6.3.2).
