Spectral Characterization of a Velocity Selector Type Monochromator for Energy-Selective Neutron Imaging

The mechanical velocity selector is a device that can be used as wavelength monochromator for energy-selective neutron imaging applications. Its use is desirable in case of moderate wavelength resolution and short exposure times. The resulting beam wavelength distribution is, however, not uniform over the imaging field of view. The effect is inherent to the use of a velocity selector and generated by the change in incident beam's horizontal divergence over the field of view. In this work, the incident beam wavelength change was characterized thoroughly using wavelength scans of iron and vanadium plates and time of flight measurements. Suggestions are made about possible corrections and/or exploitation of this phenomenon-.