High q-resolution neutron scattering technique using triple-axis spectrometers

We present a new technique which brings a substantial increase of the wave-vector $q$-resolution of triple-axis-spectrometers by matching the measurement wave-vector $q$ to the reflection $\tau_a$ of a perfect crystal analyzer. A relative Bragg width of $\delta/Q \sim 10^{-4}$ can be achieved with reasonable collimation settings. This technique is very useful in measuring small structural changes and line broadenings that can not be accurately measured with conventional set-ups, while still keeping all the strengths of a triple-axis-spectrometer.