New designs for high intensity specular neutron reflectometers

Presently, neutron reflectometers can be divided in two main classes: monochromatic and time-of-flight instruments. Both types of instruments have been optimized in the last 2 decades and allow now the measurement of reflectivities below 10-6 which is sufficient for most experiments. The next big step is to perform specular reflectivity measurements in matters of minutes rather than hours. In order to take this step, a significant improvement in flux must be achieved. In the past few years, several proposals have been made to radically change the way reflectometers are operated. Methods based either on space-time, energy-space or spin-space encoding have been proposed. They all have the potential to increase the flux for specular reflectivity measurements by one to two orders of magnitude. We discuss the advantages and shortcomings of these different techniques. (authors)