Cold neutron sources that are providing a high cold neutron flux at neutron scattering instruments are at the core of almost all neutron scattering facilities. Recently, a special kind of cold moderators made of liquid para-hydrogen was developed at the European Spallation Source. They employ a remarkable feature of para-hydrogen: the drastic, more than an order of magnitude difference in total neutron scattering cross-sections for cold and thermal neutrons, that leads to the difference in their mean free paths, about 1 cm and 10 cm, respectively. This allows to squeeze usually large voluminous moderators to the flat shape (so-called pancake geometry). Low-dimensional para-hydrogen moderators are now getting more and more attention and are considered for many newly designed high power and compact neutron sources.

   Recently we developed a concept of staircase moderator assembly providing both high flux and high brilliance, while being optimally adapted to the needs of particular instrument. In this project we aim to build up on our previous results by 1) further investigation of the staircase concept and searching for its better implementation; 2) expansion of the concept to other moderator materials. We plan to develop computational methods based on machine learning, use analytical calculations and PHITS simulations as well as neutron experiments.