Beschreibung
The concept of a novel cold neutron source allowing for the generation of wide neutron beams with simultaneously increased brightness and intensity compared to present-day para-hydrogen-based cold neutron sources with an equal cold neutron beam cross-section, whether flat or voluminous, is proposed.
The design employs chessboard or staircase assemblies of high-aspect ratio rectangular para-hydrogen moderators with well-developed and practically fully illuminated surfaces of the individual moderators. Model calculations indicate that gains of up to approximately 2.5 in both brightness and intensity are achievable.
An analytic approach for calculating the brightness of para-hydrogen moderators, which assumes the prevailing single collision process during thermal-to-cold neutron conversion, is introduced. The obtained results are in excellent agreement with MCNP calculations.
The concept of ‘low-dimensionality’ in moderators is explored, explaining why additional compression of the moderator along the longest direction, effectively giving it a tube-like shape ("finger moderators"), does not result in a significant brightness increase comparable to the flattening of the moderator.
