Re-entrant cones for moderator chamber of a neutron imaging system

A method comprising

• producing source neutrons at a beam target of a central neutron source of a neutron imaging system, the neutron imaging system further comprising a moderator chamber surrounding at least a portion of the beam target, the moderator chamber housing a moderator;
• and
• receiving source neutrons with a re-entrant cone that extends into the moderator chamber, the re-entrant cone comprising a cone chamber and an entrance surface having a concave curvature facing the beam target, wherein:
• the cone chamber is at least partially defined by the entrance surface to isolate the cone chamber from the moderator.

A neutron imaging system comprising:

• a central neutron source configured to produce source neutrons, wherein the central neutron source comprises a beam target;
• a moderator chamber surrounding at least a portion of the beam target, the moderator chamber housing a moderator;
• and
• a re-entrant cone extending into the moderator chamber, wherein:
• the re-entrant cone comprises an entrance surface facing the beam target;
• the entrance surface at least partially defines a cone chamber, isolating the cone chamber from the moderator;
• and
• the entrance surface is shaped such that source neutrons produced at the beam target impinge the entrance surface with a neutron flux that varies by 20% or less along the entrance surface.