@radiohacktive "moderates to thermal energy" - I'm not familiar with this expression.
Do you mean the neutron beam is contained by the Aluminium and it heats up... Or, what do you mean?
@radiohacktive thanks... This makes sense although I'll need to learn more...
@bigkafka Please excuse my brevity, I was staying in character limits!
"Thermal neutron energy" (0.025 electronvolts) relates to a certain speed; neutron speed is inversely related to its likelihood of hitting a target, my sample.
A neutron moderator is a material upon which "fast neutrons" impact until the neutrons are room-temperature: the speed from colliding with thermal nuclei. Indeed the moderator will heat up, but the beam continues through the other side with just thermal neutrons.