Fusion produces neutrons which dissipate energy from the reaction.

Experimental nuclear fusion reactors produce free neutrons as a waste product.

However, the Utah technology produces far fewer neutrons than would be expected.

It produced neutrons for use in research.

This can be achieved with water, polyethylene, or graphite to produce thermal neutrons.

Usually an imaging system is designed and set up to produce thermal or cold neutrons.

When these experiments started producing neutrons of their own only a few weeks later, the fusion research world reached a high point.

Cosmic radiation will produce secondary neutrons if it hits spacecraft structures.

Electron capture in very dense parts of the infalling matter may produce additional neutrons.

There is lots more to it of course - in order to get the reaction going you have to produce neutrons.