Nuclear fusion reactors and neutrons The majority of energy produced by nuclear fusion is harnessed by neutrons or protons that split out from the product.
Given the dominant fusion method today is Deuterium + Tritium which produces He and a neutron (a neutron that has most of the energy from the fusion), what do current experimental fusion reactors do to harness the energy from said neutrons?
This question is asked using the context that neutrons cannot be controlled using electromagnetic forces. Hence, the energy contained in neutrons would (in my mind, at least) be difficult to capture without resorting to some sort of fission technique.
 A: In fusion power plants the energy from neutrons is captured in the blanket, which is immediately behind the first wall that surrounds the plasma. One candidate for the blanket is FLiBe molten salt, which is also being studied in the context of fission and concentrated solar power, and another candidate is dual-coolant Lead-Lithium/Helium. An important aspect of the blanket is also to ensure very little neutron energy is absorbed by the superconducting magnets and support structures. The neutron energy is carried away as thermal energy in the liquid blanket and then used to power a steam turbine.
The neutron energy is also used to breed Tritium in the liquid blanket with the reaction:
$^6\text{Li} + \text{n} \rightarrow \alpha  + \text{T}  + 4.78 \text{ MeV}$
This Tritium can then be used as fusion fuel, while the Tritium decay product Helium-3 is rare on earth and important for neutron radiation detectors and magnetic resonance imaging of the lung. While Tritium is currently bred inside fission reactors (e.g. by replacing some control rods with rods containing Lithium), a major research goal is for fusion power plants to generate their own Tritium.
A: This is known as the "first wall" problem of fusion: what do you wrap a fusion reactor with (the first wall), so as to capture the neutron energy without being destroyed by the intense neutron flux?
More specifically, the objective of the first wall is to rattle the neutron flux around so as to "thermalize" the neutrons (transfer their kinetic energy into lattice vibrations which show up as heat, which then can be carried off by some heat transfer medium to boil water into steam, etc.) without being ruined (from a materials science standpoint) by damage from the neutrons. Doing so is essential from an energy balance standpoint to make the fusion reaction products all "pay their way" towards breakeven by harvesting their kinetic energy before they zoom right out of the reactor volume and escape.
This remains as an unsolved problem in fusion technology. For example, superalloy metals get their constituent atoms knocked out of their lattice positions from neutron impacts,  which interferes with ductility mechanisms (rendering the metal incapable of exhibiting resistance to thermal and mechanical shock). In addition, neutron capture leads to transmutation of the alloy constituents into new elements which lack high-temperature corrosion resistance while also generating hydrogen atoms within the lattice which lead to swelling and embrittlement.
This is an extremely difficult business!
