Text: When fast neutrons have been slowed down until the average energy of the neutrons is equal to the average thermal energy of the atoms of the medium, the neutrons are called thermal neutrons. The energies and corresponding velocities of the neutrons then depend upon the temperature of the medium. The distribution of the velocities approaches the Maxwell distribution dn(v) = Av2e-Mv2/2kTdv where v is the neutron velocity, M its mass, k is Boltzmann's constant and T the absolute temperature. The maximum number of neutrons will have the energy kT. The value of kT at 20°C is approximately 0.025 ev.

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Source: 67