Cyclotrons and synchotrons use electric and magnetic fields to accelerate charged particles.
A fission nuclear reactor harnesses the energy released by the natural decay of heavy elements to heat water and generate electricity.
A fusion nuclear reactor harness the energy released by the fusion of light elements to heat water and generate electricity. To overcome the repulsion between protons, particles in a fusion reactor need to be completely ionised and then collide at high speeds. A tokamak-type fusion reactor can be thought of as a particle accelerator. It would probably be a synchotron.
