Pulsar star. The neutron star retains most of its angular momentum, and since it has only a tiny fraction of its progenitor's radius (and therefore its moment of inertia is sharply reduced), it is formed with very high rotation speed. A beam of radiation is emitted along the magnetic axis of the pulsar, which spins along with the rotation of the neutron star. The magnetic axis of the pulsar determines the direction of the electromagnetic beam, with the magnetic axis not necessarily being the same as its rotational axis. This misalignment causes the beam to be seen once for every rotation
Beam dump beams to be absorbed can run into the megajoules. Materials used for such beam dumps include blocks of copper, aluminium, carbon, beryllium, and tungsten. The block often has a long conical hole, where the beam hits it, so as to spread the heating over a larger region of the block. If the beam to be absorbed is high-powered, these blocks may be up to several meters long and water-cooled. Pools of mercury have also been used. If the particles in the beam are energetic enough, induced radioactivity, production of neutrons by spalling, radiation embrittlement, and production of secondary particles can