Pulsar Pulsar A pulsar (from "pulse" and "-ar" as in quasar) is a highly magnetized rotating neutron star that emits a beam of electromagnetic radiation. This radiation can be observed only when the beam of emission is pointing toward Earth (much like the way a lighthouse can be seen only when the light is pointed in the direction of an observer), and is responsible for the pulsed appearance of emission. Neutron stars are very dense, and have short, regular rotational periods. This produces a very precise interval between pulses that ranges from milliseconds to seconds for an individual pulsar. Pulsars are
Electron-beam lithography cold emission sources, in spite of the former's slightly larger beam size, because they offer better stability over typical writing times of several hours. Both electrostatic and magnetic lenses may be used. However, electrostatic lenses have more aberrations and so are not used for fine focusing. There is no current mechanism to make achromatic electron beam lenses, so extremely narrow dispersions of the electron beam energy are needed for finest focusing. Typically, for very small beam deflections electrostatic deflection "lenses" are used, larger beam deflections require electromagnetic scanning. Because of the inaccuracy and because of the finite number of steps