Neutron star to neutrons, or ultra-dense quark-degenerate matter. Neutron stars are detected from their electromagnetic radiation. Neutron stars are usually observed to pulse radio waves and other electromagnetic radiation, and neutron stars observed with pulses are called pulsars. Pulsars' radiation is thought to be caused by particle acceleration near their magnetic poles, which need not be aligned with the rotational axis of the neutron star. It is thought that a large electrostatic field builds up near the magnetic poles, leading to electron emission. These electrons are magnetically accelerated along the field lines, leading to curvature radiation, with the radiation being strongly polarized
Electron-beam welding source of electrons for electron-beam welders, the material must fulfill certain requirements: These and other conditions limit the choice of material for the emitter to metals with high melting points, practically to only two: tantalum and tungsten. With tungsten cathodes, emission current densities about 100 mA/mm can be achieved, but only a small portion of the emitted electrons takes part in beam formation, depending on the electric field produced by the anode and control electrode voltages. The type of cathode most frequently used in electron-beam welders is made of a tungsten strip, about 0.05 mm thick, shaped as shown in