Neutron star between 10 and 10 (100 million to 1 quadrillion) times as strong as that of the Earth. The gravitational field at the neutron star's surface is about (200 billion) times that of the Earth. As the star's core collapses, its rotation rate increases as a result of conservation of angular momentum, hence newly formed neutron stars rotate at up to several hundred times per second. Some neutron stars emit beams of electromagnetic radiation that make them detectable as pulsars. Indeed, the discovery of pulsars by Jocelyn Bell Burnell in 1967 was the first observational suggestion that neutron stars exist. The
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