Glow Discharge at Low Pressure Between Coaxial Cylinders in an Axial Magnetic Field

摘要

The movement of electrons in vacuum between coaxial cylinders in an axial magnetic field is considered. If the cathode is sufficiently smooth and if the magnetic field is sufficiently parallel everywhere, then the elecrons are recaptured by the cathode after the first loop 3 or 4 of the cycloidal path. If the magnetic field exceeds a certain value, then the anode current drops to zero. However, if there is a little gas in the tube, then some of the electrons will collide with a gas molecule before returning to the cathode. If an electron thereby loses an amount of energy greater than the emission energy, then a return to the cathode becomes impossible. The electron then covers a much greater path and is ionized much more frequently than without a magnetic field. For a magnetron, the current in the presence of gas becomes very large precisely for the value of magnetic field at which it goes to zero in vacuum. In the self-sustained low-pressure glow discharge, the magnetic field by prolonging the electron paths exerts the same influence as a pressure increase. The starting potential and the characteristic of the glow discharge for a coaxial cylinder in an axial magnetic field at very low pressure are examined.