An investigation of a magnetron injection gun suitable for use in cyclotron resonance masers

The requirements of an electron-beam source suitable for use in cyclotron resonance masers are discussed. The beam source of preference, a magnetron injection gun with its emission temperature limited, is studied by use of a numerical simulation code. This computer code includes the effect of external magnetic fields, the beam's azimuthal self-magnetic field, and space charge in a self-consistent manner. By use of this program, a prediction of gun operation, particularly as it affects gyrotron performance, can be made. Of particular interest are the effects of varying such control parameters as the magnitude of the electric and magnetic fields, the shape of the electric and magnetic fields, and the current. It is demonstrated that, for a particular optimized gun design, the gun operation is very sensitive to both the applied electric and magnetic fields at the cathode. However, the gun shows no strong dependence on other factors such as the temperature-limited beam current or the magnetic-field taper used to compress the beam.