Studies of relativistic backward wave oscillator with low magnetic field

Summary form only given. The one of applications of the relativistic Backward Wave Oscillator (BWO) is its use as a source of high power pulsed microwaves for nanosecond radiolocation To realise of 10 GHz high-power nanosecond radar, superconductive magnets were employed. Strong axial magnetic field (3 T) produced by the magnets provided the formation of a thin-wall tubular electron beam with low transverse velocities and its transportation through a slow-wave structure (SWS). The application of strong magnetic fields is inspired by the fact that the BWO efficiency tends to decrease, as the field value becomes lower. Two effects cause this. The first is due to cyclotron resonant interaction between the electrons and backward electromagnetic wave, so as a result the wave power is converted into transverse oscillations of electrons (resonant field is about 1.3 T for 500 keV electron energy and 10 GHz frequency). The second is determined by the deficiently high quality of the electron beam produced in the coaxial magnetically insulated vacuum diode with cold emission cathode. The level of 0.5-0.7 T was of primary concern because the permanent magnets in this case are real. The interest in improving the BWO efficiency in a low magnetic field were connected with idea of increasing the diameters of the SWS and cathode. This allows a reduction in the transverse electric fields both near the cathode and inside the SWS which makes the transverse interaction less important. However, for an oversized SWS the mode selection should be provided.