Cathode And Anode Plasma Research Of Intense Diode And Influence On Relativistic Backward Wave Oscillator

Extending pulse width is an important method to increase the energy of single pulse for high power microwave source.At present,increasing pulse width is facing the problem of pulse shortening.The unexpected plasma in diode is an important reason for pulse shortening.In this paper,the effects of cathode plasma,electron beam velocity distribution and collector plasma on relativistic backward wave oscillator are studied by theoretical analysis,numerical solution and particle simulation.The main contents include:Firstly,plasma is discussed from the axial and transverse directions by using the fluid dynamic.The axial acceleration of the plasma is mainly determined by the density gradient.The transverse velocity is inversely proportional to the magnetic field strength and directly proportional to the pressure gradient.The boundary velocity of onedimensional plasma is derived.The edge velocity of the plasma is proportional to its center and sound velocity.The numerical solution velocity of plasma is in the order of cm/?s.The time-space distribution of plasma pressure is obtained by solving the fluid equation with Mac Cormack method.Secondly,the effect of electron beam on microwave output is studied by using particle simulation program.The results show that the energy dispersion of the electron beam will reduce the microwave output.The conclusion is as follows: the existence of the included angle changes speed of the electron beam,so as to reduce the microwave power output;the existence of the standard deviation of the speed distribution will reduce the consistency of the electron speed of the electron beam and reduce the microwave power output;at the same angle,the negative included angle effect is greater than the positive included angle effect.And 10 ° angle can reduce the power by about 10%.Based on this,the methods of restraining the negative effects are given: increasing the axial magnetic field to restrain the axial expansion speed in order to control the distribution of electrons in all directions;using the cathode material with high conductivity to reduce Joule heat,reduce the temperature,and reduce the influence of thermal speed;using the hollow electron beam with large radius to reduce the space charge field.A method of measuring the energy of electron beam is proposed.The measurement principle is verified by particle simulation.The error analysis shows that the accuracy of this method is 2%.Finally,the effect of collector plasma on microwave output is studied by particle simulation.According to the simulation results,one of the ways that collector plasma affects microwave output is to release additional electrons into the beam wave interaction region.The collector structure is optimized,and the microwave output is reduced by600 MW at 50 ns.