The beam temperature and energy broadening of a charged-particle beam in an axially symmetric magnetic field

Abstract

The beam temperature and energy broadening of a charged-particle beam in an axially symmetric magnetic field are investigated in consideration of the space charge effect. The result shows that this kind of energy broadening consists of three parts: the thermal motion broadening, the space charge broadening, and the magnetic-field broadening. For the nonscalloping beam (including the space charge equilibrium flow and Brillouin flow) held by the equilibrium between the magnetic-field convergence and the space charge divergence, the energy broadening ΔE is directly proportional to the square of the equilibrium magnetic induction intensity Be and the beam radius R, and inversely proportional to the mass of beam particles. For the immersed flow (magnetic shield coefficient M = 1), the magnetic field does not result in an energy broadening, and the energy broadening caused by space charge is dominant. The beam temperature is defined by the mean square deviation of the velocity of beam particles. The beam temperature in the θ direction is much higher, whereas the beam temperature in the meridian direction is much lower than the temperature of the thermal cathode.