Restraint of focus spot drift of electron-beam in bremsstrahlung radiation

Focus spot drift of electron-beam seriously influences the radiation experimental efficiency of electronic devices. A simple method was introduced which could restrain the focus spot drift of electron-beam in the paper. A small stainless cathode was designed and experimented. The experimental results of small cathode were compared with the results of classical annular velvet cathode. It is shown that the probability of the spot stays at the center of anode is about 67%,and the probability of the spot stays at the circle area with diameter of 35 mm is about 100%. Focus spot drift was obviously restrained using the small stainless cathode, while the probability of the spot stays at the center of anode is only about 20%, and the probability of the spot stays at circle area with diameter of 40-60 mm is higher than 60% for the annular velvet cathode.