A NEW APPROACH FOR HIGH-POWER ELECTRON-BEAM GUN DESIGN USING SCALING RULES

A method is presented to extrapolate the design of a currently exploit ed gun into a new family of similar guns with new preferable technolog ical parameters, for example with higher electron beam power, accelera ting voltage, electron brightness and so on. The method is based on th e scaling theory of electron-optical devices (EOD). According to the t heory only EOD with small space charge, i.e., with perveance G < 0.01 mu P, can be size and/or voltage scaled. EOD containing relatively big space charge (G greater than or equal to 0,01 mu P), such as high ene rgy Pierce type electron guns applied in thermal technological machine s, generally cannot be scaled, because of their nonlinear space charge nature. Nevertheless, also in these cases a special procedure of scal ing can be applied. The reason is that the electron charge distributio n in the gun is not uniform. Near the anode the density of electron ch arge is much smaller than in the cathode region. The concept of high p erveance electron gun designing using scaling rules is based on the id ea to apply the scaling rules only to the anode zone of the gun. The p rocedure for scaling a low power 25 kV and 150 mA electron extract sys tem with a cylindrical electron beam into a high power 75 kV and 150 m A electron extract system is described in this paper. An experimental investigation confirmed the good technological quality of a high volta ge, high power gun constructed according to the above concept.