High repetition rate electron beam chopping system for electron beam testing at microwave frequencies

Abstract

A new beam deflection-chopping system has been developed which circumvents the limitation of electron pulse generation at maximum repetition rates of a few GHz with low energy beams using conventional deflection-chopping techniques. In an electron-optical arrangement involving two sets of orthogonal deflectors placed above and below a multislot chopping aperture immersed in a magnetic lens field, electron pulses are generated at regular deflection phase increments as the beam, scanned in a circle, traverses the radial slots. This results in beam pulse generation at a frequency which is the product of the deflection frequency and the number of slots. By changing the deflection amplitude, the beam transmission ratio can be altered, shorter electron pulses being generated at larger amplitudes. Time-resolved electron pulse measurements demonstrate pulse production at frequencies of up to 64 GHz while 18 GHz waveforms on a coplanar waveguide have been measured with an electron-beam testing system incorporating this beam chopper. The system’s electron-optical performance and issues concerning the integration of the beam chopper into a testing system are discussed.