A high brightness electron beam produced by a ferroelectric cathode

We report experimental measurements of a high brightness electron beam produced by a ferroelectric cathode. The experiments were carried out with a cathode of area 3.7 cm², up to 36 A of current (10 A/cm²) were obtained at a voltage of 22.5 kV. The emission of the electron current was carried out with a DC voltage held between the cathode and ground anode. Emission was gated by a 1-2 kV pulse applied across the sample by a solid state or krytron switch. The beam emittance was measured with a mask, phosphor screen and CCD camera; it was found to be 5π mm mrad yielding a normalized rms beam brightness of 1.2×10¹¹ A/m²rad². This is the first reported measurement of the brightness of a ferroelectric cathode beam; it exceeds that of a thermionic cathode and is close to that of a photocathode. The results for the ferroelectric cathode may be directly compared with a preliminary experiment carried out in the same geometry with a thermionic cathode. The ferroelectric cathode yielded higher current density