Magnetically confined high power thermionic line source emitter assembly

A directly heated thermionic high power electron beam source was constructed. The circular cross-section tungsten line cathode of length 140 mm with diameter 0.9 mm was used. Different gun design parameters were investigated and their results are discussed in detail. A uniform external magnetic field of 50 G was employed for focusing of electron beam at 180 ° deflection. The gun delivers uniform emission current density throughout the emission surface. The dimensions of the electron beam at worksite were comparable with the line cathode. The beam power of 57 kW was successfully achieved well below the saturation limit. The spring action mechanism was especially designed to avoid any cathode deformation. The gun design facilitates the reported length and emitting surface temperature of the cathode to be further increased to obtain higher emission values. The important gun features are operational reproducibility and long time stability. The evaporation rates for stainless steel have been achieved up to 1 kg/hr. An area of (280×120 mm2) could be heat treated with the line source electron beam in few milliseconds. The gun is extremely useful for melting, evaporation and heat treatment.