Therefore, the control, monitoring and analysis of the processes accompanying EBW requires analysis of some secondary signal parameters, such as secondary electron or ion emission, optical emission, X-rays, etc.Popular focus-control methods include systems for measuring the secondary emission parameters while scanning the joint being welded [10�C12]. Sharp focusing is www.selleckchem.com/products/Tipifarnib(R115777).html determined based on the maximum amplitude of the secondary signal��s peaks when the beam crosses the joint. Similar to this system are the raster scanning systems that register the signal of reflected electrons [12]. These methods allow the electronic beam focus to be preset at low power before welding starts. However, for operating welding modes, the focusing current should be adjusted experimentally depending on the materials, thickness and types of electron beam guns used.Other control methods are based on the correlation between secondary emission parameters in the welding area and the specific power of the electron beam. In [13], X-rays are used to control the EBW parameters. In [14,15], there is a description of the correlation between focusing mode and the average values and amplitudes of the reflected and secondary currents, ionic current, as well as X-ray density. These results helped Mitsubishi Electric Corporation develop automatic electronic-beam focus control systems [15], which use electronic-beam with focusing control at low power as reference points.One of the specific processes caused by the impact of the dense electron beam to the metal during EBW is the formation of plasma in the operational area [16�C21]. The parameters of the plasma are closely connected with the electron beam thermal effect on the metal being welded. In [22�C27], plasma current parameters are suggested for electron beam focusing control.All the above methods use extreme correlations between the secondary emissions and the focusing coil current. These correlations are characterized by dead zones and two values of the focusing coil current that ensure similar signal parameters. That is why the adaptive electronic-beam focus stabilization systems support low-frequency scanning [28], which significantly limits their performance and welding joint quality.In recent years, control and monitoring of electron beam and laser-based welding has become more and more popular [29�C38]. Laser technologies and electron beam welding are based on similar principles. New research opportunity provided by modern signal processing is finding an increased interest by researchers. Older methods only allowed inspection of amplitude ratios, while today we can analyze the structure of the secondary current signal in the plasma during EBW [39,40].