The image of a 60x60 mm section in size containing the weld, the weld pool and the joint forms three times per second when the beam scans over the surface of the component whithin a short period. The process of electron beam welding does not exclude the possibility of its interruption for this short period of time tint = 0,1 d_e/v_w, where d_e is the affected diameter of the beam; v_w is the welding speed. For d_e=1 mm (the size of the beam typical of powerful guns) at v_w= 6 m/h (1,7 mm/s) the interruption of the welding process for tint <60 ms does not cause any disturbance in weld formation. At v_w=60 m/h (17 mm/s) this time period decreases to 6 ms. During these periods the welding beam maybe switched  to the probing mode and the weld pool and the weld in the immediate vicinity of the pool maybe visualised, and the joint line can also be aligned with the centre of the weld. At the same time, the system automatically computes the value of mismatch between the position of the joint and the weld during welding and usind mechanisms or a deflection system aligns the beam with the butt line.