Vacuum cathode arc root for a current of 10A on a silver contact

The cathode spot is theoretically analyzed here for a 10A current and a silver contact in vacuum. The main equations leading to the values of physical characteristics are detailed and resolved according to the radius r in the domain 0.5-1.5μm. The choice of this field is imposed by the limits of the current density and time of appearance of the metal vapour. The findings show that when they are created the spots have cathode radius that fall to low values of field. Under the action of saturated vapour pressures higher radius of the spot will grow but its growth is limited by its lifetime.