Large area ring-shaped LaB6 cathode

In this paper we reported a ring-shaped LaB6 cathode with a large emission area of 115 mm2. The direct emission current density of the LaB6 was more than 40 A/cm2 when the temperature of LaB6 was 1 873 K. The heating power for the LaB6 cathode was only 173 W when the temperature of LaB6 cathode was as high as 1 873 K, in which an electron beam source was employed as the heater. The heating power decreased 66%, compared to that when the conversional graphite acted as the heater. It presented excellent emitting performance even after the cathode was exposed to the air many times.