Cathode unit with field emitter from carbon fiber

In the beginning of 1990s, the cathode unit with the fiber field emitter for use in devices of surface searching and treatment was developed in SSPE "Toriy" (Afanasyev et al., 1992; Barsov et al., 2003). The cathode emitter is the carbon fiber with 7/spl mu/m diameter and with specially formed tip. The tip has the shape of a bullet with micro-pit on the top. Due to the pit geometry it makes focusing of the electron beam emitted by the fiber tip, so that beam is inside a small solid angle along axis of the device. Our calculations show that due to this effect the fiber emitter has high stability of emission, repeatability of characteristics for different samples of the cathode and higher level of electron optical brightness.