Investigation of the Concept of a Miniature X-ray Source Based on Nanoscale Vacuum Field-emission Triode Controlled by Cut-off Grid Voltage

Nowadays, there is a revived interest in the field of vacuum nanoelectronics, which is due to the prospect of creating low-power, high-frequency, radiation-resistant and scalable electronic devices with nanosized vacuum channel. In particular, it provides good motivation for developing a miniature X-ray source using triode-type field-emission structures to generate an electron beam with diameter reduced down to nanometer scale by the grid electrode. In this paper we propose the concept of Xray source based on vertical field-emission vacuum triode containing transmission-type beryllium target on a metal anode and nanoscale cathode, the cold emission from which is controlled by a negative cut-off grid voltage. The optimal geometric parameters of this triode are found, sufficient to obtain the maximum electric field on the cathode surface up to 107 V/cm. It is shown that for an optimal design of vacuum triode the diameter of the electron spot is narrowed to about 100 nm, while the cut-off grid bias varies in the range from -10 to -40 V for the anode potential closing to 2-2.5 kV, that is required for achieving maximum conversion of electron energy into soft X-ray radiation. The results obtained can be widely used in the development of X-ray sources for portable diagnostic systems, as well as medical and lithographic equipment [1-3].