Development of micro-focused X-ray source by using carbon nanotubes field emitter

A micro-focused X-ray source developed by use of carbon nanotubes as cold cathode and of an electrostatics lens with simple configuration is reported. A variation of total emission current with time is measured at a fixed cathode potential of -6.5 kV. The emission current decreases with time down to 400 μA and becomes steady after 17 hours from the start of measurement. Fluctuation of the anode current also decreases to 1.2% from 7.4% in 25 hours. The intensity of X-ray passing through the Be window is measured as well using a dose rate meter placed at a position 150 mm away from anode. Using an X-ray transmission image of a dried sardine as an example, it is suggested that the X-ray with small source size has high coherency, and is suitable as a probe for high resolution X-ray radiography.