Compact X-ray Tube with Carbon Nanotube Cathode

The primary goal of Phase II is to produce an X-ray tube with a small focal spot suitable for an X-ray Diffraction instrument that can be used for in situ analysis of materials in industrial and planetary exploration environments. A base model, based on a previously developed miniature, carbon nanotube X-ray tube, was designed and fabricated during Phase I. Four tubes will be delivered at intervals during Phase II. Each tube will incorporate improvements converging on the objective specifications, 40 kV operating voltage, 100 microamps of current and a focal spot of 40 microns. Design improvements will be achieved with electron optics simulation computer code that was modified to model emission from CNT cathodes and the electron beam analyzer that was design and constructed during Phase I. Improvement in the emission stability and uniformity will be sought using the cathode test and evaluation station that was constructed and operated during Phase I. The cathode evaluation system has already been used to select cathodes and develop CNT cathode processing regimens that resulted in improving the acceptance rate, from 50% to 90%,of CNT cathode X-ray tubes being produced at Oxford X-ray Technologies for hand held XRF Spectrometers.