WE‐E‐204B‐07: A Cold Cathode X‐Ray Source Based on TiO2 Nanotube Field Emission

Abstract

Purpose: To assess the viability of titanium dioxide (TiO2) nanotube arrays in field emission based x ray sources. Methods and Materials: Aligned TiO2 nanotube (NT) arrays with diameter and height in the range 30–100 nm and 1–10 μm, respectively, were grown by electrochemical oxidation from titanium (Ti) sheets in a glycerol+HF electrolyte. Anodization voltage was varied in the range 13–40 V to control TiO2 NT parameters. As‐grown amorphous TiO2 NTs were annealed at 500° C in air for 1 hour. Field emission properties were tested in a dynamic vacuum of 5×10−7 Torr and the current was measured as a function of applied electric field. The test setup utilizes a copper mesh grid spaced 400μm from a grounded NT array with a mesh density of 70%. A 2 mm diameter copper anode is spaced 10 mm from the grid and held at 60 kV potential for the production of X‐rays, which pass through the stainless steel vacuum chamber via a borosilicate glass window. Radiographs of phantoms were produced using a charge integrating flat panel detector. Results: From current‐voltage characterization a clear Fowler‐Nordheim (F‐N) relationship relating applied NT array electric field and the resulting primary anode current and corresponding X‐ray flux is observed. Initial results show that with an applied electric field of 4.5 V/μm, a stable 1.5 mA/cm2 field effect current density is generated with 80 nm diameter NTs, providing sufficient flux for radiography. This configuration produces a minimum measured horizontal resolution of 3.1 line pairs (lp)/mm. Conclusions: The results show that aligned TiO2 NTs can be used as a field effect emission cold cathode to produce x ray emission.