Microstructures for high‐energy x‐ray and particle imaging applications

Coded imaging techniques using thick, micro‐Fresnel zone plates as coded apertures have been used to image x‐ray emission (2–20 keV) and 3.5 MeV Alpha particle emissions from laser driven micro‐implosions. Image resolution in these experiments was 3–8 μm. Extension of this coded imaging capability to higher energy x rays (∠100 KeV) and more penetrating charged particles (e.g., ∠15 MeV protons) requires the fabrication of very thick (50–200 μm), high aspect ratio (10:1), gold Fresnel zone plates with narrow linewidths (5–25 μm) for use as coded apertures. A reactive ion etch technique in oxygen has been used to produce thick zone plate patterns in polymer films. The polymer patterns serve as electroplating molds for the subsequent fabrication of the free‐standing gold zone plate structures.