Fig. 1. Comparison of x-ray absorption in SU-8 and other lens materials

The photoresist SU-8 contains one antimony atom per formula unit which generates an increase in the absorption above the antimony K-edge at 30.5 keV by a factor of more than 2 (see Figure 1). Below this energy, beryllium is far superior to SU-8. Above the edge, the absorption is comparable to aluminium. However, the metallic lens materials have further advantages like absence of radiation damage, high heat conductivity, and the possibility of manufacturing two-dimensional parabolic profiles.