Absorption in SU8
Fig. 1. X-ray absorption in SU8

The resist SU8 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 more than 2 (see Figure 1). Below this energy, beryllium is far superior to SU8. Above, 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 manufactoring two-dimensional parabolic profiles.