Single Crystal Diamond Compound Refractive Lenses

Statement of the problem: Next generation light sources, diffraction-limited storage rings, and high repetition rate free electron lasers will significantly increase the average brightness of the generated X-ray beams. These machines will require X-ray refractive optics with precise dimensional control and smooth surfaces that are capable of handling large heat loads. How the problem is being addressed: In this project we will machine refractive lenses out of single crystal diamonds by femtosecond laser pulses. The key advantage of this approach is in the short duration of the laser pulse. Unlike nanosecond pulses from standard laser cutters, femtosecond pulses only ablate the material and do not lead to thermal fatigue, subsequent crystalline defect formation and reduction in the quality of X-ray optical properties. What will be done in Phase I: We will fabricate a set of diamond X-ray lenses by fs-laser cutting followed by diamond slurry polishing. We plan to perform white-beam X-ray topography on the diamond sample before and after laser cutting to quantify the crystal damage induced by laser cutting. The lens geometry and surface roughness before and after polishing will be characterized by optical profilometry. Applications and benefits: The technology developed here is required to utilize X-ray beams at fourth generation light sources to maximum potential. Diamond is virtually the only material that can withstand the heat load of the next generation light sources. If an inexpensive manufacturing method is established, diamond refractive optics would supersede its current alternative, which is based on beryllium and has safety concerns. Key words: X-ray, diamond, compound refractive lens, femtosecond laser Summary for members of congress: We are developing the next generation of optics for focusing the X-ray beams from free electron lasers and synchrotrons. These machines are high quality X-ray sources that have already made a great scientific impact and will continue be an essential research tool for future research and development in medicine, materials science, and basic science.