Simulating the optical performances of the LCLS bendable mirrors using a 2D physical optics approach

What is it about?

The Linac Coherent Light Source (LCLS), a US Department of Energy Office of Science X-ray facility operated by the Stanford University, is being upgraded with a second source to provide eight beamlines (five existing and three under construction) with either high-repetition or high-intensity pulses and highly coherent X-ray beams. The photon transportation and distribution to each beamline relies on, among other elements, elliptically- bendable mirrors, often in Kirkpatrick-Baez (K-B) configuration. One of the crucial tasks in beamline design and performance prediction is the self-consistent simulation of the final point spread function of the complete optical system, simultaneously accounting for diffractive effects, mirror deformations, and surface finishing defects. Rather than using ray-tracing routines, which cannot manage diffractive effects, and rather than employing the first-order scattering theory, which cannot be applied when the optical path differences exceed the radiation wavelength, a wavefront propagation formalism can be used to treat all the aspects at the same time. For example, the WISE code, initially developed for astronomical X-ray mirrors at INAF-OAB, and subsequently used to simulate X-ray reflective systems at the Fermi light source, is now a part of the well-known OASYS simulation package. In this paper, we extend the model to a two-dimensional imaging and show performance simulations of two elliptical mirrors to form a complete Kirkpatrick-Baez system.

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