Compensation of heat load deformations using adaptive optics for the ALS upgrade: a wave optics study

A realistic wave optics simulation method has been developed to study how wavefront distortions originating from heat load deformations can be corrected using adaptive X‐ray optics. Several planned soft X‐ray and tender X‐ray insertion‐device beamlines in the Advanced Light Source upgrade rely on a common design principle. A flat, first mirror intercepts the white beam; vertical focusing is provided by a variable‐line‐space monochromator; and horizontal focusing comes from a single, pre‐figured, adaptive mirror. A variety of scenarios to cope with thermal distortion in the first mirror are studied by finite‐element analysis. The degradation of the intensity distribution at the focal plane is analyzed and the adaptive optics that correct it is modeled. The range of correctable wavefront errors across the operating range of the beamlines is reported in terms of mirror curvature and spatial frequencies. The software developed is a one‐dimensional wavefront propagation package made available in the OASYS suite, an adaptable, customizable and efficient beamline modeling platform. A simple and complete one‐dimensional wavefront propagation model for beamline analysis is developed in the WOFRY package in OASYS. It is used to analyze how the thermal load of the white‐beam mirror degrades the wavefront. This can be corrected by an adaptive mirror, with some limitations that are studied.