The Advanced Light Source Upgrade (ALS-U) will increase soft X-ray coherent flux by 100×. We developed two new beamlines, engineered to minimize loss of brightness and utilize the advanced coherence of the light source. Each beamline uses a minimalist optical layout: a cryogenically-cooled silicon M1 mirror, a monochromator with variable-line-spacing gratings, and a final focusing M3 mirror. Optics are designed for Strehl ratio > 0.8 and sub-100 nrad vibration. A piezo-bimorph M3 mirror paired with a wavefront sensor allows for wavefront optimization. Fabrication is underway. New test data include at-wavelength efficiency measurements for blazed gratings, and motion performance of piezo-actuated pitch/roll flexure systems at cryogenic temperatures, granite air-bearing positioners, and monochromators.
Bergeret et al. (2026) studied this question.