Autonomous Focusing of a Capillary Optic for Angle-Resolved Photoemission Spectroscopy

Low-dimensional optimization problems in complex experimental environments are common and often take the form of black-box optimization problems. We present a protocol for automated alignment of a capillary optic that focuses extreme-ultraviolet light for angle-resolved photoemission spectroscopy (ARPES). This alignment is a demanding procedure typically performed by expert beamline scientists and is generally inaccessible to non-expert users. In spatially resolved ARPES, a small beam spot is essential for measurements of challenging materials and functional devices. We compare several optimization methods in simulations based on experimental data and demonstrate successful automated focusing in experiments at the SGM4 microARPES beamline of the ASTRID2 synchrotron radiation source in Aarhus.