Recent upgrades of synchrotron light source facilities towards ultra-low electron beam emittances allow increased photon beam brightness and coherence. New techniques for online modeling and control, taking advantage of modern Machine Learning approaches are required to fully utilize these new photon capabilities. We present recently developed reduced models for x-ray propagation that may enable an array of fast optimization methods for beamline alignment and reconfiguration. In particular, we have extended the analysis of the partially coherent Gaussian Schell model to include physical apertures and expressed it in terms of a Wigner function such that only second moment and centroid propagation is required. We have implemented this formalism within the SHADOW ray tracing code, providing fast, convenient transfer matrix computation down an x-ray beamline and subsequent moment propagation, including beam size, divergence and coherence properties. For the fully coherent case, we are developing tools for efficient Linear Canonical Transforms. On the optimization front, we have used Bayesian Optimization with Gaussian Processes and performed proof of principle automated alignment experiments on the Tender Energy Spectroscopy (TES) beamline at NSLS-II. These software tools are being integrated into the Sirepo web-based simulation framework as well as combined with the Bluesky control software suite in a dedicated package called Sirepo-Bluesky. We present an outlook on the progress we have made thus far, along with a future vision for this work.
Synchrotron beamline alignment is often a cumbersome and time-intensive task due to the many degrees of freedom and the high sensitivity to misalignment of each optical element. We develop an online learning model for autonomous optimization of optical parameters using data collected from the Tender Energy X-ray Absorption Spectroscopy (TES) beamline at the National Synchrotron Light Source-II (NSLS-II). We test several optimization methods, and discuss the effectiveness of each approach, as well as their application to different optimization problems and benchmarks for beamline performance. We also discuss the practical concerns of implementing autonomous alignment systems at NSLS-II, and their potential use at other facilities.
We present a novel approach to the accurate and rapid propagation of general 2D wavefronts via linear canonical transforms. An operator splitting approach divides both the crystal and the amplified laser pulse into slices, so that the algorithms remain 2D for an intrinsically 3D problem. The Synchrotron Radiation Workshop (SRW) code uses these matrices to transform the wavefront with physical optics. We are also developing a Python library for linear canonical transforms, which will enable wavefront propagation via more general ABCD matrices. Comparisons with experimental data are presented.
We describe a reduced model approach to x-ray transport down synchrotron radiation beamlines. The method uses a ray tracing code for computation of a transfer matrix for sections including drift spaces and focusing elements separated by physical apertures. The transport matrix along the beamline is analyzed analogously to charged particle beam optics. For coherent radiation, the wavefront is propagated by the transport matrix via linear canonical transformation. For the partially coherent case, the matrix can be applied directly to the Wigner function. We apply this method to a beamline section comprised of a KB focusing system and compare results between Synchrotron Radiation Workshop and SHADOW. Machine learning methods are also used for 2-D automated alignment. Plans for use of the reduced model within a beamline control system and more advanced used of machine learning methods for automation and reconfiguration are discussed.
The brightness and coherence of modern light sources is pushing the limits of X-ray beamline design. The open source Synchrotron Radiation Workshop (SRW) provides physical optics based algorithms for correctly simulating such beamlines.1 We present new SRW capabilities to calculate source brightness and related quantites for undulators. The Sirepo cloud computing framework2, 3 includes a browser-based GUI for SRW.4–6 In addition to high-accuracy wavefront simulations, the Sirepo interface now supports analytical calculations for flux, photon beam size, divergence and photon brightness. We have included the effects of detuning from resonance and electron beam energy spread, which can be important in realistic operational conditions. We compare our results to features previously available in the Igor Pro interface to SRW, to analytical formulae available in the literature, and also to the results of simulated wavefront propagation. Differences between the various approaches are explained in detail, so that all the assumptions, conventions and ranges of validity can be better understood.