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.
Detailed physical optics simulations of beamlines and experiments offer great value towards efficiently utilizing light source facilities. They make it possible to study their predicted behaviors under configurations which can be controlled more precisely than in physical experiments. Synchrotron Radiation Workshop (SRW) is a state-of-the-art software package for such simulations. Through its Python-based interface and browser-based interface Sirepo, SRW supports the definition of detailed optical schemes with many types of optical elements, and the simulation of radiation propagation through them. SRW has been mainly focused on CPU-based calculations; however, due to many of the operations being embarrassingly parallel, there is significant potential for accelerating these calculations using general-purpose GPU computation. In this work, the application of GPU accelerated computing to SRW for accelerating time-dependent coherent x-ray scattering experiments is discussed. A detailed simulation of a typical X-ray Photon Correlation Spectroscopy experiment for characterizing the dynamics of a colloidal sample was performed. Large improvements in simulation speed were demonstrated by converting the radiation propagation operations for the associated optical elements to use GPU computation. Combined with coherent mode decomposition, this resulted in a qualitative leap forward in the calculation speed and level of detail at which similar partially coherent scattering experiments can be simulated. These improvements have wide-ranging applications, such as assisting in the development of improved data processing methods and allowing for more detailed analysis of proposed experiments before using beam time.
The Sirepo-Bluesky library allows the performing of various types of Bluesky scans with Sirepo simulations acting as virtual beamlines and registration of the results with the Databroker library. We report on the progress made since the previous SPIE’2020. In particular, the support for Shadow3 and MAD-X simulation codes in Sirepo was added to the Sirepo-Bluesky library, and the API for the support of the Sirepo/SRW code was refactored. Significant efforts were put into reliable testing and documentation. A “digital twin” of the future NSLS-II ARI beamline was created and the future Bluesky scans were prototyped using the Sirepo/SRW simulations. This approach enables new optimization methods for automated instrument alignment based on the Ophyd/Bluesky and makes them transferable from simulated to various hardware backends.
The autonomous alignment of synchrotron beamlines is typically a high-dimensional, high-overhead optimization problem, requiring us to predict a fitness function in many dimensions using relatively few data points. A model that performs well under these conditions is a Gaussian process, upon which we can apply the framework of classical Bayesian optimization methods. We show that even with no prior data, a tailored Bayesian optimization algorithm is capable of autonomously aligning up to eight dimensions of a digital twin of the TES beamline at NSLS-II in only a few minutes. We implement this approach in a software package for automatic beamline alignment, which is available out-of-the-box for any facility that leverages the Bluesky environment for beamline manipulation and data acquisition.
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.
Detailed simulations of experiments carried out at modern light sources are directly related to the most efficient and productive use of these facilities for research in multiple branches of science and technology. The “Synchrotron Radiation Workshop” computer code with its Python interface, and Sirepo web-browser-based graphical user interface, currently supports physical optics simulations of coherent X-ray scattering and imaging experiments on user-defined virtual samples. We present examples of simulations of coherent scattering experiments that are typically performed at the Coherent Hard X-ray beamline at Brookhaven National Laboratory’s (BNL) National Synchrotron Light Source II. We also present several comparisons of the simulations with the results of actual coherent X-ray scattering experiments with nano-fabricated test samples produced at BNL’s Center for Functional Nanomaterials.
Simulation of beamlines at light sources is an essential part of their design and commissioning. Such simulations can be performed by the Synchrotron Radiation Workshop (SRW) code, which now has a user-friendly, browser- based interface, Sirepo. The simulations, utilizing a concept of a "virtual" beamline, can aim to optimize the specific aspects of a beamline, such as maximization of the flux, minimization of the beam size, etc. These tasks are also performed at the physical beamlines using various alignment procedures. At NSLS-II these procedures are executed by the Bluesky data collection framework. The Sirepo-Bluesky interface leverages both systems to allow for the multiparameter optimization of the X-ray source and beamline optics with the power of bluesky's plans used for the daily experiments at NSLS-II, and databroker's capabilities to retrieve the captured data and metadata to perform further analysis. Such a "collaboration" between the frameworks can be used to store the simulated results in the same database as for the experimental data, and seamlessly apply the same analysis pipelines, demonstrated in recent publications. In a simulation, multiple parameters can be changed at once and be stored as a snapshot of the "virtual" beamline in time along with the corresponding results of the simulations. A global optimization algorithm (e.g., a genetic algorithm) can then utilize the data to find the best configuration for the desired outcome. Such an optimization procedure can be seamlessly applied to the real hardware by substituting the virtual motors and detectors by the real ones.
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.
“Sirepo” is an open source cloud-based software framework which provides a convenient and user-friendly web-interface for scientific codes such as Synchrotron Radiation Workshop (SRW) running on a local machine or a remote server side. SRW is a physical optics code allowing to simulate the synchrotron radiation from various insertion devices (undulators and wigglers) and bending magnets. Another feature of SRW is a support of high-accuracy simulation of fully- and partially-coherent radiation propagation through X-ray optical beamlines, facilitated by so-called “Virtual Beamline” module. In the present work, we will discuss the most important features of Sirepo/SRW interface with emphasis on their use for commissioning of beamlines and simulation of experiments at National Synchrotron Light Source II. In particular, “Flux through Finite Aperture” and “Intensity” reports, visualizing results of the corresponding SRW calculations, are being routinely used for commissioning of undulators and X-ray optical elements. Material properties of crystals, compound refractive lenses, and some other optical elements can be dynamically obtained for the desired photon energy from the databases publicly available at Argonne National Lab and at Lawrence Berkeley Lab. In collaboration with the Center for Functional Nanomaterials (CFN) of BNL, a library of samples for coherent scattering experiments has been implemented in SRW and the corresponding Sample optical element was added to Sirepo. Electron microscope images of artificially created nanoscale samples can be uploaded to Sirepo to simulate scattering patterns created by synchrotron radiation in different experimental schemes that can be realized at beamlines.
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