Abstract
The data systems for X-ray free-electron laser (FEL) experiments at the Linac coherent light source (LCLS) are described. These systems are designed to acquire and to reliably transport shot-by-shot data at a peak throughput of 5 GB/s to the offline data storage where experimental data and the relevant metadata are archived and made available for user analysis. The analysis and monitoring implementation (AMI) and Photon Science ANAlysis (psana) software packages are described. Psana is open source and freely available.
Highlights
Since the Linac coherent light source (LCLS) facility started operating in 2009, it has accumulated many petabytes of complex data for analysis, and the timely processing of this data has proven to be a challenge for the community
AMI refers to a collection of software implemented in C++ and QT consisting of (1) a shared memory server, a generic application that receives datagrams from the data acquisition (DAQ) private network via user datagram protocol (UDP), builds them into events, and pushes them into shared memory, (2) a custom application that receives these events from shared memory, performs analyses, and exports viewable data such as plots, and (3) online_ami, the QT-based graphical user interface (GUI) that runs on the control room consoles and serves as a network client to the ami server, receiving users’ analysis configurations and displaying resulting plots
The GUI has a set of simple operations that can be cascaded to achieve a variety of monitoring measures
Summary
Since the LCLS facility started operating in 2009, it has accumulated many petabytes of complex data for analysis, and the timely processing of this data has proven to be a challenge for the community. Because of the intrinsic pulsed nature of the FEL source, experimental solutions must acknowledge that every shot is different and that a wide range of information needs to be recorded to interpret a single-shot event. The LCLS data systems must acquire all relevant shot-by-shot data at the 120 Hz repetition rate of the LCLS light source, provide user-friendly display and analysis of critical realtime information, write multiple GB/s to storage, and provide analysis software for the timely processing of this large and complex dataset. We describe the data acquisition (DAQ) and data analysis systems developed for LCLS and briefly describe a case study of the quasi-real-time nanocrystallography pipeline as an example of LCLS computing capabilities
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