A High Throughput Data Pipeline for MHz XPCS: Online Analysis

We give an overview of the online analysis pipeline for MHz XPCS at the Materials Imaging and Dynamics (MID) instrument at the European XFEL. The pipeline gives instantaneous feedback on a train by train basis as well as run-based averages for MHz XPCS experiments with the AGIPD detector at MID. The data rate of the AGIPD and the computation speed of the results allow us to process every second train (every 0.2 seconds), that is, 50% of all the measured data. For a user defined ROI made up of concentric annuli, the pipeline enables real time inspection of (i) the average photon count per pixel for the entire ROI, (ii) the probability of measuring photon counts from 0 – 9 for the entire ROI, (iii) for each ROI the Two Time Correlation Function and g2 function (a) for each train, (b) as an average of the last few trains, (c) as an average over the current run, (iv) for each ROI the speckle contrast based off of an exponential decay fit to the corresponding g2 function, (v) the single shot speckle contrast based off of single shot photon count statistics on a train by train basis.