MAX IV Staff R&D. Selecting the important track from 1018: How to use Monte Carlo in complex environments

by Stuart Ansell (Max-IV)

Tuesday 23 Apr 2019, 11:00 → 12:00 Europe/Stockholm

MAX III meeting room (MAX IV Laboratory)

Abstract

Monte Carlo methods work by following example tracks through the process or model and assuming that the problem space is statistically sampled. MAX  IV has 1018 electrons tracks passing  through each undulator every second, and the dose map pictures SSM expects are average less than  1 track per second. Simple track Monte Carlo will not  get a statistical viable result less than a human lifetime. Computational techniques are needed to improve the speed in the order of > 1012.

The basic modeling system with CombLayer will be presented, with the main focus on an algorithmic level introduction to two of the mathematical techniques use to improve the computing performance and that may be applicable in other x-ray analysis fields: Boolean al- gebra optimization by Shannon expansion and Forward Weighted Consistent Adjoint Driven Importance Sampling (FW-CADIS).

These techniques have allowed a complex beamline model which includes detailed magnetic fields to be modeled and simulation done for various configurations of the undulators. The results will  be shown in comparison  to the benchmark measurements on MAXPEEM showing the surprisingly large effect of the undulator gap and polarization on the bremsstrahlung radiation field in the optics hutch.