Recent developments of Monte-Carlo codes Molflow+ and Synrad+

Molflow+ and Synrad+ are Monte Carlo simulation tools for ultra-high vacuum and synchrotron radiation, respectively. Over the years they have become a common tool for designing and analysing the vacuum system of particle accelerators. This contribution gives a short summary about new features added since the last IPAC contribution [1]. Synrad+ now supports low flux mode, a weighted Monte Carlo technique where the represented number of photons is reduced at every reflection, providing significantly better statistics at low flux regions. As for Molflow+, angle maps allow recording the molecules’ directional distribution at any point, and then desorb a reduced gas quantity according to the recording. In linear systems, this allows iterative simulations that have been proven to treat systems up to 7 orders of magnitude of pressure difference. Without the new technique the computing time would be prohibitively slow on desktop computers, which is what most users of the two codes use. Both codes now have a built-in geometry builder that allows creating simple models through a set of 3D operations and modifying those imported from CAD tools. Molflow+ has been extended with additional diagnostic tools, such as a logger that records properties of all hits on a scoring surface, and histogram plotters that visualize the distribution of the number of bounces, the distance to absorption and the time of flight of the gas molecules. The codes have recently become open source, and it has been made compatible with, and tested on different versions of Linux and macOS.