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Setting up coupled SR / photodesorption simulations

Synrad+ and Molflow+ were meant to be use together as a package. The latest beta versions allow you to do a SR simulation in Synrad+, then import the absorbed flux map to Molflow+, convert it to a desorption map, and do a standard vacuum simulation, this time having the walls as outgassing source. Follow the steps below for the whole procedure.

Part 1: Synrad+ simulation

In this example, we will use a short sample tube which receives SR light from an upstream dipole.


Full user guide

The user guide for Molflow is available for download:


This describes all functions up to date (version Now we will focus on adding new, time-dependent physics.


New variables in Formula Editor

With MolFlow 2.3.5, two long-requested features have been added to the expressions that you can use in Formula Editor.

1) Mean Free Path / Mean Pumping Path

Adding the "MFP" or "MPP" variables will display the mean free/pumping path in centimeters, that is, the total length travelled by particles in the system divided by the number of hits / number of absorbed particles.




2) Sums for selection groups

MolFlow now fully supports defining part of the geometry as selection groups. In the formula editor, it is now possible to refer to a group of facets and perform sum operation on them. The syntax is the following:


where prefix can be:

  • AR (area of facets)
  • A (number of absorbed particles)
  • H (nimber of hits on the facets)
  • D (number of particles desorbed from the facets)


  • sum(A,S3) will calculate the total number of particles absorbed on facets that are part of selection group 3
  • sum(AR,S1) tells the total area of all facets in selection group 1

SynRad quick start tutorial

The best way to start using SynRad is to set up a simple sytem with two dipoles and interpret results. There is a 10-minute quick start guide to do just that:


You can also see how eactly the tutorial is solved on this Youtube video (set quality to 720p to see text):


SynRad released

SynRad is a new MC simulator for calculating flux and power distribution of synchroton radiation in geometries of arbitrary complexity. It has a similar interface to Molflow and both programs read each other's file formats. You can also export the flux distribution and use it as an outgassing map in Molflow.


Try it out in the downloads section.



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