3D modeling in CAD programs requires a steep learning curve and expensive software.

Using Molflow's built-in editor to create a sequence of apertures and connect them manually is tiresome.

A helper tool, OpticsBuilder can automate the process: it takes a series of apertures (either parametric shapes like circles, racetracks, or custom imported ones).


2019 had four important changes concerning the future of Molflow:

  • In the beginning of the year, cross-platform support was added. For this, the separation of GUI (mollfow.exe) and the workers (molflowSub.exe) had to be ended, using instead a single binary with multithreading (Mollfow versions 2.7 and later)
  • In late April, the development of Molflow was put on hold, except for minor bugfixes
  • In June, a PhD student in computer science joined the Molflow team
  • In November, the development resumed, with a new build (2.7.9) released the first time in 6 months

As of the end of 2019, our plan is to...


Following user requests, a diagnostic tool has been added to Molflow, providing insight to the behavior of your vacuum system. It can show the dsitribution of the...

  • number of bounces
  • flight distance
  • flight time

...of test particles until they are pumped:

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The new particle logger window can record a certain number of hits on one facet, and export the list of hits either to the clipboard or to a CSV file.

Two remarks:

Angle maps

Starting from version 2.6.58, facets in Molflow+ can have angle maps. 


  • You can record the distribution of the incident angles on a facet
  • You can desorb gas (i.e. generate outgoing angles) according to a recorded distribution
  • You can combine the two modes above: record incident angles on a facet, then use the recorded distribution to generate outgoing angles, either on the same or on a different facet

Originally, Molflow+ was intended to be used as a simulator, not a CAD editor - the source of the geometry always had to be an STL file.

Over the years, editing options were added to perform quick fixes on the geometry - such as plugging holes, rotating facets, etc. These functions cumulated, and - whereas Molflow won't ever be able to compete with a dedicated editor - now the user has a handful of editing options.

Starting from scratch

Molflow now starts with an empty geometry by default, and it is possible to start drawing accelerator shapes from scratch:

Designing geometries is now possible thanks to a few new, handy functions:

[click read more for the full article]


A previous blog entry called Attaching files and images in comments contained a step-by-step guide to... ...well, attaching files and images in comments. Unfortunately the first method relying on the Image Picker module has to be removed, as that module is no longer maintained and poses a security risk. Now we have to use the same method for inserting images as for inserting files:

First we need to upload the the file. For this we click on the Image button on the top of the editor:


Originally added for a simple Gaede pump modelling, Molflow can treat certain facets as "Moving parts", and add a certain velocity vector to the normal rebounce directions of molecules hitting a facet. The velocity vector itself can be set globally through the Tools/Moving parts menu: