MoBSTer is an open-source software, written to allow the design and accurate simulation of molecular beam scattering apparatus through the joining of modular instrument functions. The software allows users to calculate the propagation of particles through their scattering machines, and test new instrument ideas in context.

MoBSTer makes no assumptions about the 3D geometry of the apparatus or the alignment of instruments, to reflect the reality of a laboratory. Users can place components in a simulation with all 6 degrees of spatial freedom, allowing for the testing of the effect of instrument misalignment and machine geometry on scattering signal.

MoBSTer is capable of accounting  for full quantum-mechanical spin-state propagation through magnetic fields, allowing the simulation of spin-echo machines. The user can visualise the path of every successful trajectory through a constructed simulation, and information on each particle such as position, velocity, spin-state, time propagated and particle weight can be accessed at any simulation time-step.

The versatile structure-based method of data propagation allows MoBSTer to be highly customisable for each individual user. Additionally, framework is provided to allow users to easily create and integrate their own instruments, including a general component template and a UI for testing. Many components already exist in MoBSTer and can be instantly accessed, such as a source, hexapole lens, dipole, solenoid, specular sample, and various types of aperture.

The software is pre-initialised to simulate the Cambridge machine set-up for spin-1/2 particles. Example investigations of varying complexity are included, as well as an extensive user manual which explains in detail how to utilise the full capabilities of the software.

MoBSTer v1.0 was built by Fraser Birks, under the guidance of Dr Bill Allison, as part of the Cambridge Undergraduate Summer Research Program in Surface nanoPhysics and Atom-Surface Scattering.

Release – v1.0

Github –

DOI – 10.5281/zenodo.2025809

Link –

For taking part in the development of the software, please contact the Cambridge Atom Scattering Centre. Alternatively, open an issue on the GitHub project page, which is monitored by the developers.