beampipe elements with different apertures create an empty space

[Jochem Snuverink]

From Laurie: different apertures of beampipe create an empty space where particles can escape through without being recorded. Disks with thickness beampipe can be put to solve this.

[Jochem Snuverink]

a technical solution would be to add a transition method in the beam pipe factory or a special transition factory.

[Laurie Nevay]

In future, a transition piece can be added by extending the functionality of the beam pipe factories - aperture model knowledge here for each component.

From a physics point of view, a say typically 1mm thickness transition wouldn't significantly affect high energy particles. It is a little frustrating that some may escape entirely as the the vacuum is not truly enclosed, but the energy deposition would be minimal.

Some (likely very low energy particles) may have been stopped by a transition that exists in reality and may propagate and impact elsewhere causing inaccuracy, but again, this is only relevant for low energy particles.

This can be implemented in future so changing to a proposed extension rather than a bug.