local 2d particle physics in 3d

I am building a neutron emission simulation where neutrons travel through a layered container made of different materials. This simulation is shown as a 2D cut-away of a 3D container. I am using 2D physics triggers to change the behavior of particles as they travel through different material layers (not shown in the unity screenshot. that just shows straight collision).

Problem: when the container is rotated too much, the 2D physics behaves incorrectly because the simulation is perpendicular to the regular x/y 2D plane

Is there some way to create a 'localized' 2D physics world that can rotate in 3D space?