The electrons are high enough energy that they can damage the wall, yes. But also they're simply a route for energy loss from the plasma that you don't want. E.g. https://www.nature.com/articles/s41598-023-48672-7
Thanks! It's exactly what I needed, but felt too lazy to look up (which is uncharacteristic of me, but, well, why have forums if you have to look everything up yourself).
1. High energy particles destroy the container. Alpha particles, which are just Helium nuclei, are quite small and can in between metal atoms. Neutrons too. High energy electrons too; and
2. It's an energy loss for the system to lose particles this way.
Magnetic confinement works for alpha and beta particles because they're electrically charged. Neutrons are a far bigger problem, such that you have fun phrases like "neutron embrittlement".
In a disruption in a tokamak, when the plasma collapses, the current in the plasma that goes around the ring decays. This creates an electric field as in a kind of accelerator called a "betatron". The electric field can accelerate runaway electrons to relativistic speeds. This beam can hit surfaces and melt holes, like a giant arc welder.
What does it mean? Beta radiation can cause structural damage? Is it really a problem?