particle physics - Can an attractive magnetic force ever slow down an electron?

Can an attractive magnetic force ever slow down an electron? I know that electrons tend to accelerate towards the pole when place inside a cylindrical hollow magnet, but does this attraction ever cause them to lose velocity, say if they were going in the opposite direction (away from the core, towards the furthest point between the poles), or do they retain their velocity, merely, change direction and then gain more as they approach the tip of the tube

Answer

A magnetic force will not slow down an electron.

I'm not sure what kind of system you're thinking about-- it seems you have some kind of specific technology or device in mind. Perhaps you can provide more details?

The force $\vec{F}$ exerted by a magnetic field $\vec{B}$ on a moving charged particle is given by

$$\vec{F} = q(\vec{v}\times\vec{B}),$$

where $q$ is the amount of charge and $\vec{v}$ is the particle's velocity. The cross product $(\times)$ guarantees that the resulting force will always be perpendicular to the velocity, which means it will change only the particle's direction of travel, and not its speed.