Possible to draw a circle with Beam Particle?

Hi, I tried a lot to get my Beam Particle flow in a perfect circle (ideally with adjustable radius). In theory it should be possible, if target and source are at the same position and both target and source emit out in opposite directions. I have enough interpolation points and experimented with all settings, but it always twists wierd and I simply do not get a circle.

Maybe someone did this before. Do you have a hint what I might have overseen?

Did you ever found out how to do it? I would like to make a beam circle with noise to visualize audio.