Volume material rendering results in pixel error

Hi guys,

I am currently hoping to render an object the shape of a cylinder as a kind of light cone.

Since both ends need to be capped, I cannot use a spot light, hence the solution to use a volume material. Most of the volume render correctly but some regions around the edges seem to have pixel errors.

Does anyone know how to work around the effect/what is causing it, any hint on a solution?

Thanks, KAi!

Found out the problem is the step-size. this needs to be reduced to increase accuracy of the light.