You either have a hole at the top that is letting those particles thru or your “Permeability” setting in “Deflection” is not 0.00. If it still lets particles slip thru then try to put another, invisible mesh there to help deflect.
To make it look hot on top you need to set the Halo Size smaller, set the Hard higher (or do both until you have each halo looking right) and give your Vect Setting a positive value (greater than 0.00) so they look like sparks. Then you can use a Blend Texture that goes from transparent (before it hits any metal) to white (where it is hottest) to yellow, to orange to red.
