Plasma gun with Sweep air

[gibum.park]

Hello,

I'm developing the coating process that the area of the part is very narrow and curved. So there is much porosity and oxide on the corner and side wall.
When we evaluate the microstructure always can't meet the requirement even though we apply 5% rule about microstructure.

CA recommend to use sweep air. So I searched what is sweep air and how to adjust our plasma gun, but I couldn't find it.

Can you inform me what is sweep air and the part for sweep air is purchasable or is made by ourselves?