concentrator

Short definition from Wiktionary

Noun

1. 1
   One who concentrates.
2. 2
   A hub.
3. 3
   An apparatus for the separation of dry comminuted ore, by exposing it to intermittent puffs of air.
4. 4
   A frame or ring of wire or hard paper fitting into the cartridge case used in some shotguns, and holding the shot together when discharged, to secure close shooting; also, a device for slightly narrowing the bore at the muzzle for the same purpose.