Impurity,whichisinducedbytheinteractionbetweenplasmaandthefirstwallsuchaslimiter,isoneofthekeyissuesimpactedthequalityoftokamakplasma.Itisalsothesourceoftheradiationandcoldelectronintokamak,andcanhaveasignificantinfluenceonthebalanceofplasmaenergyandparticleaswellastheprofilesofdensity,temperatureandcurrent.Thesteadystateoperationandtransportfeatureoftokamakplasmaareaffectedbyimpuritytoo.