An apparatus for low temperature plasma treatment of powder particles for modifying the surface properties thereof, comprising means for the creation of a low pressure zone and, in association therewith, at least one cascade arc torch generator to form a plasma torch which is directed into said low pressure zone, means for the supply by gravity of powder particles to be treated into said low pressure zone and conduit means for the removal of the treated powder particles from said low pressure zone, said cascade arc generator having an orientation such that said plasma torch enters said low pressure zone at a downward angle (.alpha.) to the horizontal of from about 15.degree. to about 60.degree., and said conduit means being directed away from said plasma torch at an upward angle (.beta.) to the horizontal of from about 15.degree. to about 80.degree.;a process for low temperature plasma treatment of powder particles;said apparatus and process enabling a high degree of reproducability and uniform particle size distribution.