impactorn.

1916 Chambers's Jrnl. Dec. 830/2 The impactor golf-machine is a new invention.

1950 J. H. Perry Chem. Engineers' Handbk. (ed. 3) 1129/2 The Impactor..is a reversible hammer crusher without a discharge grating or cage.

1966 McGraw-Hill Encycl. Sci. & Technol. (rev. ed.) V. 471/1 To increase the effectiveness of the forging blows, the impacter forging machine was developed.

1945 K. R. May in Jrnl. Sci. Instrum. 22 187 (heading) The cascade impactor: an instrument for sampling coarse aerosols.

1945 K. R. May in Jrnl. Sci. Instrum. 22 188 The method which has been adopted for depositing the sample is direct impaction of the particles on to glass slides which may be coated with a suitable medium... The terms ‘impactor’ and ‘impaction’ were suggested by Prof. J. H. Gaddum to avoid confusion with ‘impinger’ instruments... In ‘impingers’ a fine jet of air is directed at very high speed on to a flat surface to obtain the maximum efficiency of deposition of small particles. In the case of ‘impactors’ jet speeds are lower and larger particles are dealt with.

1956 P. L. Magill et al. Air Pollution Handbk. x. 30 Most cascade impactors are now operated using high air velocities.

1956 P. L. Magill et al. Air Pollution Handbk. x. 29 A single-stage impactor..is often useful because of its simplicity of operation.

1964 K. Stewart in White & Smith High-Efficiency Air Filtration ii. 57 All impactors make use of the inertia effect which particles exhibit when the gas stream in which they are suspended is constrained to turn abruptly. The particle under suitable conditions cannot follow the stream lines and is impacted against a collecting plate.

1971 Nature 12 Feb. 501/1 Partition of single uredospores between the first and second stage of a cascade impactor indicated a terminal velocity of 0·6 cm s^—1.