Comparison of spatter ejection for SS316L and Ti64 powder in 10−3 Torr Vac and 760 Torr Ar over 5 ms time frame. (a) Histogram of brightness which is taken as the sum of the total number photons (“N total”) above the background with bin size = 255. “Mean, Std, Min, Max” on the Table, indicates the mean, standard deviation, minimum and maximum brightness. For SS316L, in Ar, there are 5 × more ejections that appear with 2 × higher intensity. Ti64 had more ejections than SS316L in Ar and vacuum. Experimental images recorded for SS316L and shown in (b) argon and (c) vacuum were taken at a camera frame rate of 100 kfps and an exposure time of 8 μs. Laser power P = 200 W, scan speed u = 1.5 m/s.