Kenneth Ross MacKenzie (June 15, 1912 &ndash; July 3, 2002) was an American nuclear physicist. Together with Dale R. Corson and Emilio Segrè, he synthesized the element astatine, in 1940.  MacKenzie received his PhD under Ernest Lawrence at Lawrence Livermore National Laboratory. Lawrence, MacKenzie, and their colleagues devised the first cyclotron.  
MacKenzie was a professor of physics at the University of California, Los Angeles (UCLA), where he and Reg Richardson built UCLAs first cyclotron and later a bevatron.  MacKenzie devised MacKenzie buckets which are plasma sources created by lining vacuum chamber walls with permanent magnets of alternating polarity to suppress plasma electron losses, that are widely used to this day.  He later traveled around the world, helping to troubleshoot various countrys cyclotron problems.  Later in life, he studied plasma physics and dark matter.