In 1948 Varian Associates founded by Russel and Sigurd F. Varian, William Hansen, and Edward Ginzton to sell the klystron, the first tube which could generate electromagnetic waves at microwave frequencies, and other electromagnetic equipment. In 1999, Varian Associates set up Varian Semiconductor for its semiconductor equipment business, and Varian, Inc. for its scientific equipment business. The remaining medical equipment company renamed itself as Varian Medical Systems.