Cymer Inc., a supplier of excimer light sources used in semiconductor manufacturing, announced it shipped its new XLA 100 argon fluoride (ArF) light source to a leading lithography system supplier on Feb. 1. The company said it has also received orders for the XLA 100 light source from three lithography system suppliers, to be delivered in the first quarter of this year.   . . .   Essex Corp., a developer of signal processing algorithms and optical solutions for defense and intelligence applications, announced that retired Rear Adm. Don H. McDowell is joining retired US Army Lt. Gen. Claudia J. Kennedy and retired US Air Force Lt. Gen. Kenneth A. Minihan on the Essex National Programs Advisory Board. The board "provides strategic guidance on the application of Essex technology and products to solve high-priority national security problems and requirements," Essex said.