Description of the RHIC Sequencer System

The movement of the Relativistic Heavy Ion Collider (RHIC) through its various states (eg. injection, acceleration, storage, collisions) is controlled by an application called the Sequencer. This program orchestrates most magnet and instrumentation systems and is responsible for the coordinated acquisition and saving of data from various systems. The Sequencer system, its software infrastructure, support programs, and the language used to drive it are discussed in this paper. Initial operational experience is also described.