Controlling LEP/SPS accelerator equipment

Abstract

An object-oriented design for the distributed computer control system of the LEP/SPS rings is presented. A generic High Energy Physics design is presented that is inherited by a concrete design for the beam loss monitors subsystem. I. SUMMARYThe pilot project for a new design of the software of CERN's LEP/SPS control system is described. The main deliverables produced during this project are: 0 An object-oriented design for generic access to LEP/SPS HEP (High-Energy Physics) equipment.0 An implementation/specialization of this design for Beam Loss Monitors one type of equipment, viz. (BLMs).The design follows the OMT method [l]. The general design principles developed in 121 have been used as starting point. A generic object model is created which represents a possible accelerator-complex. This model is used (inherited) for the definition of the object model of a subsystem (BLMs) of the SPS/LEP accelerators. The dynamic behavior of the BLMs is modelled with state diagrams. ACCELERATORSIn the following subsections, a short description is given of the SPS and LEP accelerators. A. The Super Proton Synchrotron (SPS)The SPS is a large particle accelerator which has been operational since 1976 [3]. During the first ten years , it has operated mainly in a mode where particles are accelerated to high energy and then extracted to experiment zones. Since the coming of a larger accelerator, the LEP, the SPS also serves as an injector to LEP [4]. Specifically, it is now required to perform a series of injection-accelerationextraction cycles in a repetitive fashion. Such a sequence is called an elementary cycle. 0018-9499/96$05 B. The Large Electron-Positron Storage RangThe LEP [5] storag,e ring is newer and larger than the SPS: it has been operational since 1989. The LEP is a storage ring collider. Such a collider offers possibilities for performing experiments with head-on collisions between two equal particles or a particle and its anti-particle.In the LEP accelerator, two particle beams, one made up out of electrons and the other out of positrons are counterrotating inside a single ring. GENERIC (~B J E C T MODEL OF LEP/SPS E~QUIPMENT CONTROLA hierarchical class model is made to reflect the control structure of the accelerator complex. A . AnalysisThe LEP/SPS machine is considered to be the top level in the control structure. The LEP/SPS machine consists of four main parts: 0 accelerators, 0 transfer lines: a transfer line is a vacuum pipe that connects two accelerators or an accelerator and an experiment zone, 0 extraction zones: an extraction zone is a part where equipment is situated for taking particles from an accelerator towards a transfer line, 0 intersection points: an intersection point is a spot where two counter-rotating beams of particles intersect, usually collider experiments are performed at these spots.Every cited part consists of a number of subsystems, like a vacuum subsystem or a beam observation subsystem. Each of these subsystems contain equipment. Within a subsystem, this equipment is controIled by o...