Controls for the vacuum system of LEP

Abstract

The very large size (27-km circumference) of LEP (CERN Large Electron Positron storage ring) makes it mandatory to provide extensive remote control for installation, commissioning, and operation. The control facilities will be available both at fixed locations and in the form of mobile consoles which will follow the installation teams. All operations must be accessible to vacuum technicians, who may have little or no computing knowledge. Therefore, menu driven consoles, using a screen and light pen, will be made available to the operators. The large number of pumps, gauges, and valves makes it necessary to find solutions to reduce the cabling costs. An original way of powering the sputter ion pumps uses a single power supply and cable for up to eight pumps, yet allows individual current monitoring for each pump. An ionization gauge power supply for eight heads is economical and saves rack space by multiplexing the ion currents while powering and regulating continuously all filaments. All power supplies must be integrated in the general control system of the LEP machine. This is done by using so-called intelligent equipment controllers, which exchange messages with the main control room by a network of multidrop buses. A sophisticated data base management system is required in order to keep track of the numerous items connected to the vacuum system.