Michel Rabany

Equipment industrially controlled

Abstract With its chain of accelerators and its large experimental physics detectors, CERN is one of the worlds most important research centres for particle physics. CERN builds and operates a number of classical and advanced technical utilities to serve its research activities. These utilities are generally equipped with industrial control components purchased with the equipment itself. This paper describes some of the utilities and their controls and proposes a strategy for the integration of diverse industrial control systems into a coherent industrial environment of communication and supervision.

The beam synchronous timing system for the LEP instrumentation

Abstract The beam instrumentation group of LEP has constructed a number of detectors distributed around the collider: these instruments are interfaced to approximately 100 VME-based computers which acquire and process data autonomously. In order to ensure the coherence of a measurement and to correlate measurements of different instruments, it is essential that the data are acquired at the same moment on all the systems. The beam synchronous timing system ensures this by broadcasting messages that describe to all instruments the action to be performed. The instructions are guaranteed to arrive at exactly the same moment to all stations around the 27 km circumference by careful compensation of the delay for each station. The heart of the system is a commercial 25 MHz 68020-based VME module coupled to an in-house designed message assembler: these are able to synthesize instructions for up to six different kinds of instruments in a single LEP revolution (89 μs). Each listening station provides the hardware with pulses derived from the incoming message, filters the messages according to the addresses and passes them to real-time tasks which set the hardware or acquire the data. A reverse channel, peripheral station to the control room, allows up to eight different signals to inform the master of locally detected events such as beam loss or high background. Special recovery instructions can then be broadcast.

A distributed-data acquisition and monitoring system for the beam instrumentation of LEP

Abstract The beam instrumentation for LEP is comprised of a number of detectors such as current transformers, split-foil monitors, interaction and background monitors and electrostatic pickups. These instruments are interfaced using about 100 VME crates spread over 25 stations located around the 27 km circumference of LEP. The crates are connected to the control system using MIL/STD-1553, an Olivetti M380 running XENIX and an IBM token-ring. Each crate is equipped with a Themis TSVME106 CPU board which runs the Motorola RMS68K operating system kernel. A set of services (alarms, communications, I/O system, libraries, log book, timing, etc.) has been implemented and constitutes a comfortable environment for the application programs. Most of the programming is done in PASCAL, using a cross compiler developed and maintained at CERN. A set of utilities running in the Olivetti M380 and in the crates provides system monitoring, system and application reload, and surveillance of the behaviour of the system and of the application task.

Specification, installation and commissioning of a large industrial control system for the LEP2 cryogenics

Abstract CERN is upgrading the LEP e+-e− collider for energies above the Z0 particle by installing super-conducting cavities. The cryogenic system attached to these cavities is controlled by a distributed, industrial control system, having been the object of a tender. The issues relate to the software specification, the management of the contract, the installation and the gradual commissioning of the system. The experience with a fully farmed- out solution is reported.

Drift chamber electronics with multi-hit capability for time and current division measurements

Drift chambers have been installed for luminosity measurements in intersection 5 of the SPS accelerator working in pp colliding mode. The required electronics is described. The system is able to process up to 16 hits per wire with a double pulse resolution of 40 ns; drift time and current division, with 1.25 ns and 1.6% resolution respectively, are recorded. Transconductance preamplifiers and discriminators are directly mounted on the chamber; 160 m of twisted-pair cable bring the signals to the digitizer unit. Coarse time is measured using RAM techniques, while fine time is obtained by means of a microstrip delay associated with a 100 K ECL priority encoder. Current division used a single 50 MHz Flash ADC which allows 26 dB dynamic range with 6 bit resolution. First operational results are reported.

A Fast Sparse-Data-Scan System Using CAMAC Compatible Elements

Hodoscopes are used to measure the momentum of individual particles of the high intensity CERN SPS Muonbeam. They are read out through the fast Sparse-DataScan System described below which can be shared among several users.

Spectrometer Instrumentation for CERN SPS Secondary Beams

At the CERN SPS (Super-Proton-Synchrotron) most of the secondary beams are provided with a momentum measuring section. Each spectrometer consists of four multiwire proportional chambers with a fast readout system allowing a multi-user access. The chambers are operated with an Ar/CO2/ Freon gas mixture so as to withstand beam intensities of ¿ 107 particles/s with efficiency close to 100 % and without significant ageing effects. The system, being fully computer-controlled, has a fast diagnostics capability through a powerful software.

The Orbit Measurement System of the CERN 800 MeV PS Booster

Previous experience at CERN led to the choice of an electrostatic type sensor; different types have been rnvisaged3: circular, elliptic, parallelepipedic (rectangle, square, rhomb) , Among various possible locations within a period the interior of the multipoles offers the maximum length and the circular cylinder is well suited to the shape of the beam there. One C electrode and one set of vertical and horizontal electrodes are all located on a same “pick-up electrode”.

Use of real-time kernels in process control: An application to beam instrumentation

Abstract Process-control system components have evolved from a state where they provided a simple digital and analog interface to the world, to very sophisticated dedicated computers offering a service. The software in these devices has followed the same evolution: on the one hand it has continued satisfying the real-time constraints dictated by process control, on the other hand it has coped with the complexity of the fully developed computer system which it has now become. The beam instrumentation of LEP consists of several types of instruments ion which are distributed over the whole perimeter of the collider and are interfaced to the control system using approximately 100 VME crates. Since most of the applications needed the same type of facilities, protection mechanisms and systems services, it seemed justified to provide a common environment to all. The embedded applications environment is built around a commercially available operating-system kernel and provides services such as alarm management, communications, logbook, etc. The design goals and benefits of this approach and the description of this environment are discussed.

The readout system for the multiwire proportional chambers of the CERN SPS secondary beams

Abstract To provide CERN-SPS experiments with accurate momentum measurement of incoming beam particles associated to their events, we had to take into consideration the high fluxes in the secondary beams ( 7 pps) and the multi-user access to the spectrometer data. The very fast readout system described here, permitting decisions at several levels, fulfills these requirements.