Recommendations for the Use of Programmable Logic Controllers (PLCs) at CERN

Programmable Logic Controllers (PLCs) have been increasingly used at CERN for several years. In future control solutions, PLCs will initially be considered for the rejuvenation of old and obsolete systems, and then for the control of new equipment to be installed in technical services, accelerators and experiments. Many industrial systems will be installed for the control of equipment during the next 5 to 10 years, particularly for the construction of the LHC project. In order to increase efficiency, to reduce the initial investment and to minimise the long term maintenance costs in terms of money and human resources the Working Group recommends that all CERN equipment control projects, based on PLCs, select or specify PLCs from the product lines of the recommended PLC manufacturers

Thermohydraulics of Resistive Transitions of the LHC Prototype Magnet String: Theoretical Modeling and Experimental Results

In preparation for the Large Hadron Collider (LHC) project, a 40 m-long prototype superconducting magnet string, representing a half-cell of the machine lattice, has been built and operated. The superconducting magnets which comprise this string normally operate in a pressurized static bath of superfluid helium at a pressure of 1 bar and at a temperature of 1.9 K. At 13.1 kA they have about 15.3 MJ of stored magnetic energy. A series of tests was performed to assess the thermohydraulics of resistive transitions (quenches) of the string of magnets. These measurements provide the necessary foundation for describing of the observed pressure rise as the combination of two processes, each acting on a different time scale. The measurements are presented and an explanatory model description of the events is given

The LHC test string: first operational experience

CERN operates the first version of the LHC Test String which consists of one quadrupole and three 10-m twin aperture dipole magnets. An experimental programme aiming at the validation of the LHC systems started in February 1995. During this programme the string has been powered 100 times 35 of which at 12.4 kA or above. The experiments have yielded a number of results some of which, like quench recovery for cryogenics, have modified the design of subsystems of LHC. Others, like controlled helium leaks in the cold bore and quench propagation bewteen magnets, have given a better understanding on the evolution of the phenomena inside a string of superconducting magnets cooled at superfluid helium temperatures. Following the experimental programme, the string will be powered up and powered down in one hour cycles as a fatigue test of the structure thus simulating 20 years of operation of LHC