Evolution of the SPS Power Converter Controls towards the LHC Era

By the end of the nineties, the power converter control system (Mugef) of the CERN proton accelerator (SPS) had undergone a complete modernization. This resulted in newly developed hardware for function generation, measurement and I/O in a VME environment, under the LynxOS real-time operating system. This has provided a platform on which extensions can be developed for future operation in the Large Hadron Collider (LHC) era. This paper describes some of these extensions, in particular a fast Surveillance and Interlock system for monitoring the power converter output currents. This will be mandatory for the safe operation of the SPS transfer lines TI2 & TI8 to LHC and for similar applications in the future. The strategies employed to cope with various failure modes of the power converters and the timely activation of the interlock are outlined. The new SPS controls infrastructure now under development, will give rise to new modes of operation for the Mugef systems. Integration with the proposed middleware must be undertaken in a structured evolution, while retaining compatibility with the current usage.Comment: Paper is 3 pages for ICAPEPCS 01 27 - 30 November 2001 San Jose. John C L Brazier is the principal author and a consultant to CERN (hence the CERN Email address but UK Organisation

Evolution in controls methods for the SPS power converters

In common with much accelerator specific material, there is a constant need to improve both hardware and software for power converter control. Maintenance and performance improvements of older systems have become extremely tedious and in some areas impossible. By using modern real-time software and the latest high-performance processors, such problems should be substantially reduced. This paper describes the software concepts and the hardware chosen for the upgrade of the existing facilities. Using the UNIX compatible LynxOS real time kernel, running on a PowerPC 603 in a VME environment, this new approach provides excellent performance while retaining the desired flexibility for future enhancements. The 64 channel system is implemented as a set of cooperating processes, several of which are multi-threaded. Processes include analogue function generation, analogue measurement and digital I/O, all of which are accurately scheduled by the accelerator timing system. This generalised structure, which performs complex sequences of operations is described in detail, as well as how it can be adapted to a wide variety of accelerator tasks

The All-digital Approach to LHC Power Converter Current Control

The design of the LHC machine imposes severe demands upon the control of current in the 1700 magnet circuits. This has required the use of novel methods for the control of individual power converters and of the magnet current control system as a whole. This paper will review the chosen hardware and software methods and architectures. The digital regulation techniques used to achieve the overall targets for short-term stability (<3ppm) and reproducibility (<10ppm) of the 24 principal LHC circuits will be discussed. While the proposed system architecture will follow the canonical three-layer design, so successfully exploited in LEP, the software will be far from traditional. This software must be more reliable and maintainable than ever before, and will need to integrate with advanced object-oriented applications via commercial middleware. These challenges will be faced by applying object-oriented techniques throughout the system and by harnessing the power of XML for system definition

A statistical interpretation of the correlation between intermediate mass fragment multiplicity and transverse energy

Multifragment emission following Xe+Au collisions at 30, 40, 50 and 60 AMeV has been studied with multidetector systems covering nearly 4-pi in solid angle. The correlations of both the intermediate mass fragment and light charged particle multiplicities with the transverse energy are explored. A comparison is made with results from a similar system, Xe+Bi at 28 AMeV. The experimental trends are compared to statistical model predictions.Comment: 7 pages, submitted to Phys. Rev.

Circumstantial Evidence for a Critical Behavior in Peripheral Au + Au Collisions at 35 MeV/nucleon

The fragmentation resulting from peripheral Au + Au collisions at an incident energy of E = 35 MeV/nucleon is investigated. A power-law charge distribution, $A^{-\tau}$ with $\tau \approx 2.2$, and an intermittency signal are observed for events selected in the region of the Campi scatter plot where "critical" behavior is expected.Comment: 11 pages, RevTex file, 4 postscript figures available upon request from [email protected]

Searching for the Nuclear Liquid-Gas Phase Transition in Au + Au Collisions at 35 MeV/nucleon

Within the framework of Classical Molecular Dynamics, we study the collision Au + Au at an incident energy of 35 MeV/nucleon. It is found that the system shows a critical behaviour at peripheral impact parameters, revealed through the analysis of conditional moments of charge distributions, Campi Scatter Plot, and the occurrence of large fluctuations in the region of the Campi plot where this critical behaviour is expected. When applying the experimental filters of the MULTICS-MINIBALL apparatus, it is found that criticality signals can be hidden due to the inefficiency of the experimental apparatus. The signals are then recovered by identifying semi-peripheral and peripheral collisions looking to the velocity distribution of the largest fragment, then by selecting the most complete events.Comment: RevTex file, 21 pages + 19 figures available upon request from [email protected]

Non-Thermal Behavior in Multifragment Decay

This research was sponsored by the National Science Foundation Grant NSF PHY-931478

Assessing the Evolutionary Nature of Multifragment Decay

This research was sponsored by the National Science Foundation Grant NSF PHY-931478