P. D. V. van der Stok

A Method for Increasing the Multiturn Injection Efficiency in AG Proton Synchrotrons by Means of Skew Quadrupoles

An increase of the injection efficiency due to linear coupling [already known at the Cosmotron in 19531)] is shown to work in AG Proton Synchrotrons for QH - QV = P. The system is in operational use at the CERN Proton Synchrotron Booster (PSB) to reach intensities above 1013 ppp. An intensity increase of 20% is achieved at the expense of a slight vertical blow-up, which is however not noticeable for high-intensity beams as their emittance is already increased because of an integer stop-band. In this paper a comprehensive model is presented, which describes the efficiency as a function of several parameters, such as the coupling strength, injection geometry and Q-values. Provided enough vertical acceptance is available, the same scheme may be profitable for other accelerators using betatron stacking for |QH - QV - P| < 0.1; ¿H >> ¿V.

An Interpretive Approach for Interactive Real-Time Control Through a Network

Abstract The CERN Super Proton Synchrotron (SPS) accelerator represents a large industrial control problem, with the additional complication that the control strategies are not fixed. Right from the beginning, it was decided to use an interpretive language for the control process. The main goal of this approach was to reduce the amount of programming effort needed for a proper control of the accelerator, by allowing the actual users — physicists, engineers and technicians — to write the control programs they needed. It very quickly appeared that this method was ideal for providing interactive tools for a control system based on a network. The requirement for interactive network control has been implemented by leaving to the user the choice of those parts of the network best suited for the execution of sections of his program. For that reason interpreter instructions have been defined, allowing the user to define where in the network a logical unit of his algorithm should be executed, and where individual items of the data should be stored. This strategy allows easy access to all the hardware through a distributed data-base. The interpreter being basically a string handler, equipment control can be packed into a module which is called from the program through a name with a standard input-output scheme. All this allows algorithm exportation, while network transfers are minimized. Such a system has been in operation since 1976. Many non-professional programmers are regularly writing or modifying ‘network procedures’ for ever-changing control purposes. The simplicity and flexibility of the interpretive method has enabled many technical innovations to be installed over the years, and some of these are described.

The Message Architecture of the LEP Control System

The LEP control system will be constructed as a global communication system where microprocessors will be used everywhere, from the management of the communication mechanisms, the execution of complex control procedures, and the supervision of the equipment. To achieve this, the global control problem has been cut into sizeable functions which will be encapsulated into microprocessor modules containing enough hardware for the function to be mostly self-contained. This leads to a function architecture where messages are exchanged between the functions on miscellaneous media. It will be shown how these message exchanges can be organized into a uniform flow of data all through the system.

ESSENTIAL FEATURES OF THE CERN SPS DISTRIBUTED CONTROL SYSTEM

ABSTRACT The SPS accelerator presents a considerable industrial control problem with the additional complication that the control procedures are never fixed. Right from the beginning it was decided to base the control system on a distributed network making use of an interpretive language for the control processes. The success of these decisions can be seen from the fact that over the last six years, the system has grown to a network of more tha~ 50 computers spread over a ten square kilometer site, all the time controlling an ever-changing accelerator complex. This paper will discuss the major elements of the strategy used and explain the reason for their choice. Microprocessors have become very popular in the field of. industrial control and the SPS control system is going to integrate this trend with little difficulty. The paper will show that the SPS approach is ideally suited to the construction of a real-time control network making use only of microprocessor based units.

A Simple Model for Multiturn Injection into A.G. Proton Synchrotrons

Analytical expressions are derived in order to compute the optimum injection parameters for betatron stacking into a chosen fraction of the total accelerator acceptance in the Q range N + 0.1 ? Q ? N + 0.9. The example of the CERN PS Booster (PSB) is worked out. The efficiency of the process is calculated using standard numerical integration algorithms with a Gaussian distribution of the incoming beam. Other types of distribution can also be dealt with. The results show that the installation of pulsed dipole and quadrupole supplies to obtain steering and focusing conditions which vary during the injection process will improve the injected current by only 3% in the case of the PSB. The measured performance of the PSB injection system is reported and compared with model prediction. Estimates of injected currents prove to be about 10% higher than the actual values. Some considerations on the influence of space-charge forces, which might explain this effect are presented.