Study of the unified control system of the magnets in the KEKB/PF-AR accelerators

KEKB is a double-ring, asymmetric-energy, electron-positron collider, which is pursuing luminosity frontier. In order to improve its luminosity, commissioning has been continued incessantly. Because various machine tunings are frequently necessary during the commissioning, the control system is required to be highly responsive and flexible. Especially for the magnets and magnet power supplies, which define optics of the accelerators, the efficiency and flexibility of the control system are essentially important. To achieve these requirements the design and the construction of the control system of the magnet power supplies have been carried out with the following view points. The most important point is the unified treatment of the magnet power supplies. KEKB has wide variety of the magnet power supplies, from the large power supplies for the main bending magnets to the small power supplies for the steering magnets. The bending magnets, quadrupole magnets, sextupole magnets and steering magnets require different type of power supplies and are operated in the different manner. The magnet can be iron core or air core, superconducting or normal conducting, with or without auxiliary windings, and so on. There are many different types of the magnet power supplies, in the scale, in the regulation scheme, bipolar or unipolar, with or without pole changer, and so on. Although such differences exist, focusing on the common properties of the magnet power supplies, the hardware of the interface and the software of the control system have been designed not separately for each type but designed as universal for the all types as possible. Another important point is reliability. Although resources of the budget and the man power to construct KEKB have been limited, it has been required to keep the control system reliable. Not only in the construction phase but also in the maintenance phase, reliability should be considered. In order to maintain reliability in such conditions, the design strategy adapted is simplification. Especially it is important how to simplify the interface to the magnet power supply with the control computer. It greatly influences the reliability of the control system. In the previous, TRISTAN, control system CAMAC was adopted as the standard interface. Between the CAMAC module and the magnet power supply there were wired signal lines for each signal one by one. If KEKB adopted the same scheme, the amount of wires could be huge because the number of magnet power supplies in KEKB is large, more than double. In KEKB, instead of the parallel wiring, one serial line has been introduced for a magnet power supply. All signals are exchanged through the single serial line. Thus, considering unification and simplification as the important principles, the magnet power supply control system has been developed. There are two major tasks in the development. One is the development of the interface between the control computers and the magnet power supplies. The other is the development of the control software. KEKB control system has adopted EPICS (Experimental Physics and Industrial Control System) as the core software framework. And two types of computers have been installed. One is IOC (Input/Output Controller), which directly controls the equipments through its own hardware connection to the equipments.　The other is OPI (Operator Interface), which runs various high level applications like operator interface. The synchronous operation of multiple magnet power supplies is required in order to change optics without loosing stored beams. For this purpose, the synchronous setting has been designed that the tracking data are calculated in the IOC and sent to the magnet power supply beforehand and then the synchronous start signal triggers the synchronous tacking. In this method the magnet power supply is required to store the array data for the tracking and to set them in sequence with the interval clock. Although it requires some intelligence in the magnet power supply, total system can be simplified and flexible operation is possible. ARCNET (Attached Resource Computer NETwork) has been adopted as the serial interface. It supports relatively long packet and communication speed is enough for our purpose. The twisted-pair cable with RS485 type differential driver has been chosen as the media of ARCNET. This configuration allows multi-drop wiring. The synchronous start signal is also delivered by the cable combined with ARCNET. Thus, the simplification of the wirings has been achieved. For the implementation of the ARCNET interface, the PSICM (Power Supply Interface Controller Module) has been developed. It is the plug-in module in the magnet power supply and has an ARCNET interface and a microcomputer with the control software (firmware). PSICM has been designed to be universal for any type of the power supplies. All of the magnet power supplies can be controlled in single manner using PSICM. In the development ...

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