Beck, F

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THE OPERATOR INTERFACE OF THE 300 GeV ACCELERATOR F. Beck CERN Lab II, Geneva, Switzerland The new CERN accelerator is controlled through a large computer network with the help of a specially designed real-time interpretive language. This has enabled the problem of designing an operator interface to be separated from that of producing control mechanisms. The paper discusses the appearance of this inter-face, and some of the facilities which it will provide for machine operators. Introduction The new accelerator to be built by CERN will be almost exclusively computer-controlled. That is, all remotely-controllable or remotely-monitored functions of the machine can be accessed by executing suitable interpretive statements in one more central computers. It is not the purpose of this paper to describe the mechanism of this control (see paper by T. Hyman in these proceedings), but rather to explain how it has enabled us to make certain very desirable innovations at the operator interface. Purpose of the Control Room The control room is used for two distinct functions when the accelerator is running: One is to supervise the machine when it is running and to make small operational adjustments. At such times there may well be only one operator in the control room. The other use of the control room is for the so-called machine physics studies, where several groups of workers may be operating more or less independently on different parts of the accelerator. A third use of the control room is when the accelerator is temporarily shut down. Safety requirements dictate the need for some hard-wired circuits, but these can be augmented by computer control to give extra flexibility when the computer is available. The Consoles The machine physics and supervision functions can be fulfilled by supplying a number of consoles with controls and displays on them. Each console is inter-faced to the control system by means of its own computer, and the consoles are interchangeable in every way, taking their individual functions on a temporary basis from the control program currently loaded. This interchangeability means that the breakdown of one console or its computer reduces the flexibility of the rest of the system, but leaves it workable. The committment to identical facilities on each console places a premium on multi-purpose equipment, and strictly excludes any item specifically dedicated to one piece of hardware on the accelerator. The number of consoles is not difficult to decide. In view of the price of having a computer per console, it should be as small as possible. The requirement to have several teams working at once implies several consoles. Three was decided on as a practical compromise. Control-room layout Thus we arrive at a central control complex with three identical consoles and a personnel access desk, and a computer room next door containing the central part of the control equipment, including eight mini-computers (three console computers, a display computer, a library computer, a computer to handle alarms, a service computer, and one which does message-switching for the whole control system). The control room itself, except for a silent printer and some wall displays, contains nothing else. Fig. 1 gives the general layout. Design of the Console The console itself is designed to allow access to everything by a seated operator. There is a nearly vertical surface for diplays, a nearly horizontal surface for controls, and a table-top. Everything is in 19-inch rack units for convenience, and the console is arranged in a gentle curve with 20° between successive rack elements. With five units in the curve an operator sitting at the middle unit can see and reach everything and two or three people can stand behind him, or he can move over for a colleague to sit beside him. It was proved to be possible to design the console so that the table-top can clear the operator's knees, and for him simultaneously to see wall-displays and other consoles over the displays on his own. Fig. 2 shows the general form of the console which will be used. Two multi-purpose devices enable us to keep the number of controls on the console small. One is a general purpose knob which can be changed under program control to one of various types of control devices and the other is a set of touch-buttons with programmable legends which can be used to choose from a programmable selection of possibilities with a touch of the finger. Displays The general-purpose displays are standard TV monitors, some in colour and some in black and white. All pictures are in the form of 625-line, 50 frame-per-second raster signals, and are driven from an external synchronisation line. Addition of certain pictures is possible, up to three pictures contributing to any monitor input. Possible sources of pictures are CCTV, dot-pictures on 1024 × 625 mesh from scan converters, a computer-driven cursor and 64 × 24 character arrays in up to four colours. Picture-sources and monitors are connected to a computer-controlled video crossbar with summing amplifiers, and the effect of this is to enable the operator to allocate any screen for the output of his program. This picture can subsequently be moved or copied on operator request to any other screen in the system, as well as to remote lines and to a printer (See Fig. 3). 499 The program which does the video switching is driven by the programmable touch buttons, but the monitors are identified by a single button under each. Thus on touching the button marked "move", the operator is presented with the question "which picture do you want to move?" and then by the question "where do you want to move this picture?". In each case identification is done, if possible, by pressing the identifying button under the screen in question. When this is not possible, as with moves to remote buildings or to a printer, a touch-button is temporarily dedicated to each such purpose. Hard Copy Hard copy is obtained by channeling the chosen signal to a special device which traps each TV line sequentially in a 1024 - bit buffer and uses the next TV frame time to read it into a computer, which prints it on a xerographic dot-printer. In the absence of buffering, which is not currently envisaged, only one picture at a time may be requested on the general-purpose printer, which is silent. A frame will take about 10 seconds to print. Wall Displays In addition to the displays on the console, displays are also provided on the wall. Projection TV has been considered, but requires a rather low ambient light level as well as having a rather restricted life. At the moment large TV monitors are being considered. These can be in colour, and by supplying two or three on the front wall and one especially for visitors looking in on the double height control room from windows on the top floor, it may be possible to avoid the use of projection TV. Information which changes only rarely may be displayed on indicators of the airport "flap" type, which can now be obtained in a relatively silent version with a full 64-character facility. We are still looking into alternative methods of displaying large characters. Analog Signals The general layout of the consoles and the electrical interconnections between the components is shown in Fig. 3. The four-beam oscilloscopes available on each console can be connected to chosen remote lines by a computer-controlled switch, the operator can make such connections by means of a touch panel dedicated to this purpose, and a display gives the names of the signals currently connected. Ambient Conditions Accoustical disturbances to the operator's concentration will be avoided where possible. The air conditioning system is isolated from the control room by concrete walls without doors, except for the necessary under-floor and over-ceiling ducts. By careful use of the pressure difference from this system it is hoped to dispense with the use of cooling fans in most, if not all of the equipment in the consoles. A xerographic printer has been found which is silent. The typing machine on the safety desk will be chosen with this characteristic in view. The walls and floor of the control room will have finishes chosen for sound absorption. Lighting will in general be at a low level, in order to allow the displays to have their maximum effect. A light-lock system using circularly polarized light and suitable filters over the display screens is being investigated. This, if successful would enable the desk tops and the printer to be adequately illuminated without destroying thecontrast of the displays. Use of the System The major test of the control room and its system is - will it allow an accelerator to be controlled? The answer, judging from experience of systems of this kind at NAL, SLAC, LAMPF and elsewhere, is that the degree of control available can be made to approach that of a hard-wired system but not to equal it. Using the knob, the ball, the touch-buttons and the graphics system, a program for the control and monitoring of a subsystem can be written quite quickly. Such a program will be written in interpretive language, usually by a worker engaged with the subsystem, rather than by a central controls programmer. A general selection program makes all such subsystems available at the touch of a button. The real-time monitor in each console computer makes it practical to launch a monitoring or data-collecting program which will run while the operator performs other operations, reporting its results on one of the many screens in the system. At all times an alarm computer processes reports of unusual conditions and transmits them to a dedicated screen on each console. Thus the operator can have an overview of the entire accelerator while he is studying one subsystem. Will the system work? Most individual components of the control-room system have now been tested singly. The interpretive language and its hardware interfaces work. All components of the graphics system have been demonstrated. The message transfer system connecting the console computer to the rest of the system, including the library and graphics facilities which are properly part of it, is the only component which is at the current state of the art, but its specification is very conservative. The greatest risk inherent in a system of this kind is the basic one that the overall reliability of such a lot of electronic hardware may be below a tolerable level. This risk is known, and attempts have been made to reduce it byvarious features of the design. There are undoubtedly those who regret the passing of the old type of control room, with its racks of specialised controls each dealing with a subsystem. With a machine of this size, even if it were economically realisable , the indications are that a control system of this type will in the end actually prove to be more convenient for the operator seeking either an overview of the whole machine or control of particular parts of it. 500 Fig. 1 General Layout of Control Room Fig. 2 General Form of Console 501 Fig. 1 General Layout of Consoles and Electrical Interconnections between Components 502 

The operator interface of the 300-GeV accelerator

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