Martin R. Kraimer

The Experimental Physics and Industrial Control System architecture: Past, present, and future

Abstract The Experimental Physics and Industrial Control System (EPICS), has been used at a number of sites for performing data acquisition, supervisory control, closed-loop control, sequential control, and operational optimization. The EPICS architecture was originally developed by a group with diverse backgrounds in physics and industrial control. The current architecture represents one instance of the “standard model”. It provides distributed processing and communication from any local area network (LAN) device to the front end controllers. This paper presents the current architecture, performance envelope, current installations, and planned extensions for requirements not met by the current architecture.

CCD sensors in synchrotron X-ray detectors

Abstract The intense photon flux from advanced synchrotron light sources, such as the 7-GeV synchrotron being designed at Argonne, require integrating-type detectors. Charge-coupled devices (CCDs) are well suited as synchrotron X-ray detectors. When irradiated indirectly via a phosphor followed by reducing optics, diffraction patterns of 100 cm 2 can be imaged on a 2 cm 2 CCD. With a conversion efficiency of ∼ 1 CCD electron/X-ray photon, a peak saturation capacity of > 10 6 X-rays can be obtained. A programmable CCD controller operating at a clock frequency of 20 MHz has been developed. The readout rate is 5 × 10 6 pixels/s and the shift rate in the parallel registers is 10 6 lines/s. The test detector was evaluated in two experiments. In protein crystallography diffraction patterns have been obtained from a lysozyme crystal using a conventional rotating anode X-ray generator. Based on these results we expect to obtain at a synchrotron diffraction images at a rate of ∼ 1 frame/s or a complete 3-dimensional data set from a single crystal in ∼ 2 min. In electron energy-loss spectroscopy (EELS), the CCD was used in a parallel detection mode which is similar to the mode array detectors are used in dispersive EXAFS. With a beam current corresponding to 3 × 10 9 electron/s on the detector, a series of 64 spectra were recorded on the CCD in a continuous sequence without interruption due to readout. The frame-to-frame pixel signal fluctuations had σ = 0.4% from which DQE = 0.4 was obtained, where the detector conversion efficiency was 2.6 CCD electrons/X-ray photon. These multiple frame series also showed the time-resolved modulation of the electron microscope optics by stray magnetic fields.

CCD-based synchrotron x-ray detector for protein crystallograph-performance projected from an experiment

The intense x radiation from a synchrotron source could, with a suitable detector, provide a complete set of diffraction images from a protein crystal before the crystal is damaged by radiation (2-3 min). An area detector consisting of a 40 mm dia. x-ray fluorescing phosphor, coupled with an image intensifier and lens to a CCD image sensor, was developed to determine the effectiveness of such a detector in protein crystallography. The detector was used in an experiment with a rotating anode x-ray generator. Diffraction patterns from a lysozyme crystal obtained with this detector are compared to those obtained with film. The two images appear to be virtually identical. The flux of 10/4 x-ray photons/s was observed on the detector at the rotating anode generator. At the 6-GeV synchrotron being designed at Argonne, the flux on an 80×80 mm2 detector is expected to be ≫ 109 photons/s. The projected design of such a synchrotron detector shows that a diffraction-peak count ≫ 106 could be obtained in ˜0.5 s. With an additional ˜0.5 s readout time of a 512×512 pixel CCD, the data acquisition time per frame would be ˜1 s so that ninety 1o diffraction images could be obtained, with approximately 1% precision, in less than 3 min.

Status and design of the Advanced Photon Source control system

This paper presents the current status of the Advanced Photon Source (APS) control system. It discusses the design decisions which led us to use industrial standards and collaborations with other laboratories to develop the APS control system. The system uses high performance graphic workstations and the X-windows graphical user interface (GUI) at the operator interface level. It connects to VME/VXI-based microprocessors at the field level using TCP/IP protocols over high performance networks. This strategy assures the flexibility and expansibility of the control system. A defined interface between the system components will allow the system to evolve with the direct addition of future, improved equipment and new capabilities.<<ETX>>

Experience with EPICS in a wide variety of applications

Currently more than 70 organizations have obtained permission to use EPICS, a set of software packages for building real-time control systems. In this paper representatives from four of these sites discuss the reasons their sites chose EPICS, provide a brief discussion of their control system development, and discuss additional control system tools obtained elsewhere or developed locally.

PLUME RISE DETERMINATION: A NEW TECHNIQUE WITHOUT EQUATIONS.

Information on plume rise is important in determining the resulting concentrations of a pollutant on the ground. Practical use of plume rise values may be made in connection with stack design, the use of urban air pollution models, and in evaluating the hazards to a population complex. This paper presents a new equationless technique for estimating plume rise as well as a comparison of seventeen commonly used plume rise formulas. Data from 10 sets of experiments, involving 615 observations and 26 different stacks, were used to study the relation between plume rise and related meteorological and stack parameters. An independent data set was used to test the derived methods for determining plume rise. These data were obtained by Bringfelt of Sweden and contained measurements from stacks smaller than that at the Argonne National Laboratory to those approaching the TVA stacks. A significant improvement in the prediction of plume rise from meteorological and stack parameters resulted from the use of a new tech...

Data Acquisition and Control System for the IPNS Time-of-Flight Neutron Scattering Instruments

The Argonne Intense Pulsed Neutron System (IPNS-I) presently under construction at Argonne National Laboratory will include a number of neutron scattering instruments. This paper investigates the data acquisition requirements of these instruments and proposes three alternative multiprocessor systems which will satisfy these requirements. All proposals are star configurations with a super-mini as the central node or HOST. The first proposal is based on front-ends composed of two or more 16-bit microcomputers, the second proposal is based on front ends consisting of a combination of a mini and microcomputers, and the third is based on a minicomputer with an intelligent CAMAC controller.

The Advanced Photon Source control system

The Advanced Photon Source (APS), along with its injection accelerators, is to be controlled and monitored with a single, flexible, and expandable control system. The control system must be capable of operating the APS storage ring alone, and in conjunction with its injector linacs, positron accumulator, and injector synchrotron for filling as well as operating both storage ring and injection facilities as machines with separate missions. The control system design is based on the precepts of high-performance workstations as operators consoles, distributed microprocessors to control equipment interfacing and preprocess data, and an interconnecting network. The current design includes about 45 distributed microprocessors and five console systems, which may consist of one or more workstations. Hardware and software organization is discussed for this control system.<<ETX>>

I/O subnets for the APS Control System

Although the Advanced Photon Source Control System allows for microprocessor-based input/output controllers (IOCs) to be distributed throughout the facility, it is not always cost-effective to provide such capability at every location where an interface to the control system is required. For greatest flexibility, the subnets must support connections to equipment that requires several discrete I/O points, connections to GPIB and RS232 instruments, and a network connection to custom designed intelligent equipment. An approach is described that supports all of these interfaces with one subnet implementation, BITBUS. In addition to accommodating several different interfaces on a single subnet, this approach also circumvents several limitations of GPIB and RS232 which would otherwise restrict their use in a harsh, industrial environment.<<ETX>>

Alarm handler for the Advanced Photon Source control system

The Advanced Photon Source (APS) will have a control system employing graphics workstations at the operator interface level and VME-based microprocessors operating with a distributed database at the field level. The alarm handler is an application utilizing X-Windows running on one or more operator interface workstations which monitors alarms generated by the VME-based microprocessors. Alarms can be grouped in a hierarchical manner. The operator can monitor, acknowledge, and mask alarms either individually or aggregately. Alarm changes of state and all operator modifications are logged. When alarms occur, display windows are automatically generated conveying system and subsystem relationships and severity. Menus are used to modify the alarm action configuration files and to obtain help. Since alarm groups are defined via an alarm configuration file, the alarm handler is a general purpose application which can be customized to monitor a single subsystem or configured to monitor the entire accelerator complex.<<ETX>>