[en] It is shown that the reaction field induced in an atom by a strong magnetic field is of order Bα in atomic units (for magnetic field strength B and fine structure constant α). The reaction field causes a dipole-dipole interatomic potential energy to exist between a pair of atoms of order B^3/2α^7/2, such that B must be of order α^-7/3 for the interatomic energy to be of order one atomic unit. B of this order corresponds to a field strength of 1.66 x 10¹² G, which is within the regime of field strengths considered in recent studies of atoms and molecules in the presence of a strong magnetic field

[en] The continuity equation for electromagnetic (EM) energy flow is used to describe radiation flow in the transport regime. The scheme of a discrete representation of H_z and a stochastic representation of H_x, H_y gives an effectively continuous representation of directed energy in the x-y plane, such that the ray effect of transport theory is absent. Since the in-plane amplitudes are generated at each time step, it is necessary to store only the perpendicular amplitudes and the results appear to be robust with respect to the coarse of this discretization

No abstract available

[en] The Advanced Light Source (ALS) at the Lawrence Berkeley Laboratory (LBL) is a 1.5 GeV synchrotron light source facility consisting of a 120 keV electron gun, 50 MeV linear accelerator, 1.5 Gev booster synchrotron, 200 meter circumference electron storage ring, and many photon beamline transport systems for research. The Radiation Safety System for the ALS has been designed and built with a primary goal of providing protection against inadvertent personnel exposure to gamma and neutron radiation and, secondarily, to enhance the electrical safety of select magnet power supplies

[en] Implementation of a high performance computer control system tailored to the requirements of the SuperHILAC accelerator is described. This system uses a distributed (star-type) structure with fiber optic data links; multiple CPU's operate in parallel at each node. A large number (20) of the latest 16-bit microcomputer boards are used to get a significant processor bandwidth (exceeding that of many mini-computers) at a reasonable price. Because of the large CPU bandwidth, software costs and complexity are significantly reduced and programming can be less real-time critical. In addition all programming can be in a high level language. Dynamically assigned and labeled knobs together with touch-screens allow a flexible operator interface. An X-Y vector graphics system allows display and labeling of real-time signals as well as general plotting functions. Both the accelerator parameters and the graphics system can be driven from BASIC interactive programs in addition to the pre-canned user routines. This allows new applications to be developed quickly and efficiently by physicists, operators, etc. The system, by its very nature and design, is easily upgraded (via next generation of boards) and repaired (by swapping of boards) without a large hardware support group. This control system is now being tested on an existing beamline and is performing well. The techniques used in this system can be readily applied to industrial control systems

[en] The Advanced Light Source (ALS) is a third generation 1--2 GeV synchrotron radiation source designed to provide ports for 60 beamlines. It uses a 50 MeV electron linac and 1.5 GeV, 1 Hz, booster synchrotron for injection into a 1--2 GeV storage ring. Interesting control problems are created because of the need for dynamic closed beam orbit control to eliminate interaction between the ring tuning requirements and to minimize orbit shifts due to ground vibrations. The extremely signal sensitive nature of the experiments requires special attention to the sources of electrical noise. These requirements have led to a control system design which emphasizes connectivity at the accelerator equipment end and a large I/O bandwidth for closed loop system response. Not overlooked are user friendliness, operator response time, modeling, and expert system provisions. Portable consoles are used for local operation of machine equipment. Our solution is a massively parallel system with >120 Mbits/sec I/O bandwidth and >1500 Mips computing power. At the equipment level connections are made using over 600 powerful Intelligent Local Controllers (ILC-s) mounted in 3U size Eurocard slots using fiber-optic cables between rack locations. In the control room, personal computers control and display all machine variables at a 10 Hz rate including the scope signals which are collected though the control system. Commercially available software and industry standards are used extensively. Particular attention is paid to reliability, maintainability and upgradeability. 10 refs., 11 figs

[en] This paper describes the design and operating experience with a high performance control system tailored to the requirements of the SuperHILAC accelerator. A large number (20) of the latest 16-bit microcomputer boards are used in a parallel-distributed manner to get a high system bandwidth. Because of the high bandwidth, software costs and complexity are significantly reduced. The system by its very nature and design is easily upgraded and repaired. Dynamically assigned and labeled knobs, together with touch-panels, allow a flexible and efficient operator interface. An X-Y vector graphics system provides for display and labeling of real-time signals as well as general plotting functions. This control system allows attachment of a powerful auxiliary computer for scientific processing with access to accelerator parameters

[en] Hydrogen atom-hydrogen atom scattering is a prototype for many of the fundamental principles of atomic collisions. In this work we present the formalism and the predictions of a time-dependent self-consistent-field description of the H + H system for scattering in the intermediate energy regime of 1-100 keV. Because of the unrestricted nature of the numerical orbital description, this method includes the effects of an unlimited basis set within each orbital. Electron exchange and a limited amount of electron correlation are included as well. We solve numerically coupled three-dimensional Schroedinger equations for the two-electron orbitals in singlet and triplet symmetries. Excitation and ionization cross sections are computed and compared with other theory and experiment. The results capture many features of the problem but illustrate a need for more quantitative experimental information concerning the H + H system in this energy range. (author)

[en] Hydrogen atom-hydrogen atom scattering is a prototype for many of the fundamental principles of atomic collisions. In this paper we present an approximation to the H+H system for scattering in the intermediate energy regime of 1-100 keV. The approximation ignores electron exchange and two-electron excitation by assuming that one of the atoms is frozen in the 1s state. We allow for the evolution of the active electron by numerically solving the 3D Schroedinger equation. This approximation is by nature most appropriate for higher-energy collisions. The results capture many features of the problem and are in harmony with recent theoretical studies. Excitation and ionization cross sections are computed and compared with other theory and experiment. New insight into the mechanism of excitation and ionization is inferred from the solutions. (author)

[en] The criteria for the design of a modern control system are discussed in the context of the special requirements for the control of the Advanced Light Source (ALS). This is followed by the description of the system being built, which has a number of special features. The emphasis has been placed on providing an extremely wide I/O and CPU bandwidth (greater than 120 Mbits/s and 1200 Mips, respectively) and on using commercially available hardware and software. The only major custom design item is the Intelligent Local Controller (ILC), of which about 600 will be used to interface to the hardware. The use of personal computers for the operator stations allows the use of a wealth of industrial standards for windows, languages and tools. (orig.)