Particle Acceleration

For many years the Fermilab physics program has been dominated by the superconducting Tevatron accelerator producing beams for many fixed target and the proton-antiproton colliding beam experiments CDF and D0. More recently, major experiments have used beam from intermediate accelerators. The MiniBooNE and MINOS experiments use 8 and 120 GeV beam respectively for neutrino oscillation studies. Several other experiments and test beams have also used 120 GeV beam. This paper describes the control system for the accelerator complex that was originally developed for the start of Tevatron operation in 1983. This system is common to all accelerators in the chain, and has been successfully evolved to accommodate new hardware, new software platforms, new accelerators, and increasingly complex modes of operation.

A radio heliograph operating in the frequency range of 1200–1700 MHz is planned by INPE, Brazil, for investigations of time evolution of active regions, which will lead to better understanding of the physics of the flares energy release and particle acceleration, in order to suggest better criteria for the prediction of solar flares, Coronal Mass Ejections (CME), and solar terrestrial relations, such as geomagnetic storms and radio blackouts. In the first phase, the Brazilian Decimetric Array (BDA) will be a T shaped array 256 m by 144 m, consisting of 26 parabolic dish antennas of 4 m diameter. This array will produce full disk images of the sun with a spatial resolution of 3 by 5 arc minutes at 1420 MHz with a time resolution of 100 ms and sensitivity of ∼ 10 Jy. In the second phase, in addition to the compact T array there will be 6 more 7 m diameter antennas on an East-West baseline of 2560 m to obtain higher spatial resolution and better sensitivity. Thus, finally this radioheliograph will have wide field of view and couple of arcsec spatial resolution and high time resolution (100 ms).

The low-latitude boundary layer (LBL) and its separation from the cusp have previously been identified using observations of particle precipitation at magnetosheath energies. Using $3-3 satellite observations, we have determined that these identifications can also be made from energetic particle observations on polar-orbiting satellites. It is found that the equatorward boundary of the LBL is identifiable as an approximately discontinuous decrease in 33-keV electron fluxes from low to high latitudes. Both the energetic ion and electron fluxes decrease discontinuously at the boundary between the LBL and the cusp or polar cap. A distinct LBL is nearly always identifiable in energetic particle measurements in the 10-14 MLT region when counting rates are statistically significant. The identifications obtained using the energetic particle measurements have been compared to those obtained using criteria developed by Newell and Meng (1988, 1989) for magnetosheath energy particle precipitation. In this way, we have evaluated the accuracy of both techniques and used the energetic particle measurements to supplement the identifications obtained using the Newell and Meng criteria. We propose that the Newell and Meng threshold on ion energy flux can be reduced by a factor of 6. This modification provides identification of the LBL for lower ion intensity levels than has previously [_een thought possible. Source, acceleration, and scattering processes have also been studied within _nd in the vicinity of the LBL. Observed trapped pitch angle distn'butions of energetic electrons imply that the LBL is at least partially on closed field lines. Strong scattering of energetic protons is found within and equatorward of the LBL and thus must occur at least partially along closed field lines. Field-aligned electron acceleration by parallel electric fields can be discerned within and poleward of the LBL, but a more detailed analysis is necessary for a statistical study. Conical ion acceleration was seen relatively frequently within the LBL and about half as often poleward of the LBL. Neither acceleration process could be identified anywhere equatorward of the LBL.

and the calculations of Glendenning et al. (5), (GWM:neutrons) predict lower pressures. The uncertainty in the pressure due to the asymmetry term widens the range of possible EOSs that may be consistent with the experimental data. For this purpose, it is important to obtain experimental constraints on the asymmetry term (39-41) (see SOM text) and to complement them with improved constraints on the EOS of symmetric nuclear matter. We have analyzed the flow of matter in nuclear collisions to determine the pressures attained at densities ranging from two to five times the saturation density of nuclear matter. We obtained constraints on the EOS of symmetric nuclear matter that rule out very repulsive EOSs from relativistic mean field theory and very soft EOSs with a strong phase transition at densities Ͻ 3 0 , but not a softening of the EOS due to a transformation to quark matter at higher densities. Investigations of the asymmetry term of the EOS are important to complement our constraints on the symmetric nuclear matter EOS. Both measurements relevant to the asymmetry term and improved constraints on the EOS for symmetric matter appear feasible; they can provide the experimental basis for constraining the properties of dense neutron-rich matter and dense astrophysical objects such as neutron stars. Plasmas are an attractive medium for the next generation of particle accelerators because they can support electric fields greater than several hundred gigavolts per meter. These accelerating fields are generated by relativistic plasma waves-space-charge oscillations-that can be excited when a highintensity laser propagates through a plasma. Large currents of background electrons can then be trapped and subsequently accelerated by these relativistic waves. In the forced laser wake field regime, where the laser pulse length is of the order of the plasma wavelength, we show that a gain in maximum electron energy of up to 200 megaelectronvolts can be achieved, along with an improvement in the quality of the ultrashort electron beam.

We reportfor thefirsttimeon theperformanceof theSLD Central Drift Chamber (CDC) at SLC, which has been recordingdatasince 1992. The low mass of the chamber and the use-of a gas characterized by both a low drift velocity and low diffusion constant help to minimize the drift-distance measurement errors. We describe some of the calibrations and corrections applied to the dam, and report on the resolutions achlevd tius far. We measure an intrinsic drift resolution of 55-110 pm in the region of uniform fiefd. " Analysis of the full drift-pulse waveform allows for efficient double-hit resolution of about 1 mm. Momentum resolution is characterized by the formula (dp~pt2)~0.00502+ (0.010/pt)2. Used in conjunction with the SLD vertex det~tor, the CDC permits measurements of impact parameters of high-momentum tracks to the level of 10 pm in the r-~plane and 36~m in the r-z plane. A resolution of 6.4% is achieved in the measurement of dE/dx for the electrons "inBhabha scattering events.

The Advanced Light Source, a third-generation national synchrotron-radiation facility now under construction at the Lawrence Berkeley Laboratory in Berkeley, California, is scheduled to begin serving qualified users across a broad spectrum of research areas in the spring of 1993. Undulators will generate high-brightness, partially coherent, plane polarized, soft x-ray and ultraviolet (XUV) radiation from below 10 e V to above 2 ke V. Wigglers and bend magnets will generate high fluxes of x-rays to photon energies above 10 ke V. The ALS will have an extensive research program in which XUV radiation is used to study matter in all its varied gaseous, liquid, and solid forms.

The need for high]y charged heavy ions from projected particle accelerators has recently led to a re-evaluation of the complex processes of ion production in laser generated plasmas. Possible mechanisms for the production of intense beams of high charge state ions are investigated as is the experimental evidence for these mechanisms. The hypothesis that 20 keV ions are driven by "hot electrons" is not supported by experimental work to date. This work, on the other hand, suggests that 30ps pulsation is the basic mechanism for the acceleration of tantalum ions up fo charge state 8-t-whose energy increases linearly with charge state up to 24keV. For long pulses and charge states between 8-}-and 18n u, it appears that there is a secondary mechanism of electron impact ionisation by plasma electrons of approximately 200 eV in the plasma in front of the target, resulting in ions whose energy of around 24 keV is independent of charge state.

Analyses and evaluation of the life cycle number and crack propagation rate were performed on oxygen-free high-conductivity copper X-ray beamline components based on data available in the literature . Recommendations are made with respect to the safe use of materials in high-heat-load beamline component design . The available literature is critically reviewed for low-cycle fatigue properties at the elevated temperatures typically found in synchrotron operations .

In conventional thermal spraying, the spray particles are partially or fully molten when they deposit on the substrate. Cold spraying, in contrast, uses less thermal and more kinetic energy. In this process, solid particles impact on the substrate at high velocities and form excellent coatings. Due to comparatively low temperatures and typically inert process gases, cold spraying is particularly suitable for heat and oxidation sensitive materials. In recent years, modeling and computational methods have been widely used to study this relatively new spraying process, particularly to describe impact conditions of particles, to improve nozzle design, and to provide a better understanding of the thermo-mechanical processes that lead to particle bonding and deposition. This paper summarizes the state of the art in these theoretical studies, alongside a comprehensive description of the process. The paper also discusses the prediction of coating properties in the light of modeling combined with experimental investigations.

ABSTRACT A Lagrangian L of a dynamical system is a function that summarises the dynamics of the system (Goldstein et al., 2002). If the Lagrangian of a system is known, then the equations of motion of the system may be obtained by its direct substitution into the Euler‐Lagrange equation. One important advantage of the Lagrange formulation of dynamical systems is that the formulation is not tied to any particular coordinate system – rather, any convenient set of variables may be used to describe the system. Finding the Lagrangian for a system is a mix of science and art. In the following paper we will demonstrate how to find it for the case of relativistic electrodynamics as a direct application for particle accelerators. We will show how we can start from the expression of the Lagrangian in classical electrodynamics in finding its expression for relativistic cases.

The MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MES-SENGER) mission to Mercury offers our first opportunity to explore this planet's miniature magnetosphere since the brief flybys of Mariner 10. Mercury's magnetosphere is unique in many respects. The magnetosphere of Mercury is among the smallest in the solar system; its magnetic field typically stands off the solar wind only ∼1000 to 2000 km above the surface. For this reason there are no closed drift paths for energetic particles and, hence, no radiation belts. Magnetic reconnection at the dayside magnetopause may erode the subsolar magnetosphere, allowing solar wind ions to impact directly the regolith. Inductive currents in Mercury's interior may act to modify the solar wind interaction by resisting changes

Control techniques that optimize the behaviour of pulse-width modulation (PWM) rectifiers for magnet supplies are examined. Different control strategies, both with preprogrammed and variable switching patterns, are examined and compared in terms of optimization of the system performance. Optimum digital PWM, multilevel delta modulation, and hybrid PWM/delta techniques are analyzed. The validity of the control methods was verified by simulation and experimental tests on a 60 kW prototype. It was observed that, in practice, digital PWM techniques are better suited for optimizing the AC converter performance, while delta modulation techniques give better results in terms of DC current and voltage distortion.>

The plasma particle velocity distributions observed in the solar wind generally show enhanced (non-Maxwellian) suprathermal tails, decreasing as a power law of the velocity and well described by the family of Kappa distribution functions. The presence of non-thermal populations at different altitudes in space plasmas suggests a universal mechanism for their creation and important consequences concerning plasma fluctuations, the resonant and nonresonant wave -particle acceleration and plasma heating. These effects are well described by the kinetic approaches where no closure requires the distributions to be nearly Maxwellian. This paper summarizes and analyzes the various theories proposed for the Kappa distributions and their valuable applications in coronal and space plasmas.

Open-architecture machine tool controllers have been an important research subject in both academia and industry. They are hard realtime applications that require a built-in database management system to support concurrent data access and provide well-defined interfaces. These advanced applications often utilize object-oriented models to handle complex data types. Since there exists no agreed-upon real-time object model, we design a conceptual real-time object-oriented data model, called ROMPP (Real-time Object Model with Performance Polymorphism). It captures the key characteristics of realtime control applications, namely, timing constraints and performance polymorphism. It uses specialization dimensions to model timing specifications and letter class hierarchies to capture performance polymorphism. Based on the model, we develop a prototype controller on our open-architecture machine tool controller testbed. The controller has been successfully used for a 6-axis robotic table.

Due to the interaction of physics and astrophysics we are witnessing in these years a splendid synthesis of theoretical, experimental and observational results originating from three fundamental physical processes. They were originally proposed by Dirac, by Breit and Wheeler and by Sauter, Heisenberg, Euler and Schwinger. For almost seventy years they have all three been followed by a continued effort of experimental verification on Earth-based experiments. The Dirac process, e + e − → 2γ, has been by far the most successful. It has obtained extremely accurate experimental verification and has led as well to an enormous number of new physics in possibly one of the most fruitful experimental avenues by introduction of storage rings in Frascati and followed by the largest accelerators worldwide: DESY, SLAC etc. The Breit-Wheeler process, 2γ → e + e − , although conceptually simple, being the inverse process of the Dirac one, has been by far one of the most difficult to be verified experimentally. Only recently, through the technology based on free electron X-ray laser and its numerous applications in Earth-based experiments, some first indications of its possible verification have been reached. The vacuum polarization process in strong electromagnetic field, pioneered by Sauter, Heisenberg, Euler and Schwinger, introduced the concept of critical electric field E c = m 2 e c 3 /(e ). It has been searched without success for more than forty years by heavy-ion collisions in many of the leading particle accelerators worldwide.

Fast reconnection of magnetic field in turbulent fluids allows the field to change its topology and connec- tions. As a result, the traditional concept of magnetic fields being frozen into the plasma is no longer applicable. Plasma associated with a given magnetic field line at one instant is distributed along a different set of magnetic field lines at the next instant. This diffusion of plasmas and magnetic field is enabled by reconnection and therefore is termed ”reconnec- tion diffusion”. The astrophysical implications of this con- cept include heat transfer in plasmas, advection of heavy el- ements in interstellar medium, magnetic field generation etc. However, the most dramatic implications of the concept are related to the star formation process. The reason is that mag- netic fields are dynamically important for most of the stages of star formation. The existing theory of star formation has been developed ignoring the possibility of reconnection dif- fusion. Instead, it appeals to the decoupling of mass and magnetic field arising from neutrals drifting in respect to ions entrained on magnetic field lines, i.e. through the pro- cess that is termed ”ambipolar diffusion”. The predictions of ambipolar diffusion and reconnection diffusion are very different. For instance, if the ionization of media is high, am- bipolar diffusion predicts that the coupling of mass and mag- netic field is nearly perfect. At the same time, reconnection diffusion is independent of the ionization but depends on the scale of the turbulent eddies and on the turbulent velocities. In the paper we explain the physics of reconnection diffusion both from macroscopic and microscopic points of view, i.e. appealing to the reconnection of flux tubes and to the dif-
the dynamics of many key processes, including magnetic re- connection. Fast reconnection of magnetic field in turbulent fluids allows the field to change its topology and connec- tions. As a result, the traditional concept of magnetic fields being frozen into the plasma is no longer applicable. Plasma associated with a given magnetic field line at one instant is distributed along a different set of magnetic field lines at the next instant. This diffusion of plasmas and magnetic field is enabled by reconnection and therefore is termed ”reconnec- tion diffusion”. The astrophysical implications of this con- cept include heat transfer in plasmas, advection of heavy el- ements in interstellar medium, magnetic field generation etc. However, the most dramatic implications of the concept are related to the star formation process. The reason is that mag- netic fields are dynamically important for most of the stages of star formation. The existing theory of star formation has been developed ignoring the possibility of reconnection dif- fusion. Instead, it appeals to the decoupling of mass and magnetic field arising from neutrals drifting in respect to ions entrained on magnetic field lines, i.e. through the pro- cess that is termed ”ambipolar diffusion”. The predictions of ambipolar diffusion and reconnection diffusion are very different. For instance, if the ionization of media is high, am- bipolar diffusion predicts that the coupling of mass and mag- netic field is nearly perfect. At the same time, reconnection diffusion is independent of the ionization but depends on the scale of the turbulent eddies and on the turbulent velocities. In the paper we explain the physics of reconnection diffusion both from macroscopic and microscopic points of view. We make use of the Lazarian & Vishniac 1999 theory of magnetic reconnection and show that this theory is applicable to the partially ionized gas. We quantify the reconnection diffusion rate both for weak and strong MHD turbulence and address the problem of recon- nection diffusion acting together with ambipolar diffusion. In addition, we provide a criterion for correctly representing the magnetic diffusivity in simulations of star formation. We discuss the intimate relation between the processes of recon- nection diffusion, field wandering and turbulent mixing of a magnetized media and show that the role of the plasma ef- fects is limited to ”breaking up lines” on small scales and does not affect the rate of reconnection diffusion. We ad- dress the existing observational results and demonstrate how reconnection diffusion can explain the puzzles presented by observations, in particular, the observed higher magnetiza- tion of cloud cores in comparison with the magnetization of envelopes. We also outline a possible set of observational tests of the reconnection diffusion concept and discuss how the application of the new concept changes our understand- ing of star formation and its numerical modeling. Finally, we outline the differences of the process of reconnection diffusion and the process of accumulation of matter along magnetic field lines that is frequently invoked to explain the results of numerical simulations

The compact linear collider (CLIC) is the particles accelerator project proposed by the european organization for nuclear research (CERN) for high energy physics after the large hadron collider (LHC). Because of the nanometric scale of the CLIC leptons beams, the emittance growth budget is very tight. It induces alignment tolerances on the positions of the CLIC components that have never been achieved. The last step of the CLIC alignment will be done according to the beam itself. It falls within the competence of the physicists. However, in order to implement the beam-based feedback, a challenging pre-alignment is required : 10 μm at 3σ along a 200 m sliding window. For such a precision, the proposed solution must be compatible with a feedback between the measurement and repositioning systems. The CLIC pre-alignment will have to be active. This thesis does not demonstrate the feasibility of the CLIC active prealignment but shows the way to the last developments that have to be done ...

Medium energy electron synchrotrons (see page 15) used for the production of high energy photons from synchrotron radiation is an accelerator growth industry. Many of these accelerators have been built or are under construction to satisfy the needs of synchrotron light users throughout the world. Because of the long beam lifetimes required for these synchrotrons, these medium energy accelerators require the highest quality magnets of various types. Other accelerators, for instance low and medium energy boosters for high energy physics machines and electron/positron colliders, require the same types of magnets.

We have analyzed Cluster magnetic field and plasma data during a high-altitude cusp crossing in 2003. The Cluster separation was $ 5000 km and provided unique measurements of high energy particle properties both inside the DiaMagnetic Cavity (DMC) and surrounding magnetosheath. Most of the high energy electrons and protons had pitch angles of $ 901 in the cavity and the high energy particle intensities dropped as a function of distance from the cavity boundary. By assuming conservation of the first adiabatic invariant for the electrons our analysis indicates that most of the high-energy electrons in the diamagnetic cavity cannot directly originate from the magnetosheath or from the magnetosphere. Our test particle simulations in a local 3-D high-resolution MHD cusp model show that particles can gain up to 40 keV and their pitch angles become nearly 901 in the local cusp geometry due to gradients in reconnection 'quasi-potential' agreeing with the Cluster RAPID observations. These results strongly support a local acceleration of particles in the cusp diamagnetic cavities.

NASA's two spacecraft ARTEMIS mission will address both heliospheric and planetary research questions, first while in orbit about the Earth with the Moon and subsequently while in orbit about the Moon. Heliospheric topics include the structure of the Earth's magnetotail; reconnection, particle acceleration, and turbulence in the Earth's magnetosphere, at the bow shock, and in the solar wind; and the formation and structure of the D.G. Sibeck ( ) Code 674, GSFC/NASA, J. Raeder UNH, Durham, NH, USA position of the lunar surface, the effects of electric fields on dust in the exosphere, internal structure of the Moon, and the lunar crustal magnetic field. This paper describes the expected contributions of ARTEMIS to these baseline scientific objectives.

This chapter reviews the current understanding of ring current dynamics. The terrestrial ring current is an electric current flowing toroidally around the Earth, centered at the equatorial plane and at altitudes of ∼10,000 to 60,000 km. Enhancements in this current are responsible for global decreases in the Earth's surface magnetic field, which have been used to define geomagnetic storms. Intense geospace magnetic storms have severe effects on technological systems, such as disturbances or even permanent damage of telecommunication and navigation satellites, telecommunication cables, and power grids. The main carriers of the ring current are positive ions, with energies from ∼1 keV to a few hundred keV, which are trapped by the geomagnetic field and undergo an azimuthal drift. The ring current is formed by the injection of ions originating in the solar wind and the terrestrial ionosphere into the inner magnetosphere. The injection process involves electric fields, associated with enhanced magnetospheric convection and/or magnetospheric substorms. The quiescent ring current is carried mainly by protons of predominantly solar wind origin, while active processes in geospace tend to increase the abundance (both absolute and relative) of O + ions, which are of ionospheric origin. During intense geospace magnetic storms, the O + abundance increases dramatically. This increase has been observed to occur concurrently with the rapid intensification of the ring current in the storm main phase and to result in O + dominance around storm maximum. This compositional change can affect several dynamic processes, such as species-and energy-dependent charge-exchange and wave-particle scattering loss.

Though numerous algorithms exist to perform image segmentation there are several issues related to execution time of these algorithm. Image Segmentation is nothing but label relabeling problem under probability framework. To estimate the label configuration, an iterative optimization scheme is implemented to alternately carry out the maximum a posteriori (MAP) estimation and the maximum likelihood (ML) estimations. In this paper this technique is modified in such a way so that it performs segmentation within stipulated time period. The extensive experiments shows that the results obtained are comparable with existing algorithms. This algorithm performs faster execution than the existing algorithm to give automatic segmentation without any human intervention. Its result match image edges very closer to human perception.

The high-mass microquasar Cygnus X-3 has been recently detected in a flaring state by the gamma-ray satellites Fermi and Agile. In the present contribution, we study the high-energy emission from Cygnus X-3 through a model based on the interaction of clumps from the Wolf-Rayet wind with the jet. The clumps inside the jet act as obstacles in which shocks are formed leading to particle acceleration and non-thermal emission. We model the high energy emission produced by the interaction of one clump with the jet and briefly discus the possibility of many clumps interacting with the jet. From the characteristics of the considered scenario, the produced emission could be flare-like due to discontinuous clump penetration, with the GeV long-term activity explained by changes in the wind properties.

Since the last Particle Accelerator Conference, the Experimental Physics and Industrial Control System (EPICS) has been utilized for control system development and implementation on several accelerators that have recently been commissioned at the Free Electron Laser Laboratory which is operated under the auspices of the Physics Department at Duke University. The historic Mark III infrared free electron laser formerly located at Stanford University, a recently designed and constructed 280 MeV electron linear accelerator and a 1 GeV storage ring synchrotron are now operating under EPICS control. Commissioning of the new injection linac and the storage ring has gone extremely well.

■ Abstract Moving highly-charged ions carry strong electromagnetic fields that act as a beam of photons. In collisions at large impact parameters, hadronic interactions are not possible, and the ions interact through photon-ion and photon-photon collisions known as ultra-peripheral collisions (UPCs). Hadron colliders like the Relativistic Heavy Ion Collider (RHIC), the Tevatron, and the Large Hadron Collider (LHC) produce photonuclear and two-photon interactions at luminosities and energies beyond that accessible elsewhere; the LHC will reach a γ p energy ten times that of the Hadron-Electron Ring Accelerator (HERA). Reactions as diverse as the production of anti-hydrogen, photoproduction of the ρ 0 , transmutation of lead into bismuth, and excitation of collective nuclear resonances have already been studied. At the LHC, UPCs can study many types of new physics processes.

Albany, New York. Prior to joining FMT, he was the Vice President of Engineering and cofounder of Mohawk Innovative Technology. Dr. Chen has more than 25 years of experience in the design of innovative rotorbearing systems. During his tenure with Mechanical Technology Inc., he led the technology development of the world's largest active magnetic bearing system. His current research focuses on the development of foil gas bearings for high-speed turbomachinery and hybrid magnetic bearings for blood pumps and momentum energy-storage flywheel systems. Dr. was involved in research and development efforts in the tribology field and rotating machinery troubleshooting. Dr. Howarth graduated with a degree (Mechanical Engineering) from the University of Manchester, England, and was subsequently awarded his M.Sc. degree (1960) by the same institution for his work on the application of automatic control to hydrostatic bearings. During his tenure at the University of Salford, he was awarded a Ph.D. degree for his work in tribology. Bernard Geren is a Vice President and cofounder of Turbotechnology Services Corporation (TSC) of Scotia, New York. He is responsible for the design of new centrifugal compressors and aftermarket components, as well as modifications and rerating of existing compressor designs. Mr. Geren has more than 30 years of experience in the design, testing, and troubleshooting of centrifugal compressors and high-speed machinery, gained from various positions held with Mechanical Technology Inc., Turbonetics, and Atlas Copco Comptec. Mr. Geren received his BSME degree from Union College.

High-energy particle accelerator UHV systems subjected to energetic charged particle or photon bombardment are particularly sensitive to surface contamination. Well-established cleaning procedures employing solvents such as Freon and perchloroethylene to prepare vacuum system components have been used at CERN for many years. The recently adopted legislation which prescribes or strongly limits the use of some chemicals has led CERN to undertake a qualification programme using electron stimulated desorption, Auger spectroscopy and radioactive tracers to compare the cleaning efficiency of a wide range of alternative cleaning agents.

1] This paper addresses the question of particular characteristics and causes of intense space storms. We focus on several unresolved issues, which are critical to storm research and often nourish open disputes: the extent of interplanetary driving, the role of substorms in storm dynamics through the acceleration of particles to ring current energies, the identity of the lead agent of fast ring current decay right after storm maximum and the cause of the two-phase recovery of intense storms, the global morphology of the stormtime ring current, and the predictability of intense storms. Space storm physics has been driven by several more or less successful paradigms during the four decades following the dawn of the space flight era. However, recent suggestions and conclusions resulting from a number of observational and modeling studies have brought significant constraints to several of these paradigms. Thus for example, interplanetary driving through southward oriented magnetic fields is not always by itself sufficient to drive intense space storms because it is conditioned by internal magnetospheric conditions, the MLT distribution of storm-time magnetic disturbances is often asymmetric during the storm main phase, and charge exchange is not the lead agent of ring current decay at all times. Intense space storms: Critical issues and open disputes,

This paper summarizes the results obtained with the HELEOS railgun which uses a two-stage light-gas gun (2SLGG) as an injector [ 11. The high velocity 2SLGG injector pre-accelerates projectiles up to -7 km/s. The high injection velocity reduces the exposure duration of the railgun barrel to the passing high temperature plasma armature, thereby reducing the ablation and subsequent armature growth. The 2SLGG also provides a column of cool, high pressure hydrogen gas to insulate the rails behind the projectile, thereby eliminating restrike. A means to form an armature behind the injected projectile has been developed. In preliminary tests, the third stage railgun has successfully increased the projectile velocity by 1.35 km/s. Extensive diagnostics have been used to determine the behavior of the armature and rrack the launcher's performance. In some cases, velocity increases in the railgun section have been achieved, which are in close agreement with theoretical predictions, whereas in other experiments deviations from theoretical have been observed. The reasons for and implications of these results are addressed. Recent tests are reported.

The terrestrial ring current consists of energetic charged particles owing toroidally around the Earth, and creating a ring of westward electric current, centered at the equatorial plane and extending from geocentric distances of about 3-8RE. Changes in this current are responsible for global decreases in the Earth's surface magnetic ÿeld, which is the deÿning feature of geomagnetic storms. The ring current is a critical element in understanding the onset and development of space weather disturbances in geospace. This review paper discusses recent developments in ring current research, and outlines the presently hottest issues, most of which were addressed at the Ring Current

Energen, Inc. has designed, built, and demonstrated several fast and slow tuners based on its magnetostrictive actuators and stepper motor. These tuners are designed for Superconducting Radio Frequency (SRF) cavities, which are important structures in particle accelerators that support a wide spectrum of disciplines, including nuclear and high-energy physics and free electron lasers (FEL). In the past two years, Energen's work has focused on magnetostrictive fast tuners for microphonics and Lorentz detuning compensation on elliptical-cell and spoke-loaded cavities. These tuners were custom designed to meet specific requirements, which included a few to 100 micron stroke range, hundreds to kilohertz operation frequency, and cryogenic temperature operation in vacuum or liquid helium. These tuners have been tested in house and at different laboratories, such as DESY, Argonne National Lab, and Jefferson Lab. Some recent results are presented in this paper.

The description of the motion of immersed bodies in fluids is present in several manufacturing processes. In the current study, the unsteady motion of a spherical particle rolling down an inclined plane submerged in a Newtonian environment has been studied using a drag of the form given by Chhabra and Ferreira, for wide range of Reynolds numbers. An analytical solution for velocity, acceleration and position of the particle is derived, using homotopy perturbation method. Equation of motion was solved generally and for some practical conditions. The present investigation shows the effectiveness of HPM and exhibits a new application of this method for nonlinear problems.

The Los Alamos Accelerator Code Group (LAACG) is a national resource for members of the accelerator community who use and/or develop software for the design and analysis of particle accelerators, beam transport systems, light sources, storage rings, and components of these systems. Below we describe the LAACG' s activities in high performance computing, maintenance and enhancement of POISSON/SUPERFISH and related codes and the dissemination of information on the INTERNET.