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In this work we experimentally demonstrate a fully packaged one-dimensional beam steering system that is based on a fully CMOS compatible silicon photonics platform. This configuration enables multi-wavelength operation and is suitable for short-wavelength infrared (SWIR) applications from light detection and ranging (LIDAR) to telecommunication and sensing applications. The switching fabric in this system employs a 1x9 array of add/drop ring resonators that are fed by a common waveguide through a single etch input grating. The switching fabric re-directs the resonance wavelengths at each drop waveguide to the output facet at the edge of the chip and into free space. The divergent beams that exit the waveguides along the output facet are then collimated and magnified using an array of micro-lenses (pitch = 750 μm, Diameter = 700 μm) in addition to a two lens afocal system in order to enhance the fill factor and diminish any blind zones between adjacent beams. Each one of these drop waveguides is used to address portion of the steering aperture. Combined together they enable steering across the entire aperture. Multi-wavelength operation is obtained by placing individual titanium tungsten alloy (TiW) heaters on top of each ring resonator to enable wavelength tuning.

We demonstrate the DC-Kerr effect in plasma enhanced chemical vapor deposition (PECVD) silicon-rich nitride (SRN) and use it to demonstrate a third order nonlinear susceptibility, χ ( 3 ) , as high as ( 6 ± 0.58 ) × 10 − 19 m 2 / V 2 . We employ spectral shift versus applied voltage measurements in a racetrack resonator as a tool to characterize the nonlinear susceptibilities of these films. In doing so, we demonstrate a χ ( 3 ) larger than that of silicon and argue that PECVD SRN can provide a versatile platform for employing optical phase shifters while maintaining a low thermal budget using a deposition technique readily available in CMOS process flows.

We demonstrate the thermo-optic properties of silicon-rich silicon nitride (SRN) films deposited using plasma-enhanced chemical vapor deposition (PECVD). Shifts in the spectral response of Mach-Zehnder Interferometers (MZIs) as a function of temperature were used to characterize the thermo-optic coefficients of silicon nitride films with varying silicon contents. A clear relation is demonstrated between the silicon content and the exhibited thermo-optic coefficient in silicon nitride films, with the highest achievable coefficient being as high as (1.65+/-0.08) x 10-4 K-1. Furthermore, we realize an SRN Multi-Mode Interferometer (MMI) based thermo-optic switch with over 20 dB extinction ratio and total power consumption for two-port switching of 50 mW., 10 pages, 7 figures, submitted to a journal

Venous thromboembolism is recognized as a leading cause of maternal death in the United States. Thromboprophylaxis has been highlighted as a key preventive measure to reduce venous thromboembolism-related maternal deaths. However, the expanded use of thromboprophylaxis in obstetrics will have a major impact on the use and timing of neuraxial analgesia and anesthesia for women undergoing vaginal or cesarean delivery and other obstetric surgeries. Experts from the Society of Obstetric Anesthesia and Perinatology, the American Society of Regional Anesthesia, and hematology have collaborated to develop this comprehensive, pregnancy-specific consensus statement on neuraxial procedures in obstetric patients receiving thromboprophylaxis or higher dose anticoagulants. To date, none of the existing anesthesia societies' recommendations have weighed the potential risks of neuraxial procedures in the presence of thromboprophylaxis, with the competing risks of general anesthesia with a potentially difficult airway, or maternal or fetal harm from avoidance or delayed neuraxial anesthesia. Furthermore, existing guidelines have not integrated the pharmacokinetics and pharmacodynamics of anticoagulants in the obstetric population. The goal of this consensus statement is to provide a practical guide of how to appropriately identify, prepare, and manage pregnant women receiving thromboprophylaxis or higher dose anticoagulants during the ante-, intra-, and postpartum periods. The tactics to facilitate multidisciplinary communication, evidence-based pharmacokinetic and spinal epidural hematoma data, and Decision Aids should help inform risk-benefit discussions with patients and facilitate shared decision making.

The Neutralized Drift Compression Experiment-II (NDCX-II) is an induction linac that generates intense pulses of 1.2 MeV helium ions for heating matter to extreme conditions. Here, we present recent results on optimizing beam transport. The NDCX-II beamline includes a 1-m-long drift section downstream of the last transport solenoid, which is filled with charge-neutralizing plasma that enables rapid longitudinal compression of an intense ion beam against space-charge forces. The transport section on NDCX-II consists of 28 solenoids. Finding optimal field settings for a group of solenoids requires knowledge of the envelope parameters of the beam. Imaging the beam on the scintillator gives the radius of the beam, but the envelope angle is not measured directly. We demonstrate how the parameters of the beam envelope (radius, envelop angle, and emittance) can be reconstructed from a series of images taken by varying the B-field strengths of a solenoid upstream of the scintillator. We use this technique to evaluate emittance at several points in the NDCX-II beamline and for optimizing the trajectory of the beam at the entry of the plasma-filled drift section. Keywords: Charged-particle beams, Induction accelerators, Beam dynamics, Beam emittance, Ion beam diagnostics, PACS Codes: 41.75.-i, 41.85.Ja, 52.59.Sa, 52.59.Wd, 29.27.Eg

A Monte Carlo method for angle scattering of electrons in air that accommodates the small-angle multiple scattering and larger-angle single scattering limits is introduced. The algorithm is designed for use in a particle-in-cell simulation of electron transport and electromagnetic wave effects in air. The method is illustrated in example calculations.

Development of high-power superconducting applications requires the accurate estimation of AC losses in the superconductor. In applications such as superconducting magnetic energy storage, the charge/discharge/persistent switching frequency of the coil, resulting from pulse width modulation control algorithms, is usually in the kilohertz regime. Therefore, a thorough investigation of the losses in the kilohertz regime of AC currents superimposed on large DC currents is essential in order to ensure the device stable operation at a predefined temperature. We describe here a unique experimental setup designed and built for characterizing AC losses in superconducting wires and coils under such special conditions. To minimize the eddy currents induced in the apparatus, a cryostat vacuum vessel was made of Delrin, an insulating synthetic polymer. The measurement setup allows driving DC currents up to 150 A and superimposed AC currents with amplitudes up to 10 Arms and frequencies up to 18 kHz. The system utilizes conduction cooling to reach a wide range of temperatures between 6 and 100 K and allows measurements of 10 cm long superconducting wires and coils with a diameter of 40 cm. The loss is measured by the electrical method, i.e., by direct voltage and current waveform measurement, achieving a resolution better than 100 nW. The system described here will assist in developing superconducting wires and coils for high-power applications.

With two recent successful installations in a U.K. live grid, the saturated core fault current limiter (SCFCL) has become one of the leading candidates for commercial fault current limiting devices. In this work, we review the concept developed at Bar-Ilan University, which was later adapted by GridON, for a novel compact SCFCL. This SCFCL utilizes a superposition of a closed dc magnetic circuit and an open ac magnetic circuit to overcome the intrinsic problem of transformer coupling found in traditional SCFCL designs. It also allows the use of a single magnetic core for a full ac current cycle limiting. In addition, the relatively short path for the dc magnetic circuit supports copper coils as an alternative to superconducting bias coils, allowing easier market penetration. The performances of the SFCL devices installed in live grids are described.

Background: Many Wheelchair users experience adverse effects specific to their situation, some of which might be avoided if suspension systems are integrated into the wheelchair. Objectives: Our study aimed to compare the user experience using a novel wheelchair suspension system with normal wheels. We tried to quantify the user feelings and impressions while using the different wheels. Study Design: Double blinded comparative randomized study. Methods: The patients were randomized into 2 groups. One used shock absorbing wheels, and the other group had a set of standard wheels with the same exact wheelchairs. The patients were taken to a daily trip by the caregivers and given questionnaires in the second and fourth days. On the morning of the third day the wheels were interchanged, creating a cross over between the groups. We collected general and medical information from the participants. The main outcome measures were the questionnaires filled by the patients and the caregivers aiming to quantify the user experience with the suspension equipped wheels. Results: Statistical significance was reached in 2 questions referred to the patients: “In general—During the ride I didn’t feel the bumps” and “I feel very confident when riding the chair” and in one question referred to the caregiver—“It was easy to push the chair in suboptimal ground.” Conclusions: We conclude that the shock absorbing system provided a better user experience in the immediate term than standard wheels. Further study is needed to assess the long-term implications.

Physical science and engineering practice have been, over most of history, advanced through experimentation and observation, along with analysis, calculations, and analog simulation. The use of digital computer simulations is a relatively recent development, but has matured rapidly and is now a full peer to the classical approaches.

The Neutralized Drift Compression eXperiment (NDCX-II) at Lawrence Berkeley National Laboratory is an induction accelerator designed to deliver intense nano-second pulses of ions, up to several tens of nC/pulse, with ion energies up to 1.2 Me V1. Voltage pulses of different amplitudes and lengths accelerate and rapidly compress the ion bunch. The compression is achieved through an induced head-to-tail velocity tilt, which leads to a pulse length of 2 ns FWHM at the target position. A final solenoid focusses the beam to a minimum spot size of 2 mm FWHM on target.

Compact, high-quality photon sources at MeV energies are being developed based on Laser-Plasma Accelerators (LPAs), and these sources at the same time provide precision diagnostics of beam evolution to support LPA development. We review design of experiments and laser capabilities to realize a photon source, integrating LPA acceleration for compactness, control of scattering to increase photon flux, and electron deceleration to mitigate beam dump size. These experiments are developing a compact photon source system with the potential to enable new monoenergetic photon applications currently restricted by source size, including nuclear nonproliferation. Diagnostic use of the energy-angle spectra of Thomson scattered photons is presented to support development of LPAs to meet the needs of advanced high yield/low-energy-spread photon sources and future high energy physics colliders.

A long-standing challenge in the design of a Heavy Ion Fusion power plant is that the ion beams entering the target chamber, which number of order a hundred, all need to be routed from one or two multi-beam accelerators through a set of transport lines. The beams are divided into groups, each of which has a unique arrival time and may have a unique kinetic energy. It is also necessary to arrange for each beam to enter the target chamber from a prescribed location on the periphery of that chamber. Furthermore, it has generally been assumed that additional constraints must be obeyed: that the path lengths of the beams in a group must be equal, and that any delay of “main-pulse” beams relative to “foot-pulse” beams must be provided by the insertion of large delay-arcs in the main beam transport lines. Here we introduce the notion of applying “differential acceleration” to individual beams or sets of beams at strategic stages of the transport lines. That is, by accelerating some beams “sooner” and others “later,” it is possible to simplify the beam line configuration in a number of cases. For example, the time delay between the foot and main pulses can be generated without resorting to large arcs in the main-pulse beam lines. It is also possible to use differential acceleration to effect the simultaneous arrival on target of a set of beams (e.g., for the foot-pulse) without requiring that their path lengths be precisely equal. We illustrate the technique for two model configurations, one corresponding to a typical indirect-drive scenario requiring distinct foot and main energies, and the other to an ion-driven fast-ignition scenario wherein the foot and main beams share a common energy.

Neutralized drift compression offers an effective means for particle beam focusing and current amplification with applications to heavy ion fusion. In the Neutralized Drift Compression eXperiment-I (NDCX-I), a non-relativistic ion beam pulse is passed through an inductive bunching module that produces a longitudinal velocity modulation. Due to the applied velocity tilt, the beam pulse compresses during neutralized drift. The ion beam pulse can be compressed by a factor of more than 100; however, errors in the velocity modulation affect the compression ratio in complex ways. We have performed a study of how the longitudinal compression of a typical NDCX-I ion beam pulse is affected by the initial errors in the acquired velocity modulation. Without any voltage errors, an ideal compression is limited only by the initial energy spread of the ion beam, Δ E b . In the presence of large voltage errors, δU ⪢Δ E b , the maximum compression ratio is found to be inversely proportional to the geometric mean of the relative error in velocity modulation and the relative intrinsic energy spread of the beam ions. Although small parts of a beam pulse can achieve high local values of compression ratio, the acquired velocity errors cause these parts to compress at different times, limiting the overall compression of the ion beam pulse.

Neutralized drift compression offers an effective means for particle beam pulse compression and current amplification. In neutralized drift compression, a linear longitudinal velocity tilt (head-to-tail gradient) is applied to the non-relativistic beam pulse, so that the beam pulse compresses as it drifts in the focusing section. The beam current can increase by more than a factor of 100 in the longitudinal direction. We have performed an analytical study of how errors in the velocity tilt acquired by the beam in the induction bunching module limit the maximum longitudinal compression. It is found that the compression ratio is determined by the relative errors in the velocity tilt. That is, one-percent errors may limit the compression to a factor of one hundred. However, a part of the beam pulse where the errors are small may compress to much higher values, which are determined by the initial thermal spread of the beam pulse. It is also shown that sharp jumps in the compressed current density profile can be produced due to overlaying of different parts of the pulse near the focal plane. Examples of slowly varying and rapidly varying errors compared to the beam pulse duration are studied. For beam velocity errors given by a cubic function, the compression ratio can be described analytically. In this limit, a significant portion of the beam pulse is located in the broad wings of the pulse and is poorly compressed. The central part of the compressed pulse is determined by the thermal spread. The scaling law for maximum compression ratio is derived. In addition to a smooth variation in the velocity tilt, fast-changing errors during the pulse may appear in the induction bunching module if the voltage pulse is formed by several pulsed elements. Different parts of the pulse compress nearly simultaneously at the target and the compressed profile may have many peaks. The maximum compression is a function of both thermal spread and the velocity errors. The effects of the finite gap width of the bunching module on compression are analyzed analytically.

In aircraft design, tailless aircraft are an attractive concept for their aerodynamic efficiency. However, because of their unusual shape, a tailless configuration has disadvantages in stability and control (SC static derivatives, steady dynamic derivatives, and unsteady dynamic derivatives. For accurate and efficient stability estimation, several aerodynamic and numerical methods were introduced to calculate aerodynamic derivatives. These values were compared with the wind tunnel data for the validation. Finally, the stability characteristics of certain steady conditions were calculated from the results of the numerical method, and the stability performance was evaluated.

The primary objectives of this work are two-fold. First, evaluate additive manufacturing (AM) and rapid prototype (RP) testing for use in production of wind tunnel (WT) models. Second, develop an approach to incorporate stability and control (S&C) WT data into aircraft conceptual design multidisciplinary design optimization (MDO). The measures of merit for both objectives are data quality, time, and cost. FDM™ and PolyJet AM processes are used for model production at low cost and time. Several models from a representative tailless configuration, ICE 101, are printed and evaluated for strength, cost, time of production, and limits of FDM™ technology are identified. Furthermore, a NACA 0012 model with 20% chord flap is manufactured. Both models are tested in the Virginia Tech (VT) Open-Jet WT for force and moment acquisition, and limitations of this tunnel are identified. An approach for incorporating WT data is adapted from traditional surrogatebased optimization (SBO). Split-plot experimental designs are developed for implementation of the WT SBO strategy using historical data. Further advancements in AM technology and acquisition of higher quality data using a closed-section WT are needed for a more effective approach to incorporate AM and RP testing in an aircraft conceptual design MDO for costeffective design space exploration.

The upper limit of the operating current of LTS solenoids can be estimated as the coordinate of the crossing point of its load line with IC (B) line of the superconductor. For HTS coils this approach seems to underestimate the allowable operating current of the coil. A better approach is to obtain a full electric field distribution over the coil and to use it as the base for a more sophisticated coil design criteria. We developed an algorithm and a Matlab program for calculating distributions of the current density, magnetic field and electric field in HTS solenoids made of pancakes, considering the inhomogeneous current density distribution inside the anisotropic tape. I-V curves of several Bi-2223 coils are calculated and good agreeement of the calculated and measured critical currents, IC, and indexes, n, are attained. One can utilize the program in the coil design choosing his own criteria of coil's critical current, e.g., 1) The average electric field 10−4 V/m over the coil, 2) The electric field 10−4 V/m at the weak point of the coil, 3) The energy dissipation in the entire coil, 4) Distribution of local energy dissipation.

Computer simulations of intense ion beams play a key role in the Heavy Ion Fusion research program. Along with analytic theory, they are used to develop future experiments, guide ongoing experiments, and aid in the analysis and interpretation of experimental results. They also afford access to regimes not yet accessible in the experimental program. The U.S. Heavy Ion Fusion Virtual National Laboratory and its collaborators have developed state-of-the art computational tools, related both to codes used for stationary plasmas and to codes used for traditional accelerator applications, but necessarily differing from each in important respects. These tools model beams in varying levels of detail and at widely varying computational cost. They include moment models (envelope equations and fluid descriptions), particle-in-cell methods (electrostatic and electromagnetic), nonlinear-perturbative descriptions (“ δ f ”), and continuum Vlasov methods. Increasingly, it is becoming clear that it is necessary to simulate not just the beams themselves, but also the environment in which they exist, be it an intentionally created plasma or an unwanted cloud of electrons and gas. In this paper, examples of the application of simulation tools to intense ion beam physics are presented, including support of present-day experiments, fundamental beam physics studies, and the development of future experiments. Throughout, new computational models are described and their utility explained. These include Mesh Refinement (and its dynamic variant, Adaptive Mesh Refinement); improved electron cloud and gas models, and an electron advance scheme that allows use of larger time steps; and moving-mesh and adaptive-mesh Vlasov methods.

Although transcranial magnetic stimulation (TMS) is a popular tool for both basic research and clinical applications, its actions on nerve cells are only partially understood. We have previously predicted, using compartmental modeling, that magnetic stimulation of central nervous system neurons depolarized the soma followed by initiation of an action potential in the initial segment of the axon. The simulations also predict that neurons with low current threshold are more susceptible to magnetic stimulation. Here we tested these theoretical predictions by combining in vitro patch-clamp recordings from rat brain slices with magnetic stimulation and compartmental modeling. In agreement with the modeling, our recordings demonstrate the dependence of magnetic stimulation-triggered action potentials on the type and state of the neuron and its orientation within the magnetic field. Our results suggest that the observed effects of TMS are deeply rooted in the biophysical properties of single neurons in the central nervous system and provide a framework both for interpreting existing TMS data and developing new simulation-based tools and therapies.

For many issues relevant to acceleration and propagation of heavy-ion beams for inertial confinement fusion, understanding the behavior of the beam requires the self-consistent inclusion of the self-fields of the beams in multiple dimensions. For these reasons, the three-dimensional simulation code WARP3d A.Friedman was developed. The code combines the particle-in-cell plasma simulation technique with a realistic description of the elements which make up an accelerator. In this paper, the general structure of the code is reviewed and details of two ongoing applications are presented along with a discussion of simulation techniques used. The most important results of this work are presented.

We have commenced experiments with intense short pulses of ion beams on the Neutralized Drift Compression Experiment (NDCX-II) at Lawrence Berkeley National Laboratory, with 1-mm beam spot size within 2.5 ns full-width at half maximum. The ion kinetic energy is 1.2 MeV. To enable the short pulse duration and mm-scale focal spot radius, the beam is neutralized in a 1.5-meter-long drift compression section following the last accelerator cell. A short-focal-length solenoid focuses the beam in the presence of the volumetric plasma that is near the target. In the accelerator, the line-charge density increases due to the velocity ramp imparted on the beam bunch. The scientific topics to be explored are warm dense matter, the dynamics of radiation damage in materials, and intense beam and beam-plasma physics including select topics of relevance to the development of heavy-ion drivers for inertial fusion energy. Below the transition to melting, the short beam pulses offer an opportunity to study the multi-scale dynamics of radiation-induced damage in materials with pump-probe experiments, and to stabilize novel metastable phases of materials when short-pulse heating is followed by rapid quenching. First experiments used a lithium ion source; a new plasma-based helium ion source shows much greater charge delivered to the target., Comment: 4 pages, 2 figures, 1 table. Submitted to the proceedings for the Ninth International Conference on Inertial Fusion Sciences and Applications, IFSA 2015

We explore the simulation challenges and requirements for experiments planned on facilities such as the NDCX-II ion accelerator at LBNL, currently undergoing commissioning. Hydrodynamic modeling of NDCX-II experiments include certain lower temperature effects, e.g., surface tension and target fragmentation, that are not generally present in extreme high-energy laser facility experiments, where targets are completely vaporized in an extremely short period of time. Target designs proposed for NDCX-II range from metal foils of order one micron thick (thin targets) to metallic foam targets several tens of microns thick (thick targets). These high-energy-density experiments allow for the study of fracture as well as the process of bubble and droplet formation. We incorporate these physics effects into a code called ALE-AMR that uses a combination of Arbitrary Lagrangian Eulerian hydrodynamics and Adaptive Mesh Refinement. Inclusion of certain effects becomes tricky as we must deal with non-orthogonal meshes of various levels of refinement in three dimensions. A surface tension model used for droplet dynamics is implemented in ALE-AMR using curvature calculated from volume fractions. Thick foam target experiments provide information on how ion beam induced shock waves couple into kinetic energy of fluid flow. Although NDCX-II is not fully commissioned, experiments are being conductedmore » that explore material defect production and dynamics.« less

The kinetic energy spread (defined here as the standard deviation of the beam particle energies) sets the ultimate theoretical limit on the longitudinal compression that can be attained on NDCX-I and NDCX-II. Experimental measurements will inevitably include the real influences on the longitudinal phase space of the beam due to injector and accelerator field imperfections1. These induced energy variations may be the real limit to the longitudinal compression in an accelerator. We report on a numerical investigation of the energy spread evolution in NDCX-I; these studies do not include all the real imperfections, but rather are intended to confirm that there are no other intrinsic mechanisms (translaminar effects, transverse-longitudinal anisotropy instability, etc.) for significant broadening of the energy distribution. We have performed Warp simulations that use a realistic Marx voltage waveform which was derived from experimental measurements (averaged over several shots), a fully-featured model of the accelerating and focusing lattice, and new diagnostics for computing the local energy spread (and temperature) that properly account for linear correlations that arise from the discrete binning along each physical dimension (these capabilities reproduce and extend those of the earlier HIF code BPIC). The new diagnostics allow for the calculation of multi-dimensional maps ofmore » energy spread and temperature in 2-D axisymmetric or 3-D Cartesian space at selected times. The simulated beam-line was terminated at z = 3 m by a conducting plate, so as to approximately reproduce the experimental conditions at the entrance of the spectrometer that was used for mapping the longitudinal phase space. Snapshots of the beam projection and current, as well as the Marx waveform and history of beam kinetic energy collected at the end plate, are shown in Fig. 1. A two-dimensional axisymmetric map of energy spread from simulations of a typical NDCX-I configuration is shown in Fig. 2 (a). The energy spread starts at 0.1 eV at the source and rapidly rises to a few eV, then fluctuates between a fraction of an eV and tens of eV, ending near the exit in a range of a few eV at the outer edge of the beam to a few tens of eV near the axis. The higher value on-axis is associated with greater numerical noise there, due to the axisymmetric geometry of the calculation, resulting in poorer simulation-particle statistics at small radius. A scatter plot of the macroparticles kinetic energy (KE) versus radius (R) and longitudinal position (0.28 m < z < 3 m) colored by local energy spread is shown in Fig. 2 (b). As expected, there is a correlation of the kinetic energy with radius that is clearly visible at z = 2.8 m and vanishes at the metal plate at z = 3 m. More snapshots from simulations varying the time step, grid resolution and number of macroparticles are given in Appendix II. The macro-particles were collected at the exit plate and their kinetic energy history is plotted in Fig. 3 (left) and contrasted to an experimental measurement using a streak camera shown in Fig. 3. For some types of measurements, averaging over several pulses to improve signal-to-noise will contribute an additional spread that may not be present on any single beam pulse. The upper bound for the energy spread is in the range of a few 100 eV for the experiment while in the range of a few eV for the reported Warp simulations. The Marx voltage exhibits variations in the range of up to several hundreds of volts, playing a significant role in the experimentally measured energy spread, which may account for the difference between the experimental and the simulated bounds.« less

This milestone has been met. The effort contains two main components: (1) Experimental results of warm dense matter target experiments on optimized NDCX-I configurations that include measurements of target temperature and transient target behavior. (2) A theoretical model of the target response to beam heating that includes an equilibrium heating model of the target foil and a model for droplet formation in the target for comparison with experimental results. The experiments on ion-beam target heating use a 300-350-keV K{sup +} pulsed beam from the Neutralized Compression Drift Experiment (NDCX-I) accelerator at LBNL. The NDCX-I accelerator delivers an uncompressed pulse beam of several microseconds with a typical power density of >100 kW/cm{sup 2} over a final focus spot size of about 1 mm. An induction bunching module the NDCX-I compresses a portion of the beam pulse to reach a much higher power density over 2 nanoseconds. Under these conditions the free-standing foil targets are rapidly heated to temperatures to over 4000 K. We model the target thermal dynamics using the equation of heat conduction for the temperature T(x,t) as a function of time (t) and spatial dimension along the beam direction (x). The competing cooling processes release energy from the surfacemore » of the foil due to evaporation, radiation, and thermionic (Richardson) emission. A description of the experimental configuration of the target chamber and results from initial beam-target experiments are reported in our FY08 4th Quarter and FY09 2nd Quarter Milestone Reports. The WDM target diagnostics include a high-speed multichannel optical pyrometer, optical streak camera, VISAR, and high-speed gated cameras. The fast optical pyrometer is a unique and significant new diagnostic which provides valuable information on the temperature evolution of the heated target.« less

HIFAN 1757 HEAVY ION FUSION SCIENCE VIRTUAL NATIONAL LABORATORY, 3rd QUARTER 2009 MILESTONE REPORT, Upgrade plasma source configuration and carry out initial experiments. Characterize improvements in focal spot beam intensity by S. Lidia, A. Anders, F.M. Bieniosek, A. Faltens, W. Greenway, J.Y. Jung, T. Katayanagi, B.G. Logan, C.W. Lee, M. Leitner, P. Ni, A. Pekedis, M. J. Regis, P. K. Roy, P. A. Seidl, W. Waldron Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA J.J. Barnard, A. Friedman, D. Grote, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA M. Dorf, E. Gilson Princeton Plasma Physics Laboratory Accelerator Fusion Research Division Ernest Orlando Lawrence Berkeley National Laboratory University of California June 2009 This work was supported by the Director, Office of Science, Office of Fusion Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.

Intense beams of heavy ions offer a very attractive tool for fundamental research in high energy density physics and inertial fusion energy science. These applications build on the significant recent advances in the generation, compression and focusing of intense heavy ion beams in the presence of a neutralizing background plasma. Such beams can provide uniform volumetric heating of the target during a time-scale shorter than the hydrodynamic response time, thereby enabling a significant suite of experiments that will elucidate the underlying physics of dense, strongly-coupled plasma states, which have been heretofore poorly understood and inadequately diagnosed, particularly in the warm dense matter regime. The innovations, fundamental knowledge, and experimental capabilities developed in this basic research program is also expected to provide new research opportunities to study the physics of directly-driven ion targets, which can dramatically reduce the size of heavy ion beam drivers for inertial fusion energy applications. Experiments examining the behavior of thin target foils heated to the warm dense matter regime began at the Lawrence Berkeley National Laboratory in 2008, using the Neutralized Drift Compression Experiment - I (NDCX-I) facility, and its associated target chamber and diagnostics. The upgrade of this facility, called NDCX-II, will enable an excitingmore » set of scientific experiments that require highly uniform heating of the target, using Li{sup +} ions which enter the target with kinetic energy in the range of 3 MeV, slightly above the Bragg peak for energy deposition, and exit with energies slightly below the Bragg peak. This document briefly summarizes the wide range of fundamental scientific experiments that can be carried out on the NDCX-II facility, pertaining to the two charges presented to the 2008 Fusion Energy Science Advisory Committee (FESAC) panel on High Energy Density Laboratory Plasmas (HEDLP). These charges include: (1) Identify the compelling scientific opportunities for research in fundamental HEDLP that could be investigated using existing and planned facilities in support of the Office of Fusion Energy Sciences and the National Nuclear Security Administration/Defense Program missions; and (2) Identify the scientific issues of implosion and target design that need to be addressed to make the case for inertial fusion energy as a potential future energy source. Compelling research opportunities of high intellectual value that can be carried out on the NDCX-II experimental facility are briefly summarized below, grouped into four main research areas. Page 4 lists several national and internationally-attended user workshops that have provided much of the input for the experimental campaigns describe below. More detailed information can be provided upon request.« less

We describe a form of self-consistent particle-in-cell plasma simulation which is applicable to strongly inhomogeneous systems involving a wide range of space and time scales. In this multi-scale method, the plasma particles in each region of phase space are advanced using a step size appropriate to that region, as determined by accuracy considerations. While the necessity of a self-consistent field may seem to require processing of all particles in synchrony, the method overcomes that difficulty. This is accomplished by means of implicit PIC techniques, interpolating grid quantities in time to obtain the source contributions from groups of particles not advanced during the current step. For suitable problems (those in which fine space-time resolution is needed only in isolated spatial regions), most of the particles are not processed on any given step. Thus, major gains in efficiency over conventional simulations may be realized. In this paper we describe the method, and the beginnings of our investigations into its feasibility.

This milestone has been accomplished. The Heavy Ion Fusion Science Virtual National Laboratory (HIFS-VNL) has developed and implemented an initial beam-in-plasma implicit modeling capability in Warp; has carried out tests validating the behavior of the models employed; has compared the results of electrostatic and electromagnetic models when applied to beam expansion in an NDCX-I relevant regime; has compared Warp and LSP results on a problem relevant to NDCX-I; has modeled wave excitation by a rigid beam propagating through plasma; and has implemented and begun testing a more advanced implicit method that correctly captures electron drift motion even when timesteps too large to resolve the electron gyro-period are employed. The HIFS-VNL is well on its way toward having a state-of-the-art source-to-target simulation capability that will enable more effective support of ongoing experiments in the NDCX series and allow more confident planning for future ones.

Clouds of stray electrons are ubiquitous in particle accelerators and frequently limit the performance of storage rings. Earlier measurements of electron energy distribution and flux to the walls provided only a relative electron cloud density. We have measured electron accumulation using ions expelled by the beam. The ion energy distribution maps the depressed beam potential and gives the dynamic cloud density. Clearing electrode current reveals the static background cloud density, allowing the first absolute measurement of the time-dependent electron cloud density during the beam pulse.

In 1994 a Fusion Technology journal publication by Logan, Moir and Hoffman described how exploiting unusually-strong economy-of-scale for large (8 GWe-scale) multi-unit HIF plants sharing a driver and target factory among several low cost molten salt fusion chambers {at} 100MWe net power DEMO. This scoping study, at a very preliminary conceptual level, attempts to identify how we might meet the last two great challenges taking advantage of several recent ideas and advances which motivate reconsideration of modular HIF drivers: >60X longitudinal compression of neutralized ion beams using a variable waveform induction module in NDCX down to 2 nanosecond bunches, the proof-of-principle demonstration of fast optical-gated solid state SiC switches by George Caporaso's group at LLNL (see George's RPIA06 paper), and recent work by Ed Lee, John Barnard and Hong Qin on methods for time-dependent correction of chromatic focusing errors in neutralized beams with up to 10 % {Delta}v/v velocity tilt, allowing 5 or more bunches, and shorter bunches, and possibly 40 that would need higher peak beam intensities in order to reduce total driver energy below 1 MJ. In principle, both PLIA and induction accelerators might benefit from multiple short bunches (see June 24, 2005 talk by Logan on multi-pulsing in PLIA accelerators for IFE), although the PLIA approach, because of fixed circuit wave velocities at any z, requires imaginative work-arounds to handle the different bunch velocities required. George's RPIA06 paper also describes a different type of radial line induction linac that might be considered, but its unclear how the required pulse-to-pulse variable waveforms can be obtained with such pulselines. This initial MathCad analysis explores multi-pulsing in modular solenoid induction linacs (concept shown in Figure 1) considering high-q ECR sources, basic induction acceleration limits assuming affordable agile waveforms, transverse and longitudinal bunch confinement constraints, models to optimize bunch lengths, solenoid fields, core radial builds and switching. Figure 2 below illustrates one linac module for a driver example (not yet optimized) consisting of 40 linacs (20 at each end). Necessarily, this first look invokes many new ideas, but could they potentially meet the above challenges?

The authors discuss the use of discrete-particle simulations to model beam transport during the pulse-compression stage of a heavy-ion fusion accelerator. Recent efforts have concentrated on the development and application of an emittance diagnostic. They do not directly calculate the x-x' emittance of all particles which cross a particular axial plane during the current step. Instead, they work with all particles within any of several comoving windows in z. The emittance calculated for any finite-length window is erroneously large, but it is (to a good approximation) linear in the window length, for short windows that do not span the edge of a lens. Thus, the authors use overlapping windows of different lengths, and by extrapolating to zero window length, they obtain a true local x-x' (or y-y') emittance with good statistics. The authors have also developed a formalism for modeling a bent beam using a time-dependent simulation algorithm that differs only minimally from that used for a straight beam. >

An attractive feature of the inertial fusion energy (IFE) approach to commercial energy production is that the fusion driver is well separated from the fusion confinement chamber. This ''standoff'' feature means the driver is largely isolated from fusion reaction products. Further, inertial confinement fusion (ICF) target ignition (with modest gain) is now scheduled to be demonstrated at the National Ignition Facility (NIF) using a laser driver system. The NIF program will, to a considerable extent, validate indirectly-driven heavy-ion fusion (HIF) target designs for IFE. However, it remains that HIF standoff between the final focus system and the fusion target needs to be seriously addressed. In fact, there now exists a timely opportunity for the Office of Fusion Energy Science (OFES) to experimentally explore the feasibility of one of the attractive final transport options in the fusion chamber: the self-pinched transport mode. Presently, there are several mainline approaches for HIF beam transport and neutralization in the fusion chamber. These range from the (conservative) vacuum ballistic focus, for which there is much experience from high energy research accelerators, to highly neutralized ballistic focus, which matches well to lower voltage acceleration with resulting lower driver costs. Alternatively, Z-discharge channel transport and self-pinched transport in gas-filled chambers may relax requirements on beam quality and final focusing systems, leading to even lower driver cost. In any case, these alternative methods of transport, especially self-pinched transport, are unusually attractive from the standpoint of chamber design and neutronics. There is no requirement for low chamber pressure. Moreover, only a minuscule fraction of the fusion neutrons can escape from the chamber. Therefore, it is relatively easy to shield sensitive components, e-g., superconducting magnets from any significant neutron flux. Indeed, self-pinched transport and liquid wall protection endow DT fusion with many of the advantages of aneutronic fusion. The question is: will self-pinched transport work? Early theoretical studies indicated that self-pinched transport was not an option because net currents established in gas during beam injection were too small to cause beam pinching. However, recent numerical simulations using the 3D hybrid code IPROP3, including the effects of non-local ionization, indicate that self-pinched transport may be possible. The capability to test the concept exists today in scaled experiments using a high-current focused proton beam produced by the Gamble II pulsed-power accelerator at the Naval Research Laboratory. This White Paper describes the implications of the self-pinched transport approach to HIF power plant design and the relevance of proton experiments designed to test the concept. Near-term experiments and analysis are also suggested.

By manipulating a set of ion beams upstream of a target, it is possible to arrange for a smoother deposition pattern, so as to achieve more uniform illumination of the target. A uniform energy deposition pattern is important for applications including ion-beam-driven high energy density physics and heavy-ion beam-driven inertial fusion energy (“heavy-ion fusion”). Here, we consider an approach to such smoothing that is based on rapidly “wobbling” each of the beams back and forth along a short arc-shaped path, via oscillating fields applied upstream of the final pulse compression. In this technique, uniformity is achieved in the time-averaged sense; this is sufficient provided the beam oscillation timescale is short relative to the hydrodynamic timescale of the target implosion. This work builds on two earlier concepts: elliptical beams applied to a distributed-radiator target [D. A. Callahan and M. Tabak, Phys. Plasmas 7, 2083 (2000)] and beams that are wobbled so as to trace a number of full rotations ar...

To increase the size of the time step, and thereby extend the applicability of kinetic plasma simulation, analysis of the stability and accuracy of implicit time integration schemes for plasma particle-in-cell simulation and the synthesis of new algorithms have been undertaken. Three classes of implicit algorithms are considered in general form. Stability and accuracy calculations provide guidelines for the design and application of implicit simulation algorithms, as illustrated in the construction of new difference schemes with desirable properties. Of particular interest- are the relaxation of stability constraints on the time step, strong damping of unwanted high-frequency modes, accuracy of the simulation of low-frequency phenomena, numerical secular acceleration, and numerical stability of fast and slow space-charge waves. The potency of higher order accurate differencing schemes in reducing undesirable numerical effects is demonstrated.

1. Five hundred and ten patients in whom caudal analgesia was attempted were studied. 2. Eighty per cent of patients in labor were found to be suitable for caudal analgesia with 97.5 per cent complete success. 3. An increased incidence in the use of oxytocic agents and operative obstetrics was found. 4. The advantages of caudal analgesia with elective induction of labor are stressed. 5. Three babies were lost, of whom 2 had congenital abnormalities incompatible with life. This gives a corrected neonatal mortality rate of 0.2 per cent.

Summary: An evaluation of a new ECG monitor which detects and classifies ventricular extrasystoles. A device is described which is highly efficient in detecting and classifying ventricular ectopic beats. This instrument may have a significant role in patient monitoring. The system is based on analysis of a 5 electrode orthogonal system with comparison of QRS wave forms with a stored normal wave form. The design was based on a test tape derived from 26 patients and evaluated further on long recordings of 16 other patients. Results indicate that the device is highly reliable in QRS detection and in detection of ventricular ectopic beats. The problem of artefacts due mainly to patient movement is held within reasonable limits.