A set of twenty-three 20-L crystallizer runs exploring the importance of several engineering variables found that growth temperature is the most important variable controlling damage resistance of DKDP over the conditions investigated. Boules grown between 45 C and room temperature have a 50% probability of 3{omega} bulk damage that is 1.5 to 2 times higher than boules grown between 65 and 45 C. This raises their damage resistance above the NIF tripler specification for 8 J/cm{sup 2} operation by a comfortable margin. Solution impurity levels do not correlate with damage resistance for iron less than 200 ppb and aluminum less than 2000 ppb. The possibility that low growth temperatures could increase damage resistance in NIF-scale boules was tested by growing a large boule in a 1000-L crystallizer with a supplemental growth solution tank. Four samples representing early and late pyramid and prism growth are very close to the specification as best it is understood at the present. Implications of low temperature growth for meeting absorbance, homogeneity, and other material specifications are discussed.

Iron ions provide many valuable plasma diagnostics for cosmic plasmas. The accuracy of these diagnostics, however, often depends on an accurate understanding of the ionization structure of the emitting gas. Dielectronic recombination (DR) is the dominant electron-ion recombination mechanism for most iron ions in cosmic plasmas. Using the heavy-ion storage ring at the Max-Planck-Institute for Nuclear Physics in Heidelberg, Germany, we have measured the low temperature DR rates for Fe{sup q+} where q = 15, 17, 18, and 19. These rates are important for photoionized gases which form in the media surrounding active galactic nuclei, X-ray binaries, and cataclysmic variables. Our results demonstrate that commonly used theoretical approximations for calculating low temperature DR rates can easily under- or over-estimate the DR rate by a factor of {approx} 2 or more. As essentially all DR rates used for modeling photoionized gases are calculated using these approximations, our results indicate that new DR rates are needed for almost all charge states of cosmically abundant elements. Measurements are underway for other charge states of iron.

Surfaces of steel structures that enclose high-fluence, large-beam lasers have conventional and unconventional requirements. Aside from rust prevention, the surfaces must resist laser-induced degradation and the contamination of the optical components. The latter requires a surface that can be precision cleaned to low levels of particulate and organic residue. In addition, the surface treatment for the walls should be economical to apply because of the large surface areas involved, and accommodating with intricate joint geometries. Thermal sprayed coatings of aluminum (Al) and stainless steel are candidate surface materials. Coatings are produced and characterized for porosity, smoothness, and hardness. These properties have a bearing on the cleanliness of the coating. The laser resistance of Al and 3 16L coatings are given. The paper summarizes the characterization of twin-wire-arc deposited Al, high-velocity-oxygen-fueled (HVOF) deposited Al, flame-sprayed 316L, and HVOF deposited316L. The most promising candidate coating is that of HVOF Al. This Al coating has the lowest porosity (8%) compared the other three coatings and relatively low hardness (100 VHN). The as-deposited roughness (Ra) is 433 pinches, but after a quick sanding by hand, the roughness decreased to 166 pinches. Other post-coat treatments are discussed. HVOF aluminum coatings are demonstrated. Al coatings are …

Currently, large physics simulations produce 3D fields whose individual surfaces, after conventional extraction processes, contain upwards of hundreds of millions of triangles. Detailed interactive viewing of these surfaces requires powerful compression to minimize storage, and fast view-dependent optimization of display triangulations to drive high-performance graphics hardware. In this work we provide an overview of an end-to-end multiresolution dataflow strategy whose goal is to increase efficiencies in practice by several orders of magnitude. Given recent advancements in subdivision-surface wavelet compression and view-dependent optimization, we present algorithms here that provide the ''glue'' that makes this strategy hold together. Shrink-wrapping converts highly detailed unstructured surfaces of arbitrary topology to the semi-structured form needed for wavelet compression. Remapping to triangle bintrees minimizes disturbing ''pops'' during real-time display-triangulation optimization and provides effective selective-transmission compression for out-of-core and remote access to these huge surfaces.

A 'proof-of-principle' Nb{sub 3}Sn superconducting dual-bore dipole magnet was built from racetrack coils, as a first step in a program to develop an economical, 15 Tesla, accelerator-quality magnet. The mechanical design and magnet fabrication procedures are discussed. No training was required to achieve temperature-dependent plateau currents, despite several thermal cycles that involved partial magnet disassembly and substantial pre-load variations. Subsequent magnets are expected to approach 15 Tesla with substantially improved conductor.

We argue that extended technicolor augmented with topcolor requires that all mixing between the third and the first two quark generations resides in the mixing matrix of left-handed down quarks. Then, the anti-B_d--B_d mixing that occurs in topcolor models constrains the coloron and Z' boson masses to be greater than about 5 TeV. This implies fine tuning of the topcolor couplings to better than 1percent.

We point out that for solar neutrino oscillations with the mass-squared difference of Delta m^2 ~;; 10^-10 - 10^-9 eV^2, traditionally known as"vacuum oscillation'' range, the solar matter effects are non-negligible, particularly for the low energy pp neutrinos. One consequence of this is that the values of the mixing angle theta and pi/2-theta are not equivalent, leading to the need to consider the entire physical range of the mixing angle 0<=theta<=pi/2 when determining the allowed values of the neutrino oscillation parameters.

High-resolution resonant Auger electron spectra of NO measured in the vicinity of the N 1s {yields} 2{pi} core excitations are presented. The open shell electronic configuration of the molecule results in four excited electronic states, three of which are populated in the photoabsorption spectrum, {sup 2}{Delta}, {sup 2}{Sigma}{sup -} and {sup 2}{Sigma}{sup +}. Electron emission spectra obtained at different vibrational levels of the three N 1s core-excited states of NO are reported. Recently reported ab initio calculations [J. Chem. Phys. 106, 4038(1997)] are used to generate theoretical spectra for comparison with the experimental results taking lifetime vibration interference and Auger resonant Raman effects into account. Very good agreement is found for the lowest energy X {sup 1}{Sigma}{sup +} final ionic state. Spectra of the higher energy final ionic states are decomposed into contributions from the different 5{sigma}{sup -1}2{pi}{sup 1} and 1{pi}{sup -1}2{pi}{sup 1} configurations for comparison of the calculated and experimental partial Auger decay rates. A revised value for the adiabatic ionization energy of the {sup 1}{Delta} ionic state results from the deconvolution.

The authors present results from a Monte Carlo investigation of a simple bilayer model with geometrically frustrated interactions similar to those found in the mixed layer pnictide oxides (Sr{sub 2}Mn{sub 3}Pn{sub 2}O{sub 2}, Pn = As, Sb). The model is composed of two inequivalent square lattices with nearest-neighbor intra- and interlayer interactions. They find a ground state composed of two independent Neel ordered layers when the interlayer exchange is an order of magnitude weaker than the intralayer exchange, as suggested by experiment. Evidence for local orthogonal order between the layers is found, but it occurs in regions of parameter space which are not experimentally realized. Qualitatively similar results were observed in models with a larger number of layers. They conclude that frustration caused by nearest-neighbor interactions in the mixed layer pnictide oxides is not sufficient to explain the long-range orthogonal order that is observed experimentally.

A confocal microscopy imaging system was devised to selectively detect Second harmonic signals generated by biological tissues. Several types of biological tissues were examined using this imaging system, including human teeth, bovine blood vessels, and chicken skin. All these tissues generated strong second harmonic signals. There is considerable evidence that the source of these signals in tissue is collagen. Collagen, the predominant component of most tissues, is known to have second order nonlinear susceptibility. This technique may have diagnostic usefulness in pathophysiological conditions characterized by changes in collagen structure including malignant transformation of nevi, progression of diabetic complications, and abnormalities in wound healing.

The use of femtosecond lasers allows materials processing of practically any material with extremely high precision and minimal collateral damage. Advantages over conventional laser machining (using pulses longer than a few tens of picoseconds) are realized by depositing the laser energy into the electrons of the material on a time scale short compared to the transfer time of this energy to the bulk of the material, resulting in increased ablation efficiency and negligible shock or thermal stress. The improvement in the morphology by using femtosecond pulses rather than nanosecond pulses has been studied in numerous materials from biologic materials to dielectrics to metals. During the drilling process, we have observed the onset of small channels which drill faster than the surrounding material.

A proposed new heavy ion preinjector for RHIC is described. The progress made at BNL on the development of an Electron Beam Ion Source (EBIS) has increased our confidence that one can build a preinjector meeting RHIC requirements using an EBIS producing intermediate charge state heavy ions. A new RFQ and Linac will be required to accelerate beams from this source to an energy sufficient for injection into the AGS Booster. These are both straightforward devices, very similar to ones already in operation at other laboratories. Injection into the Booster will occur at the same location as the existing heavy ion injection from the Tandem Van de Graaff.

We have analyzed the motion of a Hall probe, which is rotated about an axis that is arbitrarily displaced and oriented with respect to the magnetic axis of a solenoid. We outline how the magnetic field measured by the rotating Hall probe can be calculated. We show how to compare theoretical results with actual measurements, to determine the displacement and orientation of the axis of rotation of the probe from the magnetic axis. If the center of rotation of the probe is known by surveying, the corresponding point on the magnetic axis of the solenoid can be located. This is applied to a solenoid that was built for BNL by Oxford Instruments.

A model of energy gain induced by fast ignition of thermonuclear burn in compressed deuterium-tritium fuel, is used to show the potential for 300x gain with a driver energy of 1 M J, if the National Ignition Facility (NIF) were to be adapted for fast ignition. The physics of fast ignition has been studied using a petawatt laser facility at the Lawrence Livermore National Laboratory. Laser plasma interaction in a preformed plasma on a solid target leads to relativistic self-focusing evidenced by x-ray images. Absorption of the laser radiation transfers energy to an intense source of relativistic electrons. Good conversion efficiency into a wide angular distribution is reported. Heating by the electrons in solid density CD{sub 2} produces 0.5 to 1/keV temperature, inferred from the D-D thermo-nuclear neutron yield.

Promising results are currently being obtained on the BNL Electron Beam Test Stand (EBTS), which is a prototype for the Relativistic Heavy Ion Collider (RHIC) EBIS. Based on the present-results, a proposal has been made regarding the general design of the RHIC EBIS. During the next year experiments will be made to investigate physics issues and beam properties important to the detailed design of the RHIC EBIS. Below we have outlined some of the physics issues to be explored experimentally, beam diagnostics that will be employed, and hardware modifications that are desired to go from the prototype stage to the RHIC EBIS.

Experimental study of the BNL Electron Beam Test Stand (EBTS), which is a prototype of the Relativistic Heavy Ion Collider (RHIC) Electron Beam Ion Source (EBIS), is currently underway. The basic physics and engineering aspects of a high current EBIS implemented in EBTS are outlined and construction of its main systems is presented. Efficient transmission of a 10 A electron beam through the ion trap has been achieved. Experimental results on generation of multiply charged ions with both continuous gas and external ion injection confirm stable operation of the ion trap.

A plasma related mode has been identified when EBTS operated with long trap length. The mode frequency scaling showed monotonic increased with confinement time. Initial scaling qualitatively suggested the mode to an electron beam driven ion cyclotron instability. However, a more quantitative evaluation is indicative of a drift mode. Nevertheless, the possibility of a structure mode, though unlikely, can not be completely excluded. The process of proper instability identification and stabilization is described.

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In this talk the authors present a highly accurate coarsening algorithm for constructing coarse finite element spaces to be used in algebraic multigrid methods designed for finite element problems on generally unstructured meshes. The new algorithm relies on removing certain percentage of the high oscillating components from the spectrum of local stiffness matrices corresponding to element agglomerations. By doing so, one is guaranteed that the hierarchical complement finite element subspace gives rise to a well conditioned matrix. The coarsening consists of an agglomeration step and of computing a few minimal eigenvectors of the corresponding assembled agglomerate stiffness matrix. The method requires access to the individual element matrices. Based on the topological agglomeration algorithms they employed one is able to define coarse elements and coarse element matrices thus allowing for recursive use of the same algorithm. Some numerical illustration for elliptic problems is also given.

The advantages of spectrally resolved gamma-ray imaging have previously been demonstrated for the detection of fissile materials. However, previous results have been obtained with the relatively poor spectral resolution provided by scintillator-based detectors. In this paper we present a new class of coded aperture imager based on a position-sensitive germanium detector. The use of this detector type provides a factor of 40 improvement in energy resolution which improves the quality of the images obtained while reducing the integration time required. Tight spectral cuts on known emission lines allow deeper penetration into highly attenuating objects. In addition, advanced analysis techniques can provide information on overlying material though the application of spatially resolved gamma-gauging. We describe the imager, present simulations of its capabilities and the first characterizations of a prototype detector.

The X-ray sources in the 4-7 keV energy regime can be produced by laser-irradiating high-Z gas-filled targets with high-powered lasers. A series of experiments have been performed using underdense targets that are supersonically heated with {approx} 35 W of 0.35 {micro}m laser light. These targets were cylindrical Be enclosures that were filled with 1-2 atms of Xe gas. L-shell x-ray emission is emitted from the plasma and detected by Bragg crystal spectrometers and x-ray diodes. Absolute flux measurements show conversion efficiencies of {approx} 10% in the multi-kilovolt x-ray emission. These sources can be used as bright x-ray backlighters or for material testing.

We compare the detector background situation in an e{sup -} e{sup -} interaction region at the NLC with previous studies done of the NLC e{sup +} e{sup -} interaction region. We note from previous studies that the dominant source of detector backgrounds are the beamstrahlung pairs. Since these scale with luminosity, the reduction in luminosity in e{sup -} e{sup -} collisions leads to a reduction in detector backgrounds compared to the e{sup +} e{sup -} situation.

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A critical issue for sustaining high performance, negative central shear (NCS) discharges is the ability to maintain current distributions that are maximum off axis. Sustaining such hollow current profiles in steady state requires the use of non-inductively driven current sources. On the DIII-D experiment, a combination of neutral beam current drive (NBCD) and bootstrap current have been used to create transient NCS discharges. The electron cyclotron heating (ECH) and current drive (ECCD) system is currently being upgraded from three gyrotrons to six to provide more than 3MW of absorbed power in long-pulse operation to help sustain the required off-axis current drive. This upgrade SuPporrs the long range goal of DIII-D to sustain high performance discharges with high values of normalized {beta}, {beta}{sub n} = {beta}/(I{sub p}/aB{sub T}), confinement enhancement factor, H, and neutron production rates while utilizing bootstrap current fraction, f{sub bs}, in excess of 50%. At these high performance levels, the likelihood of onset of MHD modes that spoil confinement indicates the need to control plasma profiles if we are to extend this operation to long pulse or steady state. To investigate the effectiveness of the EC system and to explore operating scenarios to sustain these discharges, we use …