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Although cooperative social networks are considered key to human evolution, emphasis has usually been placed on the functions of men’s cooperative networks. What do women's networks look like? Do they resemble or differ from men's and what does this suggest about evolutionarily inherited gender differences in reproductive and social strategies? In this paper, we test the ‘universal gender differences’ hypothesis positing gender-specific network structures against the ‘gender reversal’ hypothesis that posits women's networks looking more 'masculine' under matriliny. Specifically, we ask whether men's friendship networks are always larger than women's and we investigate measures of centrality by gender and descent system. To do so, we use tools from social network analysis and data on men’s and women’s friendship ties in matrilineal and patrilineal Mosuo communities. In tentative support of the gender reversal hypothesis, we find that women's friendship networks in matriliny are relatively large. Measures of centrality and generalized linear models otherwise reveal greater differences between communities than between men and women. The data and analyses we present are primarily descriptive given limitations of sample size and sampling strategy. Nonetheless, our results provide support for the flexible application of social relationships across genders and clearly challenge the predominant narrative of universal gender differences across space and time.

Although cooperative social networks are considered key to human evolution, emphasis has most often been placed on the functions of male cooperative networks. As a result, gender differences in social networks are under-studied and remain incompletely theorized. Variation in kinship systems may be leveraged to test and generate hypotheses that explain the causes and effects of variation in gendered social networks. Specifically, by linking socio-ecological drivers to variation in kinship systems, human behavioral ecology provides a framework to anticipate and explain divergent patterns in gendered social networks within different kinship ecologies. In this paper, we test the ‘universal gender differences’ hypothesis positing gender-specific network structures against the ‘gender reversal’ hypothesis that women’s social networks in matriliny will more closely resemble those of men’s in patriliny. We compare these hypotheses using tools from social network analyses and data on men’s and women’s social networks in matrilineal and patrilineal Mosuo communities. In support of the gender reversal hypothesis, we find that women’s networks in matriliny are more similar to men’s in patriliny. Specifically, women in matriliny have higher edge density than do men, and women have higher measures of degree centralization than do men in matriliny whereas patrilineal men have higher measures of centrality than do women. Additionally, we find that geographic proximity and relatedness together predict women’s friendships in patriliny whereas relatedness predominates in matriliny. Finally, we find that friendship predicts ties in other domains of cooperation and social support. These results support the idea that the socio-ecological factors that result in different kinship systems also impact the ways that men and women operate within these systems, underscoring the importance of human flexibility in family making, and challenging the predominant narrative of universal gender differences.

Despite billions of dollars spent on technological devices to counter the Improvised Explosive Device (IED) threat, IEDs are still responsible for roughly 50% of the casualties on today’s asymmetric battlefield. Counter IED (CIED) investments in technology and improvements to military operations are hoped to reduce these casualties. This research focuses on CIED military operations and uses computer modeling and simulation to explore two alternative patrol tactics to defeat or otherwise reduce the impact of IED strikes, damage, and casualties on friendly forces operating in contemporary and future battlefields, such as rural Afghanistan. Among other findings and inferences, research analysis indicates the “Stop and Search” tactic results in statistically significantly fewer strikes and casualties than the “Drive Through” tactic.

Developments in through silicon via (TSV) fabrication and filling have allowed for significant advancements in the microelectronics industry by enabling compact 3D integration. Copper, due to its desirable electrical properties, is the most commonly used metal for TSVs filling. TSVs are filled electrochemically by selectively reducing solvated metal ions in an electrolyte solution to confined TSV geometries via the addition of organic and inorganic additives (halides, suppressors, accelerators, levelers). Optimization of this mechanism can often be temperamental requiring alterations in the solution’s chemical makeup as well as electrical bias and fluid flow parameters. Therefore, consistent and reliable methods of characterizing electrochemical copper fill quality is critical to provide feedback necessary for process adjustments. Historically, characterizing TSV fill profile has relied on physical cross sectioning by mechanical grinding, planarization and polishing (Figure 1). These methods are effective in that they offer direct visualization of the TSV fill quality; however, they have certain inherent drawbacks. The most critical drawback is that mechanical cross sectioning is a destructive process and can only be used in process development and not on deliverable parts. Also, mechanical material removal can often be time consuming and inconsistent requiring significant effort by process technicians to generate desirable results. Implementing non-destructive methods for characterization is necessary for the advancement of TSV technology and has been explored in an effort to make TSV research more streamline and efficient. Recent work at Sandia National Laboratories has evaluated non-destructive TSV characterization processes through X-Ray Computed Tomography (CT), digital radiographs and X-ray Phase Contrast Imaging (XPCI). The benefit of X-ray evaluation of TSV filling is batch level processing of many TSVs at once (Figure 2A), digital model rendering for multidimensional analysis (Figure 2B), and complete preservation of the physical integrity of test pieces and deliverables. Each nondestructive technique for TSV characterization will be directly compared and contrasted to conventional grinding and polishing on the merits of defect detection, resolution, time consumption and reproducibility. This talk will outline the development of non-destructive methods for TSV characterization and evaluate the reliability and consistency of these approaches. Sandia National Laboratories, a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA-0003525. This paper describes objective technical results and analysis. Any subjective views or opinions that might be expressed in the paper do not necessarily represent the views of the U.S. Department of Energy or the United States Government. Figure 1

The incorporation of copper-filled, mesoscale through-silicon-vias (TSVs) as a three-dimensional integration technique allows for increased input/output per unit volume compared to wire bonded microelectronic devices. Mesoscale TSVs that span the full thickness of a silicon wafer allow for preservation of a large radius of curvature during multi-layer device fabrication and for conservation of mass in the device, which is often a requirement in MEMS applications. The damascene process is commonly implemented for Cu electrodeposition in high aspect ratio features and typically involves a three-additive system in a CuSO4-H2SO4 electrolyte. However, a single-additive system has recently been shown capable of achieving bottom-up superfilling in features with higher aspect ratios than those commonly used in damascene interconnects.[i] This resistive electrodeposition system utilizes CuSO4, methane sulfonic acid (MSA), chloride, and a poloxamine suppressor additive. Cyclic voltammetry (CV) can be used to characterize the plating solution and identify a potential range that exhibits hysteresis in the voltage-current relationship that is caused by suppressor disruption at the cathode surface during electrodeposition. This hysteretic region serves as an operating window where void-free Cu filling of high aspect ratio features may be achieved. Using this chemistry, potentiostatic and galvanostatic plating conditions for void-free filling were developed for 100 μm diameter vias that are 600 μm deep, a 6:1 aspect ratio.[ii],[iii] Cu electrodeposition in TSVs with a higher aspect ratio of 10:1 is currently under investigation. These TSVs have a 62.5 μm diameter etched into a 625 μm thick silicon-on-insulator (SOI) wafer. Conditions that produce void free, bottom-up filling for 100 μm diameter TSVs have not directly translated to fill 62.5 μm diameter TSVs. In this work, the poloxamine suppressor concentration, current, potential, and sample rotation rate were varied to analyze their effect on the fill profile in these 62.5 μm diameter TSVs. Fill profiles were analyzed after mechanically cross-sectioning and optically imaging the samples. Cu fill profiles were also obtained through X-ray computed tomography (CT) scans. This work details the experimental approach associated with determining galvanostatic and potentiostatic plating conditions for 62.5 μm diameter TSVs and presents the resultant fill profiles of Cu in these vias. Sandia National Laboratories, a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA-0003525. This paper describes objective technical results and analysis. Any subjective views or opinions that might be expressed in the paper do not necessarily represent the views of the U.S. Department of Energy or the United States Government. [i]. Moffat, T. P., and D. Josell. "Extreme bottom-up superfilling of through-silicon-vias by damascene processing: suppressor disruption, positive feedback and turing patterns." Journal of the Electrochemical Society 159.4 (2012): D208-D216. [ii]. Menk, L. A. et. al. “Bottom-Up Copper Filling of Large Scale Through Silicon Vias for MEMS Technology.” Journal of the Electrochemical Society 166.1 (2019): D3066-D3071. [iii]. Menk, L. A. et. al. “Galvanostatic Plating with a Single Additive Electrolyte for Bottom-Up Filling of Copper in Mesoscale TSVs” Journal of the Electrochemical Society 166.1 (2019).

Multi project-wafers (MPWs) offer cost-effective options for fabrication of application specific integrated circuits (ASICs) produced for entities not requiring a large volume of die from a dedicated full wafer run at an advanced semiconductor foundry. MPWs consist of a mixture of different devices shared on a single wafer; thereby reducing cost of processing by allowing the purchase of real estate allotted to each device. This practice is advantageous for those in academia or government that often only require small quantities of devices for research or niche applications. With many teams investing in a single wafer run, strict design rules must be followed on these microelectronic chips. In particular, the metal used in the final routing layer must be AlCu. This AlCu metallization is not compatible with solder connections for flip chip bonding applications because solder is unable to wet AlCu. To allow MPW die integration with flip chip bonding applications, a solder compatible under bump metallization (UBM) must be deposited on top of the AlCu. This UBM deposition can be achieved through physical vapor deposition and subsequent electrolytic plating into a photolithography defined plating mold. Unfortunately, photolithographic processes are only compatible with full wafers and not with singulated die. This leaves electroless deposition methods such as immersion tin or zinc followed by electroless nickel, electroless palladium, immersion gold (ENEPIG) or electroless nickel and immersion gold (ENIG) as the only options for depositing a wettable UBM on MPW die. Electroless deposition can be performed with a single die at a time, however this process is not well suited for manufacturing. In this work, we have developed a scheme for batch level UBM deposition on singulated semiconductor die by coupling temporary bonding with electroless deposition. A unique batch approach is proposed to electrolessly deposit UBM to terminal AlCu on MPW die. Preliminary Si sidewall passivation is used to eliminate metallization of unintended surfaces in subsequent steps. Temporary custom fixturing onto a carrier substrate is leveraged allowing a variety of devices to be processed like a full wafer, establishing feasibility for industrial scaling. The bulk aluminum oxide is then solubilized by chemical etching and replaced by reduction of Sn as a base layer for ENIG and ENEPIG processes as seen in Figure 1. After metal deposition, devices are liberated from the temporary mounting substrate making them ready for flip chip bonding. Due to creating an UBM through electroless processes, options for interposer bumps are limited and outlined in Figure 2. Solder bonds from Cu pillars topped with SnAg or electroplated with either AuSn or SnAg allow a reflow solder attachment to complete electrical contact between the two chips. Electroplated Au bumps allow for a thermocompression bond to be made between the two chips. Both methods have benefits based on circumstance. Reflow solder is advantageous for fragile chips that cannot withstand the high pressure associated with thermocompression. Cu pillars are also attractive for RF devices in that Cu offers reduced electrical parisitics. Thermocompression is advantageous because it does not require high level of uniformity in the final Au bump. In this presentation, we will provide details on the passivation, batch level handling process, uniformity, and yield statistics for the electroless deposition. Supported by the Laboratory Directed Research and Development program at Sandia National Laboratories, a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA-0003525. Figure 1

Copper (Cu) electrodeposition (ECD) in through-silicon-vias (TSVs) is an essential technique required for high-density 3-D integration of complex semiconductor devices. Cu ECD most commonly utilizes an acid sulfate electrolyte containing a finely tuned three-additive combination of inhibiting and Cu2+ aquo complex catalyzing species to produce void free deposits through the depth of high aspect ratio features. Despite their proven efficacy in filling micro- and nanoscale features, these three-additive electrolytes have not been shown to be viable for filling ICs at the mesoscale (> 100 µm). This is likely explained by the seminal curvature enhanced adsorbate coverage (CEAC) mechanism that describes the adsorption/desorption action of the additive species to an electrode surface. [1], [2] This mechanism theorizes that the interaction between the constituent additives and the rate of Cu2+ reduction is highly dependent on the local curvature of the electrode surface. In addition, these systems often require finely tuned ECD techniques like the use of pulse plating regimes, tightly controlled additive concentrations, and relatively low applied current densities (< 10 mA/cm2). To overcome the deficiencies of the three-additive acid sulfate chemistry that the CEAC mechanism describes, a single-additive chemistry was developed for the purposes of filling conformally conductive high aspect ratio features exclusively from the bottom-up by Moffat, T.P. and Josell, D. [3-5] This chemistry relies on a specific polyether suppressor additive, which induces voltammetric hysteresis and a positive feedback action as metal deposition disrupts Cl--suppressor complexes at the cathode surface. The acid sulfate resistive Cu electrolyte developed by Moffat, T.P. and Josell, D. utilizes 1 M CuSO4 + 0.5 M H2SO4 in addition to µM level concentrations of chloride and polyether suppressor species.[3-5] To investigate the functionality of a novel chemistry, the work outlined herein relies on the same mechanism and utilizes the same polyether suppressor and chloride concentration ranges, but instead uses a 1.25 M CH3SO3H + 0.25 M H2SO4 electrolyte. This electrolyte exhibits a greater Cu solubility, requires a lower concentration of acid, thus increasing the Cu plating rate while still retaining the same S-NDR mechanics as developed by Moffat, T.P. and Josell.[3-5] Upon adoption of the above-described chemistry, several issues were explored. The importance of convection on plating profiles within mesoscale (600 μm depth, 5:1 aspect ratio) blind TSVs is examined. In addition, potentiostatic methods are used to explore the process window for achieving bottom-up feature filling in the mesoscale TSVs described above. However, these potentiostatic techniques rely on the use of a reference electrode in solution, which is not a viable setup in industrial wafer-scale production tools. Thus, a galvanostatic approach is outlined and shown to be a viable alternative based on resulting fill profiles. The values used for the current density were calculated by comparing the breakdown potential of the suppressor molecule with the current reading at that set potential. Using only the area of the feature bottoms, a current density was calculated and fixed during subsequent plating experiments. This method is potentially problematic as the non -referenced electrochemical potential will maintain some unknown hysteresis, but initial results are shown to be promising. This galvanostatic approach, using the novel single additive chemistry is currently being explored for subsequent implementation into full wafer plating apparatus. Supported by the Laboratory Directed Research and Development program at Sandia National Laboratories, a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA-0003525. Andricacos, P.C., et al., Damascene copper electroplating for chip interconnections. Ibm Journal of Research and Development, 1998. 42(5): p. 567-574. Moffat, T.P., et al., Superconformal film growth: Mechanism and quantification. Ibm Journal of Research and Development, 2005. 49(1): p. 19-36. Moffat, T. P., and D. Josell. "Extreme bottom-up superfilling of through-silicon-vias by damascene processing: suppressor disruption, positive feedback and turing patterns." Journal of The Electrochemical Society 159.4 (2012): D208-D216. Josell, D., D. Wheeler, and T. P. Moffat. "Modeling extreme bottom-up filling of through silicon vias." Journal of The Electrochemical Society 159.10 (2012): D570-D576. Wheeler, Daniel, Thomas P. Moffat, and Daniel Josell. "Spatial-temporal modeling of extreme bottom-up filling of through-silicon-vias." Journal of The Electrochemical Society 160.12 (2013): D3260-D3265.

We have investigated the Ga–Pd(110) system by means of soft X-ray photoelectron spectroscopy and low energy electron diffraction, and tested its chemical properties by co-adsorbing CO. On adsorption on Pd, the Ga 3d and 2p3/2 core levels showed small shifts with respect to metallic Ga, and the density of Pd 4d states below the Fermi level was reduced. The Ga–Pd surface alloy exhibited a (1 × 2) structure. The presence of gallium reduced the CO saturation coverage and bond strength in comparison with clean Pd(110).

The high-current experiment (HCX) at LBNL is a driver scale single beam injector that provides a 1 MeV K + ion beam current of 0.18 A for 5 μs. It transports high-current beams with large fill factor (ratio of the maximum beam envelope radius to the beam pipe radius) and low emittance growth that are required to keep the cost of the power plant competitive and to satisfy the target requirements of focusing ion beams to high-power density. Beam interaction with the background gas and walls desorbs electrons that can multiply and accumulate, creating an electron cloud. This ubiquitous effect grows at higher fill factors and degrades the quality of the beam. We review simulations and diagnostics tools used to measure electron production, accumulation and its properties.

A Retarding Field Analyzer (RFA) was inserted in a drift region of the magnetic transport section of the High-Current Experiment (HCX), that is at high-vacuum, to measure ions and electrons resulting from beam interaction with background gas and walls. The ions are expelled during the beam pulse by the space–charge potential and the electrons are expelled mainly at the end of the beam, when the beam potential decays. The ion energy distribution shows the beam potential of ∼ 2100 V and the beam–background gas total cross-section of 3.1 × 10 - 19 m 2 . The electron energy distribution reveals that the expelled electrons are mainly desorbed from the walls and gain ∼ 22 eV from the beam potential decaying with time before entering the RFA. Details of the RFA design and of the measured energy distributions are presented and discussed.

This paper presents plans for neutralized drift compression experiments, precursors to future target heating experiments. The target-physics objective is to study warm dense matter (WDM) using short-duration (∼1 ns) ion beams that enter the targets at energies just above that at which dE/dx is maximal. High intensity on target is to be achieved by a combination of longitudinal compression and transverse focusing. This work will build upon recent success in longitudinal compression, where the ion beam was compressed lengthwise by a factor of more than 50 by first applying a linear head-to-tail velocity tilt to the beam, and then allowing the beam to drift through a dense, neutralizing background plasma. Studies on a novel pulse line ion accelerator were also carried out. It is planned to demonstrate simultaneous transverse focusing and longitudinal compression in a series of future experiments, thereby achieving conditions suitable for future WDM target experiments. Future experiments may use solenoids for transverse focusing of un-neutralized ion beams during acceleration. Recent results are reported in the transport of a high-perveance heavy ion beam in a solenoid transport channel. The principal objectives of this solenoid transport experiment are to match and transport a space-charge-dominated ion beam, and to study associated electron-cloud and gas effects that may limit the beam quality in a solenoid transport system. Ideally, the beam will establish a Brillouin-flow condition (rotation at one-half the cyclotron frequency). Other mechanisms that potentially degrade beam quality are being studied, such as focusing-field aberrations, beam halo, and separation of lattice focusing elements.

Electrons can accumulate in and degrade the quality of positively charged beams. This is a well-known problem in proton storage rings. Heavy-ion rings are more frequently limited by gas pressure-rise effects. Both effects may limit how closely the beam radius can approach the beam-tube radius in a heavy-ion linac. We study beams of 1 MeV K + with currents of up to 180 mA in the High-Current Experiment (HCX), and compare our work with simulations. The theory and simulation results are discussed in a companion papers. We have developed the first diagnostics that quantitatively measure the accumulation of electrons in a beam [M. Kireeff Covo, A. Molvik, A. Friedman, J.-L. Vay, P. Seidl, G. Logan, D. Baca, J.L. Vujic, Phys. Rev. Lett. 97 (2006) 054801; M. Kireeff Covo, et al., Nucl. Instr. and Meth. A, 2007, in press, doi:10.1016/j.nima.2007.02.045.]. This will enable the particle balance to be measured for each source of electrons in a linac: ionization of gas, emission from walls surrounding the beam, and emission from an end wall coupled with electron drifts upstream through quadrupole magnets, and electron-trapping efficiencies can be determined. Experiments where the heavy-ion beam is transported with solenoid magnetic fields, rather than with quadrupole magnetic or electrostatic fields, are being initiated. We discuss plans for experiments using electrode sets (in the middle and at the ends of magnets) to either expel or to trap electrons within the magnets. We observe oscillations of the electron density and position in the last quadrupole magnet when we flood the beam with electrons from an end wall. These oscillations, near 6 MHz, are observed to grow from the center of the magnet while drifting upstream against the beam, in good agreement with simulations.

To create high-energy density matter and fusion conditions, high-power drivers, such as lasers, ion beams, and X-ray drivers, may be employed to heat targets with short pulses compared to hydro-motion. Both high-energy density physics and ion-driven inertial fusion require the simultaneous transverse and longitudinal compression of an ion beam to achieve high intensities. We have previously studied the effects of plasma neutralization for transverse beam compression. The scaled experiment, the Neutralized Transport Experiment (NTX), demonstrated that an initially un-neutralized beam can be compressed transversely to � 1 mm radius when charge neutralization by background plasma electrons is provided. Here, we report longitudinal compression of a velocity-tailored, intense, neutralized 25 mA K + beam at 300 keV. The compression takes place in a 1–2 m drift section filled with plasma to provide space-charge neutralization. An induction cell produces a head-to-tail velocity ramp that longitudinally compresses the neutralized beam, enhances the beam peak current by a factor of 50 and produces a pulse duration of about 3 ns. The physics of longitudinal compression, experimental procedure, and the results of the compression experiments are presented. r 2007 Elsevier B.V. All rights reserved.

The High-Current Experiment (HCX) at Lawrence Berkeley National Laboratory is part of the US program to explore heavy-ion beam transport at a scale representative of the low-energy end of an induction linac driver for fusion energy production. Four pulsed magnetic quadrupoles are being used to study gas and electron effects with a 0.2 A, 1-MeV K + beam. The magnets, originally designed and built for a prototype pulsed magnetic quadrupole array, have an elliptical beam tube (6×10 cm) and iron yoke. The magnet coil and field length are ≈31 cm, and operating gradients are 10–40 T/m. To establish that the field quality of the prototype quadrupoles is satisfactory for the experiments, a 1-cm pickup loop was used to measure the flux B r ( θ ) at the magnet mid-plane and also at the lead and return ends. A longer probe was used to measure the integrated flux of B θ ( θ ) along the magnet. The field quality appears satisfactory for the short transport experiments through these quadrupoles.

Nitridation of GaAs(1 0 0) is performed using a double differential pumping RF cell. X-ray photoelectron spectroscopy (XPS) is used to monitor surface composition changes that result from ionic etching by Ar+ bombardment and nitridation of this substrate. We have studied the influence of temperature and pressure of nitrogen. The process of nitridation leads to the formation of a nitride layer which seems to be a ternary compound of gallium, arsenic and nitrogen. To improve the composition of the surface layer and to obtain pure GaN thin films on the surface by stopping arsenic migration, we have performed another kind of nitridation process. It consists, firstly, of a deposition of metallic gallium on the substrate surface. The system Ga/GaAs is then nitrided and the XPS measurements indicate the formation of a GaN layer on the surface.

The High Current Experiment (HCX) is being assembled at Lawrence Berkeley National Laboratory as part of the U.S. program to explore heavy ion beam transport at a scale representative of the low-energy end of an induction linac driver for fusion energy production. The primary mission of this experiment is to investigate aperture fill factors acceptable for the transport of space-charge dominated heavy ion beams at high space-charge intensity (line-charge density ∼ 0.2 μC/m) over long pulse durations (>4 μs). This machine will test transport issues at a driver-relevant scale resulting from nonlinear space-charge effects and collective modes, beam centroid alignment and beam steering, matching, image charges, halo, lost-particle induced electron effects, and longitudinal bunch control. We present the first experimental results carried out with the coasting K+ ion beam transported through the first 10 electrostatic transport quadrupoles and associated diagnostics. Later phases of the experiment will include more electrostatic lattice periods to allow more sensitive tests of emittance growth, and also magnetic quadrupoles to explore similar issues in magnetic channels with a full driver scale beam.

Health Hazard Analysis (HHA) is one major type of patient health risk assessment for medical device field performance issue. U.S. Food and Drug Administration (FDA) has an online form, listing the needed information for HHA. In this paper, we will illustrate a quantitative HHA approach, which is structured in a rigorous risk assessment framework, with several critical steps, concepts and some key statistical reliability techniques embedded. We will also propose a method using Bayesian approach in patient health risk assessment due to medical device field failure. This approach is very useful for issues identified in the manufacturing process or supply chain, when there have been no field returns yet out of the current product sales. Our work may assist the medical device industry by offering an enhanced HHA approach for patient health risk assessment.

An experiment to inject and match a $10\text{ }\text{ }\ensuremath{\mu}\mathrm{s}$, singly charged ${\mathrm{K}}^{+}$ ion bunch at an ion energy of 0.3 MeV, current of 45 mA, and dimensionless perveance of ${10}^{\ensuremath{-}3}$ into a solenoid lattice has been carried out at LBNL. The principal objective of this experiment is to match and transport the space-charge dominated ion beam and compare predicted and measured emittance. Initial investigation also presented the opportunity to study electron cloud effects and the effects of misalignments. A qualitative comparison of experimental and calculated results are presented, which include time resolved current density, transverse distributions, and phase space of the beam at different diagnostic planes.

A new 201.25 MHz RF system is being developed for the LANSCE proton drift tube linac (DTL). A planned upgrade will replace parts of the DTL RF system with new generation components. When installed for the LANSCE-R project, the new system will reduce the total number of electron power tubes from twenty-four to seven in the RF power plant. The 3.4 MW final power amplifier will use a Thales TH628 Diacrodereg. This state- of-the-art device eliminates the large anode modulator of the present triode system, and will be driven by a new tetrode intermediate power amplifier. In this mode of operation, this intermediate stage will provide 150 kW of peak power. The first DTL tank requires up to 400 kW of RF power, which will be provided by the same tetrode driver amplifier. A prototype system is being constructed to test components, using some of the infrastructure from previous RF projects. High voltage DC power became available through innovative re-engineering of an installed system. A summary of the design and construction of the intermediate power amplifier will be presented and test results will be summarized.

Beam interaction with background gas and walls produces ubiquitous clouds of stray electrons that frequently limit the performance of particle accelerator and storage rings. Counterintuitively we obtained the electron cloud accumulation by measuring the expelled ions that are originated from the beam-background gas interaction, rather than by measuring electrons that reach the walls. The kinetic ion energy measured with a retarding field analyzer (RFA) maps the depressed beam space-charge potential and provides the dynamic electron cloud density. Clearing electrode current measurements give the static electron cloud background that complements and corroborates with the RFA measurements, providing an absolute measurement of electron cloud density during a 5 mus duration beam pulse in a drift region of the magnetic transport section of the High-Current Experiment (HCX) at LBNL.

This report collects information on cathode contaminants we have gathered in the process of operating the LBNL DARHT cathode test stand. Information on contaminants is compiled from several sources. The attachment, ''Practical Aspects of Modern Dispenser Cathodes'', is from Heat Wave Corp. (TB-134) and was originally published in Microwave Journal, September 1979. Cathode contamination depends on both material choices and residual gases. Table 1 of TB-134 lists materials that can poison dispenser cathodes. These include reactive residual gases or vapors such as oxygen, water vapor, benzene, chlorine, fluorine, sulfur, silicon, and most metals other than molybdenum, rhenium, tungsten, and copper. The metals interact with the cathode surface through their vapor pressure. A paper by Nexsen and Turner, J. Appl. Phys. 68, 298-303 (1990) shows the threshold effects of some common residual gases or vapors on cathode performance. The book by Walter H. Kohl, Handbook of Materials and Techniques for Vacuum Devices, also contains useful information on cathodes and poisoning agents. A plot of the vapor pressures and poisoning effect of certain metals (from Kohl) is shown below. Note that the vapor pressure of zinc is 1.1 x 10{sup -8} Torr at 400 K = 127 C, and 2.7 x 10{supmore » -5} at 500 K = 227 C. By contrast iron reaches a vapor pressure 1 x 10{sup -8} between 800 and 900 C. Therefore it is important to eliminate any brass parts that could exceed a temperature of 100 C. Many structural components of the cathode assembly contain steel. At 500-600 C in an oxygen atmosphere chromium oxide may outgas from the steel. [Cho, et.al., J. Vac. Sci. Technol. A 19, p. 998 (2001)]. Steel may also contain silicon, and sulfur at low concentrations. Therefore use of steel should be limited or avoided at high temperature near the cathode. Materials that should be avoided in the vicinity of the cathode include brass, silver, zinc, non-OFHC copper, silicates, and sulfur-containing lubricants such molybdenum disulfide. Macor is an aluminosilicate-based insulator that is not stable at high temperature. Macor near the cathode should be replaced by a high-temperature insulator such as alumina ceramic. Other insulating materials that contain silicates, such as fiber insulating sleeves, should be avoided. Copper that is not OFHC contains oxygen and other impurities and should be avoided. Lubricating screw coatings should be chosen carefully to have no sulfur content. Common sources of contamination that can cause low emission include water, saliva, silicates such as glass dust, etc. Cathodes should be handled in near clean-room conditions to minimize the amount of water vapor on the cathode surface from breathing, etc. Cathodes should also be stored in such as a way as to avoid contact with materials such as glass dust and water vapor. Attached are plots of SEM data for several test pieces that were taken from the LBNL test stand after activation of the 311x scandate DARHT cathode. Several copper pieces in the anode region were tested, showing the presence of zinc. Two stainless steel nuts coated with a contaminant were also tested. The SEM data indicates the presence of zinc and some sulfur. The zinc has been traced to a brass piece, and the sulfur to the possible use of molybdenum disulfide lubricant on a nut in the system. Finally a swipe of contaminant on the vacuum vessel wall analyzed by a commercial testing laboratory shows again the presence of zinc. In order to improve system cleanliness, we have implemented the following modifications to the test stand: replaced the brass piece with copper-tungsten; replaced Macor insulators with alumina ceramic; used boron nitride lubricant; replaced copper beam stop with OFHC copper; and replaced steel pieces near the cathode where possible with copper or copper-tungsten. A clean fire of high-temperature components and a high-current filament test have shown no evidence to date for contaminants since the modifications.« less

Intense ion beams are difficult to maintain as non-neutral plasmas. Experiments and simulations are used to study the complex interactions between beam ions and (unwanted) electrons. Such ''electron clouds'' limit the performance of many accelerators. To characterize electron clouds, a number of parameters are measured including: total and local electron production and loss for each of three major sources, beam potential versus time, electron line-charge density, and gas pressure within the beam. Electron control methods include surface treatments to reduce electron and gas emission, and techniques to remove electrons from the beam, or block their capture by the beam. Detailed, self-consistent simulations include beam-transport fields, and electron and gas generation and transport; these compute unexpectedly rich behavior, much of which is confirmed experimentally. For example, in a quadrupole magnetic field, ion and dense electron plasmas interact to produce multi-kV oscillations in the electron plasma and distortions of the beam velocity space distribution, without the system becoming homogeneous or locally neutral.

In a first beam dynamics validation experiment for a new Pulse Line Ion Acceleration (PLIA) concept, the predicted energy amplification and beam bunching were experimentally observed. Beam energy modulation of -80 keV to +150 keV was measured using a PLIA input voltage waveform of -21 kV to +12 kV. Ion pulses accelerated by 150 keV, and bunching by a factor of four were simultaneously achieved. The measured longitudinal phase space and current waveform of the accelerated beam are in good agreement with 3-D particle-in-cell simulations.

Electron clouds limit the performance of many major accelerators and storage rings. Significant quantities of electrons result when halo ions are lost to beam tubes, generating gas which can be ionized and ion-induced electrons that can multiply and accumulate, causing degradation or loss of the ion beam. In order to understand the physical mechanisms of ion-induced electron production, experiments studied the impact of 50 to 400 keV K{sup +} ions on stainless steel surfaces near grazing incidence, using the 500 kV Ion Source Test Stand (STS-500) at LLNL. The experimental electron yield scales with the electronic component (dE{sub e}/dx) of the stopping power and its angular dependence does not follow l/cos({theta}). A theoretical model is developed, using TRIM code to evaluate dE{sub e}/dx at several depths in the target, to estimate the electron yield, which is compared with the experimental results. The experiment extends the range of energy from previous works and the model reproduces the angular dependence and magnitude of the electron yield.

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.

The cost of accelerators for heavy-ion inertial fusion energy (HIF) can be reduced by using the smallest possible clearance between the beam and the wall from the beamline. This increases beam loss to the walls, generating ion-induced electrons that could be trapped by beam space charge potential into an "electron cloud", which can cause degradation or loss of the ion beam. In order to test the physical mechanism model of ion induced electrons production we have measured the impact of K+ ions with energies up to 400 KeV on stainless steel surfaces near grazing incidence, using the ion source test stand (STS-500) at LLNL. The electron yield will be discussed and compared with experimental measurements from 1 MeV K+ ions in the High-Current Experiment at LBNL.

Electron clouds and gas pressure rise limit the performance of many major accelerator rings. We are studying these issues experimentally with ∼ 1 MeV heavy-ion beams, coordinated with significant efforts in self-consistent simulation and theory. The experiments use multiple diagnostics, within and between quadrupole magnets, to measure the sources and accumulation of electrons and gas. In support of these studies, we have measured gas desorption and electron emission coefficients for potassium ions impinging on stainless steel targets at angles near grazing incidence. Our goal is to measure the electron particle balance for each source – ionization of gas, emission from beam tubes, and emission from an end wall – determine the electron effects on the ion beam and apply the increased understanding to mitigation. We describe progress towards that goal.

Ion beam neutralization and compression experiments are designed to determine the feasibility of using compressed high intensity ion beams for high energy density physics (HEDP) experiments and for inertial fusion power. To quantitatively ascertain the various mechanisms and methods for beam compression, the Neutralized Drift Compression Experiment (NDCX) facility is being constructed at Lawrence Berkeley National Laboratory (LBNL). In the first neutralized drift compression experiment, a 280 KeV, 25 mA, K+ ion beam is longitudinally 50-fold compressed using an induction core to produce a velocity tilt. This compression ratio is measured using various diagnostics.

Gas desorption and electron emission coefficients were measured for 1 MeV potassium ions incident on stainless steel at grazing angles (between 80\ifmmode^\circ\else\textdegree\fi{} and 88\ifmmode^\circ\else\textdegree\fi{} from normal incidence) using a new gas-electron source diagnostic (GESD). Issues addressed in design and commissioning of the GESD include effects from backscattering of ions at the surface, space-charge limited emission current, and reproducibility of desorption measurements. We find that electron emission coefficients ${\ensuremath{\gamma}}_{e}$ scale as $1/\mathrm{cos} (\ensuremath{\theta})$ up to angles of 86\ifmmode^\circ\else\textdegree\fi{}, where ${\ensuremath{\gamma}}_{e}=90$. Nearer grazing incidence, ${\ensuremath{\gamma}}_{e}$ is reduced below the $1/\mathrm{cos} (\ensuremath{\theta})$ scaling by nuclear scattering of ions through large angles, reaching ${\ensuremath{\gamma}}_{e}=135$ at 88\ifmmode^\circ\else\textdegree\fi{}. Electrons were emitted with a measured temperature of $\ensuremath{\sim}30\text{ }\text{ }\mathrm{e}\mathrm{V}$. Gas desorption coefficients ${\ensuremath{\gamma}}_{0}$ were much larger, of order ${\ensuremath{\gamma}}_{0}={10}^{4}$. They also varied with angle, but much more slowly than $1/\mathrm{cos} (\ensuremath{\theta})$. From this we conclude that the desorption was not entirely from adsorbed layers of gas on the surface. Two mitigation techniques were investigated: rough surfaces reduced electron emission by a factor of 10 and gas desorption by a factor of 2; a mild bake to $\ensuremath{\sim}220\ifmmode^\circ\else\textdegree\fi{}$ had no effect on electron emission, but decreased gas desorption by 15% near grazing incidence. We propose that gas desorption is due to electronic sputtering.

Alumino-silicate sources that are used for Heavy Ion Fusion (HIF) drivers can produce high current beams, and have a long lifetime, typically many months of normal operation. The usual ion source diameter is about 10 cm with a curved emitting surface. Recently we achieved reliable fabrication of such large diameter sources with high quality alumino-silicate coating on tungsten substrates. The effects of substrate porosity, powder size distribution, coating technique, particle packing density, drying, and heat firing temperature have been investigated.

Accelerators for heavy-ion inertial fusion energy (HIF) have an economic incentive to fit beam tubes tightly to beams, putting them at risk from electron clouds produced by emission of electrons and gas from walls. Theory and PIC simulations suggest that the electrons will be radially trapped in the /spl ges/1 kV ion-beam potential. We are beginning studies on the High-Current Experiment (HCX) with unique capabilities to characterize electron production and trapping, the effects on ion beams, and mitigation techniques. We are measuring the flux of electrons and gas evolved from a target, whose angle to the beam can be varied between 78/spl deg/ and 88/spl deg/ from normal incidence. Quadrupole magnets are operating with a variety of internal charged particle diagnostics to measure the beam halo loss, net charge, electron ionization rate, and gas density.

The heavy-ion fusion program is conducting several ion source and injector experiments to support ongoing HIF beam transport experiments and to develop new injector concepts for future fusion drivers. In the area of large diameter surface source, we studied the beam optics, experimented with aperturing, and benchmarked the computer simulation code. Steady progress was made in the merging beamlet experiment. The RF plasma source was optimized to produce high current density beamlets. Computer simulation of merging beamlets had produced a design and the hardware is being fabricated. We are examining a new concept based on accel–decel injection to produce super-high line charge density for application in driving targets for high energy density physics studies. Since trapping of secondary electrons in high current positive ion beams is still a concern for HIF, we consider a backup option using negative ion beams.

The cleaning and the nitridation of GaAs(1 0 0) substrates have been studied in this work by electron energy loss spectroscopy (EELS), elastic peak electron spectroscopy (EPES) and X-ray photoelectron spectroscopy (XPS). The nitridation of GaAs(1 0 0) was performed using a double differential pumping RF cell. We have studied in a first part, the surface modifications of the substrate during ionic cleaning. In a second part, we have determined the λ i ( E ) K ( E , E n ) curves from EELS spectra using Tougaard's procedure for cleaned-GaAs(1 0 0) and nitrited-GaAs(1 0 0) substrates. The thickness of the GaN overlayer was deduced from these results.

LBNL-54716 HIFAN 1303 Experimental study of electron effects in heavy-ion beams •A.W. MOLVIK a , •With F.M. BIENIOSEK b , D. Baca b , R.H. COHEN a , A. FRIEDMAN a , M.A. FURMAN b , b. LBNL E.P. LEE b , S.M. LUND a , L. PROST b , P.A. SEIDL b , J-L. VAY b . a. LLNL •Heavy-Ion Fusion Virtual National Laboratory HIF-VNL Presented to International workshop in physics of high energy density in matter, session on gas/electron cloud effects in high-ion-current accelerators Waldemar-Petersen-Haus, Hirschegg, Austria Feb. 2-7, 2003 AWM 1 The Heavy Ion Fusion Virtual National Laboratory

Future cockpit and aviation applications require high quality airport databases. Accuracy, resolution, integrity, completeness, traceability, and timeliness are key requirements. For most aviation applications, attributed vector databases are needed. The geometry is based on points, lines, and closed polygons. To document the needs for aviation industry RTCA and EUROCAE developed in a joint committee, the DO-272/ED-99 document. It states industry needs for data features, attributes, coding, and capture rules for Airport Mapping Databases (AMDB). This paper describes the technical approach Jeppesen has taken to generate a world-wide set of three-hundred AMDB airports. All AMDB airports are DO-200A/ED-76 and DO-272/ED-99 compliant. Jeppesen airports have a 5m (CE90) accuracy and an 10-3 integrity. World-wide all AMDB data is delivered in WGS84 coordinates. Jeppesen continually updates the databases.

The promise of inertial fusion energy driven by heavy ion beams requires the development of accelerators that produce ion currents (/spl sim/100's Amperes/beam) and ion energies (/spl sim/1 - 10 GeV) that have not been achieved simultaneously in any existing accelerator. The high currents imply high generalized perveances, large tune depressions, and high space charge potentials of the beam center relative to the beam pipe. Many of the scientific issues associated with ion beams of high perveance and large tune depression have been addressed over the last two decades on scaled experiments at Lawrence Berkeley and Lawrence Livermore National Laboratories, the University of Maryland, and elsewhere. The additional requirement of high space charge potential (or equivalently high line charge density) gives rise to effects (particularly the role of electrons in beam transport) which must be understood before proceeding to a large scale accelerator. The first phase of a new series of experiments in the Heavy Ion Fusion Virtual National Laboratory (HIF VNL), the High Current Experiments (HCX), is now beginning at LBNL. The mission of the HCX is to transport beams with driver line charge density so as to investigate the physics of this regime, including constraints on the maximum radial filling factor of the beam through the pipe. This factor is important for determining both cost and reliability of a driver scale accelerator. The HCX will provide data for design of the next steps in the sequence of experiments leading to an inertial fusion energy power plant. The focus of the program after the HCX will be on integration of all of the manipulations required for a driver. In the near term following HCX, an Integrated Beam Experiment (IBX) of the same general scale as the HCX is envisioned. The step which bridges the gap between the IBX and an engineering test facility for fusion has been designated the Integrated Research Experiment (IRE). The IRE (like the IBX) will provide an integrated test of the beam physics necessary for a driver, but in addition will provide target and chamber data. This paper will review the experimental and theoretical progress in heavy ion accelerator driver research from the scaled experiments through the present experiments and will discuss plans for the IRE.

Due to their intrinsic low ion temperature, surface ionization sources with a moderate to high current density (J/spl sim/10-100 mA/cm/sup 2/) may meet the beam brightness requirement for Heavy Ion Fusion (HIF) injectors, for both, the large source and multiple-beamlet designs. However, alkali metals released by these sources can contaminate and degrade high voltage insulators, thus making neutral atom loss an important issue. We present experimental results of average emitted J's and lifetime performance of K/sup +/ and Cs/sup +/ surface ionization sources and K-aluminosilicate sources operating in pulsed modes (2-10 /spl mu/s). Fabrication of large (/spl sim/10 cm diameter) aluminosilicate sources is challenging given the surface quality required. Current work in this aspect is presented.

This paper reports progress in the HCX experimental program since the last HIF-VNL Program Advisory Committee Review (February 14-15 2002). On July 25 2002 the experiment was shut down for about four weeks to move the control room. A principal area of effort has been to obtain and evaluate the first experimental results carried out with a matched and well-aligned K + ion beam transported through 10 electrostatic transport quadrupoles. These are the main results and highlights to date: A1. There is no emittance growth within the sensitivity of the diagnostics, and little beam loss. The beam centroid is aligned to within 0.5 mm and 2 mrad of the central axis of the channel, and the envelope mismatch amplitude is

Thermoelectric (TE) materials offer engineering solutions for applications such as cooling without moving parts and conversion of waste heat to electricity. However, devices using existing thermoelectric materials suffer from poor efficiency and high cost. Electrochemical deposition (ECD) has the potential to make the synthesis of thermoelectrics more cost effective and potentially enhance thermoelectric properties. The best thermoelectrics to date are thin film super lattices, fabricated using vapor phase methods [1]. However, these materials have a greatly limited application space due to their limited thickness (~ 10 µm). In this work, ECD techniques are used to nanostructure Bi2Te3 based thermoelectric materials over large areas and thicknesses, as well as electroforming it into a mold to enable future batch fabrication. Multiple experiments were performed to better understand scalability of thermoelectric film growth. Large grain boundaries were found to affect density and stoichiometry of the material impacting TE performance. A 7 liter chemistry make-up and ECD conditions are established targeting wafer scale batch fabrication. The highest Seebeck, 85 µV/K, was found when deposited in small electroformed posts with a resistivity of 5 mΩ cm. [1] R. Venkatasubramanian, E.S., T. Colpitts, B. O'Quinn,, Nature, 2001. 413: p. 597.