On-board hydrogen storage is a key requirement for fuel cell-powered cars and trucks. Porous carbon-based materials can in principle adsorb more hydrogen per unit weight at room temperature than liquid hydrogen at -176 oC. Achieving this goal requires interconnected pores with very high internal surface area, and binding energies between hydrogen and carbon significantly enhanced relative to H2 on graphite. In this project a systematic study of carbide-derived carbons, a novel form of porous carbon, was carried out to discover a high-performance hydrogen sorption material to meet the goal. In the event we were unable to improve on the state of the art in terms of stored hydrogen per unit weight, having encountered the same fundamental limit of all porous carbons: the very weak interaction between H2 and the carbon surface. On the other hand we did discover several strategies to improve storage capacity on a volume basis, which should be applicable to other forms of porous carbon. Further discoveries with potentially broader impacts include • Proof that storage performance is not directly related to pore surface area, as had been previously claimed. Small pores (< 1.5 nm) are much more effective in storing hydrogen than larger ones, such that …

For many years at LLNL we have been developing time-correlated neutron detection techniques and algorithms for many applications including Arms Control, Threat Detection and Nuclear Material Assaying. Many of our techniques have been developed specifically for relatively low efficiency (a few %) inherent in the man-portable systems. Historically we used thermal neutron detectors (mainly {sup 3}He) taking advantage of the high thermal neutron interaction cross-sections but more recently we have been investigating fast neutron detection with liquid scintillators and inorganic crystals. We have discovered considerable detection advantages with fast neutron detection as the inherent nano-second production time-scales of fission and neutron induced fission are preserved instead of being lost in neutron thermalization required for thermal neutron detectors. We are now applying fast neutron technology (new fast and portable digital electronics as well as new faster and less hazardous scintillator formulations) to the safeguards regime and faster detector response times and neutron momentum sensitivity show promise in measuring, differentiating and assaying samples that have very high count rates as well as mixed fission sources (e.g. Cm and Pu). We report on measured results with our existing liquid scintillator array and progress on design of nuclear material assaying system that incorporates fast …

The photocathode of the proposed LCLS RF Photoinjector will be irradiated by uv laser light which is generated as the third harmonic of incident fundamental ir laser light. We have investigated quantitatively the effect of input ir spectral bandwidth on the exiting longitudinal intensity profiles, energy conversion efficiencies and spectral bandwidths that characterize the third harmonic generation (THG) process with a pair of crystals. These profiles, efficiencies and bandwidths include the residual fundamental and residual second harmonic light exiting the second crystal. The intrinsic acceptance bandwidth for THG is determined by crystal material and thickness as well as the type of phase matching that is used. For our case of BBO material with type I phase matching these bandwidths are approximately 0.9 nm*cm and 0.1 nm*cm for second and third harmonic generation respectively. Consequently for fixed crystal thicknesses and a fixed input ir longitudinal profile, the specified input ir bandwidth will determine the profiles, efficiencies and bandwidths exiting the second crystal. The results reported here are predictions of the SNLO code that is available as 'freeware' from the Sandia National Laboratories. It has been modified for this work. It is critical to note that this modification has enabled us to …

The U.S. Nuclear Regulatory Commission’s (NRC’s) endorsement of consensus standards provides a cost-effective means of enhancing the staff’s ability to review state-of-the-art designs. Although the NRC endorsed consensus standards in many technical disciplines, it yet has to do so in human factors engineering (HFE). The purpose of our study was to develop a standardized methodology whereby to evaluate a consensus HFE standard to determine its appropriateness to, and adequacy for using in licensing reviews. The high-level objective of the methodology is to ensure that the guidance meets the NRC’s requirements on scientific- and engineering-rigor that they use in developing their own guidance. We propose four criteria for endorsing a consensus standard: (1) It should meet an existing need for NRC’s licensing and safety reviews; (2) it should be based on sound HFE principles; (3) it should be thoroughly peer-reviewed; and, (4) it should address human performance issues identified in the literature. Our methodology offers a means to assess these four criteria. We used it to evaluate an Institute of Electrical and Electronics Engineers’ (IEEE) draft standard on computerized operating procedure systems. We concluded that the IEEE standard generally met the established criteria, although several areas were identified that needed further …

Radiation portal monitors used for interdiction of illicit materials at borders include highly sensitive neutron detection systems. The main reason for having neutron detection capability is to detect fission neutrons from plutonium. The currently deployed radiation portal monitors (RPMs) from Ludlum and Science Applications International Corporation (SAIC) use neutron detectors based upon 3He-filled gas proportional counters, which are the most common large neutron detector. There is a declining supply of 3He in the world, and thus, methods to reduce the use of this gas in RPMs with minimal changes to the current system designs and sensitivity to cargo-borne neutrons are being investigated. Four technologies have been identified as being currently commercially available, potential alternative neutron detectors to replace the use of 3He in RPMs. Reported here are the results of tests of a boron-lined proportional counter design variation. In the testing described here, the neutron detection efficiency and gamma ray rejection capabilities of a system manufactured by Proportional Technologies, Inc, was tested.

Phase diagrams of refractory metals remain essentially unknown. Moreover, there is an ongoing controversy over the high pressure (P) melting temperatures of these metals: results of diamond anvil cell (DAC) and shock wave experiments differ by at least a factor of two. From an extensive ab initio study on tantalum we discovered that the body-centered cubic phase, its physical phase at ambient conditions, transforms to another solid phase, possibly hexagonal omega phase, at high temperature (T). Hence the sample motion observed in DAC experiments is not due to melting but internal stresses accompanying a solid-solid transformation, as explained in more detail in our work. In view of our results on tantalum and previous work on molybdenum, as well as other published data, it is highly plausible that high-PT polymorphism is a general feature of Groups V and VI refractory metals.

We report a measurement of high-p{sub T} inclusive {pi}{sup 0}, {eta}, and direct photon production in p + p and d + Au collisions at {radical}s{sub NN} = 200 GeV at midrapidity (0 &lt; {eta} &lt; 1). Photons from the decay {pi}{sup 0} {yields} {gamma}{gamma} were detected in the Barrel Electromagnetic Calorimeter of the STAR experiment at the Relativistic Heavy Ion Collider. The {eta} {yields} {gamma}{gamma} decay was also observed and constituted the first {eta} measurement by STAR. The first direct photon cross section measurement by STAR is also presented, the signal was extracted statistically by subtracting the {pi}{sup 0}, {eta}, and {omega}(782) decay background from the inclusive photon distribution observed in the calorimeter. The analysis is described in detail, and the results are found to be in good agreement with earlier measurements and with next-to-leading order perturbative QCD calculations.

High pressure systems are important, for example, to understand the interiors of giant planets (Jupiter and Saturn), for experiments at NIF (the National Ignition Facility at Livermore) related to inertially confined fusion and for other interests of DOE. In this project, we are developing innovative simulation methods (Quantum Monte Carlo methods) to allow more accurate calculation of properties of systems under extreme conditions of pressure and temperature. These methods can use the power of current day supercomputers made of very many processors, starting from the basic equations of physics to model quantum phenomena important at the microscopic scale. During the grant period, we have settled two important questions of the physics of hydrogen and helium under extreme conditions. We have found the pressures and temperatures when hydrogen and helium mix together; this is important to understand the difference of the interiors of the planets Jupiter and Saturn. Secondly, we have shown that there exists a sharp transition as a function of pressure between molecular and atomic liquid hydrogen at temperatures below 2000K. This prediction can be confirmed with high pressure experiments.

Between 2007 and 2010 DuPont conducted a program under DOE award DE-FC36-07GO17056 to develop and improve Zymomonas mobilis as an ethanologen for commercial use in biorefineries to produce cellulosic ethanol. This program followed upon an earlier DOE funded program in which DuPont, in collaboration with the National Renewable Energy Laboratory (NREL) had developed a Zymomonas strain in conjunction with the development of an integrated cellulosic ethanol process. In the current project, we sought to maximize the utility of Zymomonas by adding the pathway to allow fermentation of the minor sugar arabinose, improve the utilization of xylose, improve tolerance to process hydrolysate and reduce the cost of producing the ethanologen. We undertook four major work streams to address these tasks, employing a range of approaches including genetic engineering, adaptation, metabolite and pathway analysis and fermentation process development. Through this project, we have developed a series of strains with improved characteristics versus the starting strain, and demonstrated robust scalability to at least the 200L scale. By a combination of improved ethanol fermentation yield and titer as well as reduced seed train costs, we have been able to reduce the capital investment and minimum ethanol selling price (MESP) by approximately 8.5% and 11% …

The nature of non-baryonic dark matter is one of the most intriguing questions for particle physics at the start of the 21st century. There is ample evidence for its existence, but almost nothing is known of its properties. WIMPs are a very appealing candidate particle and several experimental campaigns are underway around the world to search for these particles via the nuclear recoils that they should induce. The COUPP series of bubble chambers has played a significant role in the WIMP search. Through a sequence of detectors of increasing size, a number of R&amp;D issues have arisen and been solved, and the technology has now been advanced to the point where the construction of large chambers requires a modest research effort, some development, but mostly just engineering. It is within this context that we propose to build the next COUPP detector - COUPP-500, a ton scale device to be built over the next three years at Fermilab and then deployed deep underground at SNOLAB. The primary advantages of the COUPP approach over other technologies are: (1) The ability to reject electron and gamma backgrounds by arranging the chamber thermodynamics such that these particles do not even trigger the detector. (2) …

The R- & P- Reactor facilities were constructed in the early 1950's in response to Cold War efforts. The mission of the facilities was to produce materials for use in the nation's nuclear weapons stockpile. R-Reactor was removed from service in 1964 when President Johnson announced a slowdown of he nuclear arms race. PReactor continued operation until 1988 until the facility was taken off-line to modernize the facility with new safeguards. Efforts to restart the reactor ended in 1990 at the end of the Cold War. Both facilities have sat idle since their closure and have been identified as the first two reactors for closure at SRS.

The need for renewable fiber reinforced composites has never been as prevalent as it currently is. Natural fibers offer both cost savings and a reduction in density when compared to glass fibers. Though the strength of natural fibers is not as great as glass, the specific properties are comparable. Currently natural fiber composites have two issues that need to be addressed: resin compatibility and water absorption. The following preliminary research has investigated the use of Kenaf, Hibiscus cannabinus, as a possible glass replacement in fiber reinforced composites.

In particle accelerators, scattered protons with energies close to the incident particles may travel considerable distances with the beam before impacting on accelerator components downstream. To analyze such problems, angular deflection and energy loss of scattered particles are the main quantities to be simulated since these lead to changes in the beam's phase space distribution and particle loss. Simple approximations for nuclear scattering processes causing limited energy loss to high-energy protons traversing matter are developed which are suitable for rapid estimates and reduced-description Monte Carlo simulations. The implications for proton loss in the Large Hadron Collider due to nuclear scattering on collimation crystals are discussed.

We used LCLS pulses to excite thin-film and bulk graphite with various different microstructures, and probed the ultrafast ion and electron dynamics through Bragg and x-ray Thomson scattering (XRTS). We pioneered XRTS at LCLS, making this technique viable for other users. We demonstrated for the first time that the LCLS can be used to characterize warm-dense-matter through Bragg and x-ray Thomson scattering. The warm-dense-matter conditions were created using the LCLS beam. Representative examples of the results are shown in the Figure above. In our experiment, we utilized simultaneously both Bragg and two Thomson spectrometers. The Bragg measurements as a function of x-ray fluence and pulse length allows us to characterize the onset of atomic motion at 2 keV with the highest resolution to date. The Bragg detector was positioned in back-reflection, providing us access to scattering data with large scattering vectors (nearly 4{pi}/{lambda}). We found a clear difference between the atomic dynamics for 70 and 300 fs pulses, and we are currently in the process of comparing these results to our models. The outcome of this comparison will have important consequences for ultrafast diffractive imaging, for which it is still not clear if atomic resolution can truly be achieved. The …

A moving window technique for the finite element time domain (FETD) method is developed to simulate the propagation of electromagnetic waves induced by the transit of a charged particle beam inside large and long structures. The window moving along with the beam in the computational domain adopts high-order finite-element basis functions through p refinement and/or a high-resolution mesh through h refinement so that a sufficient accuracy is attained with substantially reduced computational costs. Algorithms to transfer discretized fields from one mesh to another, which are the key to implementing a moving window in a finite-element unstructured mesh, are presented. Numerical experiments are carried out using the moving window technique to compute short-range wakefields in long accelerator structures. The results are compared with those obtained from the normal FETD method and the advantages of using the moving window technique are discussed.

Experiments were conducted in 2003 and 2004 with protium and deuterium to demonstrate the hydrogen exchange properties of various catalyzed zeolites for tritium stripping purposes. A column was loaded with the experimental material and purged with either H{sub 2} or D{sub 2} as shown in Figure 1 and the effluent monitored with a Prisma Quadrupole. The purge gas was switched when the column outlet concentrations reached &gt;95% of the purge isotope. Outlet concentrations were calculated as the sum of the purge isotope in the elemental form plus the purge isotope in the oxide form (the purge stream was humidified as it passed through the column) divided by the total hydrogen isotopes in the effluent. 1.5 wt.% Pt on CBV 780 zeolite, manufactured by Zeolist International, had the best exchange characteristics, high capacity and fast kinetics, of the materials tested. This memorandum describes an approach to extrapolate previously unpublished hydrogen for deuterium exchange data collected earlier on 1.5 wt.% Pt on CBV 780 to lower concentrations for potential engineering applications.

Radiation portal monitors used for interdiction of illicit materials at borders include highly sensitive neutron detection systems. The main reason for having neutron detection capability is to detect fission neutrons from plutonium. The currently deployed radiation portal monitors (RPMs) from Ludlum and Science Applications International Corporation (SAIC) use neutron detectors based upon 3He-filled gas proportional counters, which are the most common large neutron detector. There is a declining supply of 3He in the world, and thus, methods to reduce the use of this gas in RPMs with minimal changes to the current system designs and sensitivity to cargo-borne neutrons are being investigated. Four technologies have been identified as being currently commercially available, potential alternative neutron detectors to replace the use of 3He in RPMs. These technologies are: 1) Boron trifluoride (BF3)-filled proportional counters, 2) Boron-lined proportional counters, 3) Lithium-loaded glass fibers, and 4) Coated non-scintillating plastic fibers. In addition, a few other companies have detector technologies that might be competitive in the near term as an alternative technology. Reported here are the results of tests of a boron-lined, multichamber proportional counter manufactured by LND, Inc. Also reported are results obtained with an earlier design of conventional, boron-lined, proportional counters from …

Proportional counters (PCs) are a type of gas-filled radiation detection device capable of distinguishing between a wide range of radiation types and energies. In this application, however, these devices are limited by high power consumption and high bias potentials required to operate in the proportional detection regime. Previous work performed with a single carbon nanotube (CNT) anode has shown that nanoscale-based PCs can operate at bias potentials of 10V rather than the 1000V range required for PCs. ''Proof of concept'' experiments with a single CNT as the anode exhibit a small detection volume and consequently required long count times (24 hrs). To make this a practical detector technology (i.e., decrease the count time), the effective detection volume has to be increased. Experimental data and electric field modeling show that if the pitch (spacing between individual nanotubes) of the arrays is too small, the electric field of the individual nanostructure will collapse and the nanoscale array will behaved as a single macro-scale field with the associated high bias potential required to reach the proportional region. Electric-field modeling of the affect of nanostructure pitch on the electric field distribution of these arrays predicted that a pitch of about two-and-a-times the height of …

Knowledge of poloidal velocity is necessary for the determination of the radial electric field, Er, which along with its gradient is linked to turbulence suppression and transport barrier formation. Recent measurements of poloidal flow on conventional tokamaks have been reported to be an order of magnitude larger than expected from neoclassical theory. In contrast, recent poloidal velocity measurements on the NSTX spherical torus [S. M. Kaye et al., Phys. Plasmas 8, 1977 (2001)] are near or below neoclassical estimates. A novel charge exchange recombination spectroscopy diagnostic is used, which features active and passive sets of up/down symmetric views to produce line-integrated poloidal velocity measurements that do not need atomic physics corrections. Local profiles are obtained with an inversion. Poloidal velocity measurements are compared with neoclassical values computed with the codes NCLASS [W. A. Houlberg et al., Phys. Plasmas 4, 3230 (1997)] and GTC-Neo [W. X. Wang, et al., Phys. Plasmas 13, 082501 (2006)], which has been updated to handle impurities. __________________________________________________

SLAC National Accelerator Laboratory has built and is currently operating a first generation prototype Marx klystron modulator to meet ILC specifications. Under development is a second generation prototype, aimed at improving overall performance, serviceability, and manufacturability as compared to its predecessor. It is designed around 32 cells, each operating at 3.75 kV and correcting for its own capacitor droop. Due to the uniqueness of this application, high voltage gate drivers needed to be developed for the main 6.5 kV and droop correction 1.7 kV IGBTs. The gate driver provides vital functions such as protection of the IGBT from over-voltage and over-current, detection of gate-emitter open and short circuit conditions, and monitoring of IGBT degradation (based on collector-emitter saturation voltage). Gate drive control, diagnostic processing capabilities, and communication are digitally implemented using an FPGA. This paper details the design of the gate driver circuitry, component selection, and construction layout. In addition, experimental results are included to illustrate the effectiveness of the protection circuit.

This paper presents accelerated lifetime tests on a polypropylene film capacitor. Experimental parameters (20% droop, 5 Hz repetition rate) simulate anticipated operating conditions encountered in the SLAC P2 Marx. Elevated film electric field stress is utilized as the acceleration parameter. Results indicate that, for the particular film of interest, a film stress of {approx}290 V/{mu}m corresponds to a 10{sup 5} hour lifetime. In addition, the voltage scaling exponent for this film is 13.1.

The ILC Marx Modulator is under development as a lower cost alternative to the 'Baseline Conceptual Design' (BCD) klystron modulator. Construction of a prototype Marx is complete and testing is underway at SLAC. The Marx employs solid state elements, IGBTs and diodes, to control the charge, discharge and isolation of the modules. The prototype is based on a stack of sixteen modules, each initially charged to {approx}11 kV, which are arranged in a Marx topology. Initially, eleven modules combine to produce the 120 kV output pulse. The remaining modules are switched in after appropriate delays to compensate for the voltage droop that results from the discharge of the energy storage capacitors. Additional elements will further regulate the output voltage to {+-}0.5%. The Marx presents several advantages over the conventional klystron modulator designs. It is physically smaller; there is no pulse transformer (quite massive at these parameters) and the energy storage capacitor bank is quite small, owing to the active droop compensation. It is oil-free; voltage hold-off is achieved using air insulation. It is air cooled; the secondary air-water heat exchanger is physically isolated from the electronic components. This paper outlines the current developmental status of the prototype Marx. It presents …

A simple but novel mitigation concept to enforce standoff distance and reduce shock loading on a vertical, partially-submerged structure is evaluated using scaled aquarium experiments and numerical modeling. Scaled, water tamped explosive experiments were performed using three gallon aquariums. The effectiveness of different mitigation configurations, including air-filled media and an air gap, is assessed relative to an unmitigated detonation using the same charge weight and standoff distance. Experiments using an air-filled media mitigation concept were found to effectively dampen the explosive response of the aluminum plate and reduce the final displacement at plate center by approximately half. The finite element model used for the initial experimental design compares very well to the experimental DIC results both spatially and temporally. Details of the experiment and finite element aquarium models are described including the boundary conditions, Eulerian and Lagrangian techniques, detonation models, experimental design and test diagnostics.

Predictions of elliptic flow (v{sub 2}) and nuclear modification factor (R{sub AA}) are provided as a function of centrality in U + U collisions at {radical}s{sub NN} = 200 GeV. Since the {sup 238}U nucleus is naturally deformed, one could adjust the properties of the fireball, density and duration of the hot and dense system, for example, in high energy nuclear collisions by carefully selecting the colliding geometry. Within our Monte Carlo Glauber based approach, the v{sub 2} with respect to the reaction plane v{sub 2}{sup RP} in U + U collisions is consistent with that in Au + Au collisions, while the v{sub 2} with respect to the participant plane v{sub 2}{sup PP} increases {approx}30-60% at top 10% centrality which is attributed to the larger participant eccentricity at most central U + U collisions. The suppression of R{sub AA} increases and reaches {approx}0.1 at most central U + U collisions that is by a factor of 2 more suppression compared to the central Au + Au collisions due to large size and deformation of Uranium nucleus.