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First Results of Reaction Propagation Rates in HMX at High Pressure

Description: The authors have measured the reaction propagation rate (RPR) in weapons-grade, ultrafine octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) powder in a diamond anvil cell over the pressure range 0.7-35 GPa. In order to have a cross-comparison of their experiments, they carried out a series of experiments on nitromethane (NM) up to 15 GPa. The results on NM are indistinguishable from previous measurements of Rice and Folz. In comparison to high-pressure NM, the burn process for solid HMX is between 5-10 times faster at pressures above 10 GPa.
Date: June 15, 2001
Creator: Farber, D L; Esposito, A; Zaug, J M & Aracne-Ruddle, C
Partner: UNT Libraries Government Documents Department

HFCVD of diamond at low substrate and low filament temperatures

Description: It has been discovered that the addition of a small amount of oxygen to the CH{sub 4} and H{sub 2} feed gas permits HFCVD of diamond at significantly lower filament and substrate temperatures. The effective O/C ratio here is much lower than that used in most studies of the oxygen effect. Careful control of the O/C and C/H ratios were found to be crucial to success. The effects of substrate and filament temperatures on growth rate and film quality were studied. Optimum conditions were found that gave reasonable growth rates ( {approximately}0.5 {mu}m/h ) with high film quality at filament temperatures below 1750{degrees}C and substrate temperatures below 600C. As a result, low temperature deposition has been realized. Power consumption can be reduced 50%, and the filament lifetime is extended indefinitely.
Date: March 8, 1995
Creator: Tolt, Z. L.; Heatherly, L.; Clausing, R. E.; Shaw, R. W. & Feigerle, C. S.
Partner: UNT Libraries Government Documents Department

Diamonds and Conflict: Background, Policy, and Legislation

Description: This report discusses issues surrounding "conflict diamonds" -- i.e., diamonds that have been mined and sold to support armed conflict -- as well as resulting U.S. policy responses. Policy makers' attention has also increasingly focused on the possible role that diamonds may play in the financing of terrorist operations.
Date: July 16, 2003
Creator: Cook, Nicolas
Partner: UNT Libraries Government Documents Department

Hydrogen Storage in Nano-Phase Diamond at High Temperature and Its Release

Description: The objectives of this proposed research were: 91) Separation and storage of hydrogen on nanophase diamonds. It is expected that the produced hydrogen, which will be in a mixture, can be directed to a nanophase diamond system directly, which will not only store the hydrogen, but also separate it from the gas mixture, and (2) release of the stored hydrogen from the nanophase diamond.
Date: October 13, 2008
Creator: Ghosh, Tushar K
Partner: UNT Libraries Government Documents Department

Wire Electrical Discharge Truing of Metal Bond Diamond Grinding Wheels

Description: Cylindrical wire EDM profile truing of the metal bond diamond wheel for precision form grinding of ceramics is presented in this report. First a corrosion-resistant, precise spindle with the high-electrical current capability for wire EDM truing of grinding wheel was fabricated. An arc profile was adopted in order to determine form tolerances capabilities of this process. Results show the wire EDM process can generate {micro}m-scale precision form on the diamond wheel efficiently. The wheel, after truing, was used to grind silicon nitride. Grinding forces, surface finish of ground components, and wheel wear were measured. The EDM trued wheel showed a reduction in grinding force from that of the stick dressed wheel. Surface finishes between the two truing methods were similar. In the beginning of the grinding, significant wheel wear rate was identified. The subsequent wheel wear rate stabilized and became considerably lower.
Date: January 24, 2002
Creator: McSpadden, SB
Partner: UNT Libraries Government Documents Department

Stability of the graphite and diamond phases of finite carbon cluster

Description: The stability of particulate carbon formed in the detonation of high explosives has been investigated with first principles and semiempirical molecular orbital calculations carried out on carbon clusters. The dangling surface bonds were capped wit/r hydrogen atoms and the surface contributions to the cohesive energy were removed by extrapolation as a function of the cluster size. Comparison of the calculated heat of formation of graphite and diamond particles as a function of size predicts that the graphite phase becomes more stable for IO<sup>4</sup> -10<sup5</sup> carbon atoms. Calculations were also carried out on geometry optimized carbon clusters without capping atoms, resulting in reconstructed cluster surfaces that may be a more realislic model for particulate carbon formed under the extreme conditions of detonation. The calculated energy barrier for tbe conversion of a graphitic cluster to the cubic diamond structure was in good agreement with calculations on b
Date: August 28, 1998
Creator: Ree, F & Winter, N W
Partner: UNT Libraries Government Documents Department

Testing of Critical Features of Polysilicon MEMS

Description: The behavior of MEMS devices is limited by the strength of critical features such as thin ligaments, oxide cuts joining layers, pin joints and hinges. Devices fabricated at Sandia's Microelectronic Development Laboratory have been successfully tested to investigate these features. A series of measurements were performed on samples with gage lengths of 15 to 1000 microns, using conventional and tungsten coated samples as well as samples that include the critical features of standard components in the test section. Specimens have a freely moving pin joint on one end that anchors the sample to the silicon die to allow rotation to reduce effects of bending. Each sample is loaded in uniaxial tension by pulling laterally with a flat tipped diamond in a computer-controlled Nanoindenter. Load is calculated by resolving the measured lateral and normal forces into the applied tensile force and frictional losses. The specimen cross section and gage length dimensions were verified by measuring against a standard in the SEM. Multiple tests can be programmed at one time and performed without operator assistance allowing the collection of significant populations of data.
Date: December 2, 1999
Creator: LAVAN,DAVID A. & BUCHHEIT,THOMAS E.
Partner: UNT Libraries Government Documents Department

TEM study of diamond films grown from fullerene precursors

Description: Transmission Electron Microscope (TEM) techniques are applied to study the microstructure of diamond films grown from fullerene precursors. Electron diffraction and electron energy loss spectra (EELS) collected from the diamond films correspond to that of bulk diamond. Microdiffraction, high resolution images and EELS help determine that the first diamond grains that nucleate from fullerene precursors generally form on a thin amorphous carbon interlayer and seldom directly on the silicon substrate. Grain size measurements reveal nanocrystalline diamond grains. Cross section TEM images show that the nanocrystalline diamond grains are equiaxed and not columnar nor dendritic. The microstructure of small equiaxed grains throughout the film thickness is believed responsible for the very smooth surfaces of diamond films grown from fullerene precursors.
Date: November 1, 1995
Creator: Csencsits, R.; Gruen, D.M.; Krauss, A.R. & Zuiker, C.
Partner: UNT Libraries Government Documents Department

A machining parameter study to select best conditions for SPDT of large single-crystal silicon optics

Description: The interdependence of process parameters on diamond turning of single-crystal silicon is poorly understood. An experimental design technique based on methods of statistical analysis permits the determination of a specific parameter's influence and its co-dependence on other factors. This design technique enables the creation of an experimental matrix, considering all input parameters (surface velocity; feed rate; depth of cut; tool radius; tool rake/skew angle; cutting fluid), while substantially decreasing the overall number of experiments. After an initial survey the significant parameters for a subsequent response surface methodology (RSM) study can be selected. From measurements of tool wear, surface finish and sub-surface damage (SSD) the optimum parameter settings for the diamond turning process can then be determined.
Date: March 18, 1999
Creator: Carr, J W; Davis, P J; Haack, J K; Krulewich, D A; McClellan, M R & Zimmermann, M
Partner: UNT Libraries Government Documents Department

The laser interferometer system for the large optics diamond turning machine

Description: The purpose of this report is to describe the Laser Interferometer System designed for the Large Optics Diamond Turning Machine (LODTM). To better understand the laser interferometer system, it is useful to begin with an overview of the LODTM metrology system.
Date: June 29, 1999
Creator: Baird, E D; Donaldson, R R & Patterson, S R
Partner: UNT Libraries Government Documents Department

Nanodiamonds: Their Structure and Optical Properties

Description: Nanometer sized diamond is a constituent of diverse systems ranging from interstellar dusts and meteorites [1] to carbonaceous residues of detonations [2] and diamond-like films [3-5]. Many of the properties of bulk diamond have been well understood for decades, those of nanodiamond are mostly unexplored. We present a combined theoretical and experimental study showing that diamond has unique properties not only as a bulk material but also at the nanoscale, where size reduction and surface reconstruction effects are fundamentally different from those found, e.g. in Si and Ge.
Date: May 14, 2002
Creator: Raty, J.-Y.; van Buuren, T. & Galli, G.
Partner: UNT Libraries Government Documents Department

Conflict Diamonds: Agency Actions Needed to Enhance Implementation of the Clean Diamond Trade Act

Description: A letter report issued by the Government Accountability Office with an abstract that begins "In 2003, the United States and other countries began implementing the Kimberley Process Certification Scheme (KPCS) to curtail the trade of rough diamonds that had fueled severe conflicts in Africa, known as conflict diamonds. CDTA provides the statutory framework for U.S. implementation of the KPCS. As mandated in CDTA, this report (1) describes the institutional framework established to implement the act, (2) examines implementation of the domestic provisions of the act and challenges it faces, and (3) examines how the United States has helped to strengthen the KPCS and challenges it faces."
Date: September 27, 2006
Creator: United States. Government Accountability Office.
Partner: UNT Libraries Government Documents Department

Shock Compressing Diamond to a Conducting Fluid

Description: Laser generated shock reflectance data show that diamond undergoes a continuous transition from optically absorbing to reflecting between Hugoniot pressures 600&lt;P{sub H}&lt;1000 GPa. The data are consistent with diamond having a thermal population of carriers at P{sub H}{approx}600 GPa, undergoing band overlap metallization at P{sub H}{approx}1000 GPa and melting at 800&lt;P{sub H}&lt;1000 GPa. The results agree well with an equation of state model that predicts that elemental carbon remains solid throughout the interior of Neptune.
Date: July 29, 2004
Creator: Bradley, D K; Eggert, J H; Hicks, D G; Celliers, P M; Moon, S J; Cauble, R C et al.
Partner: UNT Libraries Government Documents Department

THERMAL EMITTANCE MEASUREMENT DESIGN FOR DIAMOND SECONDARY EMISSION.

Description: Thermal emittance is a very important characteristic of cathodes. A carefully designed method of measuring the thermal emittance of secondary emission from diamond is presented. Comparison of possible schemes is carried out by simulation, and the most accessible and accurate method and values are chosen. Systematic errors can be controlled and maintained at small values, and are carefully evaluated. Aberration and limitations of all equipment are taken into account.
Date: June 25, 2007
Creator: WU,Q.; BEN-ZVI, I.; BURRILL, A.; CHANG, X.; KAYRAN, D.; RAO, T. et al.
Partner: UNT Libraries Government Documents Department

Measurements and Calculations of Halfraum Radiation Drives at the Omega Laser

Description: Thin walled gold halfraums are a common choice for producing x-ray drives in experiments at high-power laser facilities. At the Omega Laser, we use 10 kJ of laser energy in a two-pulse sequence to generate halfraum drive temperatures of 160-190 eV for {approx}3ns. This type of drive is well characterized and reproducible, with characterization of the drive radiation temperature typically performed using the Dante diagnostic. Additionally, calibrated Photoconductive Diamond Detectors (PCDs) are used to measure the drive when it is desirable to utilize the Dante elsewhere in the experiment. Measurements of halfraum drives from both Dante and PCDs are compared with calculations, with good agreement. This agreement lends the calculations a predictive capability in designing further experiments utilizing halfraum drives.
Date: January 6, 2005
Creator: MacLaren, S A; Back, C A & Hammer, J H
Partner: UNT Libraries Government Documents Department

Surface Damage Growth Mitigation on KDP/DKDP Optics Using Single-Crystal Diamond Micro-Machining

Description: A process whereby laser-initiated surface damage on KDP/DKDP optics is removed by spot micro-machining using a high-speed drill and a single-crystal diamond bit, is shown to mitigate damage growth for subsequent laser shots. Our tests show that machined dimples on both surfaces of an AR coated doubler (KDP) crystal are stable, for 526nm, {approx} 3.2ns pulses at {approx} 12J/cm{sup 2} fluences. Other tests also confirmed that the machined dimples on both surfaces of an AR coated tripler (DKDP) crystal are stable, for 351nm, {approx} 3ns pulses at {approx} 8J/cm{sup 2}. We have demonstrated successful mitigation of laser-initiated surface damage sites as large as 0.14mm diameter on DKDP, for up to 1000 shots at 351nm, 13J/cm{sup 2}, {approx} 11ns pulse length, and up to 10 shots at 351nm, 8J/cm{sup 2}, 3ns. Details of the method are presented, including estimates for the heat generated during micro-machining and a plan to implement this method to treat pre-initiated or retrieved-from-service, large-scale optics for use in high-peak-power laser applications.
Date: November 12, 2003
Creator: Hrubesh, L; Adams, J; Feit, M; Sell, W; Stanley, J; Miller, E et al.
Partner: UNT Libraries Government Documents Department

An estimate of relativistic H- stripping from a hot diamond foil

Description: An estimate is made for a 12mm x 14mm diamond foil heated by the H- beam that it is stripping. Previous thermal calculations estimate operating temperatures of &gt; 3000K. The method is to use the S.B. equation to get watts. Power is then converted to numbers of photons, then the photons are blue-shifted to two bands on either side of the peak BB wavelength that will strip one or both electrons. The bands very roughly have edges at {approx}0.75 eV and {approx}13.6 eV. All the photons in the band are capable of stripping the electron. Then use the probability of stripping formula for comparison. The calculation dutifully remembers that one BB photon is still just one photon for statistical calculations after it is Doppler-shifted. The photon energy multiplier or Beta-multiplier simply boosts the photon to high enough energy to do some work.
Date: March 1, 2005
Creator: Tomlin, Raymond E. & /Fermilab
Partner: UNT Libraries Government Documents Department

Calculation of Shock Hugoniot Curves of Precompressed Liquid Deuterium

Description: Path integral Monte Carlo simulations have been used to study deuterium at high pressure and temperature. The equation of state has been derived in the temperature and density region of 10,000 {le} T {le} 1,000,000 and 0.6 {le} {rho} {le} 2.5 g cm{sup -3}. A series of shock Hugoniot curves is computed for different initial compressions in order to compare with current and future shock wave experiments using liquid deuterium samples precompressed in diamond anvil cells.
Date: November 18, 2002
Creator: Militzer, B
Partner: UNT Libraries Government Documents Department