Showing papers in "Fusion Technology in 2000"
TL;DR: In this paper, the authors investigated the possibility of fabricating thin walled (≈ 1 μm) plastic shells, about 900 μm in diameter, for the OMEGA cryogenic experiments.
Abstract: Thin walled (≈ 1 μm) plastic shells, about 900 μm in diameter, are needed for the OMEGA cryogenic experiments. We investigated the possibility of fabricating these targets by modifying the coating ...
32 citations
30 citations
TL;DR: In this paper, the presence of new states of hydrogen was confirmed by X-ray photoelectron spectroscopy, Xray diffraction, Fourier transform infrared (FTI), Raman, and proton nuclear magnetic resonance (NMR).
Abstract: Novel compounds containing hydrogen in new hydride and polymeric states that demonstrate novel hydrogen chemistry have been isolated following the electrolysis of a K{sub 2}CO{sub 3} electrolyte with the production of excess energy Inorganic hydride clusters K[KH KHCO{sub 3}]{sub n}{sup +} and hydrogen polymer ions such as OH{sub 23}{sup +} and H{sub 16}{sup -} were identified by time-of-flight secondary ion mass spectroscopy The presence of compounds containing new states of hydrogen was confirmed by X-ray photoelectron spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, and proton nuclear magnetic resonance spectroscopy
28 citations
TL;DR: In this paper, the results of analogous investigations for the single size beryllium pebble bed are shown and equations are given to correlate the heat transfer parameters, namely thermal conductivity and heat transfer coefficient to the containing wall.
Abstract: For the next generation fusion reactors with a ceramic breeder blanket the use, as a neutron multiplier, of either a binary bed of large (= 2 mm) and small (= 0.1-0.2 mm) beryllium pebbles or a single size bed made of 1 mm or 2 mm pebbles is foreseen. The heat transfer parameters of such a binary pebble bed, namely the thermal conductivity and the heat transfer coefficient to the containing wall, have been investigated in the experimental devices PEHTRA and SUPERPEHTRA and have been reported in the companion paper at this workshop. 1 In the present paper the results of analogous investigations for the single size beryllium pebble bed are shown and equations are given to correlate the heat transfer parameters.
25 citations
TL;DR: This paper found that adding a small amount (<0.1 wt%) of high-molecular-weight poly(acrylic acid) to the water bath substantially increased the interfacial tension.
Abstract: Abstract Currently, poly(α-methylstyrene) mandrel precursors are suspended in a salt-containing water bath during curing. Matching the density of the precursors to their bath almost, but not quite, eliminates shell sagging caused by gravity. This sagging is opposed by the interfacial tension between the plastic containing oil solution and the water bath, but the tension is barely adequate to give satisfactory sphericity. We found that adding a small amount (<0.1 wt%) of high-molecular-weight poly(acrylic acid) to the water bath substantially increased the interfacial tension. Combining that change with a gentler shell curing process enabled consistent production of more spherical mandrels.
25 citations
TL;DR: In this paper, an entirely new process was discovered starting from M-doped glow discharge polymer (GDP) deposited by plasma polymerization to make M-oxide shells, which are suitable for use in cryogenic layering experiments at LLNL and are unobtainable by the routinely utilized drop-tower method.
Abstract: Abstract An entirely new process was discovered starting from M-doped glow discharge polymer (GDP) deposited by plasma polymerization1 (where M = Si or Ti) to make M-oxide shells. This process utilizing Si-GDP was developed to make large, uniform, thick-walled glass shells which are suitable for use in cryogenic layering experiments at LLNL and are unobtainable by the routinely utilized drop-tower method. We have found that in addition to controlling the geometry, the permeability and opacity may be controllable over very wide ranges by varying the processing conditions. Preliminary tests to determine the strength of SiO2 glass shells made by this process are consistent with that expected of pure silica glass.
22 citations
TL;DR: In this article, the amount of tritium adsorption on molecular sieve 5A and activated carbon, which are potential adsorbents in the cryosorption bed, at liquid nitrogen temperature were quantified using the volumetric method, and the obtained isotherms were also expressed with the two-site Langmuir model.
Abstract: The cryosorption method is useful for extracting hydrogen isotopes from a helium gas stream with a small amount of hydrogen isotopes. Therefore, in fusion reactors, this method is expected to be applied for the helium glow discharge exhaust gas processing system and the blanket tritium recovery system. To design these systems, adsorption isotherms for each hydrogen isotope are needed, making it possible to estimate the amount of adsorption in a wide pressure range. The amount of tritium adsorption on molecular sieve 5A, molecular sieve 4A, and activated carbon, which are potential adsorbents in the cryosorption bed, at liquid nitrogen temperature were quantified using the volumetric method, It was found that adsorption isotherms of tritium were also expressed with the two-site Langmuir model and that the obtained isotherms were close to the reported isotherms, the Langmuir coefficients for which were estimated using a reduced mass of hydrogen isotopes.
21 citations
TL;DR: In this paper, low-intensity nuclear emissions (neutrons and charged particles) due to exothermic deuterium desorption from a Pd/PdO heterostructure loaded with deutium by electrolysis were studied by NE213 neutron detection as well as SSB and CR-39 charged-particle detectors in low-background conditions with large statistics.
Abstract: Low-intensity nuclear emissions (neutrons and charged particles) due to exothermic deuterium desorption from Au/Pd/PdO heterostructure loaded with deuterium by electrolysis have been studied by NE213 neutron detection as well as SSB and CR-39 charged-particle detectors in low-background conditions with large statistics. Similar measurements were performed with the Au/Pd/PdO:H heterostructure as a control. It has been established that in experiments with the Au/Pd/PdO:D system, the excessive 2.45-MeV neutrons and 3.0-MeV protons are better detected than with the Au/Pd/PdO:H system, where those detection rates for n and p did not exceed the cosmic background level. The levels of neutron and proton emissions for 40- to 60-{mu}m-thick samples are found to be close to one another and after subtracting background (Au/Pd/PdO:H count rate) consist of I{sub n} = (19 {+-} 2).10{sup -3} n/s and I{sub p} (4.0 {+-} 1.0).10{sup -3} p/s in a 4{pi} solid angle, respectively. These yields of D-D reaction products in Au/Pd/PdO heterostructure comply with the mean D-D reaction rate of {lambda}{sub dd} {approx} 10{sup -23}s{sup -1} per D-D pair.
21 citations
TL;DR: In this article, the buoyancy-driven magnetoconvection in the cross section of an infinitely long vertical square duct is investigated numerically using the CFX code package, with particular reference to the Lorentz forces and the electric potential boundary conditions for arbitrary electrical conductivity of the walls.
Abstract: The buoyancy-driven magnetoconvection in the cross section of an infinitely long vertical square duct is investigated numerically using the CFX code package. The implementation of a magnetohydrodynamic (MHD) problem in CFX is discussed, with particular reference to the Lorentz forces and the electric potential boundary conditions for arbitrary electrical conductivity of the walls. The method proposed is general and applies to arbitrary geometries with an arbitrary orientation of the magnetic field. Results for fully developed flow under various thermal boundary conditions are compared with asymptotic analytical solutions. The comparison shows that the asymptotic analysis is confirmed for highly conducting walls as high velocity jets occur at the side walls. For weakly conducting walls, the side layers become more conducting than the side walls, and strong electric currents flow within these layers parallel to the magnetic field. As a consequence, the velocity jets are suppressed, and the core solution is only corrected by the viscous forces near the wall. The implementation of MHD in CFX is achieved.
21 citations
TL;DR: In this article, a planar beryllium capsule with 2% oxygen dopant instead of 0.9% copper is presented. But the capsule is more sensitive to DT ice roughness than the Be330 design, failing at 0.6μm roughness.
Abstract: Abstract Recent beryllium capsule designs have focussed on the lower temperatures and laser powers expected before the NIF laser reaches its full capability, 192 beams, 500TW, and 1.8MJ. First, several new designs are given with peak radiation temperatures for 250 to 280 eV. A 250eV design uses 2% oxygen dopant instead of 0.9% copper. Second, a radiography study of planar joints in S200D beryllium using a Cu, Au, Ag, Al, or Au/Cu braze quantified the diffusion away from the joint. LASNEX calculations show that Cu joint perturbations grow to large enough amplitude to preclude ignition. However by allowing the copper to diffuse twice as far as in these experiments (e.g. by holding at braze temperature longer), the joint calculates to be acceptable, and the capsule gives full yield. Aluminum diffuses extremely far from the joint, almost uniformly in the sample. Third, a capsule with a high Z shell and beryllium ablator calculates to ignite. As expected its ignition threshold is lower, about 70% of the implosion velocity for a capsule like the Be330. The extra tamping of DT bum by a 6 μm tungsten shell increases the yield from 17 to 32 MJ. The capsule radiates 3 MJ of this yield as X-rays. Unfortunately the capsule is more sensitive to DT ice roughness than the Be330 design, failing at 0.6μm roughness.
21 citations
TL;DR: In this article, a mandrel was overcoated with polyimide vapor deposition technology suitable for mandrel overcoating and fabrication of polyimides capsules, and the resulting mandrel capsules were used to construct polyimidimide capsules.
Abstract: Over the last three years, LLNL has developed polyimide vapor deposition technology suitable for mandrel overcoating and fabrication of polyimide capsules. Agitated mandrels were overcoated with 4,...
TL;DR: In this paper, the effects of fluid surface tension and streamline curvature on the instabilities of the shear layer of high-speed liquid jets were investigated and the most unstable wave number and the spatial growth rate of perturbation were predicted with linear stability theories and are shown to agree fairly well with experimental data for water jets.
Abstract: The instabilities of the shear layer beneath the free surface of high-speed liquid jets are investigated. Such instabilities will generate waves on liquid-metal jet targets, affecting adversely the target performance. The most unstable wave number and the spatial growth rate of perturbation are predicted with linear stability theories and are shown to agree fairly well with experimental data for water jets. The effects of fluid surface tension and streamline curvature on the instabilities are analyzed to evaluate the applicability of water data to liquid-metal curved jets. It is shown that the surface tension effects are negligible when the Weber number based on the shear layer thickness is greater than six, and also the streamline curvature effects are negligible when the radius of curvature is more than 30 times greater than the shear layer thickness.
TL;DR: In this paper, the properties and gas permeability of polyimide shells Fabricated by the Vapor Deposition Method (VDM) have been investigated in terms of mechanical properties and properties.
Abstract: OAK-B202Mechanical Properties and Gas Permeability of Polyimide Shells Fabricated by the Vapor Deposition Method
TL;DR: In this article, the influence of residual gas in a laser fusion reactor chamber at the time of pellet injection is discussed, including the lifetime of a cryogenic target, the stall by drag force, the deviation by a crosswind and the lift by spin of the pellet.
Abstract: Abstract Influence of residual gas in a laser fusion reactor chamber at the time of pellet injection is discussed, including the lifetime of a cryogenic target, the stall by drag force, the deviation by a crosswind and the lift by spin of the pellet. The pellet is assumed to be injected accurately with designated speed and direction every time. Preliminary results indicate that the vapor pressure in the chamber should be less than 0.1 Torr and the shot-to-shot variation in the wind speed must be less than 1 m/s to deliver the fuel pellet at the firing position with an accuracy of 100 μm.
TL;DR: In conventional inertial confinement fusion (ICF) as discussed by the authors, a high power laser system is used to compress a cryogenic target and create energy, and one of the challenges for ICF cryogenics is producing a homogenized target.
Abstract: In conventional inertial confinement fusion (ICF) a high power laser system is used to compress a cryogenic target and create energy. One of the challenges for ICF cryogenics is producing a homogen...
TL;DR: Magnetic fusion energy has the potential for superior safety and environmental (S&E) characteristics relative to other energy options, which is one of the main reasons for developing fusion power as mentioned in this paper.
Abstract: Magnetic fusion energy has the potential for superior safety and environmental (S&E) characteristics relative to other energy options, which is one of the main reasons for developing fusion power. ...
TL;DR: In this paper, the authors characterized the irregularities in ICF shells and found that outside and inside surface, and wall thickness fluctuations are all Raleigh-Taylor unstable and can cause a shell to fail during shell failure.
Abstract: Irregularities in ICF shells need to be characterized in detail. Outside and inside surface, and wall thickness fluctuations are all Raleigh-Taylor unstable and can cause a shell to fail during com...
TL;DR: In this paper, a triaxial compression test with monosized and binary beryllium pebble beds was performed in a temperature range between ambient temperature and 480 °C and pressures up to 8 MPa.
Abstract: Uniaxial compression tests with monosized and binary beryllium pebble beds were performed in a temperature range between ambient temperature and 480 °C and pressures up to 8 MPa. Empirical correlations for the moduli of deformation are given for the different bed types and first measurements for thermal creep are presented. Stress-strain relations depend sensitively on the initial state of the bed and with this on the filling procedure. This is of special importance for binary beds where it must be ensured that a homogeneous distribution of small pebbles in the bed is obtained. First results for triaxial compression tests for monosized and binary beds are reported. The internal friction of these beds is significantly larger than that of beds with particles with smooth surfaces.
TL;DR: An unmitigated quench of a toroidal field (TF) magnet has been proposed as an extremely unlikely event for International Thermonuclear Experimental Reactor (ITER) Engineering Design Activity safety analysis.
Abstract: An unmitigated quench of a toroidal field (TF) magnet has been proposed as an extremely unlikely event for International Thermonuclear Experimental Reactor (ITER) Engineering Design Activity safety analysis. While the frequency of such an event is highly improbable (<1 x 10{sup -6}/yr), the public safety consequences of this event must be explored because the TF magnets are located midway between the two primary confinement barriers of the ITER design. These confinement barriers are the vacuum vessel (VV) and the cryostat. An unmitigated quench has the potential for producing melting of the magnet. If molten material from the magnet were to impinge on the walls of the VV and cryostat, these walls could fail, resulting in a pathway for release of radioactive material to the environment from the VV. A model has been developed at the Idaho National Engineering and Environmental Laboratory called MAGARC to investigate the consequences of this accident. This model is described in detail, and results from this model used in ITER safety analysis are presented.
TL;DR: In this paper, the authors used Auger electron spectroscopy (AES) and X-ray diffraction to characterize the composition of beryllium composite coatings at a depth of 300 A from the surface and maintain a constant composition throughout the thickness of the coatings.
Abstract: Composite coatings containing beryllium are prepared by plasma-enhanced chemical vapor deposition at a substrate temperature as low as 250°C in a radio-frequency-induced cylindrical plasma reactor. Diethylberyllium is used as the precursor together with hydrogen as a coreactant gas. These coatings are characterized by Auger electron spectroscopy (AES), X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, atomic force microscopy, electrical resistivity, and thermogravimetric analysis. AES indicates that the composition of the coatings reaches a steady level at a depth of 300 A from the surface and maintains a constant composition throughout the thickness of the coatings. The characterization studies establish the dominant phase to be Be2C. The coatings are also resistant to oxidation and hydrolysis in dry/moist air unlike bulk Be2C. It is found that the coatings deposited close to the diethylberyllium inlet contain amorphous beryllium that is homogeneously dispersed in...
TL;DR: Amorphous hydrogenated carbon films are the nominal ablators to be used in French inertial confinement fusion (ICF) experiments These targets are developed for the future Megajoule laser (LMJ) of.
Abstract: Amorphous hydrogenated carbon films are the nominal ablators to be used in French inertial confinement fusion (ICF) experiments These targets are developed for the future Megajoule laser (LMJ) of
TL;DR: In this paper, the results of chemical reactivity experiments for Be pebbles (2-mm and 0.2mm diameter) and Be powder (14-31 pm diameter) exposed to steam at elevated temperatures were reported.
Abstract: This paper reports the results of chemical reactivity experiments for Be pebbles (2-mm and 0.2-mm diameter) and Be powder (14-31 pm diameter) exposed to steam at elevated temperatures, 350 to 900°C for pebbles and 400 to 500°C for powders. We measured BET specific surface areas of 0.12 m 2 /g for 2-mm pebbles, 0.24 m 2 /g for 0.2-mm pebbles and 0.66 to 1.21 m 2 /g for Be powder samples. These experiments showed a complex reactivity behavior for the material, dependent primarily on the test temperature. Average H 2 generation rates for powder samples, based on measured BET surface areas, were in good agreement with previous measurements for fully-dense CPM-Be. Rates for the Be pebbles, based on measured BET surface areas, were systematically lower than the CPM-Be rates, possibly because of different surface and bulk features for the pebbles, especially surface-layer impurities, that contribute to the measured BET surface area and influence the oxidation process at the material surface.
TL;DR: In this article, it was shown that a very constant DT ice layer thickness (1%) is required in order to improve the implosion process, which implies that the temperature must be uniform over the shell.
Abstract: Ignition targets for LMJ experiments require a very constant DT ice layer thickness (1%) in order to improve the implosion process. This implies that the temperature must be uniform over the shell ...
TL;DR: In this article, a beryllium ablator was used for opacity control of a NIF ignition capsule with an optimized yield of 12 MJ and a reduced drive hohlraum temperature pulse shape that peaks at 250 eV.
Abstract: A cryogenic, {beta}-layered NIF ignition capsule with a beryllium ablator that employs a BeO dopant (2% O) for opacity control is described. The design has an optimized yield of 12 MJ and uses a reduced drive hohlraum temperature pulse shape that peaks at {approx} 250 eV. Shock timing sensitivity calculations have been performed for this capsule design. Individual uncertainties of: (1) {approx}200 ps in the timing of the foot pulse; (2) {approx}5% in the x-ray flux of the foot pulse and first step; (3) {approx}10% in the ablator EOS; or (4) {approx} 5 {micro}m in the DT ice layer thickness each have a significant impact on thermonuclear yield. Combined uncertainties have greater impact than isolated, individual issues. For example, a combination of uncertainties of 200 ps in the foot + 2 eV in the foot + 5 {micro}m in the DT thickness results in a calculation that produces only {approx} 1% of the original design yield. A second, more speculative, capsule concept utilizing a liquid DT ablator is also discussed. This design produces a 5 MJ yield in a 250 eV peak drive calculation.
TL;DR: A tritium cleanup system has been conceptually developed for the large helical device (LHD) at the National Institute for Fusion Science as discussed by the authors, which is a processing device employed to remove tetranium from exhaust gas, and its decomposition and separation processes are introduced to convert various tritiated compounds into a form of hydrogen molecules of high purity.
Abstract: A tritium cleanup system has been conceptually developed for the large helical device (LHD) at the National Institute for Fusion Science. The system is a processing device employed to remove tritium from exhaust gas. In the exhaust gas discharged from the LHD in normal operation, the major part of tritium constituents should be in a form of hydrogen molecules because the fuel used in plasma experiments with the LHD is hydrogen molecules. From this viewpoint, we have designed a tritium cleanup system, which is characterized by tritium being removed and stored in a form of hydrogen molecules with less impurities, like oxygen and carbon, and its decomposition and the separation processes are introduced to convert various tritiated compounds into a form of hydrogen molecules of high purity. Besides these, there is another aspect in that getter materials are applied in both decomposition of tritiated compounds and storage of hydrogen molecules containing tritium.The system design is composed of three essential component parts: a hydrogen separator, a hydrogen absorbing vessel, and a decomposition process vessel. The hydrogen separator and the decomposition process vessel make a process loop repeat to remove hydrogen into a form of hydrogen molecules with less impurities. It ismore » important that 'less impurities' means having a less bad influence on hydrogen-absorbing materials used in the storage vessel.We think that the hydrogen separator will be manufactured by employing a palladium hydrogen purifier system, which is available in the marketplace, and the hydrogen storage vessel will also be manufactured by using hydrogen-absorbing alloys like titanium. Thus, the serious problem imposed on us is how to realize the decomposition process vessel. To develop the decomposition process vessel, we thought nonvolatile getter materials were promising and carried out performance tests of methane decomposition by the nonvolatile getter materials, where methane was used because it is hardly decomposed and there is little data for a flowing-gas system.The tritium cleanup system that was designed is presented. Also, a methane decomposition curve with ZrNi alloys used as one of the typical nonvolatile getter materials is shown, and the probability of the realization of the decomposition process vessel is examined.« less
TL;DR: In this paper, a new high-resolution algorithm obtained by symmetrizing a basic filtered backprojection algorithm was proposed for threshold target characterization, as well as a new approach to micro-object scanning based on quasi-uniform geometry.
Abstract: A precise and accurate knowledge of the characteristics of three-dimensional micro-objects such as inertial confinement fusion (ICF) targets and laser-produced plasmas is required to analyze the results of laser fusion experiments Significant advances have been made in the development of tomographic information-processing methods for application to ICF target characterization Topics discussed include (a) new high-resolution algorithm obtained by symmetrizing a basic filtered backprojection algorithm, (b) algorithms for threshold target characterization, (c) new approach to micro-object scanning based on quasi-uniform geometry, (d) ICF target preparation for tomographic characterization
TL;DR: In this article, the freestanding soft foams for laser-and ion-driven ICF were described and compared with those used for direct and indirect target experiments in continuing plasma experiments.
Abstract: Many target designs for laser- and ion-driven ICF include foam parts for direct and indirect targets to be investigated in continuing plasma experiments. The freestanding soft foams are described h...
TL;DR: In this article, the deformation relaxation rate of poly(α-methylstyrene) mandrel precursors is studied as a function of the curing time of the mandrel, and a simple test for this condition is found.
Abstract: Poly(α-methylstyrene) (PαMS) mandrel precursors (a fluorobenzene solution of PαMS surrounding a water core) must be agitated to center the core. The initially fluid PαMS solution stiffens as the organic solvent is extracted, and it eventually becomes brittle; a collision with a stirring propeller will either dent or crack the surface. Dried mandrels often exhibit dents on the surface or cracks in the wall that may result from such collisions. We have studied the deformation relaxation rate of mandrel precursors as a function of curing time. We have found a point in the cure at which the core centering process has stopped but permanent denting has not started, and have found a simple test for this condition. We can use this information to produce highly spherical plastic mandrels by controlling propeller speed as a function of time.
TL;DR: In this article, laser targets made of beryllium deuteride BeD2, nanocrystalline BER and low-density BER were used to store DT-mixture.
Abstract: Laser targets made of beryllium deuteride BeD2, nanocrystalline beryllium and of low-density beryllium are reported. Spherical laser targets are strong enough and are capable of storing DT-mixture ...
TL;DR: The first attempt at coating beryllium via CVD was done by using bis(cyclopentadienyl)beryllium, (C5H5)2Be, as the precursor material as mentioned in this paper.
Abstract: Capsules with beryllium ablators are very important targets for the DOE National Ignition Facility (NIF) laser in the Inertial Confinement Fusion Program. Two leading candidates for fabricating beryllium capsules are the machining and bonding of hemispheres, and physical vapor deposition of beryllium onto plastic or other shells. An attractive possibility would be to coat a spherical mandrel with a thin layer of beryllium by a non-line-of-sight process. This coating could be applied via the chemical vapor deposition (CVD) of beryllium.Our first attempt at coating beryllium via CVD was done by using bis(cyclopentadienyl)beryllium, (C5H5)2Be, as the precursor material. Results obtained by use of (C5H5)2Be as the precursor material is discussed.However, difficulties we encountered with use of the (C5H5)2Be precursor material led us to examine a relatively unexplored area of beryllium chemistry, namely that of its amines. This redirection also led us to change surrogate material for use in the develop...