We examine the performance of pure boron, boron carbide, high density carbon, and boron nitride ablators in the polar direct drive exploding pusher (PDXP) platform. The platform uses the polar direct ...drive configuration at the National Ignition Facility to drive high ion temperatures in a room temperature capsule and has potential applications for plasma physics studies and as a neutron source. The higher tensile strength of these materials compared to plastic enables a thinner ablator to support higher gas pressures, which could help optimize its performance for plasma physics experiments, while ablators containing boron enable the possibility of collecting additional data to constrain models of the platform. Applying recently developed and experimentally validated equation of state models for the boron materials, we examine the performance of these materials as ablators in 2D simulations, with particular focus on changes to the ablator and gas areal density, as well as the predicted symmetry of the inherently 2D implosion.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The proton probing technique is used to image quasi-static electromagnetic fields present in the wake of a high-intensity short-pulse laser propagating through an underdense plasma. Bubblelike field ...structures form along the channel filaments and expand in time.
In this work, we examine the performance of pure boron, boron carbide, high density carbon, and boron nitride ablators in the polar direct drive exploding pusher (PDXP) platform. The platform uses ...the polar direct drive configuration at the National Ignition Facility to drive high ion temperatures in a room temperature capsule and has potential applications for plasma physics studies and as a neutron source. The higher tensile strength of these materials compared to plastic enables a thinner ablator to support higher gas pressures, which could help optimize its performance for plasma physics experiments, while ablators containing boron enable the possibility of collecting additional data to constrain models of the platform. Applying recently developed and experimentally validated equation of state models for the boron materials, we examine the performance of these materials as ablators in 2D simulations, with particular focus on changes to the ablator and gas areal density, as well as the predicted symmetry of the inherently 2D implosion.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
We examine the performance of pure boron, boron carbide, high density carbon, and boron nitride ablators in the polar direct drive exploding pusher (PDXP) platform. The platform uses the polar direct ...drive configuration at the National Ignition Facility to drive high ion temperatures in a room temperature capsule and has potential applications for plasma physics studies and as a neutron source. The higher tensile strength of these materials compared to plastic enables a thinner ablator to support higher gas pressures, which could help optimize its performance for plasma physics experiments, while ablators containing boron enable the possiblity of collecting addtional data to constrain models of the platform. Applying recently developed and experimentally validated equation of state models for the boron materials, we examine the performance of these materials as ablators in 2D simulations, with particular focus on changes to the ablator and gas areal density, as well as the predicted symmetry of the inherently 2D implosion.
A comparison is made of three schemes ("angle-detuned," "polarization-mismatch," and "polarization-bypass") permitting high efficiency frequency tripling of 1 μm laser radiation. The overall ...characteristics of each are examined in terms of sensitivity to input intensity, polarization angles, and mismatch angles. The "polarization-mismatch" scheme is favored for tripling current high-power 1 μm Nd:glass laser radiation with KDP crystals, while for future systems the "polarization-bypass" scheme may be optimum. All schemes permit the tripling of some shaped pulses without substantial degradation in efficiency. The theory of tripling in KDP is reviewed.
In an earlier study a mutant Dictyostelium cell-line (plc−) was constructed in which all phospholipase C activity was disrupted and nonfunctional, yet these cells had nearly normal Ins(1,4,5)P3 ...levels (Drayer, A. L., Van Der Kaay, J., Mayr, G. W, Van Haastert, P. J. M. (1990) EMBO J. 13, 1601-1609). We have now investigated if these cells have a phospholipase C-independent de novo pathway of Ins(1,4,5)P3 synthesis. We found that homogenates of plc− cells produce Ins(1,4,5)P3 from endogenous precursors. The enzyme activities that performed these reactions were located in the particulate cell fraction, whereas the endogenous substrate was soluble and could be degraded by phytase. We tested various potential inositol polyphosphate precursors and found that the most efficient were Ins(1,3,4,5,6)P5, Ins(1,3,4,5)P4, and Ins(1,4,5,6)P4. The utilization of Ins(1,3,4,5,6)P5, which can be formed independently of phospholipase C by direct phosphorylation of inositol (Stephens, L. R. and Irvine, R. F.(1990) Nature 346, 580-582), provides Dictyostelium with an alternative and novel pathway of de novo Ins(1,4,5)P3 synthesis. We further discovered that Ins(1,3,4,5,6)P5 was converted to Ins(1,4,5)P3 via both Ins(1,3,4,5)P4 and Ins(1,4,5,6)P4. In the absence of calcium no Ins(1,4,5)P3 formation could be observed; half-maximal activity was observed at low micromolar calcium concentrations. These reaction steps could also be performed by a single enzyme purified from rat liver, namely, the multiple inositol polyphosphate phosphatase. These data indicate that organisms as diverse as rat and Dictyostelium possess enzyme activities capable of synthesizing the second messengers Ins(1,4,5)P3 and Ins(1, 3, 4, 5)P4 via a novel phospholipase C-independent pathway.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Progress in Laser Fusion Craxton, R. Stephen; McCrory, Robert L.; Soures, John M.
Scientific American,
08/1986, Volume:
255, Issue:
2
Magazine Article
Major advances in two disciplines are responsible for optimism in fusion R&D. In optics, the harmonic frequency conversion phenomenon has been exploited to generated high-powered laser beams that ...have a much Shorter wavelength than was previously possible. Laser energy can now be transferred to a fusion fuel pellet more efficiently at these wavelengths. In computer modeling, the simulation of fusion reactions initiated by lasers in fuel pellets has become increasingly detailed and realistic. Other advances in the laser fusion field are discussed in terms of temperature and density conditions, collisional energy absorption, suprathermal electrons, and frequency conversion crystals.
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BFBNIB, NMLJ, NUK, PNG, SAZU, UL, UM, UPUK
The metabolism of inositol 1,3,4-trisphosphate is a pivotal branch point of inositol phosphate turnover; its dephosphorylation
replenishes cellular inositol pools, its phosphorylation at the ...6-position supports the synthesis of inositol pentakisphosphate,
and its phosphorylation at the 5-position produces inositol 1,3,4,5-tetrakisphosphate (Shears, S.B. (1989) J. Biol. Chem.
264, 19879-19886). In order to increase understanding of the control of inositol-1,3,4-trisphosphate kinase activity, the
enzyme was highly purified from rat liver by precipitation with polyethylene glycol, MonoQ ion-exchange chromatography, heparin-agarose
affinity chromatography, and a novel affinity chromatography procedure that utilized Affi-Gel resin to which InsP6 was coupled
(Marecek, J.F., and Prestwich, G.D. (1991) Tetrahedron Lett. 32, 1863-1866). The final purification was about 26,000-fold,
with a 6% yield. This final preparation performed both 5- and 6-kinase activities in the ratio of approximately 1:5. The affinity
of the enzyme for inositol 1,3,4-trisphosphate was 0.04 microM, the highest yet determined for an inositol phosphate kinase.
Both inositol 1,3,4,5-tetrakisphosphate and inositol 1,3,4,6-tetrakisphosphate were competitive inhibitors of the kinase (Ki
values of 2-4 microM). The enzyme was determined to have a molecular mass of 36 kDa by sodium dodecyl sulfate-polyacrylamide
gel electrophoresis. Kinase activity was unaffected by Ca2+/calmodulin, protein kinase A, or protein kinase C.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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