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  • 1
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    Effects of magnetization on fusion product trapping and secondary neutron spectraa) (2015)
    American Institute of Physics (AIP)
    Details
    Publikationsdatum: 2015-05-15
    Beschreibung: By magnetizing the fusion fuel in inertial confinement fusion (ICF) systems, the required stagnation pressure and density can be relaxed dramatically. This happens because the magnetic field insulates the hot fuel from the cold pusher and traps the charged fusion burn products. This trapping allows the burn products to deposit their energy in the fuel, facilitating plasma self-heating. Here, we report on a comprehensive theory of this trapping in a cylindrical DD plasma magnetized with a purely axial magnetic field. Using this theory, we are able to show that the secondary fusion reactions can be used to infer the magnetic field-radius product, BR , during fusion burn. This parameter, not ρR , is the primary confinement parameter in magnetized ICF. Using this method, we analyze data from recent Magnetized Liner Inertial Fusion experiments conducted on the Z machine at Sandia National Laboratories. We show that in these experiments BR ≈ 0.34(+0.14/−0.06) MG cm, a ∼ 14× increase in BR from the initial value, and confirming that the DD-fusion tritons are magnetized at stagnation. This is the first experimental verification of charged burn product magnetization facilitated by compression of an initial seed magnetic flux.
    Print ISSN: 1070-664X
    Digitale ISSN: 1089-7674
    Thema: Physik
    Publiziert von American Institute of Physics (AIP)
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  • 2
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    Diagnosing magnetized liner inertial fusion experiments on Za) (2015)
    American Institute of Physics (AIP)
    Details
    Publikationsdatum: 2015-05-15
    Beschreibung: Magnetized Liner Inertial Fusion experiments performed at Sandia's Z facility have demonstrated significant thermonuclear fusion neutron yields (∼10 12 DD neutrons) from multi-keV deuterium plasmas inertially confined by slow (∼10 cm/ μ s), stable, cylindrical implosions. Effective magnetic confinement of charged fusion reactants and products is signaled by high secondary DT neutron yields above 10 10 . Analysis of extensive power, imaging, and spectroscopic x-ray measurements provides a detailed picture of ∼3 keV temperatures, 0.3 g/cm 3 densities, gradients, and mix in the fuel and liner over the 1–2 ns stagnation duration.
    Print ISSN: 1070-664X
    Digitale ISSN: 1089-7674
    Thema: Physik
    Publiziert von American Institute of Physics (AIP)
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  • 3
    Digitale Medien
    Digitale Medien
    Temperature dependence of the resistance in the Pt/Ti nonalloyed ohmic contacts to p-InAs induced by rapid thermal processing (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 4141-4150 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The temperature dependence of the resistance in the Pt(60 nm)/Ti(50 nm) nonalloyed ohmic contacts to p-InAs (Zn doped 1×1018 to 1×1019 cm−3 ) induced by rapid thermal processing in the temperature range of 300–600 °C was studied. The ohmic nature of these contacts was attributed to both the low metal-semiconductor interfacial barriers and to the heavily doped semiconductor contacting layers. A phenomenological model was used to fit the measured temperature dependence contact resistance. The results indicated conversion from thermionic emission as the dominant carriers transport mechanism across the interfacial barrier for the as-deposited sample to a combination of thermionic and field emission mechanism for the heat-treated samples.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.346256
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  • 4
    Digitale Medien
    Digitale Medien
    Damage to InP and InGaAsP surfaces resulting from CH4/H2 reactive ion etching (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 785-792 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Structural and electrical damage imparted to InP and In0.72Ga0.28As0.6P0.4 (λg(approximately-equal-to)1.3 μm) surfaces during CH4/H2 reactive ion etching (RIE) have been examined. X-ray photoelectron spectroscopy was used to monitor changes in the surface chemistry, Rutherford backscattering spectrometry was used to measure crystallographic damage, and current-voltage and capacitance-voltage measurements were made to examine electrically active damage and its depth. Two classes of damage are observed: crystallographic damage originating from preferential loss of P (As) and/or ion bombardment-induced collision cascade mixing and, for p-type material, hydrogen passivation of Zn acceptors. Etching at 13.6 MHz, 60–90 mTorr, 10% CH4/H2, and bias voltages of ∼300 V contains gross ((approximately-greater-than)1%) damage as measured by RBS to within 40 A(ring) and electrically active damage to within 200 A(ring) of the surface. This is a factor of 3–6 shallower than other RIE processes operated below 10 mT with comparable or higher bias voltages. Acceptor passivation of both InP and InGaAsP, arising from the association of hydrogen with Zn sites, occurs to a depth of 2000 A(ring) after RIE and causes a decrease in carrier concentration in this layer. The effect is reversed, however, by rapid thermal processing at temperatures between 350 and 500 °C.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.346758
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  • 5
    Digitale Medien
    Digitale Medien
    Au/Pt/Ti contacts to p-In0.53Ga0.47As and n-InP layers formed by a single metallization common step and rapid thermal processing (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 1123-1128 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We have demonstrated the viability of depositing a thick Au bonding pad on top of Pt/Ti contacts on both p-InGaAs and n-InP within a single evaporation prior to heat treatment. This eliminates the usual post-sinter Au plating process. In particular, Au (500 nm)/Pt (60 nm)/Ti (50 nm) common contacts to Zn-doped 5×1018 cm−3 p-In0.53Ga0.47As and S-doped 1×1018 cm−3 n-InP were formed within a single pumpdown electron-gun evaporation and subsequently a single sintering process by means of rapid thermal processing. The lowest resistivity of these ohmic contacts were found to be 0.11 and 0.13 Ω mm (5.5×10−7 and 8×10−6 Ω cm2) for the p and n contacts, respectively. These values were achieved as a result of heating at 450 °C for 30 sec. This heat treatment caused a limited reaction at the Au-Pt and Pt-Ti interfaces, which did not lead to any significant intermixing of the Ti and Au. Thus, no significant indiffusion of the Au thorough the Pt barrier was observed and contact degradation did not occur. The stress of the as-deposited trilayer structure on InP was found to be 3×108 dyne cm2 tensile and increased to about 2×109 dyn cm2 as a result of the rapid thermal processing at 450 °C
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.346706
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  • 6
    Digitale Medien
    Digitale Medien
    Structure of hard-particle fluids near a hard wall. IV. yw(z,θ) for homonuclear hard diatomics (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 2232-2237 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Homonuclear hard diatomics in the vicinity of a hard wall have been studied using Monte Carlo simulations. During the simulations the cavity distribution functions for parallel and perpendicular orientations with respect to the wall and their Legendre expansion coefficients were calculated. It is demonstrated that the Legendre expansion is rapidly convergent and only several coefficients are required to describe the wall-diatomic correlation function within the simulation error. In addition, two simple methods for theoretical prediction of the cavity distribution function at small distances are compared with the simulation data. These approaches require as input quantities only thermodynamic data for the bulk homogeneous fluid. Both methods yield good accuracy for the cavity correlation function at the specific orientations indicated and for the first two Legendre coefficients, but fail to accurately describe higher Legendre coefficients.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.459893
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  • 7
    Digitale Medien
    Digitale Medien
    A molecular dynamics study of the crystalline phases of potassium nitrate (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 6610-6618 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Constant pressure molecular dynamics simulations have been made for a simple ionic model for crystalline potassium nitrate at several pressures and temperatures which span the known phase diagram. The nitrate ion was modeled as a rigid four-site entity with distributed charges and a quaternion algorithm was used to solve the rotational equations of motion. Several structural features of KNO3 are reproduced in the simulations. The 300 K, 0.1 GPa aragonite-like phase II of KNO3 has been reproduced although in the model it appears at a pressure between 1 and 2 GPa. The disordering of the nitrate orientations which occurs at high temperatures has also been observed. At 3 GPa the stable phase of the model is very similar to the recently characterized phase IV of KNO3. Spontaneous phase transitions in the simulations did not always produce well ordered structures and this appears to be a problem inherent in the method.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.456277
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  • 8
    Digitale Medien
    Digitale Medien
    Measurements of the double piezoelectric effect (2000)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 71 (2000), S. 1772-1775 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: For a piezoelectric device with multiple electrodes, it should be possible to quantitatively and conveniently measure the piezoelectric coefficient d31 by use of the double piezoelectric effect, without the need for any unusual apparatus or a calibration sample. One pair of electrodes is used to excite the piezo, and another is used to measure the response. For example, for a piezoelectric tube this should allow measurement of d31 as a function of temperature or of lateral offset voltage. An important correction to the current theory is described. Measurements on two piezo tubes are presented for excitation voltages in the range of 0.5–110 Vpp. An inductive proximity sensor was used to measure the actual piezo motion. It is shown that the current theory disagrees with this and previous experiments by a simple factor of 2 for symmetric excitations. However, for asymmetric excitations the disagreement with theory is more complex, and the current theory does not accurately predict the effects of varying tube geometry. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1150535
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  • 9
    Digitale Medien
    Digitale Medien
    Simple retrofittable long-range x–y translation system for scanned probe microscopes (1996)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 67 (1996), S. 3599-3604 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: A simple, reliable system for long-range translation of scanned probe microscopy (SPM) samples is described. This system could easily be retrofitted to many existing SPMs. The sample is held magnetically onto the scan piezo tube, and is translated by stick-slip motion. The system is very reliable, and provides controllable step size ranging from 20 nm to 1 μm. Three stick-slip drive wave forms are described and tested: sawtooth, cycloid, and an "improved'' cycloid based on the resonance curve of a harmonic oscillator. Computer simulations of the stick-slip process are presented, and are in good agreement with experiment. Together, the experiments and simulations demonstrate that it is essential to consider the resonant response of the piezo when evaluating drive wave forms. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1147065
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  • 10
    Digitale Medien
    Digitale Medien
    W16.1: A new fixed wavelength diffraction station at the SRS Daresbury : Proceedings of the 5th international conference on synchrotron radiation instrumentation (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 1311-1313 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Station W16.1 is a fixed wavelength (1.4 A(ring)) x-ray diffraction station recently constructed and commissioned at the SRS. It has been designed specifically for time-resolved studies of noncrystalline and fibrous materials and optimized for low angle measurements. Wide angle diffraction will also be available with simultaneous small and wide angle scattering/diffraction a future facility. In order to perform dynamic (∼1 ms) low angle measurements on weakly scattering systems, the station design has had to incorporate several novel features so as to achieve the predicted 1×1013 photon/s at the specimen. © 1995 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1146514
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