Optical constants of uranium plasma Final report

Thermodynamic and optical properties of uranium plasma in proposed gaseous core nuclear rocket

Validity of the Gor'kov expansion near the upper critical field in type II superconductors

We have examined the validity of the Gor'kov expansion in the strength of the order parameter of type II superconductors near the upper critical field. Although the degeneracy of the electron levels in a magnetic field gives non- perturbative terms in the solution to the Bogoliubov-de Gennes equations we find, contrary to recent claims, that these non-perturbative terms cancel in the expression for the thermodynamic potential, and that the traditional Gor'kov theory is correct sufficiently close to Hc2 at finite temperature. We have derived conditions for the validity of the Gor'kov theory which essentially state, that the change in the quasiparticle energies as compared to the normal state energies cannot be too large compared to the temperature.Comment: 5 pages, 3 figures. One reference adde

Angular dependence of the magnetization of isotropic superconductors: which is the vortex direction?

We present studies of the dc magnetization of thin platelike samples of the isotropic type II superconductor PbTl(10%), as a function of the angle between the normal to the sample and the applied magnetic field ${\bf H}$. We determine the magnetization vector ${\bf M}$ by measuring the components both parallel and normal to ${\bf H}$ in a SQUID magnetometer, and we further decompose it in its reversible and irreversible contributions. The behavior of the reversible magnetization is well understood in terms of minimization of the free energy taking into account geometrical effects. In the mixed state at low fields, the dominant effect is the line energy gained by shortening the vortices, thus the flux lines are almost normal to the sample surface. Due to the geometrical constrain, the irreversible magnetization ${\bf M}_{irr}$ remains locked to the sample normal over a wide range of fields and orientations, as already known. We show that in order to undestand the angle and field dependence of the modulus of ${\bf M}_{irr}$, which is a measure of the vortex pinning, and to correctly extract the field dependent critical current density, the knowledge of the modulus and orientation of the induction field ${\bf B}$ is required.Comment: 11 pages, 6 figure

A feasibility study: California Department of Forestry and Fire Protection utilization of infrared technologies for wildland fire suppression and management

NASA's JPL has completed a feasibility study using infrared technologies for wildland fire suppression and management. The study surveyed user needs, examined available technologies, matched the user needs with technologies, and defined an integrated infrared wildland fire mapping concept system configuration. System component trade-offs were presented for evaluation in the concept system configuration. The economic benefits of using infrared technologies in fire suppression and management were examined. Follow-on concept system configuration development and implementation were proposed

Thermodynamic properties of Bi2Sr2CaCu2O8 calculated from the electronic dispersion

The electronic dispersion for Bi2Sr2CaCu2O(8+d) has been determined from angle-resolved photoelectron spectroscopy (ARPES). From this dispersion we calculate the entropy and superfluid density. Even with no adjustable parameters we obtain an exceptional match with experimental data across the entire phase diagram, thus indirectly confirming both the ARPES and thermodynamic data. The van Hove singularity is crossed in the overdoped region giving a distinctive linear-in-T temperature dependence in the superfluid density there.Comment: 5 pages, 4 figures, submitted to Physical Review Letter

Coexistence of a triplet nodal order-parameter and a singlet order-parameter at the interfaces of ferromagnet-superconductor Co/CoO/In junctions

We present differential conductance measurements of Cobalt / Cobalt-Oxide / Indium planar junctions, 500nm x 500nm in size. The junctions span a wide range of barriers, from very low to a tunnel barrier. The characteristic conductance of all the junctions show a V-shape structure at low bias instead of the U-shape characteristic of a s-wave order parameter. The bias of the conductance peaks is, for all junctions, larger than the gap of indium. Both properties exclude pure s-wave pairing. The data is well fitted by a model that assumes the coexistence of s-wave singlet and equal spin p-wave triplet fluids. We find that the values of the s-wave and p-wave gaps follow the BCS temperature dependance and that the amplitude of the s-wave fluid increases with the barrier strength.Comment: 5 pages, Accepted to Phys. Rev.

Tuning the Kondo effect with a mechanically controllable break junction

We study electron transport through C60 molecules in the Kondo regime using a mechanically controllable break junction. By varying the electrode spacing, we are able to change both the width and height of the Kondo resonance, indicating modification of the Kondo temperature and the relative strength of coupling to the two electrodes. The linear conductance as a function of T/T_K agrees with the scaling function expected for the spin-1/2 Kondo problem. We are also able to tune finite-bias Kondo features which appear at the energy of the first C60 intracage vibrational mode.Comment: 4 pages with 4 figure

Additional application of the NASCAP code. Volume 1: NASCAP extension

The NASCAP computer program comprehensively analyzes problems of spacecraft charging. Using a fully three dimensional approach, it can accurately predict spacecraft potentials under a variety of conditions. Several changes were made to NASCAP, and a new code, NASCAP/LEO, was developed. In addition, detailed studies of several spacecraft-environmental interactions and of the SCATHA spacecraft were performed. The NASCAP/LEO program handles situations of relatively short Debye length encountered by large space structures or by any satellite in low earth orbit (LEO)

Additional application of the NASCAP code. Volume 2: SEPS, ion thruster neutralization and electrostatic antenna model

The interactions of spacecraft systems with the surrounding plasma environment were studied analytically for three cases of current interest: calculating the impact of spacecraft generated plasmas on the main power system of a baseline solar electric propulsion stage (SEPS), modeling the physics of the neutralization of an ion thruster beam by a plasma bridge, and examining the physical and electrical effects of orbital ambient plasmas on the operation of an electrostatically controlled membrane mirror. In order to perform these studies, the NASA charging analyzer program (NASCAP) was used as well as several other computer models and analytical estimates. The main result of the SEPS study was to show how charge exchange ion expansion can create a conducting channel between the thrusters and the solar arrays. A fluid-like model was able to predict plasma potentials and temperatures measured near the main beam of an ion thruster and in the vicinity of a hollow cathode neutralizer. Power losses due to plasma currents were shown to be substantial for several proposed electrostatic antenna designs

Extracting joint weak values with local, single-particle measurements

Weak measurement is a new technique which allows one to describe the evolution of postselected quantum systems. It appears to be useful for resolving a variety of thorny quantum paradoxes, particularly when used to study properties of pairs of particles. Unfortunately, such nonlocal or joint observables often prove difficult to measure weakly in practice (for instance, in optics -- a common testing ground for this technique -- strong photon-photon interactions would be needed). Here we derive a general, experimentally feasible, method for extracting these values from correlations between single-particle observables.Comment: 6 page