3,317 research outputs found
On the feasibility of radiation sterilization of planetary spacecraft Final report
Feasibility study for X-ray or gamma ray sterilization of spacecraft - radiation effect
Handbook of space environmental effects on solar cell power systems
Space environmental effects on solar cell power systems for earth satellite
Non-linear effect of uniaxial pressure on superconductivity in CeCoIn5
We study single-crystal CeCoIn5 with uniaxial pressure up to 3.97 kbar
applied along the c-axis. We find a non-linear dependence of the
superconducting transition temperature Tc on pressure, with a maximum close to
2 kbar. The transition also broadens significantly as pressure increases. We
discuss the temperature dependence in terms of the general trend that Tc
decreases in anisotropic heavy-fermion compounds as they move towards
three-dimensional behavior.Comment: 6 pages, 4 figure
Free Radicals in Superfluid Liquid Helium Nanodroplets: A Pyrolysis Source for the Production of Propargyl Radical
An effusive pyrolysis source is described for generating a continuous beam of
radicals under conditions appropriate for the helium droplet pick-up method.
Rotationally resolved spectra are reported for the vibrational mode of
the propargyl radical in helium droplets at 3322.15 cm. Stark spectra
are also recorded that allow for the first experimental determination of the
permanent electric dipole moment of propargyl, namely -0.150 D and -0.148 D for
ground and excited state, respectively, in good agreement with previously
reported ab initio results of -0.14 D [1]. The infrared spectrum of the
mode of propargyl-bromide is also reported. The future application of these
methods for the production of novel radical clusters is discussed
Microstructural strain energy of α-uranium determined by calorimetry and neutron diffractometry
The microstructural contribution to the heat capacity of α-uranium was determined by measuring the heat-capacity difference between polycrystalline and single-crystal samples from 77 to 320 K. When cooled to 77 K and then heated to about 280 K, the uranium microstructure released (3±1) J/mol of strain energy. On further heating to 300 K, the microstructure absorbed energy as it began to redevelop microstrains. Anisotropic strain-broadening parameters were extracted from neutron-diffraction measurements on polycrystals. Combining the strain-broadening parameters with anisotropic elastic constants from the literature, the microstructural strain energy is predicted in the two limiting cases of statistically isotropic stress and statistically isotropic strain. The result calculated in the limit of statistically isotropic stress was (3.7±0.5) J/mol K at 77 K and (1±0.5) J/mol at room temperature. In the limit of statistically isotropic strain, the values were (7.8±0.5) J/mol K at 77 K and (4.5±0.5) J/mol at room temperature. In both cases the changes in the microstructural strain energy showed good agreement with the calorimetry
Measurement and simulation of anisotropic magnetoresistance in single GaAs/MnAs core/shell nanowires
We report four probe measurements of the low field magnetoresistance in
single core/shell GaAs/MnAs nanowires synthesized by molecular beam epitaxy,
demonstrating clear signatures of anisotropic magnetoresistance that track the
field-dependent magnetization. A comparison with micromagnetic simulations
reveals that the principal characteristics of the magnetoresistance data can be
unambiguously attributed to the nanowire segments with a zinc blende GaAs core.
The direct correlation between magnetoresistance, magnetization and crystal
structure provides a powerful means of characterizing individual hybrid
ferromagnet/semiconductor nanostructures.Comment: Submitted to Applied Physics Letters; some typos corrected and a
defective figure replace
One-to-one full scale simulations of laser wakefield acceleration using QuickPIC
We use the quasi-static particle-in-cell code QuickPIC to perform full-scale,
one-to-one LWFA numerical experiments, with parameters that closely follow
current experimental conditions. The propagation of state-of-the-art laser
pulses in both preformed and uniform plasma channels is examined. We show that
the presence of the channel is important whenever the laser self-modulations do
not dominate the propagation. We examine the acceleration of an externally
injected electron beam in the wake generated by 10 J laser pulses, showing that
by using ten-centimeter-scale plasma channels it is possible to accelerate
electrons to more than 4 GeV. A comparison between QuickPIC and 2D OSIRIS is
provided. Good qualitative agreement between the two codes is found, but the 2D
full PIC simulations fail to predict the correct laser and wakefield
amplitudes.Comment: 5 pages, 5 figures, accepted for publication IEEE TPS, Special Issue
- Laser & Plasma Accelerators - 8/200
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