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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 865 records · Page 48
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Bifurcation of space-charge wave in a plasma waveguide including the wake potential effect

The wake potential effects on the propagation of the space-charge dust ion-acoustic wave are investigated in a cylindrically bounded dusty plasma with the ion flow. The results show that the wake potential would generate the double frequency modes in a cylindrically bounded dusty plasma. It is found that the upper mode of the wave frequency with the root of higher-order is smaller than that with the root of lower-order in intermediate wave number domains. However, the lower mode of the scaled wave frequency with the root of higher-order is found to be greater than that with the root of lower-order. It is found that the influence in the order of the root of the Bessel function on the wave frequency of the space-charge dust-ion-acoustic wave in a cylindrically confined dusty plasma decreases with an increase in the propagation wave number. It is also found that the double frequency modes increase with increasing Mach number due to the ion flow in a cylindrical dusty plasma. In addition, it is found that the upper mode of the group velocity decreases with an increase in the scaled radius of the plasma cylinder. However, it is shown that the lower mode of the scaled group velocity of the space-charge dust ion acoustic wave increases with an increase in the radius of the plasma cylinder. The variation of the space-charge dust-ion-acoustic wave due to the wake potential and geometric effects is also discussed.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2018

Experimental studies of 1.5 – 1.6 μm high-power asymmetric-waveguide single-mode lasers

The current – voltage, power – current, and spectral characteristics of high-power single-mode semiconductor lasers emitting at wavelengths of 1.5 – 1.6 μm are studied experimentally. It is shown that a laser with a cavity length of 1.6 mm and a mesa-stripe width of 3 μm mounted in a housing 11 mm in diameter may emit a power higher than 300 mW. Mounting of lasers on C-mounts makes it possible to achieve powers exceeding 400 mW. In the case of mounting in standard 14 pin DIL packages, the laser power at the exit of a single-mode fibre-optic cable (FOC) was no lower than 100 mW, which, taking into account 50 % losses upon radiation coupling into the FOC, corresponds to the laser diode power higher than 200 mW. It is shown that the differential resistance of a laser depends not only on the laser crystal length but also on the type of mounting (in copper housings 11 mm in diameter or on C-mounts). The dependences of the laser wavelength and spectral width on the pump current and ambient temperature are presented. The characteristic temperatures of laser diodes are determined. (lasers)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

Modelling the spectral characteristics of 1.5 – 1.6 μm high-power asymmetric-waveguide single-mode laser diodes

Spectral characteristics of high-power single-mode laser diodes with a radiation wavelength of 1.5 – 1.6 μm are simulated with allowance for nonlinear losses. A satisfactory agreement between the calculation and experimental results as applied to the dependence of the wavelength and radiation spectrum width on the laser pump current is demonstrated. The effect of thermal resistance of a laser diode on the active region heating, spectrum width, and radiation wavelength is considered. (paper)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2019

Experimental studies of 1.5 – 1.6 μm high-power asymmetric-waveguide multimode lasers

The current – voltage, light – current, and spectral characteristics of high-power multimode semiconductor lasers emitting at wavelengths of 1.5 – 1.6 μm are studied experimentally. It is shown that the cw output power of a C-mount laser with a cavity length of 2.6 mm and a mesa-stripe contact width of 100 μm exceeds 4 W at a pump power of 15 A. The output power in a pulsed regime amounts to 20 W at a pulse duration of 100 ns, a pulse repetition rate of 5 kHz, and a pump current no higher than 80 A. The dependences of the laser wavelength and spectral width on the pump current are presented. The current – voltage and light – current characteristics, as well as the characteristic temperatures of the lasers, are calculated. (paper)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2019

Effect of Cd content in barriers on the threshold energy of Auger recombination in waveguide structures with HgTe/Cd{sub x}Hg{sub 1 – x}Te quantum wells, emitting at a wavelength of 18 μm

The threshold energy of Auger recombination in HgTe/Cd{sub x}Hg{sub 1 – x}Te heterostructures with quantum wells (QWs) is analysed numerically for different compositions of the solid solution in barriers. It is demonstrated that the threshold energy depends nonmonotonically on the cadmium content in barriers and reaches a maximum at x ∼0.6 – 0.7. A comparison of the results of numerical calculations with experimental data on the temperature quenching of stimulated emission in a Cd{sub 0.1}Hg{sub 0.9}Te/Cd{sub 0.65}Hg{sub 0.35}Te structure gives grounds to expect a more than twofold increase in the quenching temperature of stimulated emission in structures with pure HgTe QWs and barriers with a high (∼0.6) cadmium content. (paper)

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Test Results of a High-Gradient 2.856-GHz Negative Harmonic Accelerating Waveguide

We report the high-gradient tests results of a novel traveling wave accelerating structure for β=0.3 based on a novel approach of operating at the first negative spatial harmonic. Accelerating gradients of 50 MV/m and peak electric fields of 160 MV/m were achieved in a single structure consisting of 15 coupled cells during tests at the advanced photon source. This work was performed by RadiaBeam, in collaboration with the Argonne National Laboratory, as a part of a Research and Development Program for the development of an ultrahigh-gradient linear accelerator, the Advanced Compact Carbon Ion Linac, for hadron therapy.

42 ENGINEERING↗
DOE OSTI2022

Portable Waveguide-Based Optical Biosensor

Rapid, on-site diagnostics allow for timely intervention and response for warfighter support, environmental monitoring, and global health needs. Portable optical biosensors are being widely pursued as a means of achieving fieldable biosensing due to the potential speed and accuracy of optical detection. We recently developed the portable engineered analytic sensor with automated sampling (PEGASUS) with the goal of developing a fieldable, generalizable biosensing platform. Here, we detail the development of PEGASUS’s sensing hardware and use a test-bed system of identical sensing hardware and software to demonstrate detection of a fluorescent conjugate at 1 nM through biotin-streptavidin chemistry.

47 OTHER INSTRUMENTATION↗