NiO Exchange Bias Layers Grown by Direct Ion Beam Sputtering of a Nickel Oxide Target

A new process for fabricating NiO exchange bias layers has been developed. The process involves the direct ion beam sputtering (IBS) of a NiO target. The process is simpler than other deposition techniques for producing NiO buffer layers, and facilitates the deposition of an entire spin-valve layered structure using IBS without breaking vacuum. The layer thickness and temperature dependence of the exchange field for NiO/NiFe films produced using IBS are presented and are similar to those reported for similar films deposited using reactive magnetron sputtering. The magnetic properties of highly textured exchange couples deposited on single crystal substrates are compared to those of simultaneously deposited polycrystalline films, and both show comparable exchange fields. These results are compared to current theories describing the exchange coupling at the NiO/NiFe interface.Comment: 9 pages, Latex 2.09, 3 postscript figures. You can also this manuscript at http://www.wsrcc.com/alison/fixed-nio/manuscript.html To be published in _IEEE Trans. Magn._, Nov. 199

Andreev Level Qubit

We investigate the dynamics of a two-level Andreev bound state system in a transmissive quantum point contact embedded in an rf-SQUID. Coherent coupling of the Andreev levels to the circulating supercurrent allows manipulation and read out of the level states. The two-level Hamiltonian for the Andreev levels is derived, and the effect of interaction with the quantum fluctuations of the induced flux is studied. We also consider an inductive coupling of qubits, and discuss the relevant SQUID parameters for qubit operation and read out.Comment: 4 pages, 1 figur

A reactor concept for space power employing thermionic diodes and pipes

Reactor heat pipe flow system with external diode for thermionic generator power suppl

Detector Channel Combining Results from a High Photon Efficiency Optical Communications Link Test Bed

The National Aeronautics and Space Administration (NASA) Glenn Research Center (GRC) is developing a low cost, scalable, photon-counting receiver prototype for space-to-ground optical communications links. The receiver is being tested in a test bed that emulates photon-starved space-to-ground optical communication links. The receiver uses an array of single-pixel fiber-coupled superconducting nanowire single-photon detectors. The receiver is designed to receive the high photon efficiency serially concatenated pulse position modulation (SCPPM) waveform specified in the Consultative Committee for Space Data Systems (CCSDS) Optical Communications Coding and Synchronization Blue Book Standard. The optical receiver consists of an array of single-pixel superconducting nanowire detectors, analog phase shifters for channel alignment, digitizers for each detector channel, and digital processing of the received signal. An overview of the test bed and arrayed receiver system is given. Simulation and system characterization results are presented. The data rate increase of using a four-channel arrayed detector system over using one single pixel nanowire detector is characterized. Results indicate that a single-pixel detector is capable of receiving data at a rate of 40 Mbps and a four-channel arrayed detector system is capable of receiving data at a rate of 130 Mbps

Demonstration of an integrated LiNbO3 Synchronized Double Phase Modulator and its Applications to Dual-Pump Fiber Optical Parametric Amplifiers and Wavelength Converters

International audienceWe report the fabrication of an integrated LiNbO3 Y-junction synchronized double phase modulator fully packaged for RF-application up to 40 GHz. This optical modulator allows for delivering simultaneously counter-phase high-speed modulation and coupling for two input channels. It was designed for application to fiber-optical parametric amplifier and wavelength converters for suppressing idler spectral broadening and signal gain distortion caused by phase modulation itself. With this component, Idler spectral broadening suppression is experimentally demonstrated over all the parametric gain band of a twopump parametric amplifier operating in the 1.55 µm region. In addition, we present a useful technique for straightforward and full coupling of the pumps and the signal

Zero-dispersion Wavelength Mapping in Short Single-Mode Optical Fibers Using Parametric Amplification

We demonstrate a novel convenient nondestructive method based on optical parametric amplification that allows retrieval of the zero-dispersion wavelength map along a short optical fiber span with a high-spatial resolution. The improved resolution relies on the high sensitivity to the local longitudinal dispersion fluctuations of the parametric high-gain spectrum.Comment: 3 page

Surface effects on the Mott-Hubbard transition in archetypal V2_2O3_3

We present an experimental and theoretical study exploring surface effects on the evolution of the metal-insulator transition in the model Mott-Hubbard compound Cr-doped V$_2$O$_3$. We find a microscopic domain formation that is clearly affected by the surface crystallographic orientation. Using scanning photoelectron microscopy and X-ray diffraction, we find that surface defects act as nucleation centers for the formation of domains at the temperature-induced isostructural transition and favor the formation of microscopic metallic regions. A density functional theory plus dynamical mean field theory study of different surface terminations shows that the surface reconstruction with excess vanadyl cations leads to doped, and hence more metallic surface states, explaining our experimental observations.Comment: 5 pages, 4 figure

U.S. Virgin Islands Energy Road Map: Analysis

This report lays out the strategy envisioned by the stakeholders in the U.S. Virgin Islands, U.S. Department of Energy, and U.S. Department of Interior to achieve the ambitious goal of achieving a 60% reduction in business-as-usual fossil fuel demand by 2025 (60x25) within the electricity sector. This work and supporting analysis provides a framework within which decisions can begin to be made, a concrete vision of what the future might hold, and a guide to determine what questions should follow

Characterization of a Photon Counting Test Bed for Space to Ground Optical Pulse Position Modulation Communications Links

The National Aeronautics and Space Administration (NASA) Glenn Research Center (GRC) has developed a laboratory transmitter and receiver prototype of a space-to-ground optical communications link. The system is meant to emulate future deep space optical communication links, such as the first crewed flight of Orion, in which the transmitted laser is modulated using pulse position modulation and the receiver is capable of detecting single photons. The transmitter prototype consists of a software defined radio, a high extinction ratio electro-optic modulator system, and a 1550 nm laser. The receiver is a scalable concept and utilizes a single-pixel array of fiber coupled superconducting nanowire single photon detectors. The transmit and receive waveforms follow the Consultative Committee for Space Data Systems (CCSDS) Optical Communications Coding and Synchronization Standard. A software model of the optical transmitter and receiver has also been implemented to predict performance of the optical test bed. This paper describes the transmitter and receiver prototypes as well as the system test configuration. System level tests results are presented and shown to align with predictions from software simulations. The validated software model can be used to in the future to reduce the design cycle of optical communications systems