Photoionization of photoexcited cesium

A new method for obtaining the cross section for photoionization of photoexcited cesium is presented. The salient feature of this experiment is to use three crossed beams, i.e., two light beams intersecting a beam of cesium atoms. The cross section is determined by counting the ions produced by the two step process: Cs (6S) + h[upsilon]₁ --\u3e Cs (6P) ; Cs (6P) + [upsilon]₂ --\u3e Cs⁺ + e⁻ The relative cross section for the second step has been obtained from threshold (5060 Å) to 2500 Å. The excitation light source used in obtaining this cross section was a rf resonance lamp, but the possibility of using a GaAs laser as this light source was also investigated. A GaAs laser was thermally tuned to the 6S - 6P transition wavelength in cesium, 8521 Å, and it was found that in this way the hyperfine levels of the ground state of cesium could be selectively depopulated. Although excellent results were obtained in this portion of the study, the low duty cycle of the lasers that we had available made them unsuitable for the photoionization experiment --Abstract, page i

Photoionization Of The 6P32,122 Fine-structure Levels In Cesium

The relative photoionization cross sections for cesium atoms selectively excited to the 6P32,122 states have been measured in a triple-crossed-beam experiment. A cesium discharge lamp produced resonant wavelengths of 8521 and 8944 for the excitation process. A Hg-Xe lamp combined with a grating monochromator was used for the actual ionization in the wavelength region from 2500 to 5000. Background counts due to photoionization of ground-state cesium atoms and dimers as well as various surface effects were discriminated against by chopping the excitation light source. The data are compared with results from radiative-recombination measurements in which the fine-structure levels are not resolved and with recent model-potential calculations. The wavelength () dependence of the cross section indicates a 2 dependence at threshold (5000) and a 4 behavior at lower wavelengths. © 1975 The American Physical Society

Analysis of the Power Quality Impact of Multiple Directed Energy Loads on an Electric Ship Power System

The electrical power system of an all-electric ship has been modeled in Simulink for the case of a ship supporting several high power directed energy loads, among which are a Free Electron Laser (FEL), an Active Denial System (ADS), and a Laser Weapon System (LaWS). Starting from a load centered approach, and a physical description of the components of the various loads, individual models of each load plus a combined model for a system supporting simultaneously one instance of all loads have been developed. Sample case studies are presented corresponding to expected operational scenarios for a US Navy ship and to potential emergency conditions. The models have been designed to be interactive, allowing the operator to change key settings dynamically while the simulation is running, thus mimicking an actual operation of the power system on a ship in real time. A preliminary graphical user interface has also been developed to demonstrate the ability of these models to be converted into top-level training tools for Navy personnel supported by a realistic representation of the ship power system

Coordination of Large Pulsed Loads on Future Electric Ships

The article of record as published may be found at http://dx.doi.org/10.1109/TMAG.2006.887676Part of the technical versatility of future all-electric ships is the potential ability to share large amounts of power among a variety of high-power loads. To help evaluate this potential and to provide information to help guide technology selection, a physics-based model of a power train for an electric ship has been developed and implemented on three modeling platforms. Using this model, three different investigations have been carried out to explore aspects of the behavior of a rotating machine power source for a shipboard rail launcher. These were: 1) influence of rapid charging of the rotating machine system on the ship power system; 2) use of the stored energy in the rotating machines to improve ship power quality; and 3) use of the stored energy in the rotating machines to power a pulsed free-electron laser. Each study highlighted different integration opportunities and challenges. The first showed that, because the charging of the rail launchers was through 5-MW motors, there could be a voltage sag for a few cycles, but this could easily be managed so that the sag could be reduced to an inconsequential level. The second study showed that, with appropriate power electronics, the stored energy in the rail launcher power supply can be used to correct power quality problems introduced by other ship systems. Finally, the stored energy in the launcher power supply can be used to fire a free electron laser for ship defense. This feature opens the possibility of routine operation of the entire ship at highest efficiency, i.e., with the smallest number of gas turbines operating near full power, while providing stored energy needed for ship defense.This work was supported by the Office of Naval Research

Comprehensive evaluation of algal biofuel production: Experimental and target results

Worldwide, algal biofuel research and development efforts have focused on increasing the competitiveness of algal biofuels by increasing the energy and financial return on investments, reducing water intensity and resource requirements, and increasing algal productivity. In this study, analyses are presented in each of these areas—costs, resource needs, and productivity—for two cases: (1) an Experimental Case, using mostly measured data for a lab-scale system, and (2) a theorized Highly Productive Case that represents an optimized commercial-scale production system, albeit one that relies on full-price water, nutrients, and carbon dioxide. For both cases, the analysis described herein concludes that the energy and financial return on investments are less than 1, the water intensity is greater than that for conventional fuels, and the amounts of required resources at a meaningful scale of production amount to significant fractions of current consumption (e.g., nitrogen). The analysis and presentation of results highlight critical areas for advancement and innovation that must occur for sustainable and profitable algal biofuel production can occur at a scale that yields significant petroleum displacement. To this end, targets for energy consumption, production cost, water consumption, and nutrient consumption are presented that would promote sustainable algal biofuel production. Furthermore, this work demonstrates a procedure and method by which subsequent advances in technology and biotechnology can be framed to track progress.Mechanical Engineerin

GOVERNMENT ACTIVITY TO INCREASE BENEFITS FROM THE GLOBAL STANDARDS SYSTEM ∗

Abstract In this paper,we review the factors influencing the evolution of the global standards system. We then discuss some of the approaches that governments have taken or are exploring in order to modify the system for the benefit of domestic and worldwide economic development. We use as an example an effort of the U.S.National Institute of Standards and Technology to encourage voluntary consensus standards for interoperable broadband wireless access systems. This article has been accepted for publication in the Proceedings of the 2nd IEE

Hardware-in-the-loop test for real-time economic control of a DC microgrid

Microgrids (MGs) utilising both renewables and energy storage to optimise onsite energy consumption rather than importing power form the utility grid, require a tertiary-level energy management system (EMS). The EMS must monitor and control the energy exchange within the nodes of MG to maximise any solar energy generation and benefit from installed storage. This paper considers a single-family house as the MG that has DC distribution circuit model. The look-ahead EMS is formulated as a linear programming problem, which has been tested in both offline simulation and hardware-in-the-loop (HIL) simulation environment. The simulation results indicate that the proposed look-ahead EMS can effectively reduce the DC MG operation cost without any operational constraint violation. In addition, the proposed look ahead energy optimisation approach has the potential to be used in a large-scale system such as a community MG with multiple buildings.Peer reviewe

Rotating machines using trapped field magnets and related methods

Rotors with trapped-field magnet (TFM) bulks, machines with TFM rotors, and methods of activating and/or using machines with TFM rotors.Board of Regents, University of Texas Syste