X-Rays from long laboratory sparks in air

This collective book provides a review of research concentrated on runaway electron beams and X-rays in an inhomogeneous electric field with different gases at increased pressure. Attention is also given to supershort avalanche electron beam (SAEB) in the optimal conditions. New experimental techniques and equipment, including those with picosecond time resolutions, were required for diagnostics of electrical and optical signals. The book consists of twenty-four chapters, some of which were written jointly by researchers of different teams. Some chapters consider the range of SAEB applications.Postprint (published version

Entropy-based feature extraction for electromagnetic discharges classification in high-voltage power generation

This work exploits four entropy measures known as Sample, Permutation, Weighted Permutation, and Dispersion Entropy to extract relevant information from Electromagnetic Interference (EMI) discharge signals that are useful in fault diagnosis of High-Voltage (HV) equipment. Multi-class classification algorithms are used to classify or distinguish between various discharge sources such as Partial Discharges (PD), Exciter, Arcing, micro Sparking and Random Noise. The signals were measured and recorded on different sites followed by EMI expert’s data analysis in order to identify and label the discharge source type contained within the signal. The classification was performed both within each site and across all sites. The system performs well for both cases with extremely high classification accuracy within site. This work demonstrates the ability to extract relevant entropy-based features from EMI discharge sources from time-resolved signals requiring minimal computation making the system ideal for a potential application to online condition monitoring based on EMI

Analysis of the electromagnetic interference field by the radiation method for transposed and untransposed transmission lines

A general method for predicting the electromagnetic interference field (EMI) performance from HV transmission lines has been proposed. The developed method utilizes a direct modal analysis using frequency dependent, electrical transmission line parameters. Carson\u27s equivalent conductors representing the earth return were included in the line parameter calculation. The impact of transposed and untransposed lines on the EMI has been studied. Transposition has been represented with two models, namely, the equivalent model and the physical model;The EMI has been analyzed using the quasi-static method and the radiation method. The radiation method has been introduced to extend and validate the study of EMI spectrum to FM and television frequencies;A Fortran computer program has been developed. This program calculates the EMI based on the minimum input data

Recent Topics in Electromagnetic Compatibility

Recent Topics in Electromagnetic Compatability discusses several topics in electromagnetic compatibility (EMC) and electromagnetic interference (EMI), including measurements, shielding, emission, interference, biomedical devices, and numerical modeling. Over five sections, chapters address the electromagnetic spectrum of corona discharge, life cycle assessment of flexible electromagnetic shields, EMC requirements for implantable medical devices, analysis and design of absorbers for EMC applications, artificial surfaces, and media for EMC and EMI shielding, and much more

Laser Atmospheric Wind Sounder (LAWS) phase 1. Volume 1: Executive summary

The laser atmospheric wind sounder (LAWS) will provide a new space based capability for the direct measurement of atmospheric winds in the troposphere. LAWS will make a major contribution toward advancing the understanding and prediction of the total Earth system and NASA's Earth Observing System (EOS) Program. LAWS is designed to measure a fundamental atmospheric parameter required to advance weather forecasting accuracies and investigate global climatic change. LAWS has a potential added benefit of providing (global) concentration profiles of large aerosols including visible and subvisible cirrus clouds, volcanic dust, smoke, and other pollutants. The objective of this Phase One study was to develop a LAWS concept and configuration. The instrument design is outlined in this first volume of three

An optic fiber sensor for partial discharge acoustic detection

Partial discharge (PD) is a very common problem in operating power transformers and is one of the factors that could lead to failure of power transformers, leading to power outage and expensive repairs. The acoustic wave induced by PD can be measured and used for monitoring, diagnosing, and locating potential failures in power transformers. The effects of the temperature of the transformer and transformer oil are one of the very important parameters in PD and these effects are investigated in detail. The Fast Fourier Transform (FF1\u27) is used to synthesize the measured data and results show that for periodic PD events, the dominant components of the energy of the PD shift to higher frequencies as the temperature increases. The experimental results are consistent with theoretical expectations. Fiber optic-based sensors have been shown to be attractive devices for PD detection because of a number of inherent advantages including small size, high sensitivity, electrical nonconductivity, and immunity to electromagnetic interference (EMI). A fiber optic sensor based on a Fabry-Perot interferometry is constructed by a simple micromachining process compatible with MEMS (Microelectromechanical system) technology. The sensor is used in a transformer to measure PD acoustic waves. The experimental results show that the sensor not only has an inherent high signal to noise capability, but is able to accurately localize the PD sources inside the transformer

Definition and preliminary design of the LAWS (Laser Atmospheric Wind Sounder), volume 2, phase 2

Accurate knowledge of winds is critical to our understanding of the earth's climate and to our ability to predict climate change. Winds are a fundamental component of highly nonlinear interactions between oceans, land surfaces, and the atmosphere. Interactions at these interfaces are the focus of much climate change research. Although wind information is critical for advancing our understanding, currently most of our description of atmospheric motion is obtained indirectly - i.e., derived from observations of temperature and moisture through geostrophic relationships. Direct measurement of winds over the globe is limited to land-based rawinsonde surface stations and a few ship/aircraft reports. Cloud track winds using satellite imagery are calculated but must be used with great care. The LAWS mission objective, therefore, is to provide diurnal and global direct observations of winds - an observation that will incrementally enhance our knowledge of the earth's climate and physical processes responsible for its change. This document is Volume 2 of the LAWS Phase 2 Final Study Report and describes the definition and preliminary design of the LAWS instrument, together with details of the laser breadboard program conducted during the last 18 months of the program

Analysis of electrical transients created by lightning

A series of flight tests was conducted using a specially-instrumented NASA Learjet to study the electrical transients created on an aircraft by nearby lightning. The instrumentation included provisions for the time-domain and frequency-domain recording of the electrical signals induced in sensors located both on the exterior and on the interior of the aircraft. The design and calibration of the sensors and associated measuring systems is described together with the results of the flight test measurements. The results indicate that the concept of providing instrumentation to follow the lightning signal from propagation field, to aircraft skin current, to current on interior wiring is basically sound. The results of the measurement indicate that the high frequency signals associated with lightning stroke precursor activity are important in generating electromagnetic noise on the interior of the aircraft. Indeed, the signals produced by the precursors are often of higher amplitude and of longer duration that the pulse produced by the main return stroke

Laser Atmospheric Wind Sounder (LAWS) phase 1. Volume 2

This report summarizes and documents the results of the 12-month phase 1 work effort. The objective of phase 1 was to establish the conceptional definition of the laser atmospheric wind sounder (LAWS) sensor system, including accommodations analyses to ensure compatibility with the Space Station Freedom (SSF) and the Earth Observing System (EOS) Polar Orbiting Platform (POP). Various concepts were investigated with trade studies performed to select the configuration to be carried forward to the phase 2 Preliminary Design Definition. A summary of the LAWS system and subsystem trade studies that were performed leading to the baseline design configuration is presented in the appendix. The overall objective of the LAWS Project is to define, design, and implement an operational space based facility, LAWS, for accurate measurement of Earth wind profiles. Phase 1 addressed three major areas: (1) requirements definition; (2) instrument concepts and configurations; and (3) performance analysis. For the LAWS instrument concepts and configurations, the issues which press the technological state of the art are reliable detector lifetime and laser performance and lifetime. Lag angle compensation, pointing accuracy, satellite navigation, and telescope design are significant technical issues, but they are considered to be currently state of the art. The primary issues for performance analysis concern interaction with the atmosphere in terms of backscatter and attenuation, wind variance, and cloud blockage. The phase 1 tasks were formulated to address these significant technical issues and demonstrate the technical feasibility of the LAWS concept. Primary emphasis was placed on analysis/trade and identification of candidate concepts. Promising configurations were evaluated for performance, sensitivities, risks, and budgetary costs. Lockheed's baseline LAWS configuration is presented

Fast pulse interactions on a transmission system - (A novel EMP measuring technique using new designed loop probes)

Ideally, a pulsed signal guided through its intended transmission medium, should be subjected to a small attenuation and negligible degradation to its wave shape. In practice, this condition is difficult to achieve, since all transmission mediums will impose some form of interference or distortion on a travelling pulse. Also no practical transmission medium is completely loss-free. The amount of attenuation/distortion imposed on a travelling pulse is a sensitive measure of the transmission performance of the medium. This thesis reports a novel attempt to investigate the effects of the transient electromagnetic (EM) fields produced by the pulse propagation pattern, and its interactions with single element antenna probes. Also to characterise and measure this distortion accurately, as a pulse travels through an open conductor-plane transmission system. In order to carry out the investigations, new loop probes which act as magnetic- and/or electric-field sensors, were analysed and designed for this purpose. The measurement technique consists of a pulser, purposely built in a coaxial arrangement which was used to generate fast (sub-nanosecond) risetime pulses for injection into the test line. An SF6 insulated hemispherical-electrode pulser was also used as a simulator for an impulse voltage generator. Detection of the pulses as they travelled along the line was by directional couplers employing these B-dot/D-dot loop probes, the directional couplers being placed at strategic points in the earthplane. Simultaneous electric- and magnetic-field measurements using a single loop antenna element is useful for the near-field electromagnetic measurements where the magnitude and phase of the wave impedance are not known. This type of loop probe, described, is not only useful to measure the polarisation ellipses of the electric- and magnetic-field vectors in the near-field region, but also measurements of the time-dependent Poynting vector so as to describe the energy flow. By altering the geometry of the loop (as opposed to adding resistors in the loop circuit as reported previously), it was found that the loop exhibited a unique coupling characteristic such that it responded equally to the components of the time derivative electric- and magnetic-fields. This important practical feature is explained. In addition to electromagnetic pulse (EMP) applications, the versatility of the coupling loop readily lends itself for use in electromagnetic compatibility (EMC) measurements and as a tool for fault detection and location on power systems network. These applications were investigated. A theoretical concept for pulse propagation on a transmission line, using circuit and field theories, is presented. An attempt is made to link the circuit theory with the field theory, with a view to describe the experimental results. Full mathematical theory of the loop is reviewed in which new equations were developed to satisfy the general loading condition of the loop. Descriptions and design specifications of the devices used in the experimental studies are given and their performances in transient field measurements have been verified in a number of unique applications. This demonstrates the integrity of the measurement system and the sensitivity characteristics of the directional coupler. With suitable angular adjustments, it was shown that the loop can be made to couple only to a pulse travelling in one direction