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An electromagnetic induction method for underground target detection and characterization

Description: An improved capability for subsurface structure detection is needed to support military and nonproliferation requirements for inspection and for surveillance of activities of threatening nations. As part of the DOE/NN-20 program to apply geophysical methods to detect and characterize underground facilities, Sandia National Laboratories (SNL) initiated an electromagnetic induction (EMI) project to evaluate low frequency electromagnetic (EM) techniques for subsurface structure detection. Low frequency, in this case, extended from kilohertz to hundreds of kilohertz. An EMI survey procedure had already been developed for borehole imaging of coal seams and had successfully been applied in a surface mode to detect a drug smuggling tunnel. The SNL project has focused on building upon the success of that procedure and applying it to surface and low altitude airborne platforms. Part of SNL`s work has focused on improving that technology through improved hardware and data processing. The improved hardware development has been performed utilizing Laboratory Directed Research and Development (LDRD) funding. In addition, SNL`s effort focused on: (1) improvements in modeling of the basic geophysics of the illuminating electromagnetic field and its coupling to the underground target (partially funded using LDRD funds) and (2) development of techniques for phase-based and multi-frequency processing and spatial processing to support subsurface target detection and characterization. The products of this project are: (1) an evaluation of an improved EM gradiometer, (2) an improved gradiometer concept for possible future development, (3) an improved modeling capability, (4) demonstration of an EM wave migration method for target recognition, and a demonstration that the technology is capable of detecting targets to depths exceeding 25 meters.
Date: January 1, 1997
Creator: Bartel, L.C. & Cress, D.H.
Partner: UNT Libraries Government Documents Department

Reduction of ripple voltage in a dynamitron

Description: We determined that a precise neutralization of the RF ripple voltage on the high-voltage terminal of a Dynamitron has previously been prevented by a nonegligible phase shift of RF currents in the two halves of the approx. 100-kHz class C oscillator tank circuit, which is actually constituted of two slightly unequal high-Q coupled circuits because it has two ground points: the inescapable center-tap-ground in the capacitive legs and a center-tap-ground lead to the induction coil. The latter is needed to prevent damage by flashover transients; equivalent to its removal was the adjusting of RF ground return current to a null by aid of a current transformer on this lead and the suitable adjusting of trimmer capacitance. While the phase shift was thus held to a null, the actual ripple amplitude on the hv terminal was minimized by adjusting additional trimmer capacitances installed in the terminal of the machine. Then p/p 100-kHz ripple at 2-MV dc output was reduced to about 50V and RMS resolution by (p,..gamma..) resonance threshold data near 1 MV was about 250 V. The limit to resolution has various causes including mechanical vibrations and unbalanced harmonics of the RF.
Date: January 1, 1982
Creator: Langsdorf, A. Jr.
Partner: UNT Libraries Government Documents Department

Multiparameter data acquisition and display program. [MUL, DREF, DUPD]

Description: A general-purpose multiparameter data acquisition, histo-gramming, and display program is presented. The 32 input parameters of the program consist of up to 16 CAMAC words of 16 bits, and up to 16 algebraic functions of these words. Up to 64 one- and two-dimensional histograms based on these parameters can be constructed, subject to up to 144 correlated conditions imposed on the input parameters. The display system consists of a rapid refresh scope with 10-bit X and Y resolution and a push-botton panel, specifically designed to interact dynamically with either the display or the data acquisition programs. Typical event rates vary between 300 Hz and 10 kHz, depending on the number of histograms generated and on their filtering conditions. 1 figure.
Date: January 1, 1979
Creator: Sunier, J.W.; Poore, R.V. & McMillan, D.E.
Partner: UNT Libraries Government Documents Department

Unmanned airborne vehicle (UAV): Flight testing and evaluation of two-channel E-field very low frequency (VLF) instrument

Description: Using VLF frequencies, transmitted by the Navy`s network, for airborne remote sensing of the earth`s electrical, magnetic characteristics was first considered by the United States Geological Survey (USGS) around the mid 1970s. The first VLF system was designed and developed by the USGS for installation and operation on a single engine, fixed wing aircraft used by the Branch of Geophysics for geophysical surveying. The system consisted of five channels. Two E-field channels with sensors consisting of a fixed vertical loaded dipole antenna with pre-amp mounted on top of the fuselage and a gyro stabilized horizontal loaded dipole antenna with pre-amp mounted on a tail boom. The three channel magnetic sensor consisted of three orthogonal coils mounted on the same gyro stabilized platform as the horizontal E-field antenna. The main features of the VLF receiver were: narrow band-width frequency selection using crystal filters, phase shifters for zeroing out system phase variances, phase-lock loops for generating real and quadrature gates, and synchronous detectors for generating real and quadrature outputs. In the mid 1990s the Branch of Geophysics designed and developed a two-channel E-field ground portable VLF system. The system was built using state-of-the-art circuit components and new concepts in circuit architecture. Small size, light weight, low power, durability, and reliability were key considerations in the design of the instrument. The primary purpose of the instrument was for collecting VLF data during ground surveys over small grid areas. Later the system was modified for installation on a Unmanned Airborne Vehicle (UAV). A series of three field trips were made to Easton, Maryland for testing and evaluating the system performance.
Date: December 1, 1998
Partner: UNT Libraries Government Documents Department

Magnetic Fields of AM Band Radio Broadcast Signals at the Richmond Field Station

Description: Non-invasive sensing of the shallow subsurface is necessary for detection and delineation of buried hazardous wastes, monitoring of the condition of clay containment caps, and a variety of other purposes. Electromagnetic methods have proven to be effective in environmental site characterization where there is a need for increased resolution in subsurface characterization. Two considerations strongly suggest the use of frequencies between 100 kHz and 100 MHz for such applications: 1) the induction response of many targets is small due to small size, and 2) a need to determine both the electrical conductivity and dielectric permittivity which are related to chemistry and hydrology. Modeling and physical parameter studies confirm that measurements at frequencies between 1 and 100 MHz can resolve variations in subsurface conductivity and permittivity. To provide the necessary technology for shallow subsurface investigations, we propose to exploit the concept of electromagnetic impedance, the ratio of orthogonal horizontal electric and magnetic fields. Prior to assembling the equipment for measuring surface impedance using controlled, local source it was felt prudent to measure the surface impedance of geological materials at the University of California at Berkeley's Richmond Field (RFS) using ambient energy in the broadcast band. As a first step toward this intermediate goal, we have examined and characterized local AM band radio signals in terms of both signal strength and polarization of the magnetic component as received at RFS. In addition, we have established the viability of a commercial radio-frequency magnetic sensor.
Date: December 1, 1998
Creator: Becker, Alex & Frangos, William
Partner: UNT Libraries Government Documents Department

Modulating the Neutron Flux from a Mirror Neutron Source

Description: A 14-MeV neutron source based on a Gas-Dynamic Trap will provide a high flux of 14 MeV neutrons for fusion materials and sub-component testing. In addition to its main goal, the source has potential applications in condensed matter physics and biophysics. In this report, the author considers adding one more capability to the GDT-based neutron source, the modulation of the neutron flux with a desired frequency. The modulation may be an enabling tool for the assessment of the role of non-steady-state effects in fusion devices as well as for high-precision, low-signal basic science experiments favoring the use of the synchronous detection technique. A conclusion is drawn that modulation frequency of up to 1 kHz and modulation amplitude of a few percent is achievable. Limitations on the amplitude of modulations at higher frequencies are discussed.
Date: September 1, 2011
Creator: Ryutov, D D
Partner: UNT Libraries Government Documents Department

Development and evaluation of systems for controlling parallel high di/dt thyratrons

Description: Increasing numbers of high power, high repetition rate applications dictate the use or thyratrons in multiple of hard parallel configurations to achieve the required rate of current rise, di/dt. This in turn demands the development of systems to control parallel thyratron commutation with nanosecond accuracy. Such systems must be capable of real-time, fully-automated control in multi-kilohertz applications while still remaining cost effective. This paper describes the evolution of such a control methodology and system.
Date: January 1, 1982
Creator: A., Litton. & McDuff, G.
Partner: UNT Libraries Government Documents Department

Unified model of the rf plasma sheath: Part 2, Asymptotic connection formulae

Description: A previously-developed approximation to the first integral of the Poisson equation enables one to obtain solutions for the voltage- current characteristics of a radio-frequency (rf) plasma sheath that are valid over the whole range of inertial response of the ions to an imposed rf voltage or current-specified conditions. The theory reproduced the time-dependent voltage-current characteristics of the two extreme cases corresponding to the Lieberman rf sheath theory and the Metze-Ernie-Oskam theory. In this paper the sheath model is connected to the plasma bulk description, and a prescription is given for the ion relaxation time constant, which determines the time-dependent ion impact energy on the electrode surface. It appears that this connected model should be applicable to those high density, low pressure plasmas in which the Debye length is a small fraction of the ion mean free path, which itself is a small fraction of the plasma dimension.
Date: August 1, 1996
Creator: Riley, M.E.
Partner: UNT Libraries Government Documents Department

Straw man 900-1000 GeV crystal extraction test beam for Fermilab collider operation

Description: A design for a 900-1000 GeV, 100 khz parasitic test beam for use during collider operations has been developed. The beam makes use of two bent crystals, one for extraction and the other one for redirecting the beam in to the present Switchyard beam system. The beam requires only a few modifications in the A0 area and largely uses existing devices. It should be straight-forward to modify one or two beam lines in the fixed target experimental areas to work above 800 GeV. Possibilities for improvements to the design,to operate at higher fluxes are discussed.
Date: October 1, 1996
Creator: Carrigan, R.A. Jr.
Partner: UNT Libraries Government Documents Department

Interpretation of electromagnetic extra-low-frequency soundings in the Randsburg, California, Known Geothermal Resource Area

Description: An electromagnetic (EM) controlled source survey was made during the period November 30, 1977, to December 13, 1977, in the Randsburg, California, Known Geothermal Resource Area (KGRA). The observed extra-low-frequency (ELF) data and least squares interpretation using a computer program developed by Anderson (1977) are summarized. The results are given in tabular form along with observed and calculated amplitude and phase plots. In addition, one vertical electrical sounding (VES) was obtained and a graphical solution is included via a Schlumberger inversion program developed by Zohdy (1973).
Date: January 1, 1978
Creator: Anderson, W.L.
Partner: UNT Libraries Government Documents Department

Magnetic switching, final chapter, Book I: the ATA upgrade prototype

Description: Efforts directed at finding a 10 kHz switch to replace the current 1 kHz gas blown spark gap have culminated in a prototype for an upgrade of ATA. The design and performance of this prototype as well as possible options and recommendations concerning an eventual upgrade are described. 4 references, 9 figures.
Date: March 22, 1983
Creator: Birx, D.; Cook, E.; Hawkins, S.; Poor, S.; Reginato, L.; Schmidt, J. et al.
Partner: UNT Libraries Government Documents Department

The LASI high-frequency electromagnetic subsurface-imaging system: System description and demonstration site-characterization survey at the Idaho National Engineering Laboratory

Description: A high-frequency, high-resolution, electromagnetic imaging system has been developed for environmental geophysics surveys. Some key features include: (1) rapid surveying to allow dense spatial sampling over a large area, (2) high-accuracy measurements which are used to produce a high-resolution image of the subsurface, (3) measurements which have excellent signal-to-noise ratio over a wide bandwidth (31 kHz to 32 MHz), (4) large-scale physical modeling to produce accurate theoretical responses over targets of interest in environmental geophysics surveys, (5) rapid neural network interpretation at the field site, and (6) visualization of complex structures during the survey. A field survey was conducted at INEL, Nov. 28-Dec. 1, 1995, over the Cold Test Pit, which simulates waste pits at INEL and other DOE sites.
Date: December 31, 1996
Creator: Sternberg, B.K. & Poulton, M.M.
Partner: UNT Libraries Government Documents Department

Observation of SOL Current Correlated with MHD Activity in NBI-heated DIII-D Tokamak Discharges

Description: This work investigates the potential roles played by the scrape-off-layer current (SOLC) in MHD activity of tokamak plasmas, including effects on stability. SOLCs are found during MHD activity that are: (1) slowly growing after a mode-locking-like event, (2) oscillating in the several kHz range and phase-locked with magnetic and electron temperature oscillations, (3) rapidly growing with a sub-ms time scale during a thermal collapse and a current quench, and (4) spiky in temporal behavior and correlated with spiky features in Da signals commonly identified with the edge localized mode (ELM). These SOLCs are found to be an integral part of the MHD activity, with a propensity to flow in a toroidally non-axisymmetric pattern and with magnitude potentially large enough to play a role in the MHD stability. Candidate mechanisms that can drive these SOLCs are identified: (a) toroidally non-axisymmetric thermoelectric potential, (b) electromotive force (EMF) from MHD activity, and (c) flux swing, both toroidal and poloidal, of the plasma column. An effect is found, stemming from the shear in the field line pitch angle, that mitigates the efficacy of a toroidally non-axisymmetric SOLC to generate a toroidally non-axisymmetric error field. Other potential magnetic consequences of the SOLC are identified: (i) its error field can introduce complications in feedback control schemes for stabilizing MHD activity and (ii) its toroidally non-axisymmetric field can be falsely identified as an axisymmetric field by the tokamak control logic and in equilibrium reconstruction. The radial profile of a SOLC observed during a quiescent discharge period is determined, and found to possess polarity reversals as a function of radial distance.
Date: March 26, 2004
Creator: Takahashi, H.; Fredrickson, E.D.; Schaffer, M.J.; Austin, M.E.; Evans, T.E.; Lao, L.L. et al.
Partner: UNT Libraries Government Documents Department

Low-frequency nuclear quadrupole resonance with a dc SQUID

Description: Conventional pure nuclear quadrupole resonance (NQR) is a technique well suited for the study of very large quadrupolar interactions. Numerous nuclear magnetic resonance (NMR) techniques have been developed for the study of smaller quadrupolar interactions. However, there are many nuclei which have quadrupolar interactions of intermediate strength. Quadrupolar interactions in this region have traditionally been difficult or unfeasible to detect. This work describes the development and application of a SQUID NQR technique which is capable of measuring intermediate strength quadrupolar interactions, in the range of a few hundred kilohertz to several megahertz. In this technique, a dc SQUID (Superconducting QUantum Interference Device) is used to monitor the longitudinal sample magnetization, as opposed to the transverse magnetization, as a rf field is swept in frequency. This allows the detection of low-frequency nuclear quadrupole resonances over a very wide frequency range with high sensitivity. The theory of this NQR technique is discussed and a description of the dc SQUID system is given. In the following chapters, the spectrometer is discussed along with its application to the study of samples containing half-odd-integer spin quadrupolar nuclei, in particular boron-11 and aluminum-27. The feasibility of applying this NQR technique in the study of samples containing integer spin nuclei is discussed in the last chapter. 140 refs., 46 figs., 6 tabs.
Date: July 1, 1991
Creator: Chang, J.W.
Partner: UNT Libraries Government Documents Department

Modulus dispersion and attenuation in tuff and granite

Description: The effects of loading frequency, strain amplitude, and saturation on elastic moduli and attenuation have been measured in samples of the Topopah Spring Member welded tuff. Four different laboratory techniques have been used to determine Young`s modulus and extensional wave attenuation at frequencies ranging from 10{sup {minus}2} to 10{sup 6} Hz. The results are compared with data acquired for Sierra White granite under the same conditions. The modulus and attenuation in room dry samples remain relatively constant over frequency. Frequency dependent attenuation and modulus dispersion are observed in the saturated samples and are attributed to fluid flow and sample size. The properties of tuff were independent of strain amplitude in room dry and saturated conditions.
Date: December 23, 1991
Creator: Haupt, R.W.; Martin, R.J. III; Tang, X.; Dupree, W.J. & Price, R.H.
Partner: UNT Libraries Government Documents Department

Advances in high repetition rate, ultra-short, gigawatt laser systems for time-resolved spectroscopy

Description: The objective of this article is to emphasize the current advances in the development of high-repetition rate amplifier pumps. Although this review highlights amplifier pump development, any recent data from achieved outputs via the tunable amplifier section is also discussed. The first section describes desirable parameters attributable to the pump amplifier while the rest of the article deals with specific examples for various options. The pump amplifiers can be characterized into two distinct classes; those achieving operation in the hundred hertz regime and those performing at repetition rates {ge}1kHz. 23 refs., 4 figs.
Date: January 1, 1991
Creator: DiMauro, L.F.
Partner: UNT Libraries Government Documents Department