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Los Alamos National Laboratory plans for a laboratory microfusion facility

Description: Los Alamos National Laboratory is actively participating in the National Laboratory Microfusion Facility (LMF) Scoping Study. We are currently performing a conceptual design study of a krypton-fluoride laser system that appears to meet all of the diver requirements for the LMF. A new theory of amplifier module scaling has been developed recently and it appears that KrF amplifier modules can be scaled up to output energies much larger than thought possible a few years ago. By using these large amplifier modules, the reliability and availability of the system is increased and its cost and complexity is decreased. Final cost figures will be available as soon as the detailed conceptual design is complete.
Date: January 1, 1988
Creator: Harris, D.B.
Partner: UNT Libraries Government Documents Department

Computational Complexity of Subspace Detectors and Matched Field Processing

Description: Subspace detectors implement a correlation type calculation on a continuous (network or array) data stream [Harris, 2006]. The difference between subspace detectors and correlators is that the former projects the data in a sliding observation window onto a basis of template waveforms that may have a dimension (d) greater than one, and the latter projects the data onto a single waveform template. A standard correlation detector can be considered to be a degenerate (d=1) form of a subspace detector. Figure 1 below shows a block diagram for the standard formulation of a subspace detector. The detector consists of multiple multichannel correlators operating on a continuous data stream. The correlation operations are performed with FFTs in an overlap-add approach that allows the stream to be processed in uniform, consecutive, contiguous blocks. Figure 1 is slightly misleading for a calculation of computational complexity, as it is possible, when treating all channels with the same weighting (as shown in the figure), to perform the indicated summations in the multichannel correlators before the inverse FFTs and to get by with a single inverse FFT and overlap add calculation per multichannel correlator. In what follows, we make this simplification.
Date: December 1, 2010
Creator: Harris, D B
Partner: UNT Libraries Government Documents Department

Subspace Detectors: Theory

Description: Broadband subspace detectors are introduced for seismological applications that require the detection of repetitive sources that produce similar, yet significantly variable seismic signals. Like correlation detectors, of which they are a generalization, subspace detectors often permit remarkably sensitive detection of small events. The subspace detector derives its name from the fact that it projects a sliding window of data drawn from a continuous stream onto a vector signal subspace spanning the collection of signals expected to be generated by a particular source. Empirical procedures are presented for designing subspaces from clusters of events characterizing a source. Furthermore, a solution is presented for the problem of selecting the dimension of the subspace to maximize the probability of detecting repetitive events at a fixed false alarm rate. An example illustrates subspace design and detection using events in the 2002 San Ramon, California earthquake swarm.
Date: July 11, 2006
Creator: Harris, D B
Partner: UNT Libraries Government Documents Department

Waveform correlation methods for identifying populations of calibration events

Description: An approach for systematically screening large volumes of continuous data for repetitive events identified as mining explosions on basis of temporal and amplitude population characteristics. The method extends event clustering through waveform correlation with a new source-region-specific detector. The new signal subspace detector generalizes the matched filter and can be used to increase the number of events associated with a given cluster, thereby increasing the reliability of diagnostic cluster population characteristics. The method can be applied to obtain bootstrap ground truth explosion waveforms for testing discriminants, where actual ground truth is absent. The same events, if associated with to a particular mine, may help calibrate velocity models. The method may also assist earthquake hazard risk assessment by providing what amounts to blasting logs for identified mines. The cluster event lists can be reconciled against earthquake catalogs to screen explosions, otherwise hard to identify from the catalogs.
Date: July 1, 1997
Creator: Harris, D.B.
Partner: UNT Libraries Government Documents Department

Overview of the Los Alamos National Laboratory Inertial Confinement Fusion Program

Description: The Los Alamos Inertial Confinement Fusion (ICF) Program is focused on preparing for a National Ignition Facility. Target physics research is addressing specific issues identified for the Ignition Facility target, and materials experts are developing target fabrication techniques necessary for the advanced targets. We are also working with Lawrence Livermore National Laboratory on the design of the National Ignition Facility target chamber. Los Alamos is also continuing to develop the KrF laser-fusion driver for ICF. We are modifying the Aurora laser to higher intensity and shorter pulses and are working with the Naval Research Laboratory on the development of the Nike KrF laser. 9 refs., 1 fig., 2 tabs.
Date: January 1, 1991
Creator: Harris, D.B.
Partner: UNT Libraries Government Documents Department

Megajoule-class single-pulse KrF laser test facility as a logical step toward inertial fusion commercialization

Description: The cost and efficiency of megajoule-class KrF laser single pulse test facilities have been examined. A baseline design is described which illuminates targets with 5 MJ with shaped 10-ns pulses. The system uses 24 main amplifiers and operates with an optics operating fluence of 4.0 J/cm/sup 2/. This system has 9.0% efficiency and costs $200/joule. Tradeoff studies indicate that large amplifier modules and high fluences lead to the lowest laser system costs, but that only a 20% cost savings can be realized by going to amplifier modules larger than 200 kJ and/or fluences greater than 4 J/cm/sup 2/. The role of the megajoule-class single-pulse test facility towards inertial fusion commercialization will also be discussed.
Date: January 1, 1985
Creator: Harris, D.B. & Pendergrass, J.H.
Partner: UNT Libraries Government Documents Department

Design optimization of single-main-amplifier KrF laser-fusion systems

Description: KrF lasers appear to be a very promising laser fusion driver for commercial applications. The Large Amplifier Module for the Aurora Laser System at Los Alamos is the largest KrF laser in the world and is currently operating at 5 kJ with 10 to 15 kJ eventually expected. The next generation system is anticipated to be a single-main-amplifier system that generates approximately 100 kJ. This paper examines the cost and efficiency tradeoffs for a complete single-main-amplifier KrF laser fusion experimental facility. It has been found that a 7% efficient $310/joule complete laser-fusion system is possible by using large amplifier modules and high optical fluences.
Date: January 1, 1985
Creator: Harris, D.B. & Pendergrass, J.H.
Partner: UNT Libraries Government Documents Department

KrF laser cost/performance model for ICF commercial applications

Description: Simple expressions suitable for use in commercial-applications plant parameter studies for the direct capital cost plus indirect field costs and for the efficiency as a function of repetition rate were developed for pure-optical-compression KrF laser fusion drivers. These simple expressions summarize estimates obtained from detailed cost-performance studies incorporating recent results of ongoing physics, design, and cost studies. Contributions of KrF laser capital charges and D and M costs to total levelized constant-dollar (1984) unit ICF power generation cost are estimated as a function of plant size and driver pulse energy using a published gain for short-wavelength lasers and representative values of plant parameters.
Date: January 1, 1985
Creator: Harris, D.B. & Pendergrass, J.H.
Partner: UNT Libraries Government Documents Department

The Laboratory Microfusion Facility standardized costing methodology

Description: The DOE-organized Laboratory Microfusion Facility (LMF) has a goal of generation 1000 MJ of fusion yield in order to perform weapons physics experiments, simulate weapons effects, and develop high-gain inertial confinement fusion (ICF) targets for military and civil applications. There are currently three options seriously being considered for the driver of this facility: KrF lasers, Nd:glass lasers, and light-ion accelerators. In order to provide a basis for comparison of the cost estimated for each of the different driver technologies, a standardized costing methodology has been devised. This methodology defines the driver-independent costs and indirect cost multipliers for the LMF to aid in the comparison of the LMF proposal cost estimates. 10 refs., 4 tabs.
Date: January 1, 1988
Creator: Harris, D.B. & Dudziak, D.J.
Partner: UNT Libraries Government Documents Department

Subspace Detectors: Efficient Implementation

Description: The optimum detector for a known signal in white Gaussian background noise is the matched filter, also known as a correlation detector [Van Trees, 1968]. Correlation detectors offer exquisite sensitivity (high probability of detection at a fixed false alarm rate), but require perfect knowledge of the signal. The sensitivity of correlation detectors is increased by the availability of multichannel data, something common in seismic applications due to the prevalence of three-component stations and arrays. When the signal is imperfectly known, an extension of the correlation detector, the subspace detector, may be able to capture much of the performance of a matched filter [Harris, 2006]. In order to apply a subspace detector, the signal to be detected must be known to lie in a signal subspace of dimension d {ge} 1, which is defined by a set of d linearly-independent basis waveforms. The basis is constructed to span the range of signals anticipated to be emitted by a source of interest. Correlation detectors operate by computing a running correlation coefficient between a template waveform (the signal to be detected) and the data from a window sliding continuously along a data stream. The template waveform and the continuous data stream may be multichannel, as would be true for a three-component seismic station or an array. In such cases, the appropriate correlation operation computes the individual correlations channel-for-channel and sums the result (Figure 1). Both the waveform matching that occurs when a target signal is present and the cross-channel stacking provide processing gain. For a three-component station processing gain occurs from matching the time-history of the signals and their polarization structure. The projection operation that is at the heart of the subspace detector can be expensive to compute if implemented in a straightforward manner, i.e. with direct-form convolutions. The purpose of this report ...
Date: July 26, 2006
Creator: Harris, D B & Paik, T
Partner: UNT Libraries Government Documents Department

Superresolution with Seismic Arrays using Empirical Matched Field Processing

Description: Scattering and refraction of seismic waves can be exploited with empirical matched field processing of array observations to distinguish sources separated by much less than the classical resolution limit. To describe this effect, we use the term 'superresolution', a term widely used in the optics and signal processing literature to denote systems that break the diffraction limit. We illustrate superresolution with Pn signals recorded by the ARCES array in northern Norway, using them to identify the origins with 98.2% accuracy of 549 explosions conducted by closely-spaced mines in northwest Russia. The mines are observed at 340-410 kilometers range and are separated by as little as 3 kilometers. When viewed from ARCES many are separated by just tenths of a degree in azimuth. This classification performance results from an adaptation to transient seismic signals of techniques developed in underwater acoustics for localization of continuous sound sources. Matched field processing is a potential competitor to frequency-wavenumber and waveform correlation methods currently used for event detection, classification and location. It operates by capturing the spatial structure of wavefields incident from a particular source in a series of narrow frequency bands. In the rich seismic scattering environment, closely-spaced sources far from the observing array nonetheless produce distinct wavefield amplitude and phase patterns across the small array aperture. With observations of repeating events, these patterns can be calibrated over a wide band of frequencies (e.g. 2.5-12.5 Hertz) for use in a power estimation technique similar to frequency-wavenumber analysis. The calibrations enable coherent processing at high frequencies at which wavefields normally are considered incoherent under a plane wave model.
Date: March 24, 2010
Creator: Harris, D B & Kvaerna, T
Partner: UNT Libraries Government Documents Department

Inertial fusion in the nineties

Description: The 1980s has proven to be an exicting time for the inertial confinement fusion (ICF) program. Major new laser and light-ion drivers have been constructed and have produced some encouraging results. The 1990s will be a crucial time for the ICF program. A decision for proceeding with the next facility is scheduled for the early 1990s. If the decision is positive, planning and construction of this facility will occur. Depending on the time required for design and construction, this next-generation facility could become operational near the turn of the century. 21 refs., 4 figs.
Date: January 1, 1987
Creator: Harris, D.B.; Dudziak, D.J. & Cartwright, D.C.
Partner: UNT Libraries Government Documents Department

Final Scientific Report, Integrated Seismic Event Detection and Location by Advanced Array Processing

Description: In the field of nuclear explosion monitoring, it has become a priority to detect, locate, and identify seismic events down to increasingly small magnitudes. The consideration of smaller seismic events has implications for a reliable monitoring regime. Firstly, the number of events to be considered increases greatly; an exponential increase in naturally occurring seismicity is compounded by large numbers of seismic signals generated by human activity. Secondly, the signals from smaller events become more difficult to detect above the background noise and estimates of parameters required for locating the events may be subject to greater errors. Thirdly, events are likely to be observed by a far smaller number of seismic stations, and the reliability of event detection and location using a very limited set of observations needs to be quantified. For many key seismic stations, detection lists may be dominated by signals from routine industrial explosions which should be ascribed, automatically and with a high level of confidence, to known sources. This means that expensive analyst time is not spent locating routine events from repeating seismic sources and that events from unknown sources, which could be of concern in an explosion monitoring context, are more easily identified and can be examined with due care. We have obtained extensive lists of confirmed seismic events from mining and other artificial sources which have provided an excellent opportunity to assess the quality of existing fully-automatic event bulletins and to guide the development of new techniques for online seismic processing. Comparing the times and locations of confirmed events from sources in Fennoscandia and NW Russia with the corresponding time and location estimates reported in existing automatic bulletins has revealed substantial mislocation errors which preclude a confident association of detected signals with known industrial sources. The causes of the errors are well understood and are ...
Date: January 30, 2007
Creator: Kvaerna, T.; S.J., Gibbons.; Ringdal, F & Harris, D.B.
Partner: UNT Libraries Government Documents Department

Integrated Seismic Event Detection and Location by Advanced Array Processing

Description: The principal objective of this two-year study is to develop and test a new advanced, automatic approach to seismic detection/location using array processing. We address a strategy to obtain significantly improved precision in the location of low-magnitude events compared with current fully-automatic approaches, combined with a low false alarm rate. We have developed and evaluated a prototype automatic system which uses as a basis regional array processing with fixed, carefully calibrated, site-specific parameters in conjuction with improved automatic phase onset time estimation. We have in parallel developed tools for Matched Field Processing for optimized detection and source-region identification of seismic signals. This narrow-band procedure aims to mitigate some of the causes of difficulty encountered using the standard array processing system, specifically complicated source-time histories of seismic events and shortcomings in the plane-wave approximation for seismic phase arrivals at regional arrays.
Date: February 9, 2007
Creator: Kvaerna, T; Gibbons, S J; Ringdal, F & Harris, D B
Partner: UNT Libraries Government Documents Department

Mapping Diffuse Seismicity Using Empirical Matched Field Processing Techniques

Description: The objective of this project is to detect and locate more microearthquakes using the empirical matched field processing (MFP) method than can be detected using only conventional earthquake detection techniques. We propose that empirical MFP can complement existing catalogs and techniques. We test our method on continuous seismic data collected at the Salton Sea Geothermal Field during November 2009 and January 2010. In the Southern California Earthquake Data Center (SCEDC) earthquake catalog, 619 events were identified in our study area during this time frame and our MFP technique identified 1094 events. Therefore, we believe that the empirical MFP method combined with conventional methods significantly improves the network detection ability in an efficient matter.
Date: January 21, 2011
Creator: Wang, J; Templeton, D C & Harris, D B
Partner: UNT Libraries Government Documents Department

Seismic discrimination between earthquakes and explosions in the Middle East and North Africa

Description: The recently signed Comprehensive Test Ban Treaty provides for an international network of primary and auxiliary seismic monitoring stations (IMS) to verify its compliance. Calibration is required to confidently use these stations to identify and discriminate between earthquakes, mine-related events and clandestine nuclear explosions, particularly for small to moderate seismic events recorded regionally at only a few stations. Given the lack of regional recordings of underground nuclear tests in most of the world, we are making use of mining and industrial explosions to test discriminants. For example we use the Multimax compiled dataset of small earthquakes and quarry explosions in Israel to test regional discriminants at local distances with mixed results. Further complicating calibration is the fact that many INK sites have not yet been installed and others have very short operating histories. When IMS data is available, there is often a lack of independent information (ground truth ) on the seismic sources. Here we describe a procedure for calibrating stations with limited data and apply it to the IMS auxiliary station MDT in Morocco. Data was initially available for three months in 1990 when MDT was operated as part of MEDNET. An event detector was run over the continuous data and regional events identified and roughly located using S-P time and back azimuth. The procedure uses spatial and temporal clustering to identify ''known'' mine blasts. The spatial clustering is done using the waveform correlation technique of Harris (1991) to find events with similar sources and locations. Temporal clustering looks at the time of day and repetition in time of events with the mine blasts occurring during working hours and days repeatedly over a period of time. A set of ''known'' earthquakes is also determined using location, time of day, distribution in time and size criteria. With these independent libraries ...
Date: July 1, 1997
Creator: Walter, W.R.; Harris, D.B. & Myers, S.C.
Partner: UNT Libraries Government Documents Department

Development of KrF lasers for inertial confinement fusion

Description: Recent reviews of the Inertial Confinement Fusion (ICF) program have resulted in recommendations that promise to focus the research effort on the examination of the feasibility of pellet ignition at 1 MJ of energy on target. If successful, the next major step in the program has been defined to be the construction of an Ignition Facility. Los Alamos National Laboratory has developed a plan to reach single-pulse multimegajoule ICF facilities using the electron-beam-pumped KrF laser. The Los Alamos plan, its relation to the development of ICF for energy production, and the major features and design issues associated with ICF drivers will be covered in this presentation. 3 figs., 1 tab.
Date: January 1, 1990
Creator: Sullivan, J.A. & Harris, D.B.
Partner: UNT Libraries Government Documents Department

Characterizing source regions with signal subspace methods: Theory and computational methods

Description: A mathematical approach is developed for empirically characterizing a given source region using waveforms from a collection of calibration events. A region is considered to be adequately characterized if the waveforms from any event in the source region can be represented as a linear combination of calibration event waveforms. The purpose of such characterizations is to build waveform recognizers'' for specific regions for precision location applications, and to provide a means of separating superimposed waveforms from multiple events in different source regions. The particular form of characterization used is insensitive to variations in the source time function and to anything but changes from the normal range of source mechanisms encountered in the source region. The standard waveform correlation coefficient used to estimate event clustering is generalized to estimate separation between single events and event clusters, and between two clusters of events. The generalized correlation coefficient is insensitive to variations in source time function and, to some extent, mechanism. The statistics of waveform correlation coefficients are developed, and show that conventional estimates made from single station data are often developed for network or array data removes the ambiguity. 23 refs., 4 figs.
Date: December 1, 1989
Creator: Harris, D.B.
Partner: UNT Libraries Government Documents Department

Mapping acoustic emissions from hydraulic fracture treatments using coherent array processing: Concept

Description: Hydraulic fracturing is a widely-used well completion technique for enhancing the recovery of gas and oil in low-permeability formations. Hydraulic fracturing consists of pumping fluids into a well under high pressure (1000--5000 psi) to wedge-open and extend a fracture into the producing formation. The fracture acts as a conduit for gas and oil to flow back to the well, significantly increasing communication with larger volumes of the producing formation. A considerable amount of research has been conducted on the use of acoustic (microseismic) emission to delineate fracture growth. The use of transient signals to map the location of discrete sites of emission along fractures has been the focus of most research on methods for delineating fractures. These methods depend upon timing the arrival of compressional (P) or shear (S) waves from discrete fracturing events at one or more clamped geophones in the treatment well or in adjacent monitoring wells. Using a propagation model, the arrival times are used to estimate the distance from each sensor to the fracturing event. Coherent processing methods appear to have sufficient resolution in the 75 to 200 Hz band to delineate the extent of fractures induced by hydraulic fracturing. The medium velocity structure must be known with a 10% accuracy or better and no major discontinuities should be undetected. For best results, the receiving array must be positioned directly opposite the perforations (same depths) at a horizontal range of 200 to 400 feet from the region to be imaged. Sources of acoustic emission may be detectable down to a single-sensor SNR of 0.25 or somewhat less. These conclusions are limited by the assumptions of this study: good coupling to the formation, acoustic propagation, and accurate knowledge of the velocity structure.
Date: September 1, 1991
Creator: Harris, D.B.; Sherwood, R.J.; Jarpe, S.P. & Harben, P.E.
Partner: UNT Libraries Government Documents Department