David J. Fields

Short wavelength x-ray laser research at the Lawrence Livermore National Laboratory*

Laboratory x‐ray lasers are currently being studied by researchers worldwide. This paper reviews some of the recent work carried out at Lawrence Livermore National Laboratory. Laser action has been demonstrated at wavelengths as short as 35.6 A while saturation of the small signal gain has been observed with longer wavelength schemes. Some of the most successful schemes to date have been collisionally pumped x‐ray lasers that use the thermal electron distribution within a laser‐produced plasma to excite electrons from closed shells in neon‐ and nickel‐like ions to metastable levels in the next shell. Attempts to quantify and improve the longitudinal and transverse coherence of collisionally pumped x‐ray lasers are motivated by the desire to produce sources for specific applications. Toward this goal there is a large effort underway to enhance the power output of the Ni‐like Ta x‐ray laser at 44.83 A as a source for x‐ray imaging of live cells. Improving the efficiency of x‐ray lasers in order to produce s...

Imaging Fourier transform spectrometer

The operating principles of an Imaging Fourier Transform Spectrometer (IFTS) are discussed. The advantages and disadvantages of such instruments with respect to alternative imaging spectrometers are discussed. The primary advantages of the IFTS are the capacity to acquire more than an order of magnitude more spectral channels than alternative systems with more than an order of magnitude greater etendue than for alternative systems. The primary disadvantage of IFTS, or FTS is general, is the sensitivity to temporal fluctuations, either random or periodic. Data from the IRIFTS (ir IFTS) prototype instrument, sensitive in the infrared, are presented having a spectral sensitivity of 0.01 absorbance units per pixel, a spectral resolution of 6 cm-1 over the range 0 to 7899 cm-1, and a spatial resolution of 2.5 mr.

Livermore Imaging Fourier Transform Infrared Spectrometer (LIFTIRS)

Lawrence Livermore National Laboratory is currently operating a hyperspectral imager, the Livermore Imaging Fourier Transform Infrared Spectrometer. This instrument is capable of operating throughout the infrared spectrum from 3 to 12.5 micrometers with controllable spectral resolution. In this presentation we report on its operating characteristics, current capabilities, data throughput, and calibration issues.

Hyperspectral imaging in the infrared using LIFTIRS

In this article, recent characterization measurements made with LIFTIRS, the Livermore imaging Fourier transform infrared spectrometer, are presented. A discussion is also presented of the relative merits of the various alternative designs for imaging spectrometers.

Detecting buried objects by fusing dual-band infrared images

The authors have conducted experiments to demonstrate the enhanced detectability of buried land mines using sensor fusion techniques. Multiple sensors, including visible imagery, infrared imagery, and ground penetrating radar (GPR), have been used to acquire data on a number of buried mines and mine surrogates. Because the visible wavelength and GPR data are currently incomplete, the paper focuses on the fusion of two-band infrared images. The authors use feature-level fusion and supervised learning with the probabilistic neural network (PNN) to evaluate detection performance. The novelty of the work lies in the application of advanced target recognition algorithms, the fusion of dual-band infrared images and evaluation of the techniques using two real data sets.<<ETX>>

Buried object remote detection technology for law enforcement

A precise airborne temperature-sensing technology to detect buried objects for use by law enforcement is developed. Demonstrations have imaged the sites of buried foundations, walls and trenches; mapped underground waterways and aquifers; and been used to locate underground military objects. The methodology is incorporated in a commercially available, high signal-to-noise, dual-band infrared scanner with real-time, 12-bit digital image processing software and display. The method creates color-coded images based on surface temperature variations of 0.2 degree(s)C. Unlike other less-sensitive methods, it maps true (corrected) temperatures by removing the (decoupled) surface emissivity mask equivalent to 1 degree(s)C or 2 degree(s)C; this mask hinders interpretation of apparent (blackbody) temperatures. Once removed, it is possible to identify surface temperature patterns from small diffusivity changes at buried object sites which heat and cool differently from their surroundings. Objects made of different materials and buried at different depths are identified by their unique spectral, spatial, thermal, temporal, emissivity and diffusivity signatures. The authors have successfully located the sites of buried (inert) simulated land mines 0.1 to 0.2 m deep; sod-covered rock pathways alongside dry ditches, deeper than 0.2 m; pavement covered burial trenches and cemetery structures as deep as 0.8 m; and aquifers more than 6 m and less than 60 m deep. The technology could be adapted for drug interdiction and pollution control. For the former, buried tunnels, underground structures built beneath typical surface structures, roof-tops disguised by jungle canopies, and covered containers used for contraband would be located. For the latter, buried waste containers, sludge migration pathways from faulty containers, and the juxtaposition of groundwater channels, if present, nearby, would be depicted. The precise airborne temperature-sensing technology has a promising potential to detect underground epicenters of smuggling and pollution.

Experiments to support the development of techniques for hyperspectral mine detection

Under the sponsorship of the DARPA Hyperspectral Mine Detection program, a series of both non-imaging and imaging experiments have been conducted to explore the physical basis of buried object detection in the visible through thermal infrared. Initially, non-imaging experiments were performed at several geographic locations. Potential spectral observables for detection of buried mines in the thermal portion of the infrared were found through these measurements. Following these measurements with point spectrometers, a series of hyperspectral imaging measurements was conducted during the summer of 1995 using the SMIFTS instrument from the University of Hawaii and the LIFTIRS instrument from Lawrence Livermore National Laboratory. The SMIFTS instrument (spatially modulated imaging Fourier transform spectrometer) acquires hyperspectral image cubes in the short-wave and mid-wave infrared and LIFTIRS (Livermore imaging Fourier transform infrared spectrometer) acquires hyperspectral image cubes in the long-wave infrared. Both instruments were optimized through calibration to maximize their signal to noise ratio and remove residual sensor pattern. The experiments were designed to both explore further the physics of disturbed soil detection in the infrared and acquire image data to support the development of detection algorithms. These experiments were supported by extensive ground truth, physical sampling and laboratory analysis. Promising detection observables have been found in the long-wave infrared portion of the spectrum. These spectral signatures have been seen in all geographical locations and are supported by geological theory. Data taken by the hyperspectral imaging sensors have been directly input to detection algorithms to demonstrate mine detection techniques. In this paper, both the non-imaging and imaging measurements made to date will be summarized.

Infrared hyperspectral imaging results from vapor plume experiments

In this article, recent measurements made with LIFTIRS, the Livermore Imaging Fourier Transform Infrared Spectrometer, are presented. The experience gained with this instrument has produced a variety of insights into the tradeoffs between signal to noise ratio (SNR), spectral resolution, and temporal resolution for time multiplexed Fourier transform imaging spectrometers. This experience has also clarified the practical advantages and disadvantages of Fourier transform hyperspectral imaging spectrometers regarding adaptation to varying measurement requirements on SNR versus spectral resolution, spatial resolution, and temporal resolution.

Data fusion for the detection of buried land mines

We have conducted experiments to demonstrate the enhanced detectability of buried land mines using sensor fusion techniques. Multiple sensors, including visible imagery, IR imagery, and ground penetrating radar, have been used to acquire data on a number of buried mines and mine surrogates. We present this data along with a discussion of our application of sensor fusion techniques for this particular detection problem. We describe our data fusion architecture and discuss the some relevant results of these classification methods.

Kestrel: force protection and Intelligence, Surveillance, and Reconnaissance (ISR) persistent surveillance on aerostats

Logos Technologies has developed and fielded the Kestrel system, an aerostat-based, wide area persistent surveillance system dedicated to force protection and ISR mission execution operating over forward operating bases. Its development included novel imaging and stabilization capability for day/night operations on military aerostat systems. The Kestrel systems contribution is a substantial enhancement to aerostat-based, force protection systems which to date have relied on narrow field of view ball gimbal sensors to identify targets of interest. This inefficient mechanism to conduct wide area field of view surveillance is greatly enhanced by Kestrels ability to maintain a constant motion imagery stare of the entire forward operating base (FOB) area. The Kestrel airborne sensor enables 360° coverage out to extended ranges which covers a city sized area at moderate resolution, while cueing a narrow field of view sensor to provide high resolution imagery of targets of interest. The ground station exploitation system enables operators to autonomously monitor multiple regions of interest in real time, and allows for backtracking through the recorded imagery, while continuing to monitor ongoing activity. Backtracking capability allows operators to detect threat networks, their CONOPS, and locations of interest. Kestrels unique advancement has already been utilized successfully in OEF operations.