Absolute intensities of spectra in a dense-plasma-focus (DPF) source have been recorded and analyzed. This DPF source has been identified as one of the more promising sources for X-ray lithography. The source, developed by Science Research Laboratory, Inc., is currently undergoing testing and further development at BAE Systems, Inc. The DPF operates at 60 Hz and produces an average output pulse of ~5 J of X rays into 4π steradians in a continuous operation mode. In all runs, there was an initial number of pulses, typically between 30 to 40, during which the X-ray output increased and the DPF appeared to be undergoing a conditioning process, and after which a "steady-state" mode was achieved where the average X-ray power was relatively constant. Each spectral run was exposed to ~600 J of output, as
measured by the PIN. The X-ray spectral region between 0.8 and 3 keV was recorded on Kodak DEF film in a potassium acid phthalate (KAP) convex curved-crystal spectrograph. The source emits neon line radiation from Ne IX and Ne X ionization stages in the 900 to 1300 eV region, suitable for lithographic exposures of photoresist. Two helium-like neon lines contribute more than 50% of the total energy. From continuum shape, plasma temperatures were found to be approximately 170-200 eV. The absolute, integrated spectral outputs were verified to within 30% by comparison with measurements by a PIN detector and a radiachromic X-ray dosimeter.
Novel X-ray sources and applications may be achieved with a combination of gateable electron micro-sources and tailored electron targets. A simple, broad area X-ray source can be constructed in a biplanar geometry, one side consisting of a low atomic number, X-ray transmissive substrate with an array of emitters, and the other side a simple metallic target. The simple metallic target can be replaced with a composite target in which different areas of the surface are coated with different X-ray emitting metals. The resulting X-ray spectrum will be the composite of spectra of all the irradiated metals. The spectrum is selected with sets of separately gated field emitter arrays, each registered to a respective anode metal. Low voltage electronics control the gate array selections. With the further addition of electron focusing within the tube and an external X-ray detector, the device becomes capable of imaging the composition of the electron target. By augmenting the device with a sample handling capability, whereby the sample is put in the location of the target, this instrument then becomes capable of X-ray compositional analysis in a manner analogous to an electron microprobe or SEM with EDX attachments. Such instruments can be miniaturized and used for automated analysis systems. The potential for low power, automated analysis by small, unmanned, distributed systems could augment the capabilities already present with high power laboratory instrumentation. An important technical issue on which the practicality of these developments depends, is the robustness of gated field emitter sources. Recent progress in this area is described.
X-ray spectra of Cu plasmas at the focus of a four-beam, solid-state diode-pumped laser have been recorded. This laser-plasma X-ray source is being developed for JMAR's lithography systems aimed at high- performance semiconductor integrated circuits. The unique simultaneous overlay of the four sub-nanosecond laser beams at 300 Hertz produces a bright, point-plasma X-ray source. PIN diode measurements of the X-ray output indicate that the conversion efficiency (ratio of X-ray emission energy into 2π steradians to incident laser energy) was approximately 9 percent with average X-ray power yields of greater than 10 Watts. Spectra were recorded on calibrated Kodak DEF film in a curved-crystal spectrograph. A KAP crystal (2d = 26.6 Angstroms) was used to disperse the 900 eV to 3000 eV spectral energies onto the film. Preliminary examination of the films indicated the existence of Cu and Cu XX ionization states. Additional spectra as a function of laser input power were also recorded to investigate potential changes in X-ray yields. These
films are currently being analyzed. The analysis of the spectra provide absolute line and continuum intensities, and total X-ray output in the measured spectral range.
X-ray diffraction from dynamically compressed solids has been an area of active research for more than half a century. As early as 1950, Schall obtained submicrosecond, single-shot x-ray diffraction patterns of single crystals under dynamic deformation. Almost two decades later Q. Johnson and coworkers succeeded in obtaining diffraction patterns with an exposure time of tens of nanoseconds from an explosively shocked crystal, and were the first to demonstrate diffraction evidence for a shock induced phase transition. Over the past few years we have shown that even shorter exposure times can be achieved by using a laser-plasma as the source of x-rays, synchronous to a laser driven shock. In this paper we will review the progress made in this field, emphasising the potential applications fo time-resolved x-ray diffraction for addressing some of the fundamental problems of shock wave physics.
X-ray diffraction during transient events requires a high x-ray brightness source which is spatially collimated or spectrally concentrated, as well as synchronizable to the event. Perhaps the most demanding transient event to study is the shockwave, because the event moves at high speed and the sample possesses a high density of mechanical energy which can be hazardous to the measuring apparatus. The properties of diffraction--narrow angular acceptance, spectral requirements, shallow penetration depths, line-of-sight integration--are both enabling and limiting. This paper will discuss the factors involved in transient x-ray diffraction experiments of shocks, to include a summary of past work, and an orientation to the use of laser plasmas for both x-ray pulse production and shock generation. We have diffractively probed laser shocks in the launching of elastic compression waves and their reflection from a free surface, and have probed orthogonal lattice planes simultaneously to reveal directional differences in compression. Diffraction imaging (topography) with approximately 50 micrometers resolution has revealed microstructural effects. A focusing powder spectrum has been acquired in a static experiment. We have used x-ray streak cameras to record diffraction patterns with 50 ps resolution.
X-ray fluorescence (XRF) is a well-established, non-destructive method of determining elemental concentrations at ppm levels in complex samples. It can operate in atmosphere with no sample preparation, and provides accuracies of 1% or better under optimum conditions. This report addresses two sets of issues concerning the use of x-ray fluorescence as a sensor technology for the cone penetrometer, for shipboard waste disposal, or for other in-situ, real- time environmental applications. The first issue concerns the applicability of XRF to these applications, and includes investigation of detection limits and matrix effects. We have evaluated the detection limits and quantitative accuracy of a sensor mock-up for metals in soils under conditions expected in the field. In addition, several novel ways of improving the lower limits of detection to reach the drinking water regulatory limits have been explored. The second issue is the engineering involved with constructing a spectrometer within the 1.75 inch diameter of the penetrometer pipe, which is the most rigorous physical constraint. Only small improvements over current state-of-the-art are required. Additional advantages of XRF are that no radioactive sources or hazardous materials are used in the sensor design, and no reagents or any possible sources of ignition are involved.