Two methods of using the X pinch as a source of X-ray radiation for the radiography of dense plasmas and other objects
are presented. These methods do not use pinholes, instead taking advantage of the small source size (<1 mm, and in some
cases <1 pm) and short X-ray emission duration (< 2 ns , and < 20 ps in some cases) of the X pinch radiation. Detailed
measurements of the emission characteristics of X pinches made using different wire materials and in different energy
ranges using a set of X-ray diagnostics with high temporal and spatial resolution are presented. Several applications of
the X pinch are discussed.
We present a system for diagnostic imaging of x-ray sources using a compound refractive lens. Such a system can be built at a low cost, yet image at resolutions of 2 μm or better. The essential components of the system are the source to be imaged, a compound refractive lens and imaging detector (either electronic or film). In addition, spatial and spectral filters can be added to improve resolution and a laser alignment system can be used to rapidly align the source, lens and camera.
The X pinch plasma emits subnanosecond bursts of x-rays in the 3 - 10 keV energy range from a very small source. As such, it has been used for high-resolution point-projection imaging of small, dense, rapidly changing plasmas, as well as submillimeter thick biological samples. The very small x-ray source size of the X pinch provides high spatial coherence of the x-rays, enabling the X pinch to be used for imaging low absorption, low contrast objects with excellent spatial resolution by incorporating wave-optics effects. The reverse procedure has been used to determine the X pinch x-ray source size: well-defined micro-fabricated slits were imaged by point-projection radiography, and the detailed patterns were compared with wave-optics calculations of the expected image patterns on film as a function of x-ray source size and energy band. In addition, an x-ray streak camera was used to study the X pinch source size as a function of time. Dynamic shadow images of a boron fiber with a tungsten core and glass fiber sheathed in plastic were compared with a time-integrated radiographic image. Source sizes as small as 1.2 μm (full width at half maximum, assuming a Gaussian spatial intensity profile for the source) have been inferred.
X pinch radiation produced by electron beams accelerated in the X pinch minidiode ranging in energy from 10 to 100 keV has been studied and used to image a variety of different objects. The experiments have been carried out using the XP pulser (470 kA, 100 ns) at Cornell University and the BIN pulser (280 kA, 120 ns) at the P.N. Lebedev Physical Institute. This electron-beam-generated x-ray source's geometric, temporal and spectral properties have been studied over different energy ranges between 10 and 100 keV. The imaging was carried out in a low magnification scheme, and spatial resolution of a few tens of μm was demonstrated.
The application of the X pinch x-ray source for phase-contrast x-ray radiography of low absorption materials is demonstrated. The X pinch is a source of radiation in the 1-10 keV x-ray band with extremely small size and short pulse duration. The small source size provides high spatial coherence of the imaging x-ray beam, enabling it to be used to image low absorption, low contrast objects with excellent spatial resolution. Images with spatial resolution better than 3 micrometers of exploded, insulated 25 micrometers W wire and biological objects are presented. The advantages of the X-pinch over other x-ray sources are discussed.
Several methods of using the X pinch as a source of x-ray radiation for the radiography of dense plasmas and other objects are presented. These methods do not use pinholes, instead taking advantage of the small source size and short x-ray emission duration of the X pinch radiation. Detailed measurements of the emission characteristics of X pinches made using different wire materials and in different energy ranges using a set of x-ray diagnostics with high temporal and spatial resolution are presented. Several applications of the X pinch are discussed.
The results are presented of investigations of extremely dense plasmas generated from exploding wires using a new method, monochromatic x-ray backlighting. In this method, shadow images of a bright, dense plasma can be obtained with high spatial resolution using monochromatic radiation from a separate plasma, permitting a major reduction in the required backlighting source power. The object plasma is imaged utilizing x-ray optical elements with spherically bent mica crystals. In particular, shadow images of exploding Al wire plasmas in the 1s2-1s3p line radiation of He-like Al XII were obtained. The images confirm the existence of a low density 'corona' around the wire at an early stage of the wire explosion process, with a dense core at the original wire position. Test experiments were also done with laser produced backlighter plasmas. Spatial resolution of 10 microns was demonstrated. The scheme described here is useful for backlighting extended high density plasmas, and could be a less costly alternative to using x-ray lasers for such purposes.
Crystallographic and dispersion characteristics of muscovite at different reflection orders (2 divided by 24) for (001) lattice planes were investigated theoretically. Measurements of integral reflectivity were done for (10 divided by 38) reflection orders by using Cu and Mo X- tube radiation. Experimental results were compared with calculations for perfect and mosaic crystals. The integrated reflectivity for spherically bent mica crystals with R equals 100 and 186 mm have been calculated for various reflection orders. The results of these calculations show that muscovite crystals can be used in high reflection orders for high-resolution spectroscopy only if the crystal perfection is high enough, which provides the narrow reflection curve widths. These theoretical considerations are supported by results obtained in various plasma spectroscopic experiments. Nearly perfect muscovite crystals have been shown by using Lang and section topographic techniques for both flat and spherically bent muscovite crystals respectively. The high-quality of such crystals was also demonstrated using the scheme of obtaining a `parallel' x-ray beam and x-ray microscope schemes. Possible applications of high-quality muscovite spherical crystals are discussed.
Creation of Bragg X-ray optics based on transmitted and reflection crystals, bent on cylindrical or spherical surfaces, is discussed. Application of such optics for obtaining one and two dimensional monochromatic images of different plasma sources in the wide spectral range 1 - 20 angstroms are described. Samples of spectra obtained with spectral resolution up to (lambda) /(Delta) (lambda) approximately 1000 and spatial resolution up to 18 micrometers are presented.
X-ray spectroscopy with high spectral (up to (Delta) (lambda) /(lambda) equals 10-4) and spatial resolution (up to microns) is discussed. Devices based on crystals, diffraction, and Bragg-Fresnel elements and their application in Z- and X-pinches and laser plasma experiments are observed.
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