X-pinch plasma emits subnanosecond bursts of x rays in the 3-10-keV energy range from a small source. As such, it has been used for high-resolution point-projection imaging of small, dense, rapidly changing plasmas as well as for submillimeter-thick biological samples. In addition to the effect of source size on geometric resolution, a small source size can also provide high spatial coherence of x rays, enabling the rays to be used for imaging weakly absorbing objects with excellent spatial resolution by a method called phase-contrast imaging. To determine the source size, we microfabricated gold slits and imaged them in a point-projection radiography configuration. The shape of the shadow image pattern depends on the source size and energy band of the x rays, the shape and material used for the slits, and the geometry of the experiment. Experimental results have been compared with wave-optics calculations of the expected image pattern as a function of all the parameters listed above. For example, assuming a Gaussiansource distribution, an effective source size in 2.5-4.1 A radiation (1 A = 0.1 nm) of 1.2 +/- 0.5 microm (full width at half-maximum) was determined for a 20-microm Mo wire X pinch. Characterization of the size and structure of the x-ray bursts from X pinches by the use of different wire materials and different slit structures is made.
The effect of grain sizes on the electromagnetic properties of Mn–Zn ferrites has been studied up to MHz range. The average grain sizes ranging between 2 and 5 μm were obtained by varying the sintering time from 2 to 12 h. The total power loss at 1 MHz, 25 mT, and 100 °C increased with grain size. The hysteresis loss decreased with increasing grain size, while the eddy current loss and the residual loss increased. The residual loss showed a drastic increase at the grain size around 4 μm, which confirms that the residual loss due to the domain wall resonance should be taken into account at a grain size greater than the monodomain dimension.
The X pinch is a dense plasma X-ray source that is known to emit subnanosecond bursts of X-rays in the 2.5-8 keV energy range from a very small ( 1 m) source commonly referred to as a micropinch. As such, it has been successfully used as a point source for X-ray radiographic imaging of small biological samples with spatial resolution as good as 1-2 m. Recent experiments show that the soft X-ray emission from a micropinch extends out to as high as 15 keV, and that there is also harder radiation from a slightly displaced 100 m source with photon energies reaching above 60 keV that appears to be due to the presence of several-nanosecond electron-beam pulse. Both of these harder X-ray sources are potentially useful X-ray sources for high-resolution radiography of thicker biological samples than we have previously imaged. A characterization of these two hard X-ray radiation sources from X pinch plasmas using a slit camera with different filters, as well as imaging of a variety of biological objects on each pulse, revealed the energy range and source size of the micropinch radiation separate from the larger electron-beam source. High-resolution images (1-10 m scale resolution) of samples, such as a boron fiber with tungsten core (2.5-12 keV) as well as a several-millimeter-thick chicken wing with bone ( 10 keV), will be presented.Index Terms-Biomedical application of X-rays, plasma pinch, X-rays, X-ray imaging, X-ray source.
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