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Summary form only given. We are investigating the development of the axial instability that occurs on each exploding wire in wire-array Z-pinches. The axial instability is a growing modulation of the size of the coronal plasma around individual wires of the array that results in non-uniform ablation of material from the cold wire core. It has long been known that the wavelength of this modulation...
Summary form only given. The experiments reported here were designed to test X-pinch wire-loading configurations using a simple plastic frame that might enable the X-pinch wires to be mounted in the right position under vacuum after a pulse. The first experiments with X-pinches in plastic frames were carried out on the XP generator. In these experiments several frame configurations and materials were...
Streaked visible-light spectroscopy measurements are presented for aluminum (Al) wire-array z-pinch experiments on the 1-MA, 100-ns rise-time COBRA pulsed-power generator. For these measurements, a half-meter Czerny- Turner spectrometer was used in conjunction with the COBRA visible-light streak camera system. This allowed us to record visible-light spectra emitted from Al coronal plasma as a continuous...
Wire-array z-pinch experiments were performed on the 1 MA, 100 ns rise-time COBRA facility at Cornell University. Experiments utilized wire-arrays containing 2 pair of 5 to 7.5 micron diameter tungsten wires spaced ~240 nm apart. X-pinch x-ray backlighters were used to image breakup of the wire cores. Axially correlated ablation regions between paired wires were observed. These correlated regions...
Summary form only given. Wire-array Z pinches have been studied on the 1.2 MA peak current, 100 ns rise time COBRA generator at Cornell University using a wide range of diagnostics. In addition to the X-ray and electrical diagnostics, two framing cameras with 5 ns temporal resolution, a three frame laser shadowgraphy system with 170 ps temporal resolution and optical and X-ray streak cameras have...
Experimental results are presented which characterize the implosion dynamics and subsequent radiation output of wire-array Z-pinches on the 1-MA, 100-ns rise-time COBRA pulsed-power generator. Diagnostics fielded include an optical streak camera, a time-gated XUV framing camera, a laser shadowgraph system, filtered time-integrated pinhole cameras, an X-ray focusing spectrometer with spatial resolution...
Two different sets of new experiments with wire arrays made from Mo or W (primary material) wires together with a few Al wires (tracer material) are analyzed. The first set of experiments involved nested wire arrays and was performed on the 1 MA COBRA generator at Cornell University. These nested wire arrays consisted of 16 Mo or W wires with equal number of wires in outer and inner arrays and with...
The COBRA pulsed-power generator, with a nominal peak current of 1.1 MA and a minimum zero-to-peak rise-time of 95 ns, is being used to study the early phases of wire-array Z-pinch development with a variety of diagnostics. Here we present the results of applying point-projection X-ray radiography using up to five X pinches in the return current circuit to make accurate, high-resolution measurements...
Summary form only given. X pinch backlighting is a useful imaging technique whereby two or more wires are crossed at a single point and driven with a high current (300-500 kA). At the crossing point, a micron-scale sub-nanosecond X-ray source is produced that acts as a point source and can be used for point-projection imaging. Three new modes of X pinch imaging on COBRA have been implemented. One...
Summary form only given. X-pinch radiography has been used routinely at Cornell for more than 10 years to produce high quality X-ray images with excellent spatial and temporal resolution. This imaging technique is presently being used on the COBRA accelerator at Cornell University to study the ablation stage of wire-array z-pinches. Two of four return-current posts in the wire-array load region are...
Summary form only given. Substantial broadening and clearly visible "red" and "blue" shifts of K-shell spectral lines as a function position along the axis of wire-array Z-pinches have been observed in the time-integrated X-ray spectra from 8-32 wire Al arrays in experiments on the MAGPIE (1 MA, 240 ns risetime) and COBRA (1 MA, 100 ns risetime) pulsed-power generators. To separate...
Summary form only given. Experimental results showing wire array z-pinch implosions on the 1-MA, 100-ns rise time COBRA pulsed power generator are presented. The principal diagnostic used for these studies was an optical streak camera system, while other supporting diagnostics include a time-gated framing camera, a laser backlighting system, time-integrated pinhole cameras with various filters, and...
The majority of the X-ray emission from wire array Z-pinches is concentrated in the soft (sub-keV) part of the spectrum. In addition, the soft X-ray pulse is accompanied by significantly harder emission (multi-keV) that is generated at almost the same time. Important questions for wire array Z-pinch physics are: what fraction of the radiated energy is connected with soft versus hard X-rays? What is...
Objective-The use of synthetic vitreous fibres has increased along with a decline in the utilisation of asbestos. There remains concern that these synthetic fibres pose a health risk to workers because of the generation of respirable fibres which can enter the lung and cause adverse health effects. An improved understanding of the mechanism of fibre pathogenicity should allow more rational short-term...
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