Abstract :
Summary form only given, as follows. If someone started to talk about a - I-keV, multiply-ionized high-Z, near-solid-density plasma that lasts for 10 to 30 ps and is about 1 pm in size, it would be natural to assume that an ultra-high intensity, short-wavelength, 5 IO-ps laser was responsible for generating that plasma. In fact, such plasmas are routinely produced using the X-pinch exploding wire configuration on the 45044 peak current, 100-ns (full width at half maximum) XP pulsed power generator at Cornell University. An X-pinch plasma is produced by using two (or more) fine wires arranged so that they cross and touch at a single point, in the form of an X, as the load of a pulsed power generator. Very dense, intensely radiating plasmas, commonly called micropinches,consistently form within about 100 @m of the original cross point of the wires, where the currents in the individual wire plasmas merge. High-resolution diagnostics can, therefore, be concentrated on that portion of the wires, thereby enabling a determination of the dynamics of the plasma and its characteristics as an x-ray source with very high spatial and temporal resolution. For example, using an x-ray streak camera, we have determined that X-pinches made from several different wire materials (e.g., MO and W) produce intense, 3- to IO-keV radiation with pulse durations as short as 10 to 30 ps, and the x-ray spectra recorded by the streak camera indicate that plasma ensities can exceed 1O Z2/cm3a nd electron temperatures can reach well into the keV range. [1,2] From experiments in which slits and thin fibers were imaged, together with detailed wave-optics calculations, we have determined that the (time integrated) size of the 3 to 10-keV x-ray source can be as small as 1 pm for some wire materials (e.g., MO and Nb). [3] Imaging of one X pinch by another enables us to follow the dynamics of micropinch formation and disassembly with - 30-ps time resolution and - I-pm spatial resolution. The methods by- which these plasma properties have been determined, along with additional detail on the results, especially the source size measurements, will be discussed. Examples of the capability of an X pinch as an x-ray source for point-projection imaging will also be presented.
