X Pinches in Frames

Summary form only given. The X-pinch plasma has established itself as an extraordinarily useful tool for studying the dynamics and kinetics of hot, dense plasmas as well as for high resolution imaging. An X-pinch plasma is formed when two or more fine wires, which cross at a point to form an "X," are used as the load of a pulse power machine. When this configuration is exploded to form a plasma, a Z-pinch forms near the original cross point of the wires. This process produces small, bright plasmas that emit nanosecond scale X-ray bursts in the 1-15 keV range. For our experiments the X pinches were driven with Cornell's XP pulser, which reaches a peak current of about 450 kA in 40-50 ns. The small (micron scale) X-ray sources produced are useful for point projection X-ray imaging. Thus, in order to maximize the usefulness of X pinches we must find ways to control the unstable process that produces the X-ray bright spots. Furthermore, in order to advance the study of X-pinch plasmas it would be helpful to find a way to increase the rate at which X-pinch pulses can be taken. Consequently, we have devised a setup to improve both of these situations. Initially, we designed an X-pinch "frame" to increase the repetition rate for X-pinch pulses since many frames can be loaded in advance, reducing the setup time for each experiment. In addition, we imagine using several frames chained together in order to change the load under vacuum. In testing we found that many of the frame materials used would conduct too much of the current as result of UV induced flashover. We found that of the materials tested, fiberglass was able to hold off the UV flashover the longest without a need for additional shielding. The fiberglass frames allowed enough load current to produce a high quality bright spot while the conduction due to UV flashover prevented subsequent bursts and minimized the production of energetic electrons. All of these conditions lead to increased image quality. We also found that the intensity of higher energy X-rays (above 8 keV) was significantly reduced. Therefore, these X pinches are most useful for soft X-ray imaging. Additionally, we tested various geometries, including several X pinches in series, which can give us information from multiple X pinches in a single shot