Experiments on a table-top X-pinch

X-pinch plasma is produced with a high and pulsed current flowing through two or more fine wires that cross and touch at a single point, forming an “X”-shaped structure. A subnanosecond pulsed x-ray point source is usually formed at the crossing point of the wires. X-pinches have been used as x-ray sources for backlighting of high density plasmas such as wire-array Z-pinch plasma and for phase-contrast imaging of soft biological objects that could not be imaged by the conventional x-ray radiography. For the purpose of the clinical or biological application of X-pinch as x-ray source, a table-top X-pinch device was constructed based on a compact (2m×1m×1.5m) pulsed current generator (~ 100 kA,60ns). The whole device was put on a platform under which there are four wheels and thus it can be easily moved by a single person. The current flowing through the X-pinch load was measured with a Rogowski coil and it was almost unchanged for X-pinches made using different wires (5μm, 8μm, 10μm and 13μm Wu wire, 13μm and 25μm Mo wire), which means that the contribution of the wires to the total impedance of the X-pinch load is very small. The characteristics of the x-ray emission from the X-pinch were investigated. The time-resolved x-ray emission was measured with photoconducting detectors (PCDs) and the pattern of the x-ray source was recorded with a pinhole camera. When the above mentioned wires were used as two-wire X-pinches, X-ray pulses from the X-pinches were always observed. As the mass of the two wires increases, the time delay of the x-ray emission relative to the beginning of the current increases. The X-ray pulse consists of single peak or two overlapping peaks of subnanosecond pulsewidth. Two X-ray pulses with a time interval on the order of 10 ns were often observed for an X-pinch of a relatively small mass when the current is high enough. The appearance of the second X-ray pulse is a- tributed to the second pinch of the plasma. The total energy of the x-ray emission, obtained by the integration of the x-ray pulse over time, changes significantly from shot to shot and is in the range of 0.1J ~ 1J for x-rays of hν >; 1.5 keV. The x-ray spectrum was obtained with PCDs covered with different filters and the major part of the x-rays is with hν <; 2.5 keV. The x-ray source is usually one point or two partly overlapping points, which is consistent with the measurement of x-ray pulse. The x-ray point source has a size ranging from 5 μm to 50 μm. The experimental results show that the table-top X-pinch is suitable to be used as x-ray source for phase-contrast imaging of soft biological objects.