In order to use two paralleled X-pinches as X-ray sources for the time-resolved backlighting of wire-array Z-pinch plasma, it is necessary to make these two X-pinches emit X-rays at different but roughly preset time instants. The timing of the X-ray burst from an X-pinch independence of the current, and the wire mass of the X-pinch was investigated. The currents flowing through two paralleled X-pinches were measured and it was found that the total current is almost equally divided between these two X-pinches no matter how different the wires for these two X-pinches are. The reason for the equal current division between two paralleled X-pinches was given based on the inductance calculation of the X-pinch circuit.

Experiments of the return current post installed X-pinches were carried out on the 1-MA “QiangGuang-1” facility with the purpose of understanding X-pinch characteristics under this setup and establishing X-pinch backlighting diagnostics for the wire-array Z-pinches. Different wire-array loads along with the two-wire 30 µm Mo X-pinch backlighter were tested. The X-pinches emit the X-ray radiation with the burst time variation of ± 4 ns and the bright spot size of  ~30 µm. X-ray backlighting shadowgraphy images of the over-mass and radiation-suppressed Z-pinch wire array were obtained.

The temporal and spatial X-ray emission from PPG-X, an X-pinch driven by pulsed power generator, was studied by using diamond photo-conducting detectors and pinhole cameras. It was found that the X-ray pulse usually consists of two sub-nanosecond peaks with a time interval of about 0.5 ns, these two X-ray peaks are consistent with two point sources of X-ray recorded with pinhole camera. The total X-ray energy changes from shot to shot and is averaged to be 0.35 J for hν > 1.5 keV. The size of the X-ray point source is in the range from 100 µm to 5 µm, decreasing rapidly with the increase of the photon energy. The X-pinch was used as X-ray source for backlighting the electrical explosion of single wire and for phase-contrast imaging of a mosquito.

The test on an X-pinch device powered by a pulsed power generator (PPG-I) was carried out step by step. In the first step, a brass rod of 6 mm in diameter was used as a load to replace the X-pinch load. The results of the first step shows that all the current, about 200 kA in amplitude, output from PPG-I flows through the load and no breakdown or flashover in vacuum of the load section happens. The waveform of the current from PPG-I measured with a wall resistor coincides exactly with that of the load current measured with a Rogowski coil, which indicates that the calibrations of the wall resistor and Rogowski coil are correct. In the second step, an X-pinch load made of two molybdenum wires of 40 µm in diameter was used. It was found that the distance between the cathode and anode affects considerably the operation of the device. While breakdown in vacuum happens for the distance equal to 30 mm, it works very well for the distance equal to 16 mm. The reason for this phenomenon was given.

A ∼500 kV/400 kA/100 ns pulsed power generator (PPG-I) for x-pinch experiments was designed and constructed at Tsinghua University. It is composed of a Marx generator, a combined pulse forming line (PFL), a gas-filled V/N field distortion switch, a transfer line, and a copper-sulphate resistive load for testing. The PPG-I implements a novel design in lines that four pieces of waterline with impedance 5Ω in parallel constitute a combined PFL with 1.25Ω, and incorporate each other by a common self-break V/N switch on a matched 1.25Ω transfer line. At the peak charging voltage of the PFL, the V/N switch breaks down in multi-channel discharge mode, and electric energy is fed into the testing load through the 1.25Ω transfer line. This article presents the design and test of the PPG-I generator.