A compact nanosecond pulse generator for x-ray radiographies.

A compact nanosecond pulse generator was developed, aiming at producing high-energy flash x rays with a long lifetime. The generator was designed on the basis of a 0.67-ns pulse forming line (PFL), which is charged to ∼700 kV by an air core Tesla transformer and switched by a fast spark gap. The Tesla transformer consists of a single turn primary coil surrounding a 44-turn secondary coil using no magnetic cores. 2D magnetostatic and electrostatic simulations were carried out, and the inductance and stray capacitance of the transformer were calculated. The transformer was powered by a 40-nF capacitor bank via a hydrogen thyratron. An effective coupling co-efficiency keff of 0.55 was achieved. The PFL voltage reached its second peak of 680 kV in 395 ns when the capacitor bank was switched at 25 kV. A nanosecond pulse with a peak voltage of 510 kV, a peak power of 2.6 GW, and a pulse width of 2.1 ns was generated on a 100-Ω ceramic resistor, which is going to be replaced by a vacuum x-ray tube. Since the pulse energy is small, the x-ray tube is expected to have a long lifetime. The generator is 285 mm in diameter, 800 mm in length, and 35 kg in weight, providing a compact means for high-energy x-ray radiographies both in scientific research and industrial applications.

300 kV/6 mA integrated Cockcroft-Walton high voltage power supply for a compact neutron generator.

A high voltage power supply system for a compact neutron generator is developed. A four-stage symmetrical Cockcroft-Walton voltage multiplier circuit is adopted to produce 300 kV direct current high voltage. A two-stage 360 kV isolation transformer system is used to drive the ion source power supply. The high voltage power supply and the isolation transformer system are integrated in an epoxy bucket with a size of ϕ360 × 700 containing No. 25 transformer oil. The maximum output voltage of the power supply can reach 300 kV. The variation in the high voltage power supply is less than 0.5% when the power supply works at 300 kV/6 mA with an input voltage variation of ±8%. Meanwhile, the isolation transformer system can withstand more than 360 kV, with its output power being about 2.5 kW. No overvoltage protection devices are used in the power supply, and the protection resistors are connected in series to two pairs of rectifiers at the highest and lowest potential terminals and to the output terminal of the voltage multiplier to prevent overcurrent.

A free-standing thin foil bolometer for measuring soft x-ray fluence.

A free-standing thin foil bolometer for measuring soft x-ray fluence in z-pinch experiments is developed. For the first time, we present the determination of its sensitivity by different methods. The results showed great consistency for the different methods, which confirms the validity of the sensitivity and provides confidence for its application in z-pinch experiments. It should be highlighted that the sensitivity of a free-standing foil bolometer could be calibrated directly using Joule heating without any corrections that will be necessary for a foil bolometer with substrate because of heat loss. The difference of the waveforms between the free-standing foil bolometer and that with substrate is obvious. It reveals that the heat loss to the substrate should be considered for the latter in despite of the short x-ray pulse when the peak value is used to deduce the total deposited energy. The quantitative influence is analyzed through a detailed simulation.