Development of a 4-MV, 80-kA-Induction Voltage Adder for Flash X-ray Radiography

Abstract

An induction voltage adder (IVA) has been developed to drive rod-pinch diodes (RPDs), to produce X-rays for flash radiography. The IVA facility consists of four-stage induction cavities stacked in series, each of which is single-point driven by a 6- $\Omega $ pulseline. The prime pulsed-power source comprises two Marx generators and four de-ionized water pulselines. Each Marx generator fast charges two pulselines to about 2.2 MV in less than 370 ns. Four electrically triggered, SF6-insulated gas switches serve as energy-transfer switches from pulse-forming lines to output transmission lines, and thus without an additional intermediate energy storage. A stepped inner stalk is utilized to make the vacuum impedance of the secondary transmission line increase from $30~\Omega $ at the first cavity to $120~\Omega $ at the last cavity, to prevent the electron emission from cathode surfaces. The RPD is chosen to create bremsstrahlung X-rays, which are believed to be optimal at voltage levels of about 4 MV. In this article, the design details and experimental results concerning the main components, such as the Marx/PFLs, IVA, and RPD, are demonstrated. The electrical performances of the facility are characterized. Presently, the IVA provides voltages of up to 4.3 MV and currents of up to 85 kA. The X-ray dose is up to 15.5 Rad [lithium fluoride (LiF)] at 1 m with a spot size of 1.4 mm and a FWHM time of 55 ns.