New developments in pulsed power technology and associated electron beam transport mechanisms at the United Kingdom Atomic Weapons Establishment

The Pulsed Power Group at AWE is interested in the generation of small, intense, multi-megavolt X-ray sources for radiographic applications. One of them, E Minor, is used for research into electron beam transport and focusing studies. E Minor consists of three main sections: (1) a Marx generator incorporating 84 0.7 /spl mu/F capacitors that are slowly charged in parallel to 50 kV and then quickly switched and discharged through a series configuration via triggered spark gaps producing an output voltage of 4.2 MV; (2) this output voltage in turn pulse charges a Blumlein pulse forming line (PFL). The Blumlein PFL consists of three coaxial cylinders, 3.2 m, 2.0 m and 1.0 m in diameter. The output of the PFL is a 40 ns long 5.3 MV electrical pulse driving 38 kA into a typical electron beam load; and (3) the X-ray tube has sixteen, 92 mm thick, Lucite sections angled at 45 degrees to the electric field which, with the spacer rings, is 1.55 m long and 1.2 m in diameter. The vacuum housing acts as the outer cylinder of a magnetically insulated coaxial transmission line (MITL). The central conductor of this MITL supports the cathode stalk, and forms a line having an impedance of 190 ohms.