Immersed Bz diode studies for flash x-ray radiography at CEA

To answer future needs the CEA is working on new design of flash X-ray radiographic machines. As complements to the operational AIRIX induction linac, these accelerators should deliver several tens of rads in the range of 8-10 Me V during 50 ns. Recent developments of electron diodes have shown the potentiality of a pulsed power driven source to produce the required parameters. The CEA/PEM is studying different kind of diode geometries. The two first years of those efforts where dedicated to rod-pinch studies and immersed Bz diode in the 1-6 MV range. To complete this overview of the existing concepts, negative rod-pinch experiments are in progress this year 2004. The approach followed for those studies starts with global PIC code simulations (LSP) with precise connection between the generator used and the diode volume. This part insures the overall functioning and evaluates the "initial impedance". The effects of the main parameters are controlled during the experiment. After the experiment, more detailed LSP runs try to reproduce some specific behaviour. We present in this paper our first experimental tests of the immersed Bz diode geometry on the ASTERIX generator. This work was been made in collaboration with the DGA (CEO) and the A WE (UK) groups.