Back-streaming ion beam measurements in a self magnetic pinch (SMP) electron diode

Summary form only given. A self-magnetic pinch diode (SMP) is presently the electron diode of choice for high energy flash x-ray radiography utilizing pulsed power drivers. The Sandia National Laboratories RITS accelerator presently drives an SMP diode that generates small electron beam spots. RITS is a Self-Magnetically Insulated Transmission Line (MITL) voltage adder that adds the voltage pulse of six 1.3 MV inductively insulated cavities. The diode´s anode is made of high Z metal in order to produce copious and energetic flash x-rays for radiographic imaging of high areal density objects. In any high voltage inductive voltage adder (IVA) utilizing MITLs to transmit the power to the diode load, the precise knowledge of the accelerating voltage applied on the anodecathode (A-K) gap is problematic. This is even more difficult in an SMP diode where the A-K gap is very small (~1cm) and the diode region very hostile. The accelerating voltage quoted in the literature is from estimates based on measurements of the anode and cathode currents of the MITL far upstream from the diode and utilizing the para-potential flow theories and inductive corrections. We are currently measuring the back-streaming ion currents emitted from the anode and propagating through a hollow cathode tip and evaluating the A-K gap voltage by energy filtering techniques. Experimental results compared with LSP simulations will be presented.