Plasma dynamics in the self-magnetic-pinch diode
The self-magnetic-pinch (SMP) diode1,2 is being developed as a source for flash x-ray radiography. The high electric field stresses applied to this diode and material heating from the intense electron beam generate electrode plasmas. While these plasmas are instrumental in beam formation and focusing, rapid plasma expansion from the electrodes can degrade radiographic performance.
Overview of Self-Magnetically Pinched-Diode Investigations on RITS-6
The electron-beam-driven self-magnetically pinched diode is a candidate for future flash X-ray radiographic sources. As presently fielded on Sandia Laboratories' six-cavity Radiographic Integrated Test Stand (RITS-6), the diode is capable of producing sub 3-mm radiation spot sizes and greater than 350 rads of hard X-rays at 1 m. The diode operates between 6 and 7 MV with a slowly decreasing impedance that falls from approximately 65 to 40 Ω during the main pulse. Sensitivity in diode operation is affected by the interaction of evolving plasmas from the cathode and anode, which seem to limit stable diode operation to a narrow parameter regime. To better quantify the diode physics, high-resolution time-resolved diagnostics have been utilized which include plasma spectroscopy, fast-gated imaging, X-ray p-i-n diodes, X-ray spot size, and diode and accelerator current measurements. Data from these diagnostics are also used to benchmark particle-in-cell simulations. An overview of results from experiments and simulations is presented.
Anomalous Annealing Behavior of Arsenic Implanted Silicon as a Function of Dose and Energy
Anomalous annealing behavior of damage in As implanted Si has been investigated by channeling effect measurements. Room temperature As implants with doses from 1014 to 2 × 1016cm-2 at energies ranging from 50 to 250 keV into Si were annealed over the range of 600°C to 1100°C. Anneal temperatures ≥ 950°C reduce the disorder for ion doses of 0.5 to 1 × 1016 cm-2 at energies between 50 and 250 keV. Anomalously high residual disorder was found for the intermediate doses of 2 × 1014 to 2 × 10/cm2 implanted above 100 keV. For this intermediate dose, annealing of implants performed at liquid nitrogen temperatures did not show significant reduction in this damage. However implants at 200° to 300°C indicate a lower amount of damage compared to the room temperature implants.