radius segments correspond to MITL sections without axial electric field. This design assures constant current flow over the entire length of SABRE. The cathode electrode is 9.6-m long and includes the voltage adder (6-m long) and a constant radius (2.2 cm) extension 3.2 m in length. We present the design, analysis, and first results of the high brightness electron beam experiments currently under investigation at Sandia National Laboratories. The anticipated beam parameters are the following: energy 12 MeV, current 35-40 kA, rms radius 0.5 mm, and pulse duration 40 ns FWHM. The accelerator is SABRE [I], a pulsed LNA modified to RADLAC 11. To generate beams of millimeter sizes, the diode must be immersed in solenoidal fields of 20-30 Tesla [5,6,7]. Figure 2 shows a schematic diagram of the diode design, including the solenoidal magnet. The shape of the fringe field is tailored by a 2-cm thick a l e n u m cylinder 25-cm iflner radius coaxially enclosing the entire diode assembly.

Four monitoring techniques that can determine peak voltage (Vp) to a precision of ∼5% for high-intensity, pulsed electron accelerators operating in the 10 to 20 MV range are discussed and applied to the 14-TW HERMES III accelerator. The techniques utilize parapotential flow theory, the range of H− ions, the bremsstrahlung from electron interactions with an electron target, and the photoneutron fluence from neutrons generated in a bremsstrahlung target. Application of these techniques to HERMES III shows that when the accelerator is operating under nominal conditions, Vp=(18.7±0.7) MV.

International audienceWe investigate the operation of a load current multiplier (LCM) on a pulse-forming-line nanosecond pulse-power generator. Potential benefits of using the LCM technique on such generators are studied analytically for a simplified case. A concrete LCM design on the Zebra accelerator (1.9 Ohm, ∼1  MA, 100 ns) is described. This design is demonstrated experimentally with high-voltage power pulses having a rise time of dozens of nanoseconds. Higher currents and magnetic energies were observed in constant-inductance solid-state loads when a better generator-to-load energy coupling was achieved. The load current on Zebra was increased from the nominal 0.8–0.9 MA up to about 1.6 MA. This result was obtained without modifying the generator energetics or architecture and it is in good agreement with the presented numerical simulations. Validation of the LCM technique at a nanosecond time scale is of importance for the high-energy-density physics research

We have developed a high-speed, electro -optic camera that features a large format; eight frames; and an accompanying eight -pulse, ruby laser illuminator.This system offers greater resolution and versatility than has been previously available. The eight 75 -mm frames provide high dynamic spatial resolution (15 line pairs /mm) and time resolution (as short as 10 -ns exposure time) to record fine physical details of rapid events.Four independent two -frame (tube) cameras complete with objective optics comprise the eight -frame array. Finally, pulsed ruby laser illumination with spectral filtering allows photography in intense ambient light.

Electro-optical measurements of the electric field along solid insulator/vacuum interfaces have been made to determine the mechanisms associated with fast (ns) insulator flashover. Data showing the temporal and spatial performance of the insulator surface fields prior to and at flashover are presented. The results show that the intergap electric field is modified in a manner consistent with positive surface charging by field emitted electrons. The data also show that the enhanced intergap fields are reduced prior to flashover. Mechanisms consistent with this behavior are postulated.