W.J. DeHope

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Rod-pinch diodes utilize a small-diameter anode rod extending through and beyond the plane of a thin annular cathode. At low voltage (< 1 MV) and short pulse duration (< 20 ns), it is difficult for the space-charge-limited current (SCL) to exceed the critical current necessary for electron beam self-pinching using cathodes thinner than the anode-cathode gap(More)
A single-cell test stand has been constructed at LLNL for studies aimed at improving the performance of the FXR radiographic facility. It has guided the development of diagnostics, pulsed power improvements, machine maintenance, and interface issues relevant to the entire accelerator. Based on this work, numerous machine improvements have been made which(More)
Rod-pinch electron beam diodes were reintroduced at BEAMS'98 as small-diameter intense x-ray sources after a twenty-year hiatus. Much progress has been made recently in both analytical and particle-in-cell numerical modeling of the diode behavior and in obtaining intense x-ray sources for pulsed radiography. Rod-pinch diodes utilize a thin annular cathode(More)
Recent progress in the development and understanding of linear induction accelerator have produced machines with 10's of MeV of beam energy and multi-kiloampere currents. Near-term machines, such as DARHT-2, are envisioned with microsecond pulselengths. Fast beam kickers, based on cylindrical electromagnetic stripline structures, will permit effective use(More)
The now-mature FXR (flash X-ray) radiographic facility at Lawrence Livermore National Laboratory will be briefly described with emphasis on its pulsed power system. The heart of each accelerating cell's pulse-forming Blumlein is its sulfur hexafluoride-based triggered closing switch. FXR's recent upgrade to a recirculating SF<sub>6</sub> gas reclamation(More)
A rod-pinch diode, modified to operate in a non-pinching mode, is tested for multi-shot operation at 1 MV and 15 kA. Three different geometry diodes are used. A 3.2-mm or 4.7-mm diameter tungsten-rod anode, tapered on the end, is used to minimize anode damage and to maintain a small source size. The diode parameters are chosen to avoid beam pinching. The(More)
High-resolution radiography using high-current electron accelerators based on the linear induction accelerator principle requires the linac&#x2019; final spot on the X-ray target to be millimeter-sized. The requisite final focusing solenoid is adjusted for a specific beam energy at its entrance, hence, temporal variation of entrance beam energy results in a(More)
Summary form only given. At Lawrence Livermore National Laboratory (LLNL), our flash X-ray accelerator (FXR) is used on multi-million dollar hydrodynamic experiments. Because of the importance of the radiographs, FXR must be ultra-reliable. Flash linear accelerators that can generate a 3 kA beam at 18 MeV are very complex. They have thousands, if not(More)
Summary form only given. High-resolution radiography using high-current electron accelerators based on the induction linac principle requires the linac's final spot on the X-ray target to be millimeter-sized. The requisite final focusing solenoid must then be adjusted for a specific beam energy at its entrance. Temporal variation of entrance beam energy(More)
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