A5043398793- Pulsed Power Technology Applications
- Gyrotron and Vacuum Electronics Research
- Electrostatic Discharge in Electronics
- Particle accelerators and beam dynamics
- Plasma Diagnostics and Applications
- Laser-Plasma Interactions and Diagnostics
- Particle Accelerators and Free-Electron Lasers
- Integrated Circuits and Semiconductor Failure Analysis
- Magnetic confinement fusion research
- Nuclear Physics and Applications
- Particle Detector Development and Performance
- Metal and Thin Film Mechanics
- Crystallography and Radiation Phenomena
- Electron and X-Ray Spectroscopy Techniques
- Atomic and Molecular Physics
- Radiation Effects in Electronics
- X-ray Spectroscopy and Fluorescence Analysis
- Superconducting Materials and Applications
- Laser Design and Applications
- Laser-induced spectroscopy and plasma
- Vacuum and Plasma Arcs
- Electromagnetic Compatibility and Measurements
- Salivary Gland Disorders and Functions
- Silicon Carbide Semiconductor Technologies
- Advanced Surface Polishing Techniques
University of New Mexico
2015-2025
Michigan State University
2018
University of Colorado Boulder
2018
Naval Surface Warfare Center
2010-2013
George Mason University
2010
Sandia National Laboratories
2004-2009
n&k Technology (United States)
2007-2009
Sandia National Laboratories California
2004-2008
Atomic Weapons Establishment
2004-2008
National Technical Information Service
2006-2008
The goals of valuing social equity and using it as a guide in managing public programs are firmly rooted the Minnowbrook tradition. Although civil rights activists have long fought for equality, attendees at I conference 1968 were among first field administration to directly confront societal inequities by asserting that administrators should, addition efficiency effectiveness, stress value management distribution services. field's emphasis on continued through II was identified key concern...
The objectives of this tutorial are as follows: 1) to help students and researchers develop a basic understanding how pulsed-power systems used create high-energy-density (HED) matter; 2) new, compact, efficient technology called linear transformer drivers (LTDs); 3) understand why LTDs an attractive for driving HED physics (HEDP) experiments; 4) contrast with the more traditional Marx-generator/pulse-forming-line approach HEDP 5) briefly review history LTD well some LTD-driven research...
The design of a 6.5-MV linear transformer driver (LTD) for flash-radiography experiments is presented. based on previously tested 1-MV LTD and predicted to be capable producing diode voltages 6.5 MV 50-Omega radiographic-diode load. Several fault modes are identified, circuit simulations used determine their effect the output pulse other components. For all identified modes, peak load voltage reduced by less than 5%
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 capable of producing sub 3-mm radiation spot sizes and greater than 350 rads hard X-rays at 1 m. operates between 6 7 MV with slowly decreasing impedance that falls from approximately 65 to 40 Ω during main pulse. Sensitivity in operation affected by interaction evolving...
Outgassing remains an important issue in the context of high-power microwave system operation as it can lead to several undesirable outcomes. Hence, suppression or containment this phenomena becomes a germane issue. Here, possible solution strategy based on quasi- isentropic compression (QIC) is probed with quantitative predictions molecular dynamics (MD) simulations. Using copper hydrogen gaseous impurity example anode for MD analyses, our results show that strong and short pressure ramp...
Pulsed-power driven x-ray radiographic systems are being developed to operate at higher power in an effort increase source brightness and penetration power. Essential the design of these is a thorough understanding electron flow transmission line that couples pulsed-power driver load. In this paper, analytic theory fully relativistic particle-in-cell simulations used model several experimental transmission-line geometries fielded on Sandia National Laboratories' upgraded Radiographic...
Field electron emission cathodes were constructed from knitted fabrics comprised entirely of carbon nanotube (CNT) fibers. The consisted a top layer array ∼2 mm high looped structures and bottom that was 1 thick with flat underlying surface. (FE) experiments performed on 25.4 diameter CNT fabric in both direct current (DC) pulsed voltage (PV) modes, the results compared to those obtained film cathode. DC measurements at maximum 1.5 kV. cathode emitted 20 mA, which an 8× increase over...
The six-cell RITS-6 accelerator is an upgrade of the existing RITS-3 and next in sequence Sandia IVA accelerators built to investigate/validate critical radiographic diode issues for scaling Radiographic Integrated Test Stand (RITS) (nominally 16 MV, 156 kA, 70 ns). In number cells/cavities, PFLs, laser triggered gas switches intermediate stores being doubled. A rebuilt single 61-nF Marx generator will charge two storage capacitors. experiments have demonstrated a MITL configuration matched...
Abstract First-principles calculations coupled with Monte Carlo simulations are used to probe the role of a surface CO monolayer formation on secondary electron emission (SEE) from Cu, Ag, and Au (110) materials. It is shown that such layer increases in all systems. Analysis calculated total density states (TDOS) Au, partial (PDOS) C O confirm covalent type bonding between atoms. bond modifies TDOS extended it lower energies, which then responsible for an increase probability generation....
Thermal driven desorption of surface impurities is probed based on coupled Monte Carlo–heat flow–molecular dynamics simulations. Such adsorbates can lead to plasma formation during the operation high-power microwave systems with various negative outcomes and so need be curtailed. Our study attempts obtain temperature thresholds for desorbing different contaminants such as C2, O2, CO, CO2. The results show that carbon-based copper (chosen an example anode material) could ejected at a...
Recent experiments at Sandia National Laboratories have demonstrated an electron beam diode X-ray source capable of producing > 350 rad one meter with 1.7 mm FWHM distribution, a 50 ns pulse-width and photon endpoint energy spectrum in the 6-7 MeV range.The operates current densities ≈ 1 MA/cm 2 .The intense rapidly (≈ 5 ns) heats conversion anode/target, liberating material form low density ion emission early pulse high plasma later.This environment gives rise to beam/plasma collective...
The rod-pinch diode is a self-magnetically insulated electron beam that capable of producing very bright source hard X-rays. As fielded on the Cygnus accelerator, operates at an impedance 50 Ohms and produces short pulse ( ~50 ns) bremsstrahlung radiation with 2 MeV photon endpoint energy dose 4 rad measured one meter, X-ray spot size ~ 1 mm. can be used to image through 40 g/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> material...
The traveling wave tube (TWT) has been a reliable conventional vacuum electron device (CVED) since the 1940s. Researchers, beginning in late 1980s, extended TWT to relativistic beam regime generate 100- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{s}\cdot $ </tex-math></inline-formula> MW power notation="LaTeX">${X}$ -band. Since mid-1990s, there little advancement field. Recently, linear theory...
Vacuum electron devices (VEDs) can experience degraded performance, including complete failure, due to multipactor breakdown (MPB). This effect is tied the production and acceleration of secondary electrons impact coupling RF fields. In order better understand initiation MPB with materials interest, researchers at University New Mexico (UNM) are carrying out a study yield (SEY) contribution from various used in high power VEDs. work describes SEY data bombardment low energy regime, 10 eV 1...
RITS-3 is the three-cell, 4 MV, 156 kA, 70 ns embodiment of full twelve-cell 16 MV Radiographic Integrated Test Stand (RITS) (Ian D. Smith et al., 2000). The well-instrumented experiments (David L. Johnson 2002) now underway at Sandia are intended to investigate/validate critical design issues for scaling RITS. These use a magnetically-insulated transmission line (MITL) in which increment operating impedance MITL from cell equal individual pulse forming (pfl)/induction (8 ohms). matched load...
Sandia National Laboratories is leading an intensive research effort into fielding and diagnosing electron-beam flash radiographic X-ray sources. Several sources are presently being studied, including the self-magnetic pinched diode, immersed Bz plasma-filled flat cathode (paraxial) diode. These studies carried out on RITS-3, inductive voltage adder accelerator capable of delivering 140 kA at 5 MV with a radiation pulse 70-ns full width half maximum. The interactions electron beam plasmas...
A 1 MV linear transformer driver (LTD) is being tested with a large area e-beam diode load at Sandia National Laboratories (SNL). The experiments will be utilized to determine the repeatability of output pulse and reliability components. accelerator used feasibility designing 6 LTD for radiography experiments. peak voltage, risetime, width as well cavity timing jitter are analyzed pulse.
Summary form only given. The University of New Mexico Electrical and Computer Engineering Department is developing advanced high power microwave sources charged particle beam accelerators pulsed capabilities. This paper presents the characterization, analysis, implementation modification a Marx coupled to low impedance accelerator. 11 stage bipolarity 100 kV device each comprised main capacitor switch as well an LCR based pulse forming line fast rise time peaking switch. A numerical model...
A 1 MV linear transformer driver (LTD), capable of driving a radiographic diode load, has been built and tested. circuit model this accelerator developed using the BERTHA simulation code. Simulations are compared to data from power-flow experiments utilizing large area electron-beam load. Results show that performs well in modeling baseline operation accelerator. In addition, used predict several possible fault modes. switch prefires, main capacitor failure, vacuum insulator flashover, core...
The coupling of short wavelength electromagnetic (EM) interference to critical electronic systems in highly reverberant enclosures is a growing concern the EM interference/compatibility community. In such cavities, prior research has shown that induced fields, voltages, or currents can be modeled using wave-chaotic random model (RCM). RCM partitions interaction within cavity into universally fluctuating part, derived from matrix theory, and system-specific defined by radiation impedance...
RITS (Radiographic Integrated Test Stand) is planned to be a 12-cell, 16-MV, 150-kA, 70-ns induction voltage adder. A three-cell, 4-MV, version (RITS-3) operating routinely at its specified level Sandia. Its over-all performance will described. Advances have been made in understanding and modeling many of the pulsed power features several fundamental accelerator design guidelines developed. We summarize these. omit discussion vacuum flow symmetrization, which are subject other detailed...