We study the electric field distribution and current emission in a miniaturized geometrical diode. Using Schwarz-Christoffel transformation, we calculate exactly inside finite vacuum cathode-anode (A-K) gap with single trapezoid protrusion on one of electrode surfaces. It is found that there strong enhancement both electrodes near protrusion, when ratio A-K distance to height d/h<2. The calculations are spot checked against COMSOL simulations. effective factor for current, by...

Predictive models of field emission remain elusive, in part, due to the sensitivity this process emitter surface details at length scales ranging from macroscopic atomic. Moving towards more fully predictive requires that we develop techniques disentangle contributions features on largest scales, which can be easily measured and controlled, smaller are generally difficult measure or control. Here, specific challenges addressed, with an emphasis comparisons between a Line Charge Model (LCM)...

Researchers at The University of Michigan have constructed and tested a 1‐MA Linear Transformer Driver (LTD), the first its type to reach USA. Accelerator for Inductive Z‐pinch Experiments, (MAIZE), is based on LTD developed Institute High Current Electronics in collaboration with Sandia National Labs UM. This utilizes 80 capacitors 40 spark gap switches, arranged "bricks," deliver 1 MA, 100 kV pulse ns risetime into matched resistive load. Preliminary resistive‐load test results are...

The Buneman–Hartree condition is re-examined in a cylindrical, smooth-bore, relativistic magnetron using both the conventional, single particle model, and Brillouin flow model. These two models yield same result for only limit of planar magnetron. When b/a=1.3, where cathode radius b (>a) anode radius, difference becomes significant. b/a=4 acute, magnetic field at given voltage model exceeds four times that Such always present, whether or not. results are quantified b/a⪢1 Davidson's...

Field emission dc cold cathodes continue as an important area of research for uses such electron microscopy, novel X-ray sources, vacuum electronic devices, terahertz and high-power microwave tubes. Each these applications typically requires high current densities with high-brightness beams driven by exhibiting long lifetime in the presence deleterious conditions ion back bombardment excessive heating. The Air Force Research Laboratory (AFRL) now investigates operating mode use a traveling...

Soft metal gaskets (indium and silver) were used to reduce contact resistance between the wire electrode in an aluminum Z pinch by more than order of magnitude over best weighted case. Clamping a gasket Z-pinch compresses with greater normal force possible weights. Average was reduced from range 100–3000 Ω (depending on weight mass) 1–10 soft gaskets. Single experiments (13 μm Al 5056) 16 kA, 100 kV Marx bank showed increase light emission (97%) volume (100%) plasma for cases. The measured...

A calculation of the loading a resonant cavity by an electron beam is presented. This first to include all effects ac space-charge. The fields in are determined presence beam, including higher order structure modes. formulation also explicitly includes Ramo's space-charge waves ranks. result reduces conventional ballistic for low current. Comparison complete theory developed here with demonstrates that sufficiently accurate, typically accounting quality factor within 5%, and frequency 1%. In...

Contact resistance is important to integrated circuits and thin film devices, carbon nanotube based cathodes interconnects, field emitters, wire-array z-pinches, metal-insulator-vacuum junctions, high power microwave sources, etc. In other applications, the electrical contacts are formed by structures of a few microns thickness, such as in micro-electromechanical system (MEMS) relays microconnector systems. This paper summarizes recent modeling efforts at University Michigan, addressing...

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> Heavier wire weights reduce contact resistance, which increases the energy deposition in plasma. Images from a two-wire <formula formulatype="inline"><tex>$Z$</tex></formula>-pinch showing effects of tension on expansion performance are presented. </para>

In this paper, a novel method for the detection of external insulation defects based on ultrawideband impulse radar is proposed. The circular synthetic aperture was adopted to collect reflected signals in since detected object often has symmetric shape (e.g., insulators, bushings, etc.). mean suppression filter out clutters waveforms from different directions, and thus can be amplified. Then, defect images are extracted processed with back projection algorithm. Moreover, example objects...

Climate change is causing the soil environment to (soil temperature and moisture), which affects nitrogen cycling of vegetation. To examine this, three typical communities (grassland, shrub forests, Picea wilsonii Mast. forests) was selected cultured under different moisture levels (20, 40, 60% field water-holding capacity, referred as W20, W40, W60, respectively) temperatures (15, 25, 35 °C, T15, T25, T35, evaluate effects vegetation types on mineralization in Xinglong Mountains, Gansu...

Summary form only given. A self-magnetically insulated transmission line (MITL) has been designed to transmit a 1 MA 100 kV pulse with 70 ns rise-time from Linear Transformer Driver (LTD) wire array z-pinch load. The three stages: coaxial line, followed by radial and finally conical the geometry was chosen ease construction lower cost while maintaining low inductance. Both collisionlessand collisional MITL models were used determine limit of anode-cathode gap for line. third case assuming...

In this paper, a kind of tightly coupled array (TCA) with time-domain beam scan is developed for the radiation high-power ultrawideband (UWB) electromagnetic pulses, and peak-power pattern proposed to characterize directivity. First, active voltage standing wave ratio (AVSWR) bandwidth TCA optimized, which precondition scan. It indicates that lower-cutoff frequency (LCF) inversely proportional total length whole array; an increase in distance between ground plane could remarkably reduce LCF;...

The lumped circuit elements representing electrical contact of a single and multiple points are constructed. local is assumed to be in the form cylindrical constriction (connecting bridge) radius axial length 2h, made same material as main conducting current channel b. resistance, capacitance, inductance given terms a, b, h, from which rf properties obtained. For case surfaces with connecting bridge dimension micron size, resulting resonant frequency found terahertz regime. A statistical...

Summary form only given. It was recently found that the Buneman-Hartree (B-H) condition in a cylindrical relativistic magnetron assumes very different depending on single particle model or Brillouin flow model. Such difference is always present, whether voltage not. These two models yield same result limit of planar magnetron. As between conventional and inverted arises geometry, renewed interest because exhibits negative mass instability, which utilized our recent invention recirculating We...

Summary form only given. The Buneman-Hartree (B-H) condition is re-examined in a cylindrical relativistic magnetron using both the conventional, single particle model, and Brillouin flow model. These two models yield same result for limit of planar magnetron. When b/a = 1.3, where cathode radius b (> a) anode radius, difference becomes significant. 4, acute, magnetic field, at given voltage, model exceeds four times that Such always present, whether voltage or not. results are quantified >>...

Summary form only given. We have recently developed an analytic theory on the linear and nonlinear evolution of most unstable azimuthal clumping mode (the pi mode, in which neighboring wires pair up) a discrete wire array. This instability is violent dominates over radial motion array, both regimes. Thus, lack wire-pairing provides sensitive test maximum current that may carry. An experiment this was performed at Cornell, initially seeded 8-wire array such way it deeply regime pi-mode. The...

The contact resistance in a wire array z-pinch has significant affect on both the level and uniformity of energy deposition wires. Typically wires are held taut against electrodes by weights (-1-10 g depending material diameter). This can lead to values -90-99% load resistance. Previous techniques reduce (i.e. soldering) do not scale large number arrays (such as Z-Machine). UM experiments used 13 micron diameter Al 5056 Bench measurements for double-ended weighted (similar method Z-Machine)...

Summary form only given. Field emitter arrays have the potential to provide high current density, low voltage operation, and pulse repetition for radar communication. It is well known that packing density of field significantly affects emission <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sup> . Previously we conducted experiments using two- four-cathode configurations. Here extend our previous work present experimental results nine...

Field emitter arrays have the potential to provide high current density, low voltage operation, and pulse repetition for radar communication. It is well known that packing density of field significantly affects emission current1. Previously we conducted experiments using two-and four-cathode configurations. Here extend our previous work present experimental results nine cathodes in a square cylindrical configuration. The used with variable spacing investigate effect electric screening on...

Field emitter arrays have the potential to provide high current density, low voltage operation, and pulse repetition for radar communication. It is well known that packing density of field significantly affect emission <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sup> . Previous experiments were conducted with 1000s emitters which makes analysis electric screening difficult. Here we describe in a dual-cathode four-cathode configuration...