J.W. Luginsland

Michigan State University

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Co-Authors

Y. Y. Lau

University of Michigan–Ann Arbor

115

R. M. Gilgenbach

University of Michigan–Ann Arbor

M.D. Haworth

University of Notre Dame

Tom Spencer

University of Cambridge

Brad W. Hoff

United States Air Force Research Laboratory

J.J. Watrous

Confluence Life Sciences (United States)

Keith Cartwright

Sandia National Laboratories California

Kyle J. Hendricks

United States Air Force Research Laboratory

David Simon

United States Air Force Research Laboratory

P. Pengvanich

University of Michigan–Ann Arbor

Cooperative Institutions

United States Air Force Research Laboratory

University of Michigan–Ann Arbor

Kirtland Air Force Base

United States Naval Research Laboratory

U.S. Air Force Research Laboratory Directed Energy Directorate

Sandia National Laboratories

Michigan United

Leidos (United States)

Sandia National Laboratories California

University of New Mexico

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Virtual prototyping of directed energy weapons

Keith Cartwright L.A. Bowers Andrew Greenwood C. Fichtl M.D. Haworth

We give an overview of how RF systems, from pulsed power to antennas, can be virtually prototyped with the ICEPIC (Improved Concurrent Electromagnetic Particle-in-Cell) code. ICEPIC simulates from first principles (Maxwell's equations and Lorenz's force law) the electrodynamics and charged particle dynamics of the RF-producing part of the system. Our simulations focus on gigawatt-class sources; the relativistic magnetron is shown as an example. Such simulations require enormous computational resources. These simulations successfully expose undesirable features of these sources and help us to suggest improvements.

Code (set theory)

Particle-in-cell

Electromagnetics

Virtual Prototyping

10.1109/dodugc.2003.1253378

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Citations (3)

On the elimination of numerical Cerenkov radiation in PIC simulations

Journal of Computational Physics (2004)

Andrew Greenwood Keith Cartwright J.W. Luginsland Ernest A. Baca

Stencil

10.1016/j.jcp.2004.06.021

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Citations (95)

Constrained evolutionary optimization of the signal growth rate in an RKO with an axially varying waveguide diameter

Larry D. Merkle J.W. Luginsland

Summary form only given. The relativistic klystron oscillator (RKO) is a high power microwave (HPM) source based on enhancing mature non-relativistic klystron technology, in which the kinetic energy of a population of electrons is converted into coherent microwave radiation. There is significant interest in maximizing the growth rate of the RKO's microwave signal as a function of the RKO design parameters. A model relating the growth rate to the beam voltage, beam current, and gap separation is generalized to reflect dependence on additional device parameters. Specifically, the lumped circuit model from which resonant frequencies of the cold tube are determined is extended to allow axial variation of the waveguide diameter, and to reflect the simultaneous existence of the "zero mode" and the "pi mode." These modes have associated frequencies that are up-shifted and downshifted symmetrically (though not necessarily respectively) from the (common) resonant frequency of the driver and booster cavities. The hot tube model is also generalized to reflect the dependence of the stop current on the beam diameter and axial variation of the waveguide diameter.

Klystron

Axial symmetry

Waveguide

10.1109/plasma.1999.829509

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Citations (0)

Recent Advances in Magnetron Phase Locking: Effects of Frequency Chirps and Locking of Multiple Magnetrons

P. Pengvanich Y. Y. Lau R. M. Gilgenbach E. J. Cruz J.W. Luginsland

Summary form only given. Phase-locking is utilized today in many important applications, ranging from small scale devices such as cardiac pacemakers to large scale devices such as radar. We have recently developed a magnetron-specific model to qualitatively explain the various regimes observed in magnetron injection-locking experiments, which utilize two continuous wave magnetrons: one functions as an oscillator and the other as a driver. We have applied this model to study injection locking when the driver has a frequency chirp. The model has also recently been extended to analyze peer-to-peer locking of two magnetrons of comparable powers and frequencies. The feasibility of locking will be explored in terms of the variations in these parameters of the individual magnetrons, as well as the degree of coupling among them. Locking of a larger number of such magnetrons will be explored. A preliminary experiment is being conducted on the peer-to-peer locking of two commercial KW magnetrons.

Chirp

Cavity magnetron

Phase locking

Injection locking

10.1109/ppps.2007.4346208

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Citations (0)

Review of Cold Cathode Research at the Air Force Research Laboratory

IEEE Transactions on Plasma Science (2008)

Don Shiffler M.D. Haworth Keith Cartwright R. Umstattd M. Ruebush

Over the last decade, the Air Force Research Laboratory, Directed Energy Directorate (AFRL/DE) has engaged in a high current density field emission cathode research program. This program explored the aspects of cathode materials as well as the details of cathode geometries and emission physics. This paper summarizes the results of this ongoing research effort to date. We review the history and motivation for the program, which provide insight into the physics issues of concern for various vacuum electronic sources. One important aspect of the program consists of the investigation of new cathode materials. For many high power microwave (HPM) sources, neutral out-gassing, which ties critically with cathode materials, plays a key role in the effective operation of the source. These material properties influence plasma formation, which in turn dictates the operation of an HPM device. For a cathode material, AFRL chose to focus on cesium-iodide-coated carbon fiber cathodes, which we discuss in detail here. A second important aspect of the program consists of understanding emission physics and the optimum geometries for a cathode. This aspect couples closely with electron beam quality, which in turns effects the electron beam interaction with microwaves in the HPM structure. This paper concludes with a discussion of the implementation of the cathode material on both a Magnetically Insulated transmission Line Oscillator and a relativistic magnetron.

Cold cathode

Hot cathode

10.1109/tps.2008.926227

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Citations (91)

Two-Dimensional Space-Charge-Limited Emission: Beam-Edge Characteristics and Applications

Physical Review Letters (2001)

R. Umstattd J.W. Luginsland

There is, at present, no analytic solution that extends Child-Langmuir space-charge-limited emission beyond 1D. Herein, we investigate the characteristics of planar diode electron emission in 2D space with the emphasis on the transition region between the beam and vacuum. Current density above that predicted by Child-Langmuir is observed near the beam edges in a 2D finite element, electrostatic ray-tracing code. The properties of these increased current density "wings" are examined and then discussed in terms of their applications to cathodes which have large reservoirs of free electrons.

10.1103/physrevlett.87.145002

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Citations (116)

Development of a Renormalization Group Approach to Multi-Scale Plasma Physics Computation

J.W. Luginsland

Abstract : During this quarter, NumerEx and its associated research institutions worked on 1. Consideration of the EMPIC numerical grid heating problem from the point of view of renormalization group analysis. This work included a literature survey and presentations at conferences at the University of Wisconsin and Stanford (Caflisch, UCLA). 2. An analysis of the effect of the Coulombic collision operator on a bump on the tail of a Maxwellian distribution and its application to stabilization of cathode flicker. This work included a draft manuscript on the 1-d evolution of bump, and another on non-adiabatic evolution via extremal statistics of stochastic ODEs (Promislow, MSU). 3. Formulation of a geometric optics approach to the perturbation analysis of the Child-Langmuir-Jaffe virtual cathode problem. A manuscript was begun on this approach, and another on the stable and unstable modes of this problem (Caflisch, UCLA).

Source

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PLASMA MODELS AND CLOSURE OF MAXWELL'S EQUATIONS - THE IMPACT OF ELECTROMAGNETIC APPROXIMATIONS.

OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information) (2018)

Kristian Beckwith J.W. Luginsland

Closure (psychology)

Source

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Virtual Prototyping of Directed Energy Weapons

Matthew Tyler Bettencourt D.J. Amdahl L.A. Bowers K. Cartwright Andrew Greenwood

This paper gives an overview of how RF systems, from pulsed power to antennas, may be virtually prototyped with the improved concurrent electromagnetic particle-in-cell (ICEPIC) code. ICEPIC simulates from first principles (Maxwell's equations and Lorenz's force law) the electrodynamics and charged particle dynamics of the RF-producing part of the system. Our simulations focus on gigawatt-class sources; the relativistic magnetron is shown as an example. Such simulations require enormous computational resources. These simulations successfully expose undesirable features of these sources and help us to suggest improvements

Code (set theory)

Virtual Prototyping

Particle-in-cell

Electromagnetics

10.1109/hpcmp-ugc.2006.75

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Citations (0)

Electron dynamics and startup in crossed field microwave devices

David M. French David Simon Y. Y. Lau R. M. Gilgenbach Brad W. Hoff

Summary form only given. Recently there has been a renewed interest in the inverted magnetron because of its larger cathode area, reduction of electron end-loss, and substantially faster startup in comparison with the conventional magnetron. A recently conceived embodiment of the magnetron, called the recirculating planar magnetron, RPM [1], incorporates these attractive features. The electron dynamics for the various magnetron configurations has been re-examined with the Particle-In-Cell code MAGIC.has been shown [2] that an electron rotating under a combination of axial magnetic field Bο and a radial electric field Eο has an effective mass in the azimuthal direction, which can be either positive or negative depending on the magnitude and sign of Eο. For inverted magnetron, this effective mass is negative, therefore an azimuthal electron density bunching (a spoke) has a tendency to build up. For conventional magnetrons, this effective mass is positive, and the tendency toward azimuthal bunching disappears, at least during startup. We believe that this negative-mass property in the inverted magnetron leads to its substantially faster startup than the conventional magnetron. The results of simulations showing the initiation of bunching in several different magnetron configurations, including the RPM will be presented.

Cavity magnetron

Negative mass

10.1109/plasma.2010.5534066

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Citations (1)