C. L. Miller

Publications (5)3.34 Total impact

• Article: Locally conformal finite-difference time-domain techniques for particle-in-cell plasma simulation.

  R. E. Clark, D. R. Welch, W. R. Zimmerman, C. L. Miller, T. C. Genoni, D. V. Rose, D. W. Price, P. N. Martin, D. J. Short, A. W. P. Jones, J. R. Threadgold
  J. Comput. Physics. 01/2011; 230:695-705.
• Article: Detailed Simulation of the CYGNUS Rod Pinch Radiographic Source

  C.L. Miller, D.R. Welch, D.V. Rose, B.V. Oliver
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  ABSTRACT: In this paper, we present the results from particle-in-cell simulations of the nominally 2-MV 40-kA CYGNUS radiographic machine using a standard rod pinch diode. The rod pinch electron-beam diode consists of a small-diameter high-atomic-number anode extending through a thin cathode aperture. A significant shot-to-shot variation of the photon spectrum emerging from the anode can introduce an error in interpreting the radiograph. We present the results from these integrated simulations of the electron and photon generation and quantify the sensitivities on the photon distribution.
  IEEE Transactions on Plasma Science 11/2010; · 1.17 Impact Factor
• Article: Electromagnetic wave propagation through an overdense magnetized collisional plasma layer

  C. Thoma, D. V. Rose, C. L. Miller, R. E. Clark, T. P. Hughes
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  ABSTRACT: The results of investigations into the feasibility of using a magnetic window to propagate electromagnetic waves through a finite-sized overdense plasma slab are described. We theoretically calculate the transmission coefficients for right- and left-handed circularly polarized plane waves through a uniform magnetized plasma slab. Using reasonable estimates for the plasma properties expected to be found in the ionized shock layer surrounding a hypersonic aircraft traveling in the earth’s upper atmosphere (radio blackout conditions), and assuming a 1 GHz carrier frequency for the radio communications channel, we find that the required magnetic field for propagation of right-handed circularly polarized, or whistler, waves is on the order of a few hundred gauss. Transmission coefficients are calculated as a function of sheath thickness and are shown to be quite sensitive to the electron collision frequency. One-dimensional particle-in-cell simulations are shown to be in good agreement with the theory. These simulations also demonstrate that Ohmic heating of the electrons can be considerable. Two- and three-dimensional particle-in-cell simulations using a simplified waveguide and antenna model illustrate the same general transmission behavior as the theory and one-dimensional simulations. In addition, a net focusing effect due to the plasma is also observed in two and three dimensions. These simulations can be extended to design and analyze more realistic waveguide and antenna models.
  Journal of Applied Physics 09/2009; · 2.17 Impact Factor
• Conference Proceeding: ZR-convolute analysis and modeling: Plasma evolution and dynamics leading to current losses

  D.V. Rose, D.R. Welch, R.E. Clark, E.A. Madrid, C.L. Miller, C. Mostrom, W.A. Stygar, M.E. Cuneo, C.A. Jennings, B. Jones, D.J. Ampleford, K.W. Struve
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  ABSTRACT: Post-hole convolutes are used in high-power transmission line systems and join several individual transmission lines in parallel, transferring the combined currents to a single transmission line attached to a load. Magnetic insulation of electron flow, established upstream of the convolute region, is lost at the convolute due, in part, to the formation of magnetic nulls, resulting in current losses. At very high-power operating levels, the formation of electrode plasmas is considered likely which can lead to additional losses. A recent computational analysis of the Sandia Z accelerator suggested that modest plasma desorption rates in the convolute region could explain measured current losses. The recently completed Sandia ZR accelerator has utilized new convolute designs to accommodate changes to the parallel-plate transmission lines on ZR. Detailed particle-in-cell simulations that are fully electromagnetic and relativistic, and include plasma desorption from electrode surfaces in the post-hole convolutes, are carried out to assess the measured current losses on ZR. We find that the plasma desorption rate used to model the Z convolute also applies to three different ZR convolute designs that have been fielded. Based on these findings, the simulation model is being used to develop newer convolute designs with the goal of reducing the current losses, particularly for higher-impedance loads.
  Pulsed Power Conference, 2009. PPC '09. IEEE; 08/2009
• Article: Locally conformal finite-difference time-domain techniques for particle-in-cell plasma simulation

  R.E. Clark, D.R. Welch, W.R. Zimmerman, C.L. Miller, T.C. Genoni, D.V. Rose, D.W. Price, P.N. Martin, D.J. Short, A.W.P. Jones, J.R. Threadgold
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  ABSTRACT: The Dey–Mittra [S. Dey, R. Mitra, A locally conformal finite-difference time-domain (FDTD) algorithm for modeling three-dimensional perfectly conducting objects, IEEE Microwave Guided Wave Lett. 7 (273) 1997] finite-difference time-domain partial cell method enables the modeling of irregularly shaped conducting surfaces while retaining second-order accuracy. We present an algorithm to extend this method to include charged particle emission and absorption in particle-in-cell codes. Several examples are presented that illustrate the possible improvements that can be realized using the new algorithm for problems relevant to plasma simulation.
  Journal of Computational Physics.