N.P. Lockwood

Publications (2)0 Total impact

• Conference Proceeding: Optimized High-Resolution Simulation of a THz Traveling Wave Tube Amplifier

  S.E. Olson, N.P. Lockwood, P.D. Gensheimer
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  ABSTRACT: Modeling of complex systems typically requires many iterations of theoretical design, numerical simulation, and analysis. The goal of this project was to develop an automated optimization framework to optimize a 0.22 THz traveling wave tube (TWT) high-power amplifier design. Applications for such an amplifier include three-dimensional (3D) imaging systems for medical uses, detection of concealed hazardous materials, and high-bandwidth communications. An optimization framework was developed for the DoD Supercomputing Resource Center (DSRC) environment to automatically queue and track many simultaneous thousand CPU hour jobs. Results were automatically evaluated, collated, and used to refine simulations, thus saving many man-hours otherwise used for performing parameter scans and analysis. Prior efforts typically required thousands of manually submitted jobs over the course of three years, and resulted in a design that did not meet the desired specifications, e.g., the electron-gun (e-gun) component produced a noisy 4.4 mA, 150 μm diameter electron beam which fed into a 13 dB amplifier that exhibited detrimental backwards-wave oscillations. The automated effort produced thousands of runs over a month and met the design goals with an e-gun providing a low-noise, 10 mA, 100 μm diameter electron beam feeding into a 21 dB amplifier with no backwards-wave oscillations. The work presented here involved thousands of runs consuming around 3.8 million CPU hours. Hence, the near-exclusive access provided by the Capabilities Application Project was critical for the success of this effort.
  High Performance Computing Modernization Program Users Group Conference (HPCMP-UGC), 2010 DoD; 07/2010
• Conference Proceeding: 1.5: Development of field emission cathodes, electron gun and a slow wave structure for a terahertz traveling wave tube

  N.P. Lockwood, K.L. Cartwright, P.D. Gensheimer, D.A. Shiffler, C.Y. d'Aubigny, C.K. Walker, A. Young, S.B. Fairchild, B. Maruyama
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  ABSTRACT: High power terahertz (THz) sources and amplifiers hold the potential to greatly improve remote sensing and high bandwidth communication. To enable these applications, a Traveling Wave Tube (TWT) operating at 0.22 THz and a multi-cathode Field Emission (FE) electron gun are developed and characterized using a Particle-in-Cell simulation. Three candidate high current density cathode materials, Halfnium Carbide (HfC), carbon fibers, and Carbon Nanotubes (CNTs) were tested, characterized and their emission properties compared and used to verify simulations. A current of 3.0 mAmps for a single 100 micron diameter single walled nanotube rope was experimentally achieved and used as the basis of the FE gun design. Simulations of the FE gun and THz TWT were coupled and the effects of multiple and single tip FE gun beam characteristics on the TWT gain, bandwidth, and efficiencies are examined for several beam optic configurations.
  Vacuum Electronics Conference (IVEC), 2010 IEEE International; 06/2010