Optimized High-Resolution Simulation of a THz Traveling Wave Tube Amplifier

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.