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The requirement that the propellants used in launch vehicle systems must also provide the thermal energy to be converted to kinetic energy in the rocket nozzle has plagued rocket designers since the dawn of the space age. Beamed propulsion systems, however, avoid this constraint by placing the energy source on the ground and transmitting the energy to the spacecraft via microwaves. This work computationally models three different heat exchanger channel designs for use in a beam propulsion spacecraft. It was found that despite the very small diameter of the microchannels, each design produced extreme temperature gradients across the channel cross section., The original document contains color images. Presented at the 2013 ASME Summer Conference on Heat Transfer held in Minneapolis, MN on 14-19 Jul 2013. Prepared in collaboration with AFRL/RDHPS, Kirtland AFB, NM, and the University of Colorado, Colorado Springs.

Models for non-linear dielectrics and magnetic ferrites are developed and coded into the particle-in-cell code ICEPIC. The non-linear dielectric model includes a relaxation term to account for the physical response time of the material, which may be longer than an FDTD time step. The ferrite model accounts for the non-linearity of the Landau-Lifshitz-Gibert equation, and the magnetization update is derived from the solution of the equation on a time step. Initial testing of the models is encouraging, and work is underway on further improvement and refinement., The original document contains color images. Presented at the International Review of Progress in Applied Computational Electromagnetics (28th) held in Columbus, OH on 10-14 April 2012.

A recirculating planar magnetron (RPM), operating in the pi-mode and utilizing a compact, waveguide-based extraction scheme was simulated using ICEPIC. At an applied voltage of 300 kV and B-field of 0.140T, output power of the six-module RPM was 565 MW with 33% efficiency. The oscillator was found to operate at frequency of 2.245 GHz. Increasing the number of extracted modules in the RPM was found to result a linear increase in power at the rate of 120 MW per module., The original document contains color images.

A parallel plate nonlinear transmission line (NLTL) was constructed. Periodic loading of nonlinear dielectric slabs provides the nonlinear capacitance and the gaps between provide linear inductive interconnects, this is essentially the same design used by Ikezi [1],[2]. The NLTL was modeled in a circuit simulation code using the experimentally measured form of the nonlinear capacitance. Dielectric loss included in the model as an equivalent series resistance derived from the measured loss tangent data affects the formation of RF oscillations. The diagnostics used on the experimental system are Bdots along the line and a current viewing resistor at the load. The diagnostics provide a measurement of the pulse evolution as it travels down the line. The waveforms from the experimental line qualitatively agree with the circuit model, showing no strong RF formation as a result of the loss., Published in the 2011 IEEE Pulsed Power Conference Proceedings, 01 December 2011. The original document contains color images.

Experiments have been performed testing magnetic-priming at the cathode of a relativistic magnetron to study the effects on high-power microwave performance. Magnetic perturbations were imposed utilizing three, high-permeability nickel-iron wires embedded beneath the emission region of a 1.27 cm diameter cathode, spaced 120 degrees apart (for N/2 symmetry in an N cavity magnetron). These three, high permeability wires perturb both the axial and radial magnetic fields near the emission region of the cathode. Magnetic priming was demonstrated at UM to increase the percentage of pi-mode shots by 15% over the baseline case in the relativistic magnetron. Improvements in microwave power, pulse width, and start-oscillation time were also observed. Earlier experimental research by Neculaes and recent simulation work suggest that using permanent magnets with radially directed remanence fields centered under the cathode emission region instead of high permeability wires can yield improved magnetron performance., See also ADM002087. Published in the Proceedings of the 2008 IEEE International Vacuum Electronics Conference (9th) (IVEC 2008), p270-271, Apr 2008. Presented at the IEEE International Vacuum Electronics Conference (9th) (IVEC 2008) held in Monterey, CA on 22-24 Apr 2008. U.S. Sponsored in part by the Air Force Research Laboratory. Prepared in cooperation with the Air Force Research Laboratory, Kirtland AFB, Albuquerque, NM and L-3 Communications, Pulse Sciences Division, San Leandro, CA. Government or Federal Rights License. The original document contains color images.