An examination of the performance of backward wave CFA's in simulation and experiment

MRC will present comparisons of detailed MAGIC 3-D simulations of amplitrons (backward wave CFAs) under cold test (no electrons present) and hot tests with experimental results. These will include measurements using both methods of S/sub 11/ and S/sub 22/ parameters vs. frequency. Results both for a the so-called, "baby" amplitron, L-4717, an S-band tube currently used by the Navy, and a new, experimental, ultra-high-average-power, UHF amplitron will be presented. The baby is of interest in that it exhibits spurious output, ostensibly due to resonant phenomena caused by impedance mismatches within the tube. In order to study this in detail, MRC is performing both computer and experimental cold tests of each major section of these tubes, which includes a double ridged waveguide taper and a two-conductor TEM transmission line on both the input and the output, and the amplitron slow-wave circuit itself. Related work reported includes MAGIC hot runs on both tubes, to verify performance results against experimental runs and to study spurious behavior.