SBIR-STTR Award

A highly efficient, very wide bandwidth, diamond studded micro helix TWT for operation at 95 GHz will be designed and fabricated by means of a novel application of solid state micro fabrication technology. Because of the nature of the fabrication process proposed here, this device can be built as a single TWT or just as readily as an array of TWTs. By spatially combining the power output of several TWTs in an array, an electronically steerable power output of hundreds of Watts is quite feasible. The design will be conducted utilizing well established computational techniques first introduced by the authors and now widely adopted. The fabrication of the micro helix TWT will rely entirely upon lithography and other solid state techniques. Because this fabrication technique results in a helical circuit that is supported by a minimal amount of low permittivity dielectric, it is anticipated that the bandwidth and efficiency will be much higher than for a conventional helix.

Keywords:
Traveling Wave Tube, Helical Slow Wave Circuit, Cvd Diamond, Micro Fabricaion, Vacuum Electron Device, Diamond Studded Twt

The radical design proposed here essentially reinvents the venerable helical TWT. The cathode, electron gun, slow wave circuit, output coupler and collector would all be significantly different from current conventional practice. This is not innovation for the sake of novelty. Without radical changes, the physical limitations of the conventional helical TWT, which is the work horse of lower frequency microwave systems, prevent it from achieving operation above 60 GHz, and there only with difficulty. The physical features identified by the computer models as essential to the successful fabrication of these novel helical TWTs have been executed experimentally using modern microfabrication technology. As a baseline design the TWT would operate at 6 kV with a beam current of 32 mA. For this case, we predict that the power output would be 28.2 W, the RF efficiency 14.7%. With RF losses of 2.8 W, 1% beam interception and a collector efficiency of 75%, the overall efficiency will be 39%. The power output prediction increases dramatically for increased voltage and current. At 9 kV and 70.6 mA, the power output prediction is 109.4 Watts at an RF efficiency of 17.2%. The overall efficiency would be 43% for the same conditions as above.

Keywords:
Twt, Traveling Wave Tube, Microfabrication, Cvd Diamond, Selective Metallization, Miniaturization