Two reports present further developments in the subject of "Computation of Characteristics of a Helical TWT Slow-Wave Circuit" (LEW-16571), NASA Tech Briefs, Vol. 22, No. 4 (April 1998), page 54. The subject is computation, by use of the MAFIA (Solution of MAxwell's Equations by the Finite-Integration-Algorithm) computer program, of the cold-test electromagnetic characteristics of the helix and surrounding structures in the slow-wave circuit of a traveling-wave tube (TWT). Special attention is given to the on-axis electron-beam/slow-wave interaction impedance, which cannot be measured directly. Heretofore, this impedance has been determined indirectly from cold-test measurement of the change in the resonance frequency resulting from the introduction of a dielectric rod on the axis.

This work was done by James A. Dayton, Jr., of Glenn Research Center and Carol L. Kory of Analex Corp. To obtain copies of the reports, "Computational Investigation of Experimental Interaction Impedance Obtained by Perturbation for Helical Traveling-Wave Tube Structures," and "Accurate Cold-Test Model of Helical TWT Slow-Wave Circuits," access the Technical Support Package (TSP) free on-line at  under the Electronics & Computers.

Inquiries concerning rights for the commercial use of this invention should be addressed to

NASA Glenn Research Center
Commercial Technology Office
Attn: Steve Fedor
Mail Stop 4 – 8
21000 Brookpark Road
Ohio 44135.

Refer to LEW-16881.

NASA Tech Briefs Magazine

This article first appeared in the January, 2000 issue of NASA Tech Briefs Magazine.

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