Developments in the construction of fluted tubing for a helix support

Two novel methods are outlined for the fabrication of glass fluted tubing to be used as a precision helix support in traveling wave tubes. Also described is a method for ruggedizing (locking each turn of the helix tightly in place) the helix mounted in such a structure. Such techniques used for fluted tubing construction lead to an ideal type of helix support since the inside geometry is such that a minimum of dielectric material is in direct contact with or in proximity to the helix. The first method described for the fabrication of the fluted tubing is useful where small quantities are required for laboratory use. No special materials are required, and tubing of almost any desired inside dimensions may be obtained with a minimum of delay. The second method requires initial tooling but is better suited for production quantities. Precision mandrels of the desired inside geometry may be made cheaply and used as disposable tools in this process.