Lightweight, thermally stable disk for a coaxial travelling wave tube (CoTWT)

A co-axial traveling wave tube (CoTWT) for propagation and amplification of RF signals, comprising:

• an outer metal tube having an axis,
• an inner metal tube positioned along the axis,
• a plurality of disks spaced apart by distance d along the inner metal tube, each said disk comprising,
• a central hub having a front-to-back thickness t1 that sets the overall thickness of the disk, said central hub formed of a refractory metal selected from Tungsten, Molybdenum and Tantalum having a first coefficient of thermal expansion (CTE1) and an electrical conductivity (e1);
• one or more central ribs formed of the same refractory metal and positioned in an inner ring around the periphery of the central hub and having a front-to-back thickness t2<t1;
• a resistive ceramic having a second CTE (CTE2) matched to CTE1 of the refractory metal that encases the one or more central ribs in the inner ring and extends radially to form an outer ring, wherein the refractory metal occupies less than one-third the volume of the inner ring and less than one-fourth the volume of the outer ring which are otherwise encased in the resistive ceramic, said resistive ceramic leaving exposed refractory metal surfaces including at least a portion of an outer surface of the central hub;
• and
• a patterned metal selected from Gold, Silver and Copper that plates the resistive ceramic and exposed refractory metal surfaces to electro-magnetically connect all exposed refractory metal surfaces and to form alternating solid resistive and laminar conductive tabs in the outer ring around the periphery of the disk, wherein said metal has an electrical conductivity e2>=e1, a thickness of 10-100 microns, is not CTE matched to the refractory metal and resistive ceramic, and a Young's Modulus of less than 100 GPa that allows the plating to plasticly deform,
• wherein the disk appears electro-magnetically to the RF band as if the disk were a solid refractory metal with resistive ceramic tabs spaced around its periphery.

A disk for use in co-axial traveling wave tube (CoTWT) for propagation and amplification of RF signals, said disk comprising:

• a central hub having a front-to-back thickness t1 that sets the overall thickness of the disk, said central hub formed of a refractory metal having a first coefficient of thermal expansion (CTE1) and an electrical conductivity (e1);
• one or more central ribs formed of the same refractory metal and positioned in an inner ring around the periphery of the central hub and having a front-to-back thickness t2<t1;
• a resistive ceramic having a second CTE (CTE2) matched to CTE1 of the refractory metal that encases the one or more central ribs in the inner ring and extends radially to form an outer ring, said resistive ceramic leaving exposed refractory metal surfaces;
• and
• a patterned metal that plates the resistive ceramic and exposed surfaces of refractory metal to electro-magnetically connect all exposed refractory metal surfaces and to form alternating solid resistive and laminar conductive tabs in the outer ring around the periphery of the disk, wherein said metal has an electrical conductivity e2>=e1, is not CTE matched to the refractory metal and resistive ceramic, and a Young's Modulus of less than 100 GPa that allows the plating to plasticly deform,
• wherein the disk appears electro-magnetically to the RF band as if the disk were a solid refractory metal with resistive ceramic tabs spaced around its periphery.