A cascade voltage amplifier for producing an amplified output in pulse or continuous wave form, comprising: a) at least one non-final stage (54, 56) comprising an electron tube configured as a switching and Class A or C amplifying means; and b) a final stage comprising an electron tube configured as a switching and Class A or C amplifying means; and c) the at least one non-final stage (54, 56) and the final stage being connected in series; d) the amplified output having a voltage of at least 1000 volts; characterized in that e) each stage (54, 56 and 58) includes a cylindrical outer electrode (54a, 56a, 58a) encircling at least one concentric cylindrical grid (54b, 56b, 58b) which, in turn, encircles a concentric cylindrical inner electrode (54c, 56c, 58c); f) the radial spacing from the cylindrical inner electrode (54c, 56c, 58c) to the cylindrical grid (54b, 56b, 58b) being such as to create therebetween a circular waveguide supporting transverse electromagnetic mode; g) each non-final stage includes a linking structure for electrically joining, and being the primary mechanical support for, the outer electrode of said each non-final stage and the inner electrode of a subsequent stage; the linking structure having first and second ends and comprising: i. an electrical interconnection included between the first and second ends; ii. the first end including means for supporting the outer electrode of said each non-final stage; and iii. the second end including means for supporting the inner electrode of said subsequent stage. a) at least one non-final stage (54, 56) comprising an electron tube configured as a switching and Class A or C amplifying means; and b) a final stage comprising an electron tube configured as a switching and Class A or C amplifying means; and c) the at least one non-final stage (54, 56) and the final stage being connected in series; d) the amplified output having a voltage of at least 1000 volts; e) each stage (54, 56 and 58) includes a cylindrical outer electrode (54a, 56a, 58a) encircling at least one concentric cylindrical grid (54b, 56b, 58b) which, in turn, encircles a concentric cylindrical inner electrode (54c, 56c, 58c); f) the radial spacing from the cylindrical inner electrode (54c, 56c, 58c) to the cylindrical grid (54b, 56b, 58b) being such as to create therebetween a circular waveguide supporting transverse electromagnetic mode; g) each non-final stage includes a linking structure for electrically joining, and being the primary mechanical support for, the outer electrode of said each non-final stage and the inner electrode of a subsequent stage; the linking structure having first and second ends and comprising: i. an electrical interconnection included between the first and second ends; ii. the first end including means for supporting the outer electrode of said each non-final stage; and iii. the second end including means for supporting the inner electrode of said subsequent stage. i. an electrical interconnection included between the first and second ends; ii. the first end including means for supporting the outer electrode of said each non-final stage; and iii. the second end including means for supporting the inner electrode of said subsequent stage.