A FOUR-FREQUENCY MODE CONVERTER WITH SMALL OUTPUT ANGLE VARIATION FOR A STEP-TUNABLE GYROTRON

A new multi-frequency quasi-optical mode converter design for four frequency/mode pairs for a step-tunable gyrotron is discussed. The design frequency/mode pairs are 110 GHz/TE_22,6, 124.5 GHz/TE_24,7, 127.5 GHz/TE_25,7 and 107.5 GH/TE_21,6. The design is for an 88 mm diameter variable-spacing double-disk vacuum window. All four design frequencies have an output propagation direction angle from the window axis of 0.4° or less and a complex coupling to an ideal Gaussian beam greater than 99.45% over the window aperture.