A forced gas-cooled single-disk window using silicon nitride composite for high power CW millimeter waves

Silicon nitride composite as a candidate of a window material for high power CW (Continuous Wave) millimeter-waves was high power tested especially with a surface cooling by impinging gas nitrogen jets on the single-disk surface. Gas-cooling dramatically suppressed the temperature of the window disk even with gas flow rate of around 100 1/min. With gas cooling of 4651/min., 130kW CW power of HE₁₁ mode could be transmitted through the silicon nitride window with a diameter of 88.9mm. The peak window temperature was completely saturated on 123.6°C. Without gas-cooling it did not saturate and reached 323°C during 30 seconds pulse. A possibility of 1MW CW single disk Brewster windows with a forced gas-cooling is discussed, resulting in convinced prospects of the windows with realistic size and thickness.