A high power microwave antenna was developed based on longitudinal shunt slots of rectangular waveguides.The antenna consists of 4route rectangular waveguides and a Teflon window.To obtain high power capacity,the high power microwaves inside antenna transmit in vacuum system.To restrain the high power microwave breakdown in surface of window on the vacuum side,the window surface at vacuum side is notched periodically with triangle grooves.There are support planks between waveguides and window.The support pl...