Inward-emitting magnetically insulated line oscillator

An inward emitting magnetically insulated transmission line oscillator (MILO) is presented and a method to axially extract microwave is assumed. The inward-emitting MILO has an novel design of structure with outer cathode and inner anode, which can recycle spoke current to provide selfinsulating angular magnetic field, thus to improve the tube’s efficiency. The outer cathode has expanded emitting area, and the current density can be reduced correspondingly for a long cathode life. PIC simulation reveals the relationship between the MILO’s structure parameters and its output power. When the electron beam voltage is 890 kV and beam current is about 56.1 kA, microwave output of 3.6 GW is obtained with frequency of 8.2 GHz．