Ultralow electron emission yield achieved on alumina ceramic surfaces and its application in multipactor suppression

Abstract Alumina ceramics used in microwave systems are susceptible to the multiplication of secondary electron emission on the surface due to the influence of resonance between electrons and the radiofrequency electric field, and a detrimental multipactor effect may therefore be triggered. For the alumina-loaded microwave components, it is essential to achieve low secondary electron yield (SEY) on the inserted alumina surfaces to mitigate multipactor. In this work, to achieve an ultralow SEY surface of alumina, two recognized low-SEY treatments were combined. For the primary SEY suppression, a series of microstructures were fabricated on the alumina surfaces with varied porosity and aspect ratio at the hundred-micrometer scale by infrared laser etching. The microstructure with 52.14% porosity and 1.78 aspect ratio showed an excellent low-SEY property, which could suppress the SEY peak value ( δ m ) of alumina from 2.46 to 1.00. For the secondary SEY suppression, the SEY dependence of TiN coating on sputtering parameters was studied, and the lowest δ m of 1.19 was achieved when the gas flow ratio of Ar:N 2 was 15:7.5. Thereafter, by depositing TiN ceramic coating onto the laser-etched porous samples, an ultralow SEY, with δ m of 0.69, was achieved on the alumina surfaces. The simulation work revealed the impact of dielectric surface charge on electron multiplication and revealed a mechanism of using low-SEY surfaces to inhibit multipactor. Some coaxial filters filled with alumina were fabricated for verification; the results revealed that the multipactor threshold increased from 125 W to 425 W after applying the TiN-coated porous alumina, and to 650 W after treating another multipactor-sensitive area with the same low-SEY process. This work developed an advisable method to sharply reduce SEY, which is of great significance for the multipactor mitigation of alumina-loaded microwave components.