Fabrication of slow-wave structure by picosecond laser hybridizing with micro-milling

Abstract

The primary component of traveling-wave tube (TWT) is the slow-wave structure (SWS), which is distinguished by characteristics including a high aspect ratio (HAR), long periodicity, and an incredibly smooth surface. This structure is difficult to process and imposes higher requirements on microfabrication. Therefore, the study proposes a picosecond laser and micro-milling hybridizing processing technology (PLMM) for the processing of SWS. In this method, the picosecond laser was used for rough machining to the initial shaping of the SWS on oxygen-free copper (TU1). Subsequently, micro-milling was employed for the final shaping of SWS. The picosecond laser removes a substantial amount of TU1 and improve the machinability of the TU1. This reduces tool wear in subsequent micro-milling and improves the surface quality of SWS. This study research on the influence of picosecond laser parameters on the TU1 microgroove three-dimensional (3D) dimensions, surface morphology, and the machinability of TU1 material. Subsequently, a comparative experiment between PLMM and traditional micro-milling technology (MM) was carried out. Compared to MM, PLMM improves the surface quality of microgrooves. The chip accumulation at the bottom has been reduced and the average reduction in bottom surface roughness is 46.1 %. Additionally, PLMM reduces tool wear, enhancing tool life. This validates the superiority of PLMM. Finally, a 79-cycle SWS sample was successfully fabricated by PLMM with a width of 0.1 mm and an aspect ratio of 2.8. This research provides a promising direction for the machining of structures characterized by high aspect ratio, long periodicity, and incredibly smooth surface.