Simulations of a short Rayleigh length 100 kW FEL and mirror stability analysis

Abstract

A MW class free electron laser capable of delivering energy at the speed of light can improve ASCM defensive capability for Navy ships. Many design challenges must be overcome to make such a weapon possible. One such challenge is to maintain the power density on laser cavity mirrors at acceptable levels. The use of a short Rayleigh length to increase beam spot size at the mirror is studied as a possible solution to this problem. In this thesis, it is shown that by using a short Rayleigh length FEL, power densities at the mirrors are significantly reduced without causing a noticeable reduction in performance. For a short Rayleigh length FEL, the resonator cavity is sensitive to misalignment and vibration. The effect of mirror tilt due to vibrations is explored and the results show that as mirror tilt increases, FEL efficiency does decreases. However, a mirror tilt several orders of magnitude greater than currently achievable active alignment tolerances is required before the FEL efficiency is noticeably affected. In this thesis, it is shown that mirror tilt within achievable tolerance limits will not adversely affect the performance of a FEL.