Estimation of the Effects of Spurious Modes in Linear Microwave Systems Using a Monte Carlo Algorithm

The effects of spurious modes on the performance of microwave systems is studied using a Monte Carlo algorithm based on randomized mode mixtures. A high power microwave launcher for the heating of fusion plasmas is used as an example, but the method can be applied to arbitrary linear optical systems. The linearity allows to simulate the beam propagation only for the pure modes while the actual Monte Carlo analysis is done using linear combinations of these fundamental solutions. This significantly decreases the calculation time. The results are histograms for truncation losses on mirrors, peak power densities and the overall efficiency. These results allow the definition of safety margins when designing high power millimeter wave components. In addition, a worst-case prediction for reduction of the overall efficiency due to spurious modes can be confirmed by the Monte Carlo analysis.