Electromagnetic pulse generation in laser-proton acceleration from conductive and dielectric targets

Abstract

Laser-plasma interactions at high intensities are often accompanied by emission of a strong electromagnetic pulse (EMP) interfering with particle detectors or other electronic equipment. We present experimental evidence for significant differences in noise amplitudes in laser-proton acceleration from aluminium as compared to mylar target foils. Such dissimilarities have been consistently observed throughout two series of measurements indicating that, under otherwise identical conditions, the target conductivity is the principal parameter related to EMP generation. In addition, the lateral size of the target foils correlates with the absolute noise levels. A frequency analysis combined with numerical simulations allows for an identification of several sources of radiofrequency emission in the MHz-GHz regime. Further, the temporal evolution of single frequencies on the nanosecond scale provides information on distinct excitation mechanisms.