In 1960, R.E. Kalman published his famous paper describing a recursive solution to the discrete-data linear filtering problem. Since that time, due in large part to advances in digital computing, the Kalman filter has been the subject of extensive research and application, particularly in the area of autonomous or assisted navigation.
Hot-electron confinement can build up fields capable of accelerating ions up to MeV energies when an ultrashort 35-fs laser pulse at ∼2×1018 W/cm2 interacts with a small spherical target. Singly charged ions with different masses have similar energies. A simple phenomenological model describes how ultrashort and less-energy-consumptive pulses drive ions to MeV energies. The energetic and spatial-emission characteristics of protons, deuterons and oxygen ions released from water and heavy-water droplets of ∼15 μm in size was determined for this interaction scenario.
Deep dips in MeV ion spectra are obtained from water droplet targets irradiated by intense [(0.5-1.2) x 10(19) W/cm(2)] and ultrashort (35 fs) laser pulses. The existence of these dips is ascribed to the generation of a multielectron-temperature plasma, which is confirmed by our experiments. An existing fluid model based on hot-electron components with significantly different temperatures is consistent with the behavior we observe in the ion spectra of the femtosecond laser-driven interaction. The model provides a good simulation of the observed spectral dips and allows us to establish important parameters such as hot- and cold-electron temperatures and the respective electron density ratios. The result may be of interest for spectral tailoring of proton spectra in future applications of laser-generated proton beams.
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