Time-resolved Rayleigh scattering measurements of methane clusters for laser-cluster fusion experiments

Abstract

<jats:p>We present a time-resolved analysis of Rayleigh scattering measurements to determine the average size of methane clusters and find the optimum timing for laser-cluster fusion experiments. We measure Rayleigh scattering and determine the average size of methane clusters varying the backing pressure (<jats:italic>P</jats:italic><jats:sub>0</jats:sub>) from 11 bar to 69 bar. Regarding the onset of clustering, we estimate that the average size of methane clusters at the onset of clustering is <jats:italic>N</jats:italic><jats:sub>c0</jats:sub>≅20 at 11 bar. According to our measurements, the average cluster radius <jats:italic>r</jats:italic> follows the power law of <jats:italic>r</jats:italic>∝<jats:italic>P</jats:italic><jats:sub>0</jats:sub><jats:sup>1.86</jats:sup>. Our ion time-of-flight measurements indicate that we have produced energetic deuterium ions with <jats:italic>kT</jats:italic> = 52±2 keV after laser-cluster interaction using CD<jats:sub>4</jats:sub> gas at 50 bar. We find that this ion temperature agrees with the predicted temperature from CD<jats:sub>4</jats:sub> clusters at 50 bar with <jats:italic>r</jats:italic> = 14 nm assuming the Coulomb explosion model.</jats:p>