The development of a simulation device for the nucleation in the primordial solar nebula.

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In order to investigate the mechanism of the nucleation of solid particles and its role in the evolution of the solar system materials, we have developed an experimental apparatus that simulates the non-equilibrium homogeneous nucleation from simple molecules to polymerized clusters. Condensable gas species are collimated in molecular beams and introduced into a high-vacuum chamber. A pulsed beam of the controlled environmental gas supplied from another vacuum port crosses the previous molecular beams. This method makes the necessary conditions of the cluster formation fulfilled in a localized area of the chamber and suffices the quantitative analysis of the nucleation and condensation. We have obtained the following results during this three-year grant-in-aid project(1) We have built a system that enables the cluster formation in a clean environment A vibration-free ultra-high vacuum system have been installed.(2) We have modified a gas effusion device for high vacuum and high temperature to truncate a mili-second small pulses out of the high-temperature gas mixture. The test of the device was satisfactory.(3) We have developed a TOF mass spectrometer for an in-situ analysis of the polymerized cluster that formed by multiple collisions.(4) In order to improve the emittance from the excimer laser device purchased with a Heisei 8 grant-in-aid, we have obtained a necessary local energy flux with a use of focal lens of high transmission.(5) Following the above developments, we have performed a laboratory experiment of the non-equilibrium homogeneous nucleation. We were able to observe clusters of low mass range, but polymerized clusters of high mass range were too small in abundance to be detected. A higher laser energy flux and a much larger mass flux of the condensable gas from the effusion device will be necessary to accomplish this task..