报告题目

Filament induced precipitation in a sub-saturated zone in a cloud chamber

报 告 人

Prof. See Leang Chin, COPL, Laval University and State key lab of high laser field physics

报告地点

物理楼中楼508

报告时间

11月26日 (星期二)上午10:00-11:00

联 系 人

龚旗煌 (62765884)

报告摘要

Using a 20 cm focal length lens, a 1 kHz, 800nm, 2 mJ/pulse laser beam was focused into a cloud chamber with a cold plate at -19C at the bottom and a compartment containing wet towels sitting on a perforated plate at the top. The temperature in the wet compartment was 19C. Filaments were generated at a height of about 1 cm above the cold plate where the relative humidity was about 70% (sub-saturated) and temperature about 4C. Turbulence was created throughout the chamber. In particular, two vortex ‘tubes’ were formed below the filament zone right above the cold plate, in agreement with simulation. Precipitation in the form of snow/ice was found below the filament. We believe that precipitation occurred in the super-saturated environment inside the vortex ‘tubes’. The latter was continually fed by the moisture and condensation nuclei such as HNO3, dust particles, etc. which were pushed from above by the turbulence. At the same time, large sized precipitates would be spun out of the vortices leaving behind room for further super-saturation and precipitation.