A fibre-optic UV system for H2SO4 production in aerosol chambers causing minimal thermal effects

A novel fibre-optic UV illumination system for sulphuric acid (H2SO4) production has been developed. The illumination system described in this paper provides sufficient ultraviolet light (UV) power while causing practically no thermal effect on the aerosol chamber (temperature variation <0.005 °C at full UV illumination). A similar thermal stability has not been achieved in other comparable experimental set-ups so far. The spectrum provided by the fibre-optic UV system corresponds to the UVB region, illuminates the chamber in a reasonably uniform way and is comparable to the ground level actinic flux. The UV system has been installed for the Cosmics Leaving OUtdoor Droplets (CLOUD) chamber experiments at CERN. Precise, easily-adjustable and reproducible concentrations of H2SO4 were generated by adjusting the UV light intensity. This paper gives an overview on the design of this new system as well as insights on its performance and application.

► UV system provides sufficient UV power while causing practically no thermal effect.
► Precise concentrations of H2SO4 are generated by adjusting the UV light intensity.
► Spectrum in the UVB region is comparable to the atm. ground level actinic flux.
► The system allows for reasonably uniform illumination inside the aerosol chamber.
► Thermal inhomogeneities and warm spots on inner surface of the chamber are avoided.