Study of streamer size measurements using CCD camera system

We report on a study of correlation between readout pulses and lights of streamer produced in the glass resistive plate chamber (RPC) with six Ar gas mixtures (Ar/butane-silver/HFC134a). The streamer pulse produced by cosmic-ray are analyzed as a function of Ar/HFC134a mixing ratio using a digital oscilloscope. The streamer image due to the lights from the streamer is taken by using an image intensifier and a CCD camera. The average streamer size become larger linearly with increase Ar gas mixing ratio. The Ar/HFC134a ratio dependence of the charge and intensity were studied. The analysis of the light image of streamer might be useful for us to design the pickup pad width for the readout.