Characterization of the quartz surface quality with $\beta$-source

We present a method for characterizing the quality of the Cherenkov quartz radiator. It is based on the scanning with $^{90}$Sr radioactive source (standard deviation is 1.17 mm) of the radiator surface and measurements of the Cherenkov light rate and amplitude, detected by the PMT attached to the quartz bars. This experimental data have been compared with a Monte-Carlo simulation which repeats the same experimental configuration. This method gives an upper estimate of the radiator parameters which are related to two different quantities: (1) probability of the total internal reflection; (2) ineffective area in the corner of the quartz bar.