Study of the avalanche to streamer transition in the glass RPC exited by   UV light
  A small glass RPC filled with Ar/Isob./Freon mixture has been exposed to a UV laser light. Avalanche and streamer regimes of discharge were reached in a fixed region of the RPC exited by the UV. A dependence of avalanche to streamer transition process on the laser beam intensity and on the applied high voltage was studied. Two types of the streamer signal have been observed. Using a CCD TV camera, pictures on multi-streamer propagation over RPC were obtained. 
V. Ammosov, V. Gapienko, A. Kulemzin, A. Semak, Yu. Sviridov, V. Zaets   (Institute for High Energy Physics)