BEBC model during cooling

The observation window in the center of the dome of the chamber body can be seen with a television camera in place. The black cylinders around the dome were used for connecting electrical control circuits and for the hydrogen evacuation lines. Images 216, 216_a and 216_b.6.68 show one of the first tests ever made of the use of laser beams in a bubble chamber. The beam crosses the chamber at right angles to the axis of the camera and the black region in the centre is due to a thermocouple attached to the camera lens. These tests investigated the possibility of using crossing laser beams to fix the fiducial marks (the distance measuring reference points) in a chamber. A continuous emission argon laser (4880 Â) built at the Institut fur Angewandte Physik, Heidelberg, was used.