NEW RESULTS FROM THE CERN-SPS BEAM DEFLECTION EXPERIMENTS WITH BENT CRYSTALS

Results from five distinct bending experiments performed recently in t he 1-18 beam at CERN are presented. Firstly, deflection of a positive pion beam at 200 GeV/c is compared to the ''standard'' 450-GeV/c proto n beam for a bending angle of 3.1 mrad along the (111) plane in a 50 m m silicon crystal. Second, deflection of negative pions at 200 GeV/c i s investigated for the same crystal, for incidence along the (111) pla ne as well as the (110) axis. Small deflection effects are seen, but n o negative particles are bent through the full bending angle of the cr ystal. Third, the first results from beam deflection at high energy us ing a germanium crystal are shown. Slightly higher deflection efficien cies than for silicon are seen for large bending angles, but significa ntly smaller than expected for such a crystal with higher atomic numbe r. Fourth, deflection efficiencies using a strongly irradiated silicon crystal have been measured for the first time, and a small reduction in efficiency is seen in the irradiated region. Finally, deflection of positive particles using axial alignment of a bent silicon crystal ha s been investigated at 450 GeV/c. Qualitatively similar behaviour as i n previous experiments at 12 GeV/c is seen; the beam splits into sever al beams corresponding to the different planes, and even weak planes a re observed.