Observation of “volume reflection ” effect in

Strong effect of beam coherent scattering (“reflection”) in a field of bent crystal is observed in crystal collimation experiments performed with heavy ions and protons at RHIC and started at Tevatron collider. Detailed simulation using Monte Carlo code CATCH is done in order to understand the observations and relate them to the physics of beam coherent scattering in crystal. A.M. Taratin and S.A. Vorobiev predicted the effect of beam «volume reflection » in bent crystals in 1987. The presented data is the first manifestation of this new physical phenomenon in experiment. Bent-crystal technique [1] is well established for extracting high energy beams from accelerators. It was successfully applied at up to world highest energy [2], and simulations were able to predict the results correctly [3]. Experiments at IHEP Protvino [4] have demonstrated that this technique can be quite efficient: 85 % of the beam have been extracted using a short (2 mm) Si channeling crystal with bending of about 1 mrad, with intensity of the extracted 70-GeV beam up to 3×1012 protons per spill. Much of the IHEP physics program relies on crystal channeled beams used regularly since 1989 [5]