High-efficiency deflection of high-energy negative particles through axial channeling in a bent crystal

Deflection due to axial channeling in a silicon crystal bent along the [111] axis was observed for 150 GeV/c negative particles, mainly π− mesons, at one of the secondary beams of the CERN SPS. The whole beam was deflected to one side with the efficiency of about 90% and with the peak position at the bend crystal angle α=43 μrad. The deflection occurs mainly due to doughnut scattering of above-barrier particles by the atomic strings of the crystal. However, due to a high probability of particle recapture into bound states with the atomic strings their contribution to the deflection should be about 15% for our case according to simulation results

High-Efficiency Deflection of High-Energy Protons through Axial Channeling in a Bent Crystal

Beam deflection due to axial channeling in a silicon crystal bent along the [111] axis was observed with 400  GeV/c protons at the CERN Super Proton Synchrotron. The condition for doughnut scattering of protons by the atomic strings of the crystal was attained. Such a condition allowed one to observe a beam deflection of 50  μrad with about 30% efficiency. The contribution of hyperchanneled states of protons to the observed beam deflection was less than 2% according to simulation results