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

Abstract

Beam deflection due to axial channeling in a silicon crystal bent along the h111i 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 rad with about 30% efficiency. The contribution of hyperchanneled states of protons to the observed beam deflection was less than 2% according to simulation results.

Relaxation of axially confined 400 GeV/c protons to planar channeling in a bent crystal

“…[14] the potential of axial confinement for steering of positive beams was highlighted, despite that a strong feed in of particles into skew planar channels was recorded. Indeed, a total 90 % of deflection efficiency was reached due to SD accompanied by relaxation into skew planes.…”

“…Only recently, SD was experimentally observed for either positively [14] or negatively [15] charged particles, owing to the advent of a new generation of bent crystals [16,17], short enough to efficiently deflect high-energy particles up to the nominal bending angle of the crystal.…”

“…Apart from the result presented in Refs. [14,15], no other data collected with short crystals suitable for applications are available in the literature. As pointed out in [18], there is a need for deeper understanding about axial channeling for its exploitation in beam manipulation.…”

Deflection of MeV Protons by an Unbent Half-Wavelength Silicon Crystal

“…Many applications were also found in high-energy accelerator physics [4], i.e., the generation of electromagnetic radiation [5][6][7] and the realization of electron or positron [8] sources. In recent years, channeling in bent crystals opened up new schemes for beam manipulation and steering [9][10][11][12][13] of high-energy particle beams (a few hundred GeV energy). Beam-trajectory manipulation can be driven by either planar channeling or volume reflection (VR).…”

“…A second generation of experiments [10,12,16] employed thin crystals bent along the beam through anticlastic [17] or quasimosaic [18] effects. Such crystals considerably increased the deflection efficiency for channeling [1,9,11,19,20] because channeled protons underwent only some tens of channeling oscillation wavelengths in the crystal. Such crystals also led to the experimental demonstration of VR [10,16], which was predicted about 25 years earlier by Taratin and Vorobiev [21].…”