Volume Reflection Dependence of400  GeV/cProtons on the Bent Crystal Curvature

Abstract

The trend of volume reflection parameters (deflection angle and efficiency) in a bent (110) silicon crystal has been investigated as a function of the crystal curvature with 400 GeV/c protons on the H8 beam line at the CERN Super Proton Synchrotron. This Letter describes the analysis performed at six different curvatures showing that the optimal radius for volume reflection is approximately 10 times greater than the critical radius for channeling. A strong scattering of the beam by the planar potential is also observed for a bend radius close to the critical one.

Nuclear interactions at volume reflection: Perturbative treatment

“…The perturbative prediction for positive particles was confronted with the experimental data [14,32], both for the rate of inelastic nuclear interactions and for the angular divergence of the volume-reflected beam. The theoretical predictions are in a satisfactory agreement with the experimental data.…”

“…Then, averaging over the beam is equivalent to an unweighted averaging over . But such an average of function entering (32) gives zero due to identity…”

“…on the top of a potential barrier; its past history (which may as well include some amount of multiple scattering) is irrelevant. Let us estimate conditions at which this particle will be likely to lose a substantial fraction of its transverse kinetic energy after having rolled [32]; green-ITEP at 70 GeV, orientation (111) [2]; yellow-CERN PS at 13 GeV, orientation (110) [5]; red-PNPI at 1 GeV, orientation (111) [3]. Trianglesexperiment at CERN SPS, 180 GeV electrons and positrons, crystal orientation (111) [33].…”

“…On the other hand, thereat the dechanneling doubles, and it is unobvious whether the captured particle fraction will increase or decrease. Experimentally, it is established that at larger R, the increase of the volume reflection inefficiency with R slows down [32].…”

“…In principle, some sensitivity to 0 might emerge due to an imperfect averaging over the particle initial conditions and to the impact of the second term in Eq. (32). To check this possibility, let us estimate the range of variation of the argument under the variation of 0 in an interval 0 $ 2 rad.…”