Steering efficiency of a ultrarelativistic proton beam in a thin bent crystal

Abstract

Crystals with small thickness along the beam exhibit top performance for steering particle beams through planar channeling. For such crystals, the effect of nuclear dechanneling plays an important role because it affects their efficiency. We addressed the problem through experimental work carried out with 400 GeV/c protons at fixed-target facilities of CERN-SPS. The dependence of efficiency vs. curvature radius has been investigated and compared favourably to the results of modeling. A realistic estimate of the performance of a crystal designed for LHC energy including nuclear dechanneling has been achieved.

Observation of Quasichanneling Oscillations

“…These oscillations were treated numerically in a recent study [1] using the CRYSTAL simulation code [9,10]. Like channeling oscillations, this leads to peaks in the deflection spectrum observed from the crystal, but in this case not evenly distributed, and here arising from overthe-barrier motion, see figure 2.…”

A model for the interaction of high-energy particles in straight and bent crystals implemented in Geant4

“…As stated in Ref. [76], the discrepancy must be ascribed to the lack of knowledge of the exact density distribution between atomic planes. An important feature of Geant4 is its capability to evaluate the number of particles which suffer nuclear interaction or are scattered at large angles.…”

“…Experimental data and DYNECHA-RM++ simulations are taken from Ref. [76]. As the critical radius R = R c is approached, the discrepancy between experimental data and simulation increases.…”

Experimental evidence of independence of nuclear de-channeling length on the particle charge sign

“…Measurements proved the capability of channeling for manipulation of positively [4] and negatively [5,6] charged particle beams from MeV [7] up to hundreds of GeV [8,9], and for the generation of intense electromagnetic radiation from sub-GeV [10,11] to hundreds-GeV electron beams [12]. Moreover, channeling effects were exploited for steering [13] …”

“…In the literature [4,21,26], the channeled-particle fraction f (+) ch at depth z in the crystal holds…”