New module for channeling radiation simulation in Geant4

We present a new C++ module for simulation of channeling radiation to be implemented in Geant4 as a discrete physical process. The module allows simulation of channeling radiation from relativistic electrons and positrons with energies above 100 MeV for various types of single crystals. In this paper, we simulate planar channeling radiation applying the classical approach in the dipole approximation as a first attempt not yet considering other contributory processes. Simulation results are proved to be in a rather good agreement with experimental data.

First observation of ion beam channeling in bent crystals at multi-TeV energies

Planar channeling in bent crystals has been observed in LHC with multi-TeV proton beam in 2015. Two crystals, mounted on novel high-accuracy goniometers (one in the horizontal and one in the vertical plane), are integrated in the LHC collimation system, for studying the feasibility of the crystal-based collimation scheme. Using this experimental setup, tests with fully-stripped lead ion beams at both 450 Z and 6500 Z GeV were carried during dedicated LHC beam time. Planar channeling was observed for the first time with lead ions at these unprecedented energies surpassing by more than 1 order of magnitude the previous state-of-the-art for lead heavy ions and providing an important experimental basis for future applications of bent crystals in beam manipulations. The set of measurements performed to confirm this observation, as the local loss reduction in presence of channeling and the evidence of a deflected beam downstream of the crystal, are presented.

Изучение критического угла каналирования ионов активных металлов через тонкие пленки алюминия

The spatial distributions of ions (K+, Na+) passed through thin polycrystalline and single-crystalline Al films with the thickness from 180 to 600 Å and critical channeling angles have been studied. The ion energies have been varied within the range E0 = 10-30 keV. It has been shown that an increase in the energy of the primary ion beam leads to a decrease in the width of the maxima of the angular distribution, which is associated with a decrease in the critical channeling angle ψcr. It has been found that the value ψcr does not exceed 4-50 for axial channeling and 9-100 for planar channeling.

On the ionization loss spectra of high-energy channeled negatively charged particles

The ionization loss spectra of high-energy negatively charged particles which move in the planar channeling mode in a silicon crystal are studied with the use of numerical simulation. The case when the crystal thickness is on the order of the dechanneling length $$l_d$$ld is considered. It is shown that in this case the shape of the spectrum noticeably depends on $$l_d$$ld. The evolution of various characteristic parameters of the spectrum with the change of $$l_d$$ld is investigated. A method of the experimental determination of $$l_d$$ld on the basis of the measurement of the ionization loss spectrum is proposed.

Angular asymmetry of the nuclear interaction probability of high energy particles in short bent crystals

The rate of inelastic nuclear interactions in a short bent silicon crystal was precisely measured for the first time using a 180 GeV/c positive hadron beam produced in the North Experimental Area of the CERN SPS. An angular asymmetry dependence on the crystal orientation in the vicinity of the planar channeling minimum has been observed. For the inspected crystal, this probability is about $$\sim 20\%$$∼20% larger than in the amorphous case because of the atomic density increase along the particle trajectories in the angular range of volume reflection, whose dimension is determined by the crystal bending angle. Instead, for the opposite angular orientation with respect to the planar channeling, there is a smaller probability excess of $$\sim 4\%$$∼4%.

Energy dependence of the efficiency of high-energy negatively charged particle beam deflection by planar channeling in a bent crystal

The study of planar channeling of high-energy negatively charged particles in bent crystals was carried out. The value of the critical radius of planar channeling in the Doyle–Turner approximation for the atomic potential is determined. The dependence of the maximum angle at which a given fraction of beam particles could be deflected by means of planar channeling in a bent crystal on the particle energy was found. We identified the ideal parameters for the exploitation of planar channeling for negatively charged particle beam deflection by planar channeling in a bent crystal at current and future high-energy accelerators, e.g., SLAC, MAMI, ILC or muon colliders.