Dechanneling Length Research Articles

Channeling in single-wall nanotubes: Possible applications

The relevant potentials are calculated and used to investigate the trajectories and various characteristics of axial channeling of high-energy positively charged particles in the recently discovered single-wall nanotubes (SWNTs). The application of SWNTs in high-energy physics, specifically, in future colliders, is discussed, in view of the fact that the dechanneling length in SWNTs is much longer than in single crystals.

Investigation of the electron channeling by means of induced electronuclear reactions

The results of an experimental study of the thickness dependence of the yield of the electronuclear reaction Si 28 (e, e′3pn)Na 24 induced by 270, 1000 and 1200 MeV electrons impinging on a silicium crystal along the 〈111〉 axis are presented. The experimental data are compared with results obtained by simulation. A direct connection between the number of channeled electrons and the nuclear reaction yield is pointed out. The dependence of the dechanneling length on the energy of impinging electrons has been observed.

High energy proton deflection in bent single crystals

Abstract Fermilab experimental data on dechanneling length measurements in a bent crystal are well described by a simple model. The dechanneling length is found to be directly proportional to the potential well depth in a bent crystal. The same model could explain the temperature dependence. Optimum curvature and efficiency limit in this model are found as functions of the deflection angle.

Resonance Dechanneling in Quasiperiodic Superlattices

AbstractPlanar dechanneling of ions is investigated in strained‐layer quasiperiodic superlattices with two types of layers, A and B, arranged according to the recurrent Fibonacci rule. It is shown that in quasiperiodic superlattices with τlA + lB < λ (where lA and lB are the respective thicknesses of the layers A and B, λ is the golden section, λ the wavelength of transverse particle oscillations in the channel) the dechanneling is a resonance process. Angular dependences of the dechanneling length are asymmetric and stepwise. The resonance dechanneling in strained‐layer quasiperiodic superlattices may be used for the determination of elastic distortions even in the case when the layer thicknesses are as small as lA, lA < λ. This feature is absent in the case of periodic superlattices.

Channeling of Antiprotons and Electrons

AbstractBased on the diffusion model, the channeling fraction of antiprotons and electrons as a function of penetration depth is studied numerically. According to the calculations, the dechanneling length of antiprotons is of the same order of magnitude as that of electrons. It is found that, though the dechanneling length of antiprotons is much smaller than that of protons, a definite portion (≈ few %) of axially channeled antiprotons has anomalously large dechanneling length.

Particle channeling length in crystals

An effective channeling length is introduced as a characteristic parameter for processes related with the channeling of particles in thick crystals. It is shown that the effective length is much larger than the dechanneling length.

Channeling radiation emitted from planar channeled electrons at 350 MeV in silicon crystal

Spectra of the channeling radiation emitted by 350 MeV (HO)-planar channeled electrons in silicon crystals were observed and the dechanneling length was obtained as 31 μm. A photon spectrum, only from channeled electrons, deduced from observed aligned and random photon spectra, was compared with that calculated quantum mechanically, taking account of the experimental conditions and the efficiency of the photon detector. The result showed good agreement for the absolute intensity.

Computer simulation of the dechanneling of axially channeled electrons in the single-string approximation

Abstract A dechanneling model for axially channeled electrons in a single string approximation is proposed. Consideration is given to dechanneling due to multiple scattering by the atomic string electrons and by the thermal vibrations of nuclei. The model has been used to calculate the electron dechanneling length as a function of injection angle θ relative to the tungsten atomic string ⟨111⟩ at an electron energy of 1 GeV.

Multiple scattering of electrons at axial channeling

Abstract A classical theory of axial channeling in thick crystals is formulated and the Fokker-Planck kinetic equation is obtained. It describes the diffusion of the beam of axial channeling negative particles over the transverse energy and angular momentum due to the inelastic scattering from electrons and the thermal vibrations. Estimates of the dechanneling length of ultrarelativistic electrons are made.

Passage and radiation of relativistic channeled particles

Abstract The kinetic equation of the Fokker-Planck type for channeled positrons and electrons is discussed. The solution of the equation with the inclusion of the main dechanneling factors is obtained and the dechanneling function is calculated. At E ∼ 1 GeV the dechanneling length is of the order of several hundreds of microns for positrons and tens of microns for electrons. This indicates that in heavy elements the channeled electrons will lose a considerable part of their energy due to Kumakhov radiation.

Transition of axial to planar channeling

Abstract The transition from axial to planar channeling involves an angular region, where dechanneling is maximum. It is caused by the intermediate strong effect of the discrete atomic structure of lattice planes on the guidance of charged swift projectiles. The width of the transition region depends on the initial axial direction and the chosen tilt plane. Experimental evidence is presented in the change of the energy loss spectra of 100-MeV sulfur ions transmitted through 24-μm silicon along (110) with tilt in {112}. Computer simulations are performed with 40-MeV sulfur ions through 4.8-μm silicon along (110) with tilt in {112}. An universal analytical relation is derived to calculate the minimum tilt angle required for planar channeling to be effective. The relation is checked by comparison with a wide variety of experimental results. Finally, the experimental dechanneling length of 100-MeV sulfur ions transmitted through silicon along {112} planes is found to be about 13 μm, in agreement with estimate...

Multiple Scattering and Planar Dechanneling in Silicon and Germanium

The dechanneling of MeV protons from the planar channels of silicon and germanium is investigated. The backscattering technique and transmission technique for measuring the dechanneling rate are compared and show good agreement. The data are treated in the framework of a diffusion model which describes the observed energy dependence of the dechanneling length. Various physical mechanisms which contribute to the diffusion are discussed and estimated. Direct measurements of the multiple scattering in the channels are compared to estimates of the diffusion constants.