Abstract
In this review work, the passage of charged and neutral beams through dielectric capillary guides is described from a uniform point of view of beams channeling in capillaries. The motion of beams into the hollow channels formed by the inner walls of capillaries is mainly determined by multiple small-angle scattering (reflection) and can be described in the approximation of surface channeling. It is shown that the surface interaction potential in the case of micro- and nano-capillaries is actually conditioned by the curvature of the reflecting surface. After presenting the analysis of previously performed studies on X-rays propagation into capillaries, which is valid for thermal neutrons, too, the surface channeling formalism is also developed for charged particle beams, in particular, moving in curved cylindrical capillaries. Alternative theories explaining experimental results on the beams passage through capillaries are based on simple thermodynamic estimates, on various diffusion models, and on the results of direct numerical simulations as well. Our work is the first attempt to explain the effective guiding of a charged beam by a capillary from the general standpoint of quantum mechanics, which made it possible to analytically explore the interaction potential for surface channeling. It is established that, depending on the characteristics of a projectile and a dielectric forming the channel, the interaction potential can be either repulsive or attractive; the limiting values of the potential function for the corresponding cases are determined. It has been demonstrated that the surface channeling behaviour can help in explaining the efficient capillary guiding for radiations and beams.
Highlights
Channeling is usually associated with the passage of beams of charged particles in crystals oriented along the direction of particle motion, when the angle between the particle momentum and selected axis of the crystal does not exceed a certain fixed value determined by the critical angle [9,10].(To describe a deep penetration of charged particles into the crystals [11,12,13,14], J
After presenting the analysis of previously performed studies on X-rays propagation into capillaries, which is valid for thermal neutrons, too, the surface channeling formalism is developed for charged particle beams, in particular, moving in curved cylindrical capillaries
On the contrary, when the particle is reflected by the crystal surface, in order to determine the interaction potential with an amorphous medium, even at the small-angle scattering with respect to the medium surface, one should count the contribution by all medium atoms
Summary
Channeling is usually associated with the passage of beams of charged particles in crystals oriented along the direction of particle motion (see in [1,2,3,4,5,6,7,8]), when the angle between the particle momentum and selected axis (or plane) of the crystal does not exceed a certain fixed value determined by the critical angle [9,10] ( known as Lindhard angle). It becomes obvious that the possibility of manX-ray radiationipulating particle beams in a wide spectrum of energies and impulses by means of channeling gives rise to a whole class of applied problems exploiting the effect of particle channeling in the external electromagnetic field. The first in this series that should be mentioned is the possibility of effective deflection of a beam of charged particles in bent crystals [28,29]. In combination with the existing theories and models of transmission of particle beams by dielectric capillaries, the developed theory of surface channeling of particles along strongly curved reflective surfaces will serve as an additional factor for a more complete and complex description of the capillary guiding phenomenon
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