5. Theoretical Physics (CSN4)

Fundamental and applied aspects of particle interaction with atomic strings

by Prof. Victor Tikhomirov (Research Institute for Nuclear Problems)

Aula Seminari (LNF)

Aula Seminari


Via Enrico Fermi, 40 00044 Frascati (Roma)
When a fast particle is moving close to parallel to a chain of atoms in a crystal or nanotube, particle scattering by atoms becomes strongly correlated, being described by effective Lindhard field, the strength of which can exceed 10^11 eV/cm, equivalent to tens of kilotesla. This field can be a source of both to new fundamental phenomena and various applications. Indeed, coherent effects in particle scattering by atomic string the scattering process much more intense than that in amorphous medium. The point is that all the typical angles, in that number the ones of particle incidence w.r.t. atomic strings, decrease with energy making the scattering by the latter more and more intensive and advantageous for applications. Among the latter are the halo scraping of superconducting accelerator beams, measurement of short living neutral charm and beauty hyperon magnetic and electric dipole moments, intense coherent radiation process, which can be used both for radiation production and study of Landau-Pomeranchuk effect, greatly enhanced in comparison with amorphous substance. These possible applications rise up a question of adequate treatment of particle scattering by atomic strings. A model of chaotic or random particle scattering by the latter is known since 70-th. However both the detail experimental and computer studies of the last decade have demonstrated that this simple and attractive model is considerably violated by the particle capture into the regime of channeling in the field of planes formed by atomic strings in crystals, especially at large thicknesses of the latter. In addition, the effect of multiple volume reflection in one crystal was predicted and observed, which also demonstrates the importance of the planar effects in axial crystal orientation. Also there is no doubt that for a neutral particle, which moves mainly along straight lines, one should not expect that the field exerted by a periodic lattice on the particle trajectory will change randomly. Thus, since the random particle scattering has the mentioned applications, however can not be completely realized in single crystals, we suggest to investigate the possibility to realize it in both arrays of oriented nanotubes and sets of oriented crystalline slabs. Though the choice of the thickness of the letter is a subject of further study, one can expect that, as the typical incidence angles are quite small at high energies, the optimal slab thickness will be large enough to overcome technological problems.