Angular distribution of radiation by relativistic electrons in a thin crystal

The results of theoretical investigation of angular distributions of radiation from a relativistic electron passing through a thin crystal at a small angle to the crystal axis are presented. The electron trajectories in crystal were simulated using the binary collision model which takes into account both coherent and incoherent effects at scattering. The angular distribution of radiation was calculated as a sum of radiation from each electron. It is shown that there are nontrivial angular distributions of the emitted photons, which is connected to the superposition of the coherent scattering of electrons by atomic rows (doughnut scattering effect) and the suppression of the radiation due to the multiple scattering effect (similar to the Landau-Pomeranchuk-Migdal effect in an amorphous matter). The orientation dependence of angular distribution of radiation is also analyzed

Silicon-based nanochannel glucose sensor

Silicon nanochannel biological field effect transistors have been developed for glucose detection. The device is nanofabricated from a silicon-on-insulator wafer with a top-down approach and surface functionalized with glucose oxidase. The differential conductance of silicon nanowires, tuned with source-drain bias voltage, is demonstrated to be sensitive to the biocatalyzed oxidation of glucose. The glucose biosensor response is linear in the 0.5-8 mM concentration range with 3-5 min response time. This silicon nanochannel-based glucose biosensor technology offers the possibility of high density, high quality glucose biosensor integration with silicon-based circuitry.Comment: 3 pages, 3 figures, two-column format. Related papers can be found at http://nano.bu.ed

Passage of positively and negatively charged particles through straight and bent nanotubes

Passage of high-energy charged particles through oriented crystals and nanotubes is investigated. It is shown that the particle passage through crystals and nanotubes may to be described in the same manner. The possibility of positively and negatively charged particle deflection by bent nanotube due to axial channelling phenomenon is demonstrated. Computer simulation results for relativistic charged particle beam passage through straight and bent nanotubes are presented

On the incoherent radiation of relativistic electrons and positrons in crystal

The incoherent bremsstrahlung of high energy electrons in crystal is caused by thermal spread of atoms from their equilibrium positions in the lattice. In the present article the simulation procedure for the intensity of incoherent radiation based on the quasi-classical formulae of the bremsstrahlung theory is developed. Substantial orientation dependence of the intensity of hard incoherent radiation is demonstrated under the angles of incidence of the particles to the crystallographic plane, close to the critical angle of planar channeling. The dechanneling effect leads to decrease of that orientation dependence. The results of simulation are in a good agreement with the experimental data.Некогерентне гальмівне випромiнювання електронiв високих энергiй у кристалi обумовлено термодинамiчними флуктуацiями вiдносно рiвноважних положень атомiв у гратцi. У цiєй статтi розвинуто процедуру моделювання iнтенсивностi некогерентного випромiнювання, яка основана на квазiкласичних формулах теорiï гальмівного випромiнювання. Показано значну орiєнтацiйну залежнiсть iнтенсивностi жорсткого некогерентного випромiнювання при кутах падiння частинок на кристалографiчну площину, якi близкi до критичного кута площинного каналювання. Ефект деканалювання приводить до зменшення цiєï орiєнтацiйноï залежнiстi. Результати моделювання знаходяться у гарному узгодженнi з даними експерименту.Некогерентное тормозное излучение электронов высоких энергий в кристалле обусловлено тепловым разбросом атомов относительно их равновесных положений в решетке. В настоящей статье развита процедура моделирования интенсивности некогерентного излучения, основанная на квазиклассических формулах теории тормозного излучения. Показана существенная ориентационная зависимость интенсивности жесткого некогерентного излучения при углах падения частиц на кристаллографическую плоскость, близких к критическому углу плоскостного каналирования. Эффект деканалирования приводит к уменьшению этой ориентационной зависимости. Результаты моделирования находятся в хорошем согласии с данными эксперимента

Long-wavelength transition radiation by relativistic electrons in a pre-wave zone

The spectral-angular density of electromagnetic energy flux through the small detector in the "pre-wave zone" caused by relativistic electron in "forward" direction in the case of normal electron transition through a thin metallic transverse-bounded target is investigated. We show that detected intensity can be very differ from the spectral-angular density of radiation as well it is measured in the "wave zone" as it is measured in "pre-wave zone" by infinite detector. This distortion is depended from the detector placing in the "pre-wave zone" and from the ratio between transversal size of target and effective transversal diameter of radiation formation region

Quantum and classical effects in scattering of relativistic electrons by crystal atomic string

The results of investigation of the relativistic electron scattering by a crystal atomic string at a small incident angle to its axis are presented. The possibility of the particle rainbow scattering and orbiting in this case is shown. It is shown that the Ramsauer-Townsend-type effect of the total cross-section decrease for elastic scattering of relativistic electrons by a crystal atomic string can take place at small values of particle incidence angles

The second Born approximation in theory of bremsstrahlung of relativistic electrons and positrons in crystal

The formulae for the cross section of bremsstrahlung by relativistic electrons and positrons taking into account the contribution of the second Born approximation are obtained. The dependence of the radiation cross section in the field of atomic plane on the sign of charge of the particle is considered

Polarization of transition radiation on some sorts of targets

The problem of transition radiation under impact of relativistic particles under small angle to the atomic string of a crystal is considered. The conditions under which the non-uniformity of the electron density along the string is not substantial are obtained. In this case the problem of transition radiation is reduced to the problem of the particle radiation on the thin fiber-like dielectric target. The formulae for the spectral-angular distribution of transition radiation under both regular and random collisions of a particle with the set of fiber-like targets are obtained. The radiation of the particle on a single atomic plane and on a set of planes in crystal is also considered