Transition radiation from relativistic charged particles interacting with atomic strings in a crystal

The problem of transition radiation generated by relativistic particles incident on atomic strings in a crystal at a small angle is considered. Conditions are obtained under which the problem of transition radiation reduces to that of radiation generated by a collision with a filament-like target. It is shown that the angular distribution of transition radiation is symmetric with respect to the atomic-string axis.     

Spectral method in axial channeling theory

The energy quantization of transverse particle motion in continuous potentials of atomic chains and planes can occur when fast charged particles travel in crystals. In the proposed paper, the energy levels of electrons moving in the mode of axial channeling in a system of parallel atomic chains have been found (Si crystal [110] chains have been used as an example). The energy eigenvalues were determined numerically using the so-called spectral method, which shows itself to good advantage in the problem of the plane channeling of charged particles in crystals.     

Simulation of incoherent radiation of fast particles in an oriented crystal

Incoherent bremsstrahlung of high-energy electrons in a crystal is due to the thermal spread of atoms with respect to their equilibrium positions in the lattice. In this paper, an incoherent-radiation simulation procedure based on semiclassical formulas of bremsstrahlung theory is developed. A significant orientation dependence of the intensity of hard incoherent radiation is demonstrated for angles of electron incidence on a densely packed crystallographic axis (plane) that are close to the critical axial (plane) channeling angle. The simulation results are in good agreement with the experimental data.     

Incoherent radiation of fast electrons in a crystalline undulator

Incoherent radiation of high-energy particles in a crystal is caused by the thermal scattering of atoms relative to their equilibrium lattice positions. An earlier developed procedure for incoherent radiation simulation is applied to the case of electron motion in a sinusoidally curved crystal. The simulation results agree with the data of recent experiments at the Mainz Microtron (MAMI).     

On the Threshold of Long-Range Magnetic Order: UNi2/3Rh1/3Al and UCoAl Study

We present a comparative study of magnetism in UCoAl and UNi_2/3Rh_1/3Al single crystals. UCoAl is commonly believed to be an itinerant 5 f-electron metamagnet with B _c < 1 T with uniaxial anisotropy. Pressure and alloying effects on the ground state point to competing ferromagnetic and antiferromagnetic interactions to be responsible for the non-magnetic ground state. UNi_2/3Rh_1/3Al is a solid solution between an antiferromagnet (UNiAl) and a ferromagnet (URhAl) and may have a similar underlying microscopic mechanism of the non-magnetic ground state. Possible analogies between the two compounds are discussed.     

A calorimetric setup for measuring heat effects of processes in solutions

A calorimetric setup was developed to determine the heat effects of chemical processes in solutions with a sensitivity of ～10^?5 K and an accuracy of temperature control in the thermostat of better than ±0.001 K. The performance of the calorimeter was tested by measuring the heat effects of solution of 1-propanol (m = 0.02–0.08 mol/kg), potassium chloride (m = 0.01–0.73 mol/kg), and L-phenylalanine (m = 0.0008–0.03 mol/kg) in water at 25°C.     

On the motion of high-energy wave packets and the transition radiation by “half-bare” electron

The problem of the motion of high-energy wave packets combined of free electromagnetic waves is considered. It is demonstrated that the transformation of such packets to the packet of spherically diverging waves happens on long distances along the packet's motion direction, that substantially exceed the radiated wavelength. The transition radiation by the “half-bare” ultrarelativistic electron is considered. It is demonstrated that the transition radiation by such an electron on the targets located inside and outside the coherence length of the radiation process would be substantially different.     

Ionization energy losses of fast charged particles produced in matter

Ionization energy losses of an ultrarelativistic electron produced in matter are considered. The interference of the proper Coulomb field of the product particle and the electromagnetic wave that this particle emits is shown to be significant at impact-parameter values that make a dominant contribution to the ionization energy losses. The effect is shown to exert virtually no influence on the ionization energy losses of the particle.