Quantitative Analysis of Valley–Orbit Coupling in Germanium Doped with Group-V Donors

Semiconductors - The wave functions of electrons localized at P, As, and Sb shallow donors in Ge are calculated in the envelope function approximation taking into account valley–orbit...     

The influence of the diffusion cooling on the noise band of the superconductor NbN hot-electron bolometer operating in the terahertz range

Results of an experimental study of the noise temperature (T _n ) and noise bandwidth (NBW) of the superconductor NbN hot-electron bolometer (HEB) mixer as a function of its temperature (T _b ) are presented. It was determined that the NBW of the mixer is significantly wider at temperatures close to the critical ones (T _c ) than are values measured at 4.2 K. The NBW of the mixer measured at the heterodyne frequency of 2.5 THz at temperature T _b close to T _c was ~13 GHz, as compared with 6 GHz at Tb = 4.2 K. This experiment clearly demonstrates the limitation of the thermal flow from the NbN bridge at T _b ? T _c for mixers manufactured by the in situ technique. This limitation is close in its nature to the Andreev reflection on the superconductor/ metal boundary. In this case, the noise temperature of the studied mixer increased from 1100 to 3800 K.     

Determination of the separation factor of lithium isotopes in ion exchange

The isotopic equilibrium between the solutions of lithium salts (LiOH and LiCl) and SBS, KU-2, and Dowex-50 cationites is investigated. It is shown that, in the first place, the Li⁷ isotope was concentrated in the solution in all the cases which were investigated; in the second place, there is a dependence of the separation factor value on the nature of the cationite; in the third place, in 1 N to 5 N solutions of LiCl, the value of a does not depend on the concentration of the solution.In conclusion, we extend our sincere thanks to Professor G. K. Boreskov for his advice and continued interest in the work.     

Laser heating as a technique for manufacturing standard specimens during testing by the magnetic-powder method

Techniques for creating internal cracks in calibration blocks for the magnetic-powder flaw identification method during nondestructive testing are considered. A technology for producing internal cracks in steel specimens subjected to laser heating and external mechanical action has been developed. The degree of opening of a created crack was evaluated by means of a metallographic instrument. The advantages of the proposed method are shown.