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Vol 44, No 8 (2017)
- Year: 2017
- Articles: 7
- URL: https://journals.rcsi.science/1068-3356/issue/view/14111
Article
Irreproducibility of acoustic emission under cyclic irradiation of solids by an infrared laser pulse
Abstract
Acoustic emission (AE) caused by a stress wave in solid material samples with various thermophysical properties, i.e., copper, aluminum, and glass upon exposure to СO2 laser pulses is studied. It is found that the general AE picture (the AE signal arrival time, its amplitude, and others) is not reproduced during repeated experiments following one after another, which indicates irreversible local changes occurred in the material structure. The effect of the critical material energy density on the AE pattern during the laser exposure is demonstrated.
219-222
Orientation-patterned templates GaAs/Ge/GaAs for nonlinear optical devices. II. Investigation of properties
Abstract
GaAs/Ge/GaAs heterostructures in which GaAs layer lattices are rotated at a right angle in the substrate plane are studied. High quality of heterostructures is confirmed by X-ray diffraction and photoluminescence methods.
223-227
Increase in the efficiency of energy injection into discharge plasma and the luminous efficiency of luminescent lamps during high-frequency pumping
Abstract
It is experimentally justified for the first time that electrodeless induction pump of plasma of standard cylindrical luminescent lamps provides optimization of the high-frequency inductive–capacitive (HFI) discharge conditions. The acceptable frequency range and the effect of the capacitance between the inductor and plasma on the efficiency of resonant energy injection into discharge plasma are revealed. An increase in the luminous efficiency to 25% in the range of pump powers multiple of the lowest nominal power for the lamp under standard operating conditions is detected. Physics of the found phenomenon and the range of application of the power saving technology for electrodeless pumping of luminescent lamps with increased operation life are discussed.
228-231
Influence of defects on scintillation properties of oxyorthosilicate crystals Ce:Sc:LFS
Abstract
New scintillation crystals Ce:Sc:Li:LFS and Ce:Sc:Ca:LFS based on lutetium oxyorthosilicate are grown. Optical characteristics and the decay time of new scintillators are studied. For Ce:Sc:Ca:LFS crystals, it is shown that oxygen vacancies dominate in the energy transfer in the matrix transmission range of 3.46–6.26 eV. It is found that the high density of oxygen vacancies at the lower part of the Ce:Sc:Ca:LFS crystal leads to a decrease in the scintillation time to 22–26 ns.
232-237
Inverse problem in the LORD experiment and the possibility of diagnosing the radiation length of lunar regolith
Abstract
The inverse problem of reconstructing events in the LORD experiment is considered taking into account fuzzy information on the radiation length of lunar regolith over the lunar surface. It is shown that the solution of the inverse problem allows rather accurate diagnostics of the radiation length at various lunar surface points for a significant number of detected individual events.
238-242
Development of the device prototype based on the semiconductor–carbon nanotubes structure for optical radiation detection and study of its parameters
Abstract
A light-receiving device prototype based on the semiconductor–carbon nanotubes (CNTs) structure consisting of 16 cellular structured sensitive elements grown on the same substrate is developed. The topology of sensitive cells represents holes through metallization and insulator layers to the semiconductor from which the CNT array grows to the top metallization layer. The device prototype parameters are determined as follows: the effective wavelength range is within 400–1100 nm, the operational speed is no longer than 30 μs, the coefficients of peak sensitivity reached at wavelengths of 640 and 950 nm are 197 and 193 μA/W, respectively.
243-245
Effect of laser radiation parameters on the conductivity of structures produced on the polycrystalline diamond surface
Abstract
Graphitized structures are fabricated on the polycrystalline diamond surface using an excimer KrF (λ = 248 nm, τ = 20 ns) and a Ti:Al2O3 (λ = 400 nm, τ = 120 fs) lasers. It is shown that the conductivity of formed structures is independent of the energy density and the number of pulses per surface point in the case of the excimer laser, whereas such a dependence was observed for femtosecond pulses. The causes of the dependence of the conductivity of surface structures on laser irradiation parameters are discussed.
246-248