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New LuScSiO5 crystals with intrinsic luminescence are grown by the Czochralski method. Pulsed cathodoluminescence spectra of new scintillators and their scintillation decay times are studied for the first time. Using 662-keV γ-rays from the 137Cs source, amplitude distributions of the number of luminescence counts (so-called photopeaks) are measured for new crystals. It is shown that the light yield of LuScSiO5 crystals is 13 500 photons/MeV.

Ce3+, P5+, Ca2+, and Zn2+ ion doped Gd2SiO5 crystals are grown by the Czochralski method. The pulsed cathodoluminescence spectra, light yield, and scintillation time under gamma excitation are studied. It is first shown that additional doping with P5+ phosphorus ions decreases crystal cracking in the fabrication of scintillation elements, and increases the scintillation light yield in comparison with commercial Gd2SiO5:Ce3+ crystals.

It is found that the emission intensity of the 2+ band system of the N2 molecule (C3Πu → B3Πg transition) under electron bombardment of pyrolytic aerogel SiO2 in air at atmospheric pressure is 40–70% higher than that in the case of bombardment of aluminum under the same conditions. The dependences of the emission intensity at 337 nm (0-0 vibrational transition in the 2+ band system of the N2 molecule) on the target temperature in the range of 30–60°C are different for the aluminum and SiO2 targets, which indicates different excitation mechanisms of the N2(C3Πu) state. It is suggested that when the SiO2 target is bombarded, the N2(C3Πu) state is excited not only by direct collisions with the electrons of the primary beam and secondary electrons, but also by the energy transfer from SiO2 excitons and conduction electrons to N2 molecules upon their contact with the SiO2 surface.

Scintillation single crystals and polycrystals of gadolinium oxyorthosilicate Gd2SiO5: Ce3+,Ca2+ are grown by the Czochralski method. The effect of the doping ion concentration on pulsed cathodoluminescence spectra, light output, and scintillation time under gamma excitation is studied. It is shown that the scintillation time decreases with increasing both Ce3+ and Ca2+ ion concentrations.

We study the effect of pressing at a pressure of 1.6 MPa on the photoluminescence (PL) and pulsed cathodoluminescence (PCL) spectra of high-purity fumed silica powder at room temperature and in ambient air. PL is excited by laser radiation at 193 nm, and PCL is excited by electron beam with particle energies of 100–300 keV. Luminescence spectra of fumed silica are changed substantially after pressing. The relative intensity with respect to the luminescence intensity at 300 nm of both PL and PCL in the range 300–450 nm increase after pressing, while the relative intensity of both PL and PCL in the range 260–290 nm decrease. The pressing-sensitive luminescence band in the range 300–450 nm may be related to the defect composed of two facing surface sylilenes. The band in the range 260–290 nm is related to the other surface-related emitting center.

For the first time observed that at the initial stage of a high-current discharge, a low-divergence short ( 1 keV) with an energy of 0.6 mJ and an average power of 0.3 MW. The radiation propagates parallel to the surface in the anode direction with the angle divergence

We study the luminescence decay times of Ce3+: Lu2SiO5 scintillator, co-doped with Sc3+ and Li+ ions, under the direct photoexcitation of Ce3+ ions at 337 nm and excitation by a pulsed electron beam with energies of 100 – 300 keV. The cathodoluminescence (CL) and photoluminescence (PL) decay times of studied sample are equal within the experimental error. Two emission bands are found: in the range of 370 – 480 nm (“high-energy band”) and 500 – 570 nm (“low-energy band”). The highenergy emission band has the decay times ∼40 ns. The low-energy emission band has the maximum decay time ∼60 ns at 545 nm. The observed results show that the transport stage of Li:Sc:Ce:Lu2SiO5 scintillation mechanism is not affected by a high negative space charge and high density of electronic excitations provided by the high-power electron beam.

New scintillation orthovanadate crystals Ca:GdVO4 and Ca:YVO4 featuring intrinsic luminescence are grown. The spectra of pulsed cathodoluminescence of new scintillators and their luminescence decay time are studied. Using γ-rays with an energy of 662 keV from the 137Cs source, total absorption spectra (so-called photopeaks) for new orthovanadate crystals are measured. It is shown that the light yield of Ca:YVO4 and Ca:GdVO4 crystals is 28100 photon/MeV and 14000 photon/MeV, respectively.

The dynamics and emission characteristics of pulsed breakdown over a ferrite surface at a current amplitude of 270 kA and current rise time of 80 ns were studied experimentally. It is shown that the characteristic transverse size of the discharge region in visible radiation is ~3 mm, while that in vacuum UV (VUV) radiation is ~200 μm. The duration of the VUV pulse with an average power of ≈0.275 GW is about 80 ns.

We study the room-temperature (RT) pulsed cathodoluminescence (PCL) spectra of a set of pure synthetic (both crystalline and amorphous) silicon dioxide samples. We show that the PCL spectra of all samples (both amorphous and crystalline) possess bands with intensity maxima in the region of 487 – 500 nm (2.54 – 2.48 eV). These bands are the most intense in the PCL spectra of disordered materials. We investigate the annealing behavior of RT PCL spectra of the crystalline and amorphous samples. Annealing has no significant effect on this emission. We demonstrate that the surface area of the material plays no role in the emission of PCL bands at 415 and 490 nm in the spectra of α-quartz single crystal and crystalline powder with grain sizes of 10 – 100 μm. Our results show that the bands in the region of 2.5 eV are the universal property of all synthetic pure SiO2 samples. The nature of the SiO2 emission band in the region of 2.5 eV is not clear; we discuss two possible explanations. The first one is based on considering the intrinsic emission due to self-trapped exciton (STE) decay with the transient O-O (oxygen–oxygen) bond formation. The second one is based on the role of Li ions in the emission process.

We study the room-temperature (RT) pulsed cathodoluminescence (PCL) spectrum of a high-purity synthetic α-quartz single crystal. The spectrum consists of two wide bands with intensity maxima at 415 and 490 nm (2.99 and 2.53 eV). The band at 490 nm (2.5 eV) is polarized in the XY crystal plane (perpendicular to the third-order symmetry axis) and possesses a structure with three peaks at 480±2, 487±2, and 493±2 nm (2.58±0.01, 2.55±0.01, and 2.52±0.01 eV). The intensities of the peaks at 480±2 and 493±2 nm increased with increase in the irradiation dose up to 45 kGy. Peaks are equidistant at the energetic scale. The energy separation between the peaks Δ = 0.03 ± 0.01 eV is equal in order of magnitude to energies of Li x O y molecular vibrations and to the energy of the optical phonon in α-quartz. We propose an explanation of the experimental data obtained. According to this explanation, the structure observed may be attributed to the amplitude modulation of the quartz 2.5 eV emission band by the crystalline electric fields on frequencies of optical phonons. The nonequilibrium phonons may arise during the electron-beam irradiation.

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.

Optical and luminescence characteristics of Lu2+2ySi1-yO5+y (LFS) scintillation crystals are studied before and after irradiation with doses to 45 Mrad from a 60Co source. LFS crystals were doped with Ce3+, Sc3+, Ca2+, and Y3+ ions with various concentrations. The dependence of the radiation resistance of LFS crystals on Ce ion concentration is detected. For the crystal of composition Ce:Sc:Ca:Y:LFS, it was found that its optical transmission (OT) and pulsed cathodoluminescence (PCL) spectra before irradiation do not differ from the spectra measured after irradiation with a dose of 45 Mrad within experimental error. The nature of the radiation resistance of rare-earth lutetium oxyorthosilicates (LFS) is discussed.

The spectra of pulsed cathodoluminescence (PCL) and optical transmission (OT) of crystals grown from Lu3.01−xYxAl4.99O12 melts doped with Cr3+, Ce3+, and Sc3+ ions before and after irradiation with gamma radiation of a 60Co radioactive source are studied. The gamma radiation dose absorbed by samples was 45 Mrad. The maximum gamma-radiation-induced absorbance in the range of 525–700 nm was 0.48 cm−1. Changes in the PCL and OT spectra of all samples after irradiation were detected. It was found that the relative intensity of Cr3+ bands increased after irradiation in relation to the Ce3+ band intensity by a factor of 1.6–8; the OT spectra of all samples after irradiation lost specific features and became identical. The results obtained are qualitatively explained. According to the explanation, the induced absorption is controlled first of all by optically active Frenkel defects formed after irradiation, which include an oxygen vacancy and an interstitial oxygen ion.

To study processes in a high-current vacuum diode with a cathode in the form of a single pin made of a metallic wire 20–30 μm in diameter, the method of high-resolution projection X-ray radiography with an X-pinch as a source has been used. A strong inhomogeneity of the energy contribution to the wire has been revealed. The smallest energy release has been observed near the end of the pin, where the electric field strength is maximal. Hard X rays, as well as the ejection of matter from the anode, have been observed, indicating the generation of an electron beam with the parameters characteristic of explosive electron emission in the diode with this configuration. The data obtained indicate complex processes occurring in the diode. Possible scenarios of their development have been considered.

Effects caused by fast laser frequency sweeping across absorption lines are investigated. Oscillations in the time dependence of intensity of radiation generated by the medium, which are caused by beats between oscillations at variable excitation frequency and constant eigenfrequencies, are discovered. The time intervals between local maxima of the oscillations are inversely proportional to the difference between the eigenfrequency of the atomic oscillator and the instant frequency of the external radiation. The method of using fast frequency sweeping for determining indices of absorption at high optical densities (k 0 z ~ 100) is proposed.

Graphite cathode surface erosion in the pulseless negative corona discharge in air is studied in the point-plane electrode configuration at a pressure of 0.3–1 atm. The formation of erosion craters in the form of orderly arranged erosion cells shaped as regular polygons on the cathode tip is detected. The cell size coincideswith the negative glow diameter of the discharge torch. The formation of orderly arranged cells is associated with features of the discharge torch dynamics in the pulseless discharge type.

We consider the possibility of using spectroscopy for the diagnostics of optically dense media by recording the time-dependent intensity of transmitted light under the action of a laser field with fast-changing frequency. We compare advantages of this approach with the traditional technique based on the Beer–Bouguer–Lambert law. Reasonably accurate extinction measurements of the order of k(ω 0)l ≈ 102 and greater are realizable with the help of tunable diode lasers.

Decay times of pulsed cathodoluminescence (PCL) of Lu2SiO5 (LSO) and Lu1.8Y0.2SiO5 (LYSO) crystals are compared with decay times of luminescence of similar crystals, occurring upon exposure to gamma-radiation. It is found that decay times of PCL and gamma-luminescence of corresponding crystals are identical within experimental error.

The intensities of lines IQ(1) and IQ(3) of the vibrational transition v′ = 0 → v″ = 0 of the Fulcher band system upon excitation of hydrogen molecules by an electron beam are measured. The beamelectron energy is ɛe = 15…30 eV (Δɛe ∼ 1 eV). The effective cross sections of H2 (d3Πu, v = 0) state excitation by electron impact are estimated both without changing themolecule angular momentum and with an appreciable angular momentum transfer. Processes with an appreciable angular momentum transfer are most efficient in the subthreshold excitation energy range (Ethr = 14 eV < Ee ≤ 18 eV) and are related to the formation of an intermediate composite system, i.e., a negative ion in the quasi-discrete state.

The effect of the airflow on the negative corona discharge is studied. It is shown by use of telemicroscopy that the localization of the discharge torch on the cathode surface can be significantly affected by the aerodynamic action on the discharge gap region.

Presented are the results of experimental research of temperature and velocity fields for lead and lead-bismuth coolant flows in channels having circular and annular cross sections under varying oxygen content in the coolant and varying characteristics of insulating coatings. Tests are performed under the following operating conditions: (1) lead-bismuth eutectic—temperature T = 400−520°C, thermodynamic oxygen activity a = 10−5–100, average flow velocity of the coolant w = 0.12−1.84 m/s, value of magnetic induction B = 0−0.85 T, Reynolds number Re = (0.24–3.5) × 105, Hartmann number Ha = 0−500, and Peclet number Pe = 320−4600; (2) lead coolant-T = 400−550°C, a = 10−5−100, w = 0.1−1.5 m/s, Re = (2.36−2.99) × 105, and Pe = 500−7000.

It is shown that when estimating the positional accuracy of axial drives in automatically controlled machines, the accumulated and periodic components along a single axis can be estimated separately. Analysis of a circular path along two coordinates makes it possible to determine 17 of the most important machine parameters, including the clearances along each axis, lateral clearances, desynchronization of the drive speeds, off-perpendicular deviations of the axes, and off-parallelism along each axis.

The spectra of pulsed cathodoluminescence (PCL) of CsI:Tl, YAG:Ge3+,Tb3+, and LFS-3 crystals excited by high-power (∼10 MW) short-time (∼2 ns) action of an electron beam with an average particle energy of ∼150 keV have been compared to the spectra of steady-state luminescence of the same crystals under the action of γ-photons with an energy of 511 keV emitted from a radioactive 22Na sample. It is established that the two spectra are identical, which allows the PCL method to be used for rapid analysis of scintillation crystals.

For the first time, the regime of a micrometer-size hot spot formation is impemented for an X-pinch in a plasma, which is fed from a current generator based on low-inductance capacitors and rapid current switches. The configurations of X-pinches, which can be used effectively as point sources of soft X-rays with this type of current generator, are determined. A prototype of a small-size radiation source for high-resolution point projection X-ray radiography has been constructed. The main parameters of X-pinch as a radiation source are analyzed and compared with X-pinch parameters in high-voltage setups with shaping lines. An analysis of the data on the operation of X-pinches in generators with different parameters has led to simple relations that can be used to select optimal initial X-pinch parameters.

Experiments on electron-impact vibronic excitation of molecular hydrogen in gas discharge plasmas and by electron beams reveal significant angular-momentum transfer and change in the ortho/para ratio. The observed effects are due to excitation via formation of negative intermediate ions. A model of such processes is proposed that provides a quantitative description of experimental results. The results of chi-square significance tests suggest that the dominant process is H2(X1Σg|) + e(p) → H2−(2Πu) → H2(d3Πu, I1Πg) + e′(l). The relative probabilities of ion decay by autodetachment of s, p, and other electrons are determined.

The results of experimental investigations of the heat transfer by lead coolant in the ring-shaped gaps of a circulation loop during monitored and controlled mass transfer and mass exchange of oxygen and impurity are presented. The investigations were performed in a loop with circulation of lead coolant at temperature of 450–550°C, average velocity 0.1–1.5 m/sec, Peclet number 500–6000, and heat flux 50–160 kW/m2. The oxygen content in the loop was varied from the value for thermodynamic activity 10−5–100 to saturation and above with formation of lead oxide deposits on the heat transfer surface. The processes in a non-isothermal liquid metal loop with heating (core) and cooling (steam generator) experimental sections simulate the dependence of the heat transfer characteristics in the loop on the impurity mass transfer.

Results of experimental studies on the local characteristics of heat transfer from a lead heat carrier to the surface of a cooled tube in an annular gap are shown at control and alteration of oxygen admixture content under the conditions of power circuits with heavy liquid-metal heat-transfer agent. This work is aimed at obtaining the grounded formulas for engineering calculations of heat transfer surfaces. Investigations were carried out at the lead temperature of 400–500 °C, the average velocity of heat-transfer agent of 0.1–1.5 m/s, the range of Prandtl number of 0.0123–0.0211 and Peclet numbers of 500–7000. The heat flux changed within 50–160 kW/m2. Controllable changing content of oxygen admixture changed from the value of thermodynamic activity of oxygen from 10−5-100 to saturation and higher with deposition of lead oxides near the heat-transferring surface.

Carbon dioxide decomposition in a non-self-sustained discharge was studied by the methods of diode laser spectroscopy and mass-spectrometry. It was shown that the effective control of the mechanism of a plasmachemical reaction is possible by varying the parameter E/N. This allowed us to reduce the energy cost of dissociation CO(2) by more than on an order of magnitude as compared to the dissociation process in a self-sustained glow discharge.

Results of experimental research of lead-bismuth heat-carrier stream velocity structure in the cross-section magnetic field at a varied content of oxygen admixture and characteristics of oxide electroinsulating covers are presented. Experimental studies were carried out for the following operation parameters: the lead-bismuth eutectics temperature T = 400–420 °C; thermodynamic activity of oxygen in the coolant a = 10−4 –100 ; the eutectics flow rate through the experimental part Q = 1.8–3.0 m3 /h, the coolant velocity in the experimental part w = 1.0–1.7 m/s; the magnetic induction value B = 0–0.85 T; the Reynolds number Re = (1,6–2,7)·105 ; the Peclet number Pe = 320–4600, and the Hartmann number Ha = 0–365.Copyright © 2009 by ASME

The spectra and decay time of pulsed cathodoluminescence (PCL) of a scintillating crystals excited by the electron beam is compared to the spectra and decay time of the luminescence of the same crystals initiated by γ-rays (GL). It is shown that spectra and decay time of PCL and GL are identical within the experimental errors. The explanation of these results is based on taking into account the physical processes within the crystal media under the irradiation by high-energy particles. The results of this study confirm that the PCL method may be used for the rapid analysis of the luminescent properties of scintillators.

A special shape of modulation of laser diode injection current is provided when the frequency modulation is not accompanied with amplitude modulation. Such approach permits to suppress essentially the influence of laser emission instabilities. When being applied to gas analysis it gives the possibility of long-term remote components monitoring. The stable relative absorptions of 8xl0-7 without special calibration are demonstrated. In combination with multipass cell (50 cm between the mirrors, 90 m optical length) it gives the absorption coefficient of l.2x10-10cm-1. As an example the daily evolution of atmosphere NO2 admixtures have been measured with a precision of O.5ppb.© (2006) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The ring mode of the Trichel pulse negative corona discharge was studied in atmospheric air. The localization of the discharge flame track in the stable self-organized regular pattern of 3, 4, 5 and 6 – pointed star was found at the cathode surface. This phenomenon was observed at mean currents in the range 100-115 μA at the conditions of the experiment, when the modes with one or two rings are not stable. The conclusion was made that the ring mode of the discharge, which is caused by the symmetrical distribution of the volumetric charges in the conditions of the symmetrical electric field, may be unstable. This instability results in the spatial self-organization of these parameters and causes the organization of the discharge flame track at the cathode surface in the regular patterns.

The influence of random microfields on measurements of external regular electric field by coherent nonlinear optics is analyzed. At an electron concentration