Electron beamexcitation of wide-aperture XeCl lasers

This paper presents the results of studies aimed at seeking efficient modes of electron beam excitation ofXeCl lasers with an active volume of some tens of liters. It has been shown that a lasing efficiency of about 4% is realized at an excitation pulse duration of 300 ns with a power of 200–400 kW/cm³. Institute of High-Current Electronics, Siberian Division of the Russian Academy of Sciences. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 29–33, April, 2000.     

High-power wide-aperture electron-beam-pumped lasers on dense gases

Schemes of high-power electron-beam-pumped pulsed lasers on dense gases and the experimental results on the lasing on XeCl*, KrF*, and HF molecules are presented. The energy input and the kinetic processes in the active medium of the electron-beam-excited XeCl laser are calculated. Radiation pulse energies of 1900, 200, and 90 J are obtained at wavelengths of 308 nm, 2.8 μm, and 249 nm, respectively. Original Text ? Astro, Ltd., 2006.     

Electron-beam-pumped high-power wide-aperture exciplex lasers and laser systems

High-efficiency, high-power pulsedXeCl ^* andKrF ^* lasers pumped with an electron beam and laser systems based on these lasers have been developed. This paper describes the principles embodied in their development and design. The results of investigations on the formation of high-quality, high-power pulses are presented. Pulses with a radiation energy of up to 2000 and 100 J have been obtained at λ=308 and 249 nm, respectively, with a minimum 10 μrad divergence of the beam. Institute of High-Current Electronics, Siberian Division of the Russian Academy of Sciences. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 12–18, April, 2000.     

From multi-layered resonance tori to period-doubled ergodic tori

The Letter presents a number of new bifurcation structures that can be observed when a multi-dimensional period-doubling system is subjected to a periodic forcing. We show how multi-layered tori arise through transverse period-doubling bifurcations of the resonant saddle and node cycles, and how these multi-layered tori transform into period-doubled ergodic tori through sets of saddle-node bifurcations.     

Contrast enhancement in an electron-beam-excited wide-aperture XeCl laser

The possibility of increasing the contrast in the problem of the generation of petawatt radiation when the energy is released by a femtosecond laser pulse in the presence of a prepulse that passes through the medium of an electron-beam-excited wide-aperture amplifier prior to the main pulse is considered. It is demonstrated that such an approach does not lead to a significant increase in the contrast.     

Twistless KAM tori

A selfcontained proof of the KAM theorem in the Thirring model is discussed.Archived in mp_arc@math.utexas.edu#93-172;to get a TeX version, send an empty E-mail message     

Lower-dimensional tori in reversible systems

On a (2n+d)-dimensional manifold M consider a vector field V reversible with respect to an involution G whose fixed point manifold is of dimension n+d. It is conjectured that generically for each 0相似文献   

Asymmetric moving localized structures in a wide-aperture nonlinear interferometer

The existence of a branch of asymmetric solitary localized radiation structures moving in the transverse direction with a constant velocity is demonstrated for the slit (transversely one-dimensional) scheme of a wide-aperture interferometer with a threshold nonlinearity which is excited by external coherent radiation. This branch is shown to split off the branch of symmetric motionless structures at a certain bifurcation value of the external-radiation intensity. The generalization to other schemes, for which the existence of dissipative optical solitons is known, is discussed.     

Formation of highly coherent radiation in a wide-aperture exciplex laser

The results of experimental investigations into the feasibility of improving the spatial and temporal coherence of the radiation of aXeCl laser with a 16×12 cm output aperture and a pulse output energy up to 150 J are given. It is shown that in the injection-locked mode, 90% of the output energy can be emitted in a narrow spectral line. An unstable resonator with mirrors small in size and generalized parameters g_i>1 allows a near-diffraction-limited beam divergence to be obtained. Institute of High-Current Electronics of the Siberian Branch of the Russian Academy of Sciences. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 53–56, August, 1999.     

Birkhoff-Kolmogorov-Arnold-Moser tori in convex Hamiltonian systems

For the Hamiltonian systems of KAM type, it is proved that some lower dimensional invariant tori always exist in the resonance gaps although those maximum tori can not survive small perturbations in the generic case.     

Multi-frequency axial transmission bone ultrasonometer

The last decade has seen a surge in the development of axial transmission QUS (Quantitative UltraSound) technologies for the assessment of long bones using various modes of acoustic waves. The condition of cortical bones and the development of osteoporosis are determined by numerous mechanical, micro-structural, and geometrical or macro-structural bone properties like hardness, porosity and cortical thickness. Such complex manifestations of osteoporosis require the evaluation of multiple parameters with different sensitivities to the various properties of bone that are affected by the disease. This objective may be achieved by using a multi-frequency ultrasonic examination The ratio of the acoustic wavelength to the cortical thickness can be changed by varying the frequency of the ultrasonic pulse propagating through the long bone that results in the change in composition of the induced wave comprised of a set of numerous modes of guided, longitudinal, and surface acoustic waves. The multi-frequency axial transmission QUS method developed at Artann Laboratories (Trenton, NJ) is implemented in the Bone Ultrasonic Scanner (BUSS). In the current version of the BUSS, a train of ultrasonic pulses with 60, 100, 400, 800, and 1200 kHz frequencies is used. The developed technology was tested on a variety of bone phantoms simulating normal, osteopenic, and osteoporotic bones. The results of this study confirm the feasibility of the multi-frequency approach for the assessment of the processes leading to osteoporosis.     

Tunneling among rotation tori

We consider an integrable Hamiltonian system generated by the resonant normal form in order to study a particular mechanism of tunneling. We isolated near doublets of energy corresponding to rotation tori of the classical dynamics counterpart and the degeneracies breakdown is attributed to rotation-rotation tunneling.     

Robust tori in a double-waved Hamiltonian model

A Hamiltonian system perturbed by two waves with particular wave numbers can present robust tori, which are barriers created by the vanishing of the perturbed Hamiltonian at some defined positions. When robust tori exist, any trajectory in phase space passing close to them is blocked by emergent invariant curves that prevent the chaotic transport. Our results indicate that the considered particular solution for the two waves Hamiltonian model shows plenty of robust tori blocking radial transport.     

Regimes of a wide-aperture laser with nonlinear scattering medium

Optics and Spectroscopy - Regimes of a wide-aperture laser with a layer of a heterogeneous medium with a nonlinear refractive index placed inside the cavity are considered. The conditions of...     

Equivariant gerbes on complex tori

We explore a new direction in representation theory which comes from holomorphic gerbes on complex tori. The analogue of the theta group of a holomorphic line bundle on a (compact) complex torus is developed for gerbes in place of line bundles. The theta group of symmetries of the gerbe has the structure of a Picard groupoid. We calculate it explicitly as a central extension of the group of symmetries of the gerbe by the Picard groupoid of the underlying complex torus. We discuss obstruction to equivariance and give an example of a group of symmetries of a gerbe with respect to which the gerbe cannot be equivariant. We calculate the obstructions to invariant gerbes for some group of translations of a torus to be equivariant. We survey various types of representations of the group of symmetries of a gerbe on the stack of sheaves of modules on the gerbe and the associated abelian category of sheaves on the gerbe (twisted sheaves).     

Spectral transmission of a wide-aperture bragg acoustooptical paratellurite filter

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 52, No. 2, pp. 284–289, February, 1990.     

Application of aluminum and titanium foils in low-energy wide-aperture electron accelerators

We have reported on the results of theoretical and experimental investigations of characteristics of aluminum and titanium foils used in devices to extract electron beams from wide-aperture low-energy accelerators with a high current density. The mechanical properties of foils at different temperatures and the electron beam transmission and absorption coefficients have been compared. The results of analyzing the dependences of the efficiency of the electron beam extraction from accelerators on the type of the electron–optical system, material, and thickness of the foil for various sizes of extraction windows and the same type of the slot support grids have been presented. We have proposed an analytic model for calculating the temperature of the foil in the unit cell of the support grid. The electron transmittance and absorbance, as well as the temperature regimes of the foils, have been calculated using different methods.