The pp pi system whose quantum numbers may assume values that are forbidden for the NN system is investigated for the first time in the reaction pp --> pp pi(-)pi(+). The experiment was performed at ITEP (Moscow). The invariant-mass distribution of the pp pi(-) system reveals a resonance enhancement at M approximate to 2.06 GeV with a width about 10 MeV. The observed enhancement may signal the formation of a resonance state predicted by quark models and required for interpreting data on low-energy pion-nucleus scattering accompanied by double charge exchange.

YBa2Cu3O7-delta (YBCO) thin films with different thicknesses were prepared and patterned into the forms of microstrip ring resonators with silver grounds, for which the microwave properties were studied at temperatures above the liquid nitrogen temperature and at frequencies of 8 to 12 GHz. The effective surface resistances of the YBCO thin films were calculated using Wheeler's incremental induction rule, from which the intrinsic surface resistances were calculated with a consideration of the finite-thickness effect on the surface resistance. The effective surface resistance of a YBCO film with larger thickness can be smaller than that of a YBCO film with a smaller thickness, depending on the ratio of the film thickness to the penetration depth.

An analysis of the axially symmetric TM/sub 011/ mode in a dielectric-loaded cavity is presented and a technique of using a TM/sub 011/ mode dielectric-loaded cavity is introduced for measurements of microwave surface resistances of HTS thin films. A dielectric resonator with /spl epsiv//sub r//spl ap/39 is used for this purpose. It turned out that Q of the TM/sub 011/ mode dielectric-loaded cavity is very sensitive to the surface resistance of the material at the bottom plate, especially to the surface resistance of the area under the dielectric resonator, which can be used to investigate local microwave properties of large HTS thin films in a nondestructive, simple way. Experiments on YBCO thin films with the dimensions of /spl sim/2/spl times/2 cm/sup 2/ are performed using this technique, which revealed inhomogeneity in the microwave surface resistance of the thin films at different sites and demonstrated the usefulness of this technique.

Measurements of the plasma pressure on an aluminium target in vacuum were made in the radiation field of harmonics of a gigawatt neodymium laser. The results were combined with measurements of the plasma temperature to find the plasma density in the region of its one-dimensional expansion near the target. The plasma was found to be close to equilibrium and near-ideal. Its density, like its temperature, was governed by the laser radiation intensity and was independent of the radiation frequency.

Microwave properties of YBa2Cu3O7−δ (YBCO) microstrip ring resonators with finite thicknesses and different surface morphologies were investigated. The unloaded quality factor of a YBCO resonator made of thick film appeared smaller than that of a different YBCO resonator made of a less thick film, due to the smaller ratio of the film thickness to the penetration depth. The measured penetration depth appeared to increase due to surface roughness, resulting in a decrease of the ratio of film thickness to the penetration depth and an increase of the effective surface resistance. A method is introduced to calculate the intrinsic surface resistance of a high-Tc microstrip resonator with finite thickness. YBa2Cu3O7−δ (YBCO) microstrip ring resonators with their thicknesses in the order of the magnetic field penetration depth were prepared from YBCO thin films grown by laser ablation on LaAlO3 and their microwave properties were measured at temperatures above the liquid nitrogen temperature and frequencies in 8–12 GHz.

In the frame of classical mechanics the analytical expression has been obtained for the radiation emission spectrum, consisting of a large number of the odd harmonics. It has been shown that the high frequency boundary of the spectrum is determined by the ratio of the electron oscillation velocity to the atom size. The oscillations of the electron in a laser field take steady-state form for a time about of optical cycle. The field amplitude should be sufficient for electron tunneling through the variable in the time potential barrier created by Coulomb attractive force of a nucleus and by an alternate extracting electrical field radiation E(t). The quantum tunneling process will be exponential depending on the absolute value of E(t) and will be quasistatic under certain conditions. This statement corresponds to experimental fact of the sharp occurrence and the fast increase of high harmonics radiation intensity in the range of laser radiation intensity 1014 less than I less than 1016 W/cm2, corresponding to subatomic values of field Eo less than Ea. The electrons appear outside of the barrier at the peaks of the sinusoidal field. Consequently they have zero drift velocity and hereinafter make the forced oscillations near their 'parent' atoms. At the large laser field strength Eo greater than or equal to Ea the electrons can tunnel during a considerable part of every optical period, when field time derivative differs from a zero, and therefore they will have drift velocity Vd less than eEom(omega) . In this case the electron drift displacement for a time of laser pulse (tau) very much greater than 1/(omega) can exceed the oscillation amplitude and interatomic distance. This can result in turn in appearance of the fully ionized plasma. But in the present paper only the case Eo less than Ea is considered.

The process of fourth harmonic generation in multicascade laser installation is experimentally investigated. The operative correction of phase synchronism in nonlinear crystals permits to compensate an installation parameters drift and provides stable radiation conversion to the 4th harmonic with efficiency 0.4 divided by 0.5 at E4 approximately 10 J.

The interference structure of the laser light scattering cone behind the laser spark was observed for the first time. We propose consideration of the observed structure as a result of interference of the laser radiation, scattered by two or more self-focusing centers in laser spark air plasma. We have investigated the spatial distribution of the laser radiation scattered by the laser spark. These experiments differ from the previous ones by use of the four harmonics of Nd-laser radiation. As a source of radiation the Nd-laser installation was used with the master oscillator, operated on one transverse and longitudinal mode. The pulse duration was 10 ns, pulse energy -- up to 20 J and beam divergence -- 8 (DOT) 10-5 rad. After the frequency conversion by means of the KDP crystals the second, third, and fourth harmonics radiation appeared with the energy up to 10 J (in fourth harmonic). In each of our experiments one laser harmonic radiation was focused into the hermetical chamber, filled with air (10 divided by 760 mm Hg). For the scattered radiation registration we photographed the scattering flat white screen, illuminated by this radiation. This screen was disposed parallel to the laser beam axis at the distance of 2 - 6 mm from it. We observed a cone-like symmetric respectively to the laser beam axis radiation scattering in the spark. That enables us to determine the maximum angle alpha of laser radiation deviation as a function of pressure p and wavelength lambda (or number of harmonic N).

Target laser plasma electron temperature dependence Te(t,I) on time (t∼10 ns) and on laser flux intensity (I∼109÷1013 W/cm2) by electric potential probe technique was measured. We have shown for the first time that probe signal corresponds to the plasma electron temperature Te only if the plasma size l∼d is small in comparison with the distance L of the probe from the plane target, η=(d/L)<1. In the opposite case, when the scale parameter η>1, the probe signal changes considerably, it can even change its polarity. It is experimentally shown that in these conditions the probe signal is formed mainly as the induction signal from the target plasma toroidal current system and corresponding circular magnetic fields. It was shown that the plasma temperature does not depend on the wavelength of laser radiation in the range (1.06÷0.265)μ and its dependence on the laser radiation intensity may be approximated as Te∼Iα, where α=0.33±0.02, in the whole investigated range of experimental conditions. Maximal plasma temperature Te∼300 eV has been obtained.

Measurements were made of the electron temperature Te of a laser plasma formed on the surface of a metal target by the action of nanosecond pulses of wavelengths λ = 1060, 530, and 265 nm. The laser radiation intensity was I ≈ 109—1013 W cm-2. The electron temperature was determined from the emf of a double charge layer at the plasma boundary. Within the limits of the scatter of the experimental results, the plasma temperature was independent of the laser radiation wavelength (in the range 1060–265 nm). The dependence of this temperature on the radiation intensity obeyed approximately Te ∝ I1/3 throughout the investigated range.

The spatial distribution measurements of laser radiation, scattered in the laser spark, were accomplished for various laser radiation wavelengths (1060, 530, 353, and 265 nm) and various pressures of the gas (air at 10-760 mm Hg). The interference structure of the laser light scattering cone behind the laser spark was observed for the first time. It is proposed to consider the observed structure as a result of interference of the laser radiation, scattered by two or more self-focusing centers in laser spark air plasma. The experimental dependence of the maximal angle of the light scattering on the gas pressure and on the laser radiation wavelength was obtained. >

Spatial distributions of laser radiation scattered by a laser spark were determined at different laser radiation wavelengths (λ = 1060, 530, 353, and 265 nm) and gas pressures (air at 10–760 Torr). An interference structure of the cone of the scattered radiation behind the spark was detected for the first time. The structure was attributed to interference of the radiation scattered in two or more self-focusing centres in the laser-spark plasma in air. The dependences of the maximum scattering angle on the gas pressure and on the laser radiation wavelength were determined experimentally.

Preliminary results of the analysis of the pppi- system produced in the reaction pp-->pppi-pi+ reveal a resonance with a mass M almost-equal-to 2.06 GeV and a width < 15 MeV. The mass spectrum of the system pppi-, which can have any quantum numbers, including those forbidden in the np system, has been investigated for the first time. The observed resonance in the pppi- mass spectrum is in agreement with the quark models. and it confirms the recently proposed explanation of the peculiar features in the low-energy pionic double charge exchange on nuclei.

The implementation principles and the feasibility of construction of high-throughput multistage optoelectronic switches, capable of transmitting data in the form of two-dimensional images along interconnected pairs of optical channels, are considered. Different ways of realising compact switches are proposed. They are based on the use of polarisation-sensitive elements, arrays of modulators of the plane of polarisation of light, arrays of objectives, and free-space optics. Optical systems of such switches can theoretically ensure that the resolution and optical losses in two-dimensional image transmission are limited only by diffraction. Estimates are obtained of the main maximum-performance parameters of the proposed optoelectronic image switches.

The pion-nucleus transitions of the type A(pi,pi'p(d))X, where pi' is the leading secondary pion emitted at a small angle (theta < 8-degrees) and carrying over a half of the initial beam momentum, and p is a cumulative proton (deuteron) emitted backwards with a production angle in the 120 - 160-degrees interval, are studied. The 3.15 (1.4) GeV/c pion beam is brought into collision with the Al and Pb (Ti and Fe) targets in the FOCUS detector at ITEP. The influence of the energy transfer epsilon = E(pi) - E(pi') to the leading pion on the shape of the cumulative proton (deuteron) spectrum is investigated. The invariant cumulative proton function f=p-1dsigma/dT is fitted with a functional form C exp(-T/T0) for both the reaction under consideration and the inclusive A(pi, p)X process observed in the same experiment. The deviation of the parameter T0 at low epsilon from its inclusive value, associated with the deviation of the cumulative proton spectrum from the exponential form, is interpreted as a kinematical boundary effect. To account for the kinematical boundary, die invariant function is taken in the form f is similar to (1 - T/epsilon) epsilon/T0* for epsilon < epsilon* and f is similar to (1 - T/epsilon*)epsilon*/T0* for epsilon greater-than-or-equal-to epsilon*, where epsilon* is the mean energy of the local excitation of nuclear matter, beginning from which the function f becomes constant. The saturation of the local excitation leads to the scaling behavior of the invariant function. The global fit of all spectra of cumulative protons yields epsilon'= 0.9 - 1.0 GeV.