On the scattering of cascade radio emission by rough lunar surface during radiation emergence into vacuum

The scattering of the radio emission of an almost horizontal cascade by the rough lunar surface during radiation emergence into vacuum is considered in the Born approximation. The point approximation for the shower disk size is considered taking into account its evolution along the track. The lunar surface was set either as a sinusoidal one in the directions perpendicular to and coinciding with the shower disk velocity or as having an arbitrary shape at the point of particle incidence. Scattering associated with wave phase increment and with variations of slope of the normal to the rough surface for various rays forming the total field of the scattered wave is considered.     

On the surface cascade radio emission escape into vacuum through the rough lunar surface

The radio emission escape of an almost horizontal cascade through the rough lunar surface into vacuum is considered. The point approximation is accepted for the shower disk size, taking into account its evolution along the cascade track. The lunar surface is assumed to be flat, but having a single perturbation such as a cylindrical “hill” perpendicular to the shower disk motion direction. The perturbation is not assumed to be small. Diffraction associated with the wave phase progression and variations of the slope of the normal to the rough surface for various rays forming the total wave field in vacuum is taken into account.     

Violation of the coherence of radio waves induced by a cascade shower in the lunar regolith

It has been shown that small fluctuations of the refractive index of the lunar regolith owing to, e.g., a nonuniform density distribution, give rise to the loss of the coherence of a Cherenkov radio pulse induced by a cascade shower from an ultrahigh-energy particle and to a strong decrease in the spectral density of the radio signal. This can be one of the causes of why no events from ultrahigh-energy cosmic particles on the surface of the moon have been detected.     

Multiplicity characteristics in relativistic 24Mg-nucleus collisions

This work is concerned with the analyses of the shower and gray particle production in 4.5 A GeV/c ²⁴Mg collision with emulsion nuclei. The highest particle production occurs in the region of the low impact parameters. While the multiplicity of the shower particles emitted in the forward direction depends on the projectile mass number and energy, the multiplicity of the backward ones shows a limiting behaviour. The source of the emission of the forward shower particles is completely different from that of the backward ones. The target fragments are produced in a thermalized system of emission.     

Spatial distribution of RF radiation induced by cascade shower in lunar regolith

The results of calculation of the radiation pattern of an electron-photon shower induced by an ultrahigh-energy particle on the Moon’s surface are reported. It is found that the inclusion of dielectric characteristics of the lunar regolith radically changes the rf radiation intensity distribution at the vacuum-regolith interface.     

Angular resolution of an array of tracking-chamber detectors for use in high-energy gamma-ray astronomy

Summary We describe a method of analysis for the reconstruction of the arrival direction of a high-energy photon impacting on the top of the atmosphere by using the directions of the particles on the shower front as measured by a ground-based array of tracking chambers uniformly distributed on a square surface; as an example, an array with enclosed surface of (120×120) m² has been considered. Estimates on the accuracy of reconstruction are given, after application of the method to computer-simulated shower directions as a function of the number of ?smapling? detectors and of their accuracy in the measurement of the ?local? shower direction. Paper presented at the V Cosmic Physics National Conference, S. Miniato, November 27–30, 1990.     

Time-dependent intranuclear cascade model

An intranuclear cascade model with explicit consideration of the time coordinate in the Monte Carlo simulation of the development of a cascade particle shower has been considered. Calculations have been performed using a diffuse nuclear boundary without any step approximation of the density distribution. Changes in the properties of the target nucleus during the cascade development have been taken into account. The results of these calculations have been compared with experiment and with the data which had been obtained by means of a time-independent cascade model. The consideration of time improved agreement between experiment and theory particularly for highenergy shower particles; however, for low-energy cascade particles (with grey and black tracks in photoemulsion) a discrepancy remains at T ? 10 GeV.     

Shower age in correlation with zenith angle

The variation of lateral shower age parameter with zenith angle for different shower size ranges is studied. The observed variation is in agreement with the electron-photon cascade theory and with the other EAS observations. It is found that up to zenith angle 30°, shower ‘age’ is practically independent of zenith angle. So it is difficult to correlate the reported high ‘age’ value of the excess showers from the direction of plausible point sources with zenith angle. The change in the value of shower age with atmospheric depth is studied and is found to be consistent with the prediction of cascade theory and simulation results. From the study of the variation of shower age with shower size for two different zenith angle intervals it is found that the shower age decreases with size but the rate of change of shower age decreases at higher sizes.     

Long-wavelength (lambda approximately 8-11.5 microm) semiconductor lasers with waveguides based on surface plasmons

Laser waveguides based on surface plasmons at a metal-semiconductor interface have been demonstrated by use of quantum cascade (QC) lasers emitting in the 8-11.5-microm wavelength range. The guided modes are transverse magnetic polarized surface waves that propagate at the metal (Pd or Ti-Au)-semiconductor interface between the laser top contact and the active region without the necessity for waveguide cladding layers. The resultant structure has the advantages of a strong decrease in the total layer thickness and a higher confinement factor of the laser-active region compared with those of a conventional layered semiconductor waveguide, and strong coupling to the active material, which could be used in devices such as distributed-feedback lasers. These advantages have to be traded against the disadvantage of increased absorption losses. A peak output power exceeding 25 mW at 90 K and a maximum operating temperature of 150 K were measured for a QC laser with an emission wavelength lambda approximately 8 microm . At lambda approximately 11.5 microm the peak power levels are several milliwatts and the maximum operating temperature is 110 K.     

Localized surface waves at the interface between the linear dielectric and photorefractive medium with drift and diffusion nonlinearity

We consider the propagation of the laser beam near the interface between the linear dielectric and photorefractive medium with drift and diffusion nonlinearity. We demonstrated the possibility of the surface waves formation, found the profiles of such surface modes and investigated waveguiding properties of the dielectric-photorefractive medium boundary. The effective particle theory was used to derive an ordinary differential equation that describes the beam center trajectory during the reflection from the interface.     

Coherent thermal antenna using a photonic crystal slab

We show that a photonic crystal film can emit coherent thermal radiation. We demonstrate the key role of leaky waves existing at the air-photonic crystal interface. The frequency and direction of emission depend on the lattice parameters. This paves the way towards the design of coherent infrared antennas.     

Orientation dependences of the response of an electromagnetic spectrometer with oriented crystal converter

The experimental results of the study of orientation dependences of the response of a composite Cherenkov shower spectrometer with a converter made of a 1-mm tungsten crystal oriented along the 〈111〉 axis at an electron energy of 28 GeV and two converter temperatures, 293 and 77 K, are presented. The parameters of the cascade curve of the shower development are varied depending on the orientation angle and crystal temperature. It is found that there is a point S in the cascade curve of the shower development in the spectrometer, at which all cascade curves intersect at any converter orientation. The position of this point in the spectrometer depth depends on the converter temperature.     

Reverse orbiting of microparticles in optical vortices

We report the observation of particles trapped at an air-water surface orbiting in a reverse direction with respect to the orbital angular momentum of the light field. The effect is explained by a combination of asymmetric particle shape and confinement of the particle on the 2D air-water interface. The experiment highlights the strong influence of the particle shape on the momentum transfer, an effect that is often not considered in optical trapping experiments.     

Determining the primary cosmic ray energy from the total flux of Cherenkov light measured at the Yakutsk EAS array

We present a method for determining the energy of the primary particle that generates an extensive air shower (EAS) of comic rays based on measuring the total flux of Cherenkov light from the shower. Applying this method to Cherenkov light measurements at the Yakutsk EAS array has allowed us to construct the cosmic ray energy spectrum in the range 10¹⁵ ? 3 × 10¹⁹ eV.     

Simulation of propagating EAS Cherenkov radiation over the ocean surface

We present computing results of the Cherenkov light propagation in the air and water from an extensive air shower (EAS) over the ocean. Limits on the zenith angles of the showers, for which the registration of the flash of reflected photons by the space-detector is possible, are analyzed with consideration for waves on the ocean surface.     

Snell's laws at the interface between nonlinear dielectrics

An equivalent particle theory is developed which is effective in capturing the global behavior of surface waves at the interface between two nonlinear dielectrics.     

Experimental study of the relief of the front of steady detonation in liquid high explosives

The instability of detonation waves in a 81 : 19 nitromethane-acetone mixture is experimentally studied. The amplitude of the irregularities caused by detonation instability and the typical reaction time are estimated using a VISAR laser interferometer, which makes it possible to measure the particle velocity profiles at the explosive-window interface. The characteristic transverse dimensions of the irregularities are measured with the help of a CORDIN camera operating in the single shooting mode to record the intrinsic emission of the detonation front or the light of an outside source reflected from it.     

The angular distributions of secondaries in proton-nucleus interactions at 200 and 300 GeV

The angular distributions of shower particles from proton-nucleus collisions at 200 and 300 GeV are investigated and correlated to the nuclear parameters (heavy prong emission), the inelasticity coefficient and the angle of the leading track. A partition is made into two components, the LP component associated with a single collision and the RC component corresponding to the excess from repeated collisions at the same proton and the nucleons inside the nucleus. Results from earlier investigations on the multiplicity distributions are confirmed. The LP component exhibits an excess of about 30% as compared to the shower particle emission in proton-proton collisions at the same energy. We find that the excess particles are slow moving in the equal velocity system, i.e., the frame in which the proton and the nucleus have equal but oppositely directed velocities. The opening angle of the cone inside which the proton-nucleus distributions are similar to the proton-proton distributions at the same energy is small (? 0.5°) and is energy dependent. We also find indications of A dependence and a noticeable correlation to the inelasticity coefficient and to the angle of the leading track.     

Backscattered indicatrix from surfaces with random impedance

Intensity enhancement in the retroreflection direction is studied for waves scattered by a random interface which has a bound state (surface wave). We have found that an enhanced backscattered peak appears as the result of competition of two mechanisms: multiple scattering of a surface wave along the interface, and its leakage to upper half-space. The last one is the important distinction of surface scattering, which shifts the diffuse pole and eliminates in a natural way the divergence of second moments, which is the crucial difficulty in existing theories. New results, valid when there is no real absorption in the medium, are obtained for the diffuse scattered intensity as a function of the angles near the antispecular direction.