On the transition radiation and bremsstrahlung from a relativistic electron with a nonequilibrium field

The problem of the transition radiation from an electron with a nonequilibrium self-field appearing in view of the sharp scattering of the electron has been considered. It has been shown that the state of the electron with the nonequilibrium field is manifested in the suppression of transition radiation and in the oscillatory dependence of its characteristics on the distance from a plate on which radiation occurs to the scattering point. The problem of the measurement of the characteristics of bremsstrahlung under the conditions when macroscopic transverse distances are responsible for the scattering process has been considered. It has been shown that the results of the measurement in this case significantly depend on the size of the detector and on its position with respect to the scattering point.     

Coherent transition radiation from thin targets irradiated by high intensity laser pulses

A theoretical examination on coherent transition radiations (CTR) from the surface of thin solid density target irradiated by high intensity laser is presented. The theory is extended to consider the expansion dynamics of thin foils. The motion of target surfaces leads to the modulation on the temporal structure of micro bunches in the electron beam as well as the spectrum of CTR. The spectral shifts of radiation are owing to the enhancement of electron bunch separation and the relativistic Doppler effects. The radiation power distribution is strongly affected by the temporal coherence of electron beam structure, so thus the electron temperature and velocity dispersions. With these effects accounted for, the spectral properties of coherent transition radiation can provide insights into the expansion of thin foil targets irradiated by intense laser pulse as well as the fast electron transport through it.     

Coherent X-ray radiation from a relativistic electron in a combined medium

A theory of coherent X-ray radiation from a relativistic electron crossing a combined medium that consists of amorphous and crystal plates is constructed within the dynamic diffraction theory. The field reflection asymmetry relative to the target surface determined by the angle between the atomic planes and the target surface is taken into account in the theory. The expressions describing the spectral-angular densities of parametric X-ray and diffracted transition radiations in this medium are derived and investigated.     

VUV resonant transition radiation from relativistic electrons

The modified radiator for generation of the resonant transition radiation from relativistic electrons is presented. This radiator consists of a set of small thin foils inclined with respect to the trajectory of an emitting electron. It is shown that the photoabsorption of the emitted photons is almost completely suppressed in the considered scheme. Therefore, the possibility of generating intense beams of quasimonochromatic vacuum ultraviolet (VUV) quanta by the proposed method appears.     

Absorption spectroscopy using a coherent transition radiation millimeter wave light source

The characteristics and applicability of the absorption spectroscopy system using the coherent transition radiation light source have been investigated. The configurations of the system are relatively simple. The operational conditions of an electron linear accelerator have been evaluated. The stability of the light intensity has been within ±2–3% in a wavenumber range of 4–13 cm⁻¹. The light intensity has been found to be more than six orders of magnitude higher than that for the lowest limit for detection.     

Coherent interaction of picosecond frequency-tunable light pulses with excitons in a semiconductor

An investigation was made of the self-induced transparency effect in the semiconductor's exciton region using ultrashort frequency-tunable light pulses and an ultrafast streak camera.     

Coherent manipulation of light pulses in a multilevel atomic system

We consider the quantum memory process in general multilevel atomic systems with electromagnetically induced transparency (EIT). We discuss the pulse-matching phenomenon in this general EIT scheme. We also review a recent proposal to create tightly localized stationary pulses by using counterpropagating pump fields. The advantages in creating the stationary pulses with the general EIT system are also discussed.     

Experimental study of coherent transition radiation from relativistic electrons in a dihedral angle

Angular intensity distributions for transition radiation excited by a beam of relativistic electrons in the emitter in the form of a dihedral angle are measured in the millimeter range. The angle is formed by the intersection of two conducting planes. The source of radiation is a microtron with an electron energy of 7.4 MeV. We analyze the effect of the magnitude of the dihedral angle of the emitter, the position of the electron transition point on the surface of the angle, and the direction of motion of electrons on the angular distribution of radiation intensity. It is shown that the spectral and angular distributions of radiation intensity in the dihedral angle substantially differ from analogous distributions for a particle intersecting a planar conducting surface. The possibility of using radiation to measure the energy, spatial position, and direction of motion of charges is considered.     

Coherent effect in the radiation of relativistic electrons in the field of bent atomic crystallographic planes

The effect of the intense monochromatic radiation arising when relativistic electrons intersect periodically bent atomic crystallographic planes in a crystal is predicted. This effect is independent of the channeling of the particles in the crystal and is possible for relativistic positrons and electrons.     

Coherent forward four-wave mixing of ultrashort radiation pulses in a resonant medium

Forward four-wave mixing (FFWM) of ultrashort light pulses is considered theoretically under their coherent propagation in a resonant-absorbing medium. Nonlinear equations describing FFWM are obtained and studied and it is shown that the energy exchange between pulses of exact resonance may lead to the enhancement of weak radiation. The influence of input radiation parameters and interaction geometry on the FFWM characteristics has been studied.     

Experimental study of coherent transition radiation from relativistic electron bunches entering a dihedral angle

The angular distributions of the intensity of transition radiation from a bunch of relativistic electrons entering a dihedral angle between two conducting planes have been measured in a millimeter wavelength range. A microtron with a particle energy of 7.4 MeV is used as a source of electrons. The effect of the particle injection direction and the magnitude of the dihedral angle on the angular distribution of the radiation intensity has been analyzed. The measurements show that the character of the distribution of radiation from a charge entering the dihedral angle significantly differs from that for a charge escaping the angle. A comparatively small change in the magnitude of the dihedral angle can lead to qualitative changes in the angular distribution of radiation from a charge entering the dihedral angle.     

Coherent diffraction radiation as a source of radiation in far-infrared and terahertz range

The results of measurements of the coherent diffraction radiation yield generated by femtosecond electron beam are presented. It is shown that the simulated and experimental data agreed quite well. The coherent diffraction radiation can be considered as a real candidate to develop a source of radiation in far-infrared and terahertz range.     

Coherent X-ray radiation generated by a relativistic electron in an artificial periodic structure

A theory of coherent X-ray radiation from a relativistic electron crossing an artificial periodic layered structure in the Laue scattering geometry is constructed. The expressions describing the spectral-angular radiation parameters are obtained. It is shown that the radiation yield in such a medium may substantially exceed the radiation yield in a crystal under analogous conditions.     

Coherent anti-Stokes Raman scattering microscopy with a photonic crystal fiber based light source

A coherent anti-Stokes Raman scattering microscope based on a Ti:sapphire femtosecond oscillator and a photonic crystal fiber is demonstrated. The nonlinear response of the fiber is used to generate the additional wavelength needed in the Raman process. The applicability of the setup is demonstrated by imaging of micrometer-sized polystyrene beads.     

Coherent effect of near field of thermal microwave radiation from a heated body

It is shown that spatial variation in the temperature a periodically heated planar source causes partial spatial coherence of the near field of its microwave thermal radiation. This coherence can be revealed in the form of a peculiar interference pattern arising at a displacement of a diffraction grating along the source surface.     

Peculiarities of the spectral-angular distribution of transition radiation from a relativistic particle in a dihedral angle

The spatial distributions of transition radiation from relativistic particles entering and exiting the edge of a dihedral angle formed by perfectly conducting flat surfaces have been investigated. The angular distributions of the radiation intensity in dihedral angles with various opening angles have been calculated. The angular distributions of forward radiation (when the particle exits the dihedral angle) and backward radiation (when the particle enters the dihedral angle) are shown to differ significantly.     

Observation of THz coherent transition radiation from single-bunch beam at KURRI-LINAC as an intense pulsed light source

A single-bunch beam has been generated using a developed high-speed avalanche-type pulser in KURRI-LINAC in order to lift restrictions of the spectral resolution in the spectroscopic study and the delay time in the time-resolved measurement. Both of the rise and fall times of the developed pulser are 110 ps. The observation of CTR has confirmed the single-bunch beam. The degree of impurity of single bunch has been estimated to be 1.5% by the analysis of the interferogram.