arXiv subjects

O. V. Chefonov

Publications and source records attributed to O. V. Chefonov.

4 recordsLinked to original sources

arXiv2018

Nonlinear Transfer of Intense Few Cycle Terahertz Pulse Through Opaque n-doped Si

Intense few cycle terahertz pulses exhibit complex non-linear behavior under interaction with heavily n-doped Si. Fast increase in the transmission of a 700 fs pulse (central frequency 1.5 THz) through the Si sample (low field transmission of 0:02 %) saturates at 8 % for the external field of 5 MV/cm and then drops twofold at 20 MV/cm. An electro-optical sampling measurements revealed formation of a single cycle terahertz pulse at this field due to formation of a thin ionized layer by the first intense oscillation of the terahertz field.

physics.optics↗

arXiv2017

Giant self-induced transparency of intense few-cycle terahertz pulses in n-doped silicon

The results of high-field terahertz transmission experiments on n-doped silicon (carrier concentration of $8.7\times10^{16}$ cm$^{-3}$) are presented. We use terahertz pulses with electric field strengths up to 3.1 MV cm$^{-1}$ and a pulse duration of 700 fs. Huge transmittance enhancement of $\sim$90 times is observed with increasing of the terahertz electric field strengths within the range of 1.5--3.1 MV cm$^{-1}$.

physics.optics↗

arXiv2002

Low-Energy Electron-Beam Diagnostics Based on the Optical Transition Radiation

A possibility of a few MeV electron beam diagnostics (Lorentz factor ~ 10) using polarization characteristics of the optical transition radiation (OTR) have been considered. Determinaton of the electron beam divergence have been performed with technique based on the OTR measurements. The technique is based on measuring the ratio R=Imin/Imax, where Imin(Imax) is the photon yield in the minimum (maximum) of OTR angular distribution. It is shown that the value of R can be obtained also from the measurement of the so-called psi-scan of the OTR yield registered by a fixed detector with the aperture < gamma^(-1) by varying the target tilt angle with respect to the electron-beam. The experiment curried out at 6.1 MeV Tomsk microtron has demonstrated the feasibility of the technique proposed.

physics.acc-ph↗

arXiv2002

Investigation of resonant polarization radiation of relativistic electrons in gratings at small angles

The Resonant Optical Polarization Radiation (ROPR) in the Smith-Purcell geometry and the one from the inclined grating at the Tomsk synchrotron and 6-MeV microtron have been investigated. The polarization radiation was observed at 4.2o from the 200 MeV electron beam and at 5o from the 6.2 MeV electron beam. Two methods of measurement of ROPR maxima in these two cases have been used. In the first case (the experiment on synchrotron) we have fixed the wavelength of radiation using an optical filter; the orientation dependence of this radiation was measured. In this dependence we have observed two peaks of radiation from electrons in gold foil grating of 0.1 mm period. The first large peak is a zeroth order peak in direction of specular reflection, and the second one is the 1-st order peak of resonant polarization radiation. In the experiment on microtron the spectra of ROPR from aluminum foil strip grating of 0.2 mm period in the Smith-Purcell geometry were measured, and the peak of the 1-st order Smith-Purcell radiation in these spectra was observed. The comparison of data obtained with the simulation results has been performed.

physics.acc-ph↗