L. G. Sukhikh

Measurement of the angular characteristics of transition radiation in near and far zones

A method is developed for measuring the angular distribution of radiation in the near zone that excludes the contribution of the sizes of a radiation source to angular characteristics. Using this method, absolute measurements of the angular distribution of coherent transition radiation are performed in the millimeter wavelength range. It is shown that the measured characteristics correspond to the respective theoretical characteristics obtained in the far zone approximation.

Observation of the stimulated coherent diffraction radiation in an open resonator at LUCX facility

We present an initial test of a new type of a pre-bunched beam pumped free electron maser based on Stimulated Coherent Diffraction Radiation (SCDR) generated in an open resonator. A fast Schottky Barrier Diode (time response o1 ns) has enabled us to investigate the properties of the radiation stored in the cavity as well as the intrinsic properties of the cavity itself. We observed a turn-by-turn SCDR generated by a multibunch beam. When the cavity length was exactly a half of the bunch spacing a clear resonance was observed. Moreover, turn-by-turn measurements revealed the cavity quality factor of 72.88, which was rather high for an open resonator in the wavelength range of 3–5 mm. An exponential growth of the photon intensity as a function of the number of bunches was also demonstrated.

Investigation of coherent Čerenkov radiation generated by 6.1 MeV electron beam passing near the dielectric target

Coherent Cerenkov radiation generated by the 6.1 MeV bunched electron beam travelling near dielectric target (teflon) have been investigated theoretically and experimentally. It has been shown that the longitudinal bunch form-factor plays important role in the characteristics of coherent Cerenkov radiation. We have also compared the characteristics of coherent Cerenkov radiation and the ones of coherent diffraction radiation from a metal target in the similar conditions and have shown that coherent Cerenkov radiation is more intensive. These facts make coherent Cerenkov radiation a promising mechanism for a new noninvasive beam diagnostic technique.

Shadowing of the electromagnetic field of relativistic charged particles

In radiation processes such as a transition radiation, diffraction radiation, etc. based on relativistic electrons passing through or near an opaque screen, the electron self-field is partly shadowed after the screen over a distance of the order of the formation length γ2λ. This effect has been investigated on coherent diffraction radiation (DR) by electron bunches. Absorbing and conductive half-plane screens were placed at various distances L before a standard DR source (inclined half-plane mirror). The radiation intensity was reduced when the screen was at small L and on the same side as the mirror. No reduction was observed when the screen was on the opposite side. It is worth noting that absorbing and conductive half-plane screens produce the same shadowing effect. The shadowing effect is responsible for a bound on the intensity of Smith-Purcell radiation.

Development of microwave and soft X-ray sources based on coherent radiation and Thomson scattering

Compact, high-brightness and reliable sources in the VUV and the soft X-ray region may be used for numerous applications in medicine and biochemistry. We propose a new approach to produce the intense beams of X-rays in the range of ≤ 500 eV based on compact electron accelerator. We present our first experimental results obtained in the Laser Undulator Compact X-ray facility (LUCX) at KEK: High Energy Accelerator Research Organization devoted to the development of a compact microwave and soft X-ray source based on coherent diffraction radiation and Thompson scattering processes.

Monochromaticity of coherent Smith-Purcell radiation from finite size grating

Investigation of coherent Smith-Purcell Radiation (SPR) spectral characteristics was performed both experimentally and by numerical simulation. The measurement of SPR spectral line shapes of different diffraction orders was carried out at KEK LUCX facility. A pair of room-temperature Schottky barrier diode (SBD) detectors with sensitivity bands of

SHADOWING OF THE ELECTROMAGNETIC FIELD OF A RELATIVISTIC ELECTRON

60-90

Macroscopic effect of the shadow of the electromagnetic field of relativistic electrons

~GHz and

Observation of subterahertz monochromatic transition radiation from a grating

320-460

Investigation of Coherent Vavilov-Cherenkov Radiation in the Millimeter Wavelength Range Generated in PTFE and Paraffin Target

~GHz was used in the measurements. Reasonable agreement of experimental results and simulations performed with CST Studio Suite justifies the use of different narrow-band SBD detectors to investigate different SPR diffraction orders. It was shown that monochromaticity of the SPR spectral lines increases with diffraction order. The comparison of coherent transition radiation and coherent SPR intensities in sub-THz frequency range showed that the brightnesses of both radiation mechanisms were comparable. A fine tuning feasibility of the SPR spectral lines is discussed.