Ultra-monochromatic far-infrared Cherenkov diffraction radiation in a super-radiant regime.

Nowadays, intense electromagnetic (EM) radiation in the far-infrared (FIR) spectral range is an advanced tool for scientific research in biology, chemistry, and material science because many materials leave signatures in the radiation spectrum. Narrow-band spectral lines enable researchers to investigate the matter response in greater detail. The generation of highly monochromatic variable frequency FIR radiation has therefore become a broad area of research. High energy electron beams consisting of a long train of dense bunches of particles provide a super-radiant regime and can generate intense highly monochromatic radiation due to coherent emission in the spectral range from a few GHz to potentially a few THz. We employed novel coherent Cherenkov diffraction radiation (ChDR) as a generation mechanism. This effect occurs when a fast charged particle moves in the vicinity of and parallel to a dielectric interface. Two key features of the ChDR phenomenon are its non-invasive nature and its photon yield being proportional to the length of the radiator. The bunched structure of the very long electron beam produced spectral lines that were observed to have frequencies upto 21 GHz and with a relative bandwidth of 10-4 ~ 10-5. The line bandwidth and intensity are defined by the shape and length of the bunch train. A compact linear accelerator can be utilized to control the resonant wavelength by adjusting the bunch sequence frequency.

Observation of grating diffraction radiation at the KEK LUCX facility.

The development of linac-based narrow-band THz sources with sub-picosecond, [Formula: see text]-level radiation pulses is in demand from the scientific community. Intrinsically monochromatic emitters such as coherent Smith-Purcell radiation sources appear as natural candidates. However, the lack of broad spectral tunability continues to stimulate active research in this field. We hereby present the first experimental investigation of coherent grating diffraction radiation (GDR), for which comparable radiation intensity with central frequency fine-tuning in a much wider spectral range has been confirmed. Additionally, the approach allows for bandwidth selection at the same central frequency. The experimental validation of performance included the basic spectral, spatial and polarization properties. The discussion of the comparison between GDR intensity and other coherent radiation sources is also presented. These results further strengthen the foundation for the design of a tabletop wide-range tunable quasi-monochromatic or multi-colour radiation source in the GHz-THz frequency range.

Observation of incoherent diffraction radiation from a single-edge target in the visible-light region.

An experiment to investigate the diffraction radiation from a single edge target has been performed at the accelerator test facility of KEK with the aim of developing noninvasive beam diagnostics. The yield and the angular distribution of diffraction radiation as a function of the impact parameter was measured in the visible light region. The distributions were qualitatively consistent with the theoretical expectation. This work exhibits the first observation of the incoherent diffraction radiation in the visible light region.

Extremely low vertical-emittance beam in the accelerator test facility at KEK.

Electron beams with the lowest, normalized transverse emittance recorded so far were produced and confirmed in single-bunch-mode operation of the Accelerator Test Facility at KEK. We established a tuning method of the damping ring which achieves a small vertical dispersion and small x-y orbit coupling. The vertical emittance was less than 1% of the horizontal emittance. At the zero-intensity limit, the vertical normalized emittance was less than 2.8 x 10(-8) rad m at beam energy 1.3 GeV. At high intensity, strong effects of intrabeam scattering were observed, which had been expected in view of the extremely high particle density due to the small transverse emittance.

Resonant diffraction radiation from an ultrarelativistic particle moving close to a tilted grating.

A simple model for calculating the diffraction radiation characteristics from an ultrarelativistic charged particle moving close to a tilted ideally conducting strip is developed. Resonant diffraction radiation (RDR) is treated as a superposition of the radiation fields for periodically spaced strips. The RDR characteristics have been calculated as a function of the number of grating elements, tilted angle, and initial particle energy. An analogy with both the resonant transition radiation in an absorbing medium and the parametric x-ray radiation is noted.

[The phenomenon of adaptive immunity in exposure to nonionizing microwave radiation]. / Fenomenon adaptivnogo immuniteta pri vozdeistvii neioniziruiushchei mikrovolnovoi radiatsii.

In experiments with albino rats exposed to microwaves (500 microW/cm2), a model of adaptive immunity was developed by transferring lymphoid cells of exposed animals. The effect of microwave radiation was shown to cause autoimmune disorders that were displayed against the background of the structural and functional disturbances of the hematoencephalic barrier.

[Experimental modeling of autoimmune reactions as affected by nonionizing microwave radiation]. / Eksperimental'noe modelirovanie autoimmunnykh reaktsii pri vozdeistvii neioniziruiushchei mikrovolnovoi radiatsii.

In experiments on albino Wistar rats the autoimmune reactions were shown to be stimulated by the effect of microwaves of 50 and 500 microW/cm2. The authors showed the possibility of the autoimmunity simulation by immunization of intact animals by the brain tissue of exposed albino rats. This process was dependent on the microwave radiation intensity.

[Effect of nonionizing microwave radiation on autoimmune reactions and antigenic structure of serum proteins]. / Vliianie neioniziruiushchei mikrovolnovoi radiatsii na autoimmunnye reaktsii i antigennuiu strukturu syvorotochnykh belkov.

The authors discuss the possibility of stimulating the autoimmune reactions of the organism by microwave irradiation. The immunochemical analysis of protein fractions of blood serum has revealed a destabilization of functional activity of the immune system humoral factors at 500 W/cm2 which is manifested by the formation of a new protein with the immunoglobulin G physico-chemical properties.