V. V. Kaplin

Observation of monochromatic and tunable hard X radiation from stratified Si single crystals

Abstract X radiation by 900 MeV electrons in accurately aligned 1–100 layers of 16 μm thick monocrystalline foils of Si was measured. We found intense and well collimated monochromatic photons, i.e. self-diffracted X rays (SDX), emitted to the “Bragg angle”. The intensity of SDX was much greater than the parametric X rays from a Si plate of equivalent thickness. For 35.5 keV X rays with 100 layered Si target, absolute brightness of SDX was comparable to the synchrotron radiation from a 1.7 GeV storage ring.

X-ray generation produced by relativistic electrons in compound “multifoil structure + crystal” targets

Abstract Novel concepts of X-ray production by relativistic electrons in stratified targets are developed. It is shown that by transmitting an electron beam through a compound target, consisting of a periodic multifoil structure and a crystal, it is possible to obtain the intense, tunable, quasi-monochromatic X-rays, emitting at large (Bragg) angles with respect to the electron beam axis due to the diffraction on the crystal of resonance transition radiation, previously generated in the multilayered structure. The first results of experimental investigation of this effect for 900 MeV electrons, transmitting through the periodic stack of 10 Mylar foils and pyrolytic graphite crystal, are presented. The obtained results show that, by using of the combined radiator, it is possible to produce much more intense X-rays than parametric X-ray radiation, emitting by relativistic electrons due to the diffraction of virtual photons of electron eigenfield during the electron passage through the crystal.

X-ray emission by multiple passes of electrons through periodic and crystalline targets mounted inside a synchrotron

The number of passes of high-energy electrons through multiple foil and crystal radiators mounted inside of the Tomsk “Sirius” synchrotron, and the resulting increase in x-ray production efficiencies from these radiators, have been measured. The influence of electron transmission on the spectral and spatial distributions of parametric x radiation and on the spatial distribution of transition radiation has also been observed. We find that multiple passes increase the yields of these sources without destroying their angular distributions and spectra. Thus, multiple passes of electrons through these novel radiators may make them useful as x-ray sources for scientific and industrial purposes.

Coherent X-ray radiation of 5.7 MeV electrons from a (002) mosaic pyrolytic graphite crystal

Abstract Coherent X-ray radiation associated with so-called Parametric X-ray Radiation (PXR) has been observed from a mosaic pyrolytic graphite crystal using an electron beam energy of 5.7 MeV. The 1st order (002) PXR reflection under Bragg geometry results in emission of photons with energies peaked near 7 keV, at a large angle θD = 28° with respect to the electron beam.

ORIGINAL AND DIFFRACTED TRANSITION RADIATION FOR DIAGNOSTICS OF RELATIVISTIC ELECTRON BEAMS

Abstract The effect of finite geometrical size and angular divergence of an electron beam on original Resonance X-ray Transition Radiation (RTR) and Diffracted RTR (DTR) has been calculated for 900 MeV electron beam. It is shown that the spectral-angular distributions of RTR and DTR are very sensitive to the geometrical and angular parameters of the electron beam and that it could be used for fine diagnostic of relativistic electron or other charged particle beams.

Development of a periodically structured monocrystalline target of Si for X-ray emission

Abstract We have developed a Si monocrystalline target for producing X-rays by a relativistic electron beam. A grating structure was formed on a Si substrate by silicon micromachining technology with adequate accuracy. The targets were designed to produce 33 keV RTR X-rays from 900 MeV electrons. The width of the grating structure is the same as the thickness of the Si multi-foil targets, made for INS experiments as well as Tomsk experiments, already reported at RREPS95. All of these Si single crystal targets can be tilted at the Bragg angle condition of 33 keV RTR X-rays, to simultaneously produce 33 keV Parametric X Radiation. We can observe both of diffracted RTR and Parametric X Radiation. These results encourage us to study a new type of X-ray source based on a Si monocrystalline target using micromachining technology.

Generation of hard transition X-rays by relativistic electrons in multilayered metal targets

Abstract Spectra of resonance transition X-rays (RTR) generated in a periodical target composed of 9 Sn foils 11 μm in thickness spaced by 52 μm have been measured. They are shown to be significantly narrowed due to the influence of the K-shell photoabsorption edge. The ratio between intensities of RTR and bremsstrahlung is discussed. In the X-ray spectra measured using an equivalent continuous 100 μm Sn target the density effect is masked by the contribution of the transition radiation generated on the two surfaces.

Threshold behavior of hard X-rays in resonant transition radiation from beryllium foils

Abstract Spectral distributions of X-ray resonance transition radiation (RTR) generated by 300, 500 and 700 MeV electrons in a target consisting of as many as 125 Be foils have been measured. When the electron energy increased from 500 to 700 MeV, a rapid growth of photon yield was observed in the spectral region h ω = 5–30 keV , thus confirming the threshold effect of the on-set of the first harmonic of RTR.

Coherent quasisynchrotron radiation of 3.6–5.7 MeV electron bunches transmitting through a local magnetic field

Abstract The results of the experimental investigations of 2–6 cm coherent quasisynchrotron radiation (QSR) of 3.5–5.7 MeV electron bunches from a microtron, transmitting 16 cm diameter magnetic field, are presented. The B -dependences of QSR angular distributions in the region of the magnetic field B = 0–700 G have been measured. The differences of QSR characteristics from well known ones of usual synchrotron radiation (SR) are discussed.