S. R. Uglov

Measurement of spectral and polarization characteristics of parametric X-rays in a Si crystal

Abstract Spectral distributions of parametric X-rays (PX) have been measured for 900 MeV electrons transmitted through a Si crystal. A displacement of the PX spectral line was observed with the crystal rotation and in scanning PX radiation reflection by a detector. A high degree of linear polarization (P = 0.8) of parametric X-rays was obtained.

Observation of bright monochromatic x rays generated by relativistic electrons passing through a multilayer mirror

We have observed the emission of 15 keV x rays produced by 500 MeV electrons passing through a x-ray multilayer mirror. The mirror consisted of 300 pairs of W and B4C layers with layer spacing of 12.36 A and supported by a 100 μm Si substrate. The x rays were emitted at the Bragg angle θγ=33.15 mrad with respect to the mirror surface and at the angle θD=66.3 mrad with respect to the electron-beam direction. The spatial distribution and the spectral angular dependence of the x rays were measured and shown to be larger than the parametric x rays emitted from the Si substrate. The value of the differential photon efficiency was estimated to be about 0.22 photons/electron/str.

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.

Measurements of parametric X-rays from relativistic electrons in silicon crystals

Abstract Spectral and angular distributions of parametric X-rays have been measured for (200–900) MeV electrons from Si single crystal. The parametric X-rays were observed at an angle θ = 19° relative to the beam of electrons, which intersects the (110) or (111) Si crystallographic planes. The energetic dependence of the PX intensity was also obtained.

Observation of multiple passes of electrons through thin internal targets of a betatron

Abstract We present observations of the radiation produced by electrons making multiple passes through thin targets in a betatron. We show the influence of multiple passes on the distribution of electrons and on the angular distribution of bremsstrahlung. Measurements of electron-beam spots and bremsstrahlung distributions have been performed for 15–33 MeV electrons and target thicknesses of 10−5–3.5×10−3 radiation lengths. Estimates of the number of passes were obtained for thin targets by comparing them with 1.3 mm thick W and 1.5 mm thick Cu targets, through which electrons pass only once. The numbers of 33 MeV electron passes observed were 460 for 3 μm Mylar, 200 for 20 μm Be, 171 for 5 μm Cu and 30 for 15 μm Cu foils. The multiple pass effect can be useful in the future for increasing the efficiency of novel X-ray sources, such as transition and parametric radiators.

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.

X-ray production simulation of an electron beam recycled through a betatron's internal target

Abstract An analysis of the circulating dynamics of 6 and 35 MeV electron beams in betatron chambers with quasi-transparent internal targets has been done by means of computer simulation. The spatial and angular distributions of the electron trajectories were studied as the electrons made multiple passes through the thin targets. The beam intensities were observed as a function of the number of passes through 0.01, 0.02, 0.05, and 0.1 mm thick silicon targets. The mean number of passes that an electron makes was determined for each combination of target thickness and beam energy. Using the data obtained from the simulation, the spectral and angular distributions of parametric X-radiation have been calculated for electrons recycled through silicon crystals.

Resonance transition X-rays generated by 800–900 MeV electrons in a periodic Mylar radiator

Abstract Spectral and angular distributions of quasimonochromatic resonance X-ray transitionsradiation emitted by 800–900 MeV electrons in a layered target are measured. The high sensitivity of the angular distribution of the hard part of the radiation spectrum ( E γ = 10–40 keV ) to the electron energy is shown. The high yield of the transition radiation, which is larger than for other types of radiation from solid targets, opens good perspectives for the creation of X-ray sources with high pulse characteristics.

Detection of parametric X-ray radiation from moderately relativistic protons in crystals

The spectral maxima of parametric x-ray radiation that are emitted by moderately relativistic protons interacting with various crystals have been detected. The spectral positions of these maxima depend on the crystal orientation angle and they are consistent with the theoretical values. The measurements were carried out with silicon and graphite crystals on the 5-GeV proton beam extracted from the Nuclotron at the Laboratory of High Energies, JINR.

Tunable, monochromatic x rays using the internal beam of a betatron

Tunable, monochromatic x rays from thin radiators mounted inside a betatron have been observed. Parametric x-ray radiation (PXR) was generated by 33-MeV electrons passing multiple times through three radiators: a 43-μm-thick Si crystal, a 400-μm-thick graphite crystal, or a 310-layered-pair (W and B4C, d=14.86 A) multilayer. The pulse-height spectrum of the radiation (5 to 30 keV) was obtained and was tuned by rocking the crystal or multilayer relative to the electron-beam direction. The experimental results appear to follow theoretical predictions for PXR emission with some modification required for the curved trajectory of the electrons.