Yu. Alexandrov

Peculiarities of photon transmission through capillary systems

Abstract In this paper a theoretical model for calculation of X-ray photons characteristics under passage through capillary systems is described. The model is based on a numerical solution of a wave equation. It is shown that recently discovered interference effect under multiple reflection of X-rays is a display of wave properties of X-rays. In this report an explanation of the observed phenomenon is given.

Investigation of sensitometric characteristics of X-ray photoemulsions in the spectral range of 15–80 Å

Abstract An investigation of the sensitometric characteristics of X-ray films RAR 2497, SB-2, 101-01 (Kodak), D-7 (Agfa-Gevaert) and UFSh-0 (GNIIKhFP) has been carried out. These films are widely used in scientific research with different types of X-ray sources. The investigation was realized with the aid of a transmission grating spectrograph. An S-60 electron accelerator (P.N. Lebedev Physical Institute) was used as the source of X-ray radiation. The characteristic curves for different wavelengths (within the mentioned range) are presented, as well as the spectral dependences of absolute sensitivity and contrast for the tested films.

Electronic properties of crystalline quartz excited by photons in the 5–25 eV range

Abstract The electronic excitation multiplication process and photoelectron emission in crystalline quartz were investigated and an estimation of the energy gap is presented.

Search for the flavour-changing neutral-current decay D0 → μ+μ−

Abstract We have searched for the decay D 0 → μ + μ − among 2.0 × 10 5 μ + μ − pair produced, in the WA92 experiment, by 350 GeV/ c π − particles interacting in copper and tungsten targets. Using a high-resolution silicon-microstrip detector followed by a large-acceptance magnetic spectrometer and a muon filter we are able to measure the momentum of the muons, to visualize the event topology near their point of origin, and thus to discriminate between prompt and non-prompt muons. No D 0 → μ + μ − candidate has been found. This result allows us to set an upper limit on the branching fraction B( D 0 → μ + μ − ) of 4.1 × 10 −6 at 90 % confidence level.

Measurement of Charmed-Particle Lifetimes and Decay Branching Ratios

The lifetimes of charmed hadrons photoproduced in nuclear emulsion have been computed from a practically background-free sample of 44 neutral particle decays and 42 charged-particle decays including 27D±, 11Λc+, 1Ds+ and 3 ambiguous decays. The values obtained are τ(D0, 0) = (3.6-0.8+1.2 ± 0.7) 10-13 s, τ(D±) = (5.0-1.0+1.5 ± 1.9) 10-13 s, τ(Λc+) = = (2.3-0.6+0.9 ± 0.4) 10-13 s. Branching ratios of various decay topologies were also obtained.

Intrinsic and impurity luminescence of rare-earth trifluorides

For LaF3 crystals doped with rare-earth elements (Eu3+ and Yb3+) a steep rise of the impurity emission yield found at hv⪆17-18 eV is interpreted as being the impurity centre emmission excitation through the impact of fast photoelectrons. For other undoped rare-earth trifluorides an analogous yield rise of the intrinsic emission due to 5d-4f radiative transitions in rare-earth ions is ascribed to the impact excitation by fast photoelectrons of the intrinsic rare-earth ion emission.

Grazing-incidence cylindric mirror with multiple reflection for the soft X-ray spectral range

Abstract New possibilities of the SR beam control are opened with the use of grazing incidence elements based on the “whispering gallery” effect. Experimental investigations of such an X-ray optical element have been performed on the S-60 synchrotron at the Lebedev Institute. By using the absolute spectral characteristics of the X-ray photofilm RAR 2497 (Kodak) and the SR spectral shape we have determined the output-angle integral spectral coefficient of reflection of the studied mirror. A high value of the reflection coefficient makes it possible to use such an X-ray optical element as the effective reflector for soft X-ray beams.

Four‐channel x‐ray spectrometer on a transmission grating with a combined system of detection

We have developed a new soft x‐ray spectrometer covering the photon energy range of 50–500 eV. It employs a free‐standing transmission grating coupled to a microchannel‐plate detector (MCD). The performance of the device was tested by using radiation from a synchrotron with a continuous spectrum. The MCD shows a rather flat response over most of the useful spectral range, with an abrupt decrease in the sensitivity at the short‐wavelength end. Its simplicity of operation makes the device attractive for such applications as the study of soft x‐ray emission from laser‐produced plasmas.

Study of polarization properties of multilayer X-ray mirrors

Abstract The polarization properties of interference multilayer mirrors in the soft X-ray range are studied. The possibility of achieving a radiation polarization rate of about 0.8 is shown experimentally.

Study of polarized properties of multilayer x‐ray mirrors

Polarized properties of interference multilayer mirrors in the soft x‐ray range are studied. The possibility to achieve a radiation polarization rate of about 0.8 is shown experimentally.