V. P. Petukhov

POLARIZATION BREMSSTRAHLUNG OF RELATIVISTIC ELECTRONS IN ALUMINIUM

Abstract The spectral-angular distribution of the polarization bremsstrahlung of relativistic electrons crossing a thin aluminium foil is measured. The earlier predicted strong difference between polarization bremsstrahlung properties for amorphous and polycrystalline targets is observed for the first time.

SUPPRESSION OF POLARIZATION BREMSSTRAHLUNG OF RELATIVISTIC ELECTRONS MOVING THROUGH AN AMORPHOUS CARBON FOIL

Abstract The suppression effect of relativistic polarization bremsstrahlung in an amorphous carbon foil is observed for the first time. A theoretical explanation for this effect is discussed.

Low-energy electron transmission through dielectric capillaries

Transmission of electrons with energies from 2 to 10 keV through glass polycapillaries, tubes, and cones was experimentally studied. The dependence of the transmittance on the electron energy, beam current, capillary diameter, and irradiation time was measured. The electron transmittance through polycapillaries decreases with the beam current and measurement time. The results of measurements of the electron and X-ray spectrum at the quartz tube output suggest that a fraction of electrons incident on the wall charge it and ionize wall atoms; other electrons pass through the channel without collision with the wall, since their energy is almost unchanged. It follows from the measurement results that the electron transmission through capillaries is controlled by the potential at the inner channel surface induced by the charge injected during irradiation.

SECONDARY ELECTRON YIELD INDUCED BY SLOWLY MOVING HEAVY IONS

Abstract The secondary electron yield induced by slowly moving ( v = 0.6 v 0 , v 0 - Bohr velocity) heavy ions was researched on a thin carbon foil in forward and backward direction in respect to the ion beam. Only for the backwards electron emission an oscillatory behaviour of the yield was observed in dependence of the atomic number Z 1 of the projectiles while in forward direction the electron yield increases nearly monotonically with Z 1 . For the forward electron emission the yield is somewhat higher. The excess of electrons between forward and backward electron emission seems to be proportional to the mean charge of the emerging ions which indicates a surface effect for the forward electron emission. The Z 1 -oscillation in the backwards electron emission corresponds to oscillations as was found by energy loss measurements on an argon gas target. These oscillations correlate with the number of charge exchange events in gases. From the common oscillatory behaviour it was concluded that charge exchanges during single collision events are everywhere dominant for the energy loss of slowly moving heavy ions in gases as well in solids.

Effective generation of characteristic K-rays from large laser-excited SF6 clusters in the presence of an Ar carrier gas

The parameters of characteristic sulfur Kα-rays generated from SF6 clusters that are surrounded by argon atoms and are irradiated by intense laser radiation have been analyzed. It has been found that the formation of large SF6 clusters under the optimum experimental parameters is accompanied by the high-efficiency generation of the characteristic X rays, and the flux density of the characteristic X-ray photons is 100 photons/(mrad2 pulse) at a laser-pulse energy of 5 mJ. It has been shown that the third-harmonic generation process can be used to characterize the spatial sizes of the gas-cluster jet and the region of the cluster plasma.

RBS and XFA analysis of polyimide films from the mir space station

The elemental composition of polyimide film contamination was studied by the RBS and XFA methods. The films were exposed to the space environment aboard the Mir orbital space station during the KOMPLAST in-flight experiment. It was shown that the prevalent deposit element was silicon, which agrees with measurements performed on other spacecrafts.

Electron Emission from thin Foils Induced by Slowly Moving Heavy Ions

Abstract Secondary electron emission is a useful tool to observe electronic interactions of ions penetrating matter. For an 8 nm carbon foil we have measured the well-known Z 1 -oscillations in the electron yield in backward direction with respect to the ion beam. In forward direction we observe an excess yield relative to the backward direction which reflects the shell structure of the projectiles in a similar manner as the mean charge of the emerging ions. This enhanced electron yield in forward direction is probably caused by the capability of the projectiles to accumulate secondary electrons around the moving core. The assumption is supported by the results obtained for the ratio of the forward and backward yields as a function of the projectile energy which is nearly constant in the range below Bohr velocity.

L-shell X-ray production cross sections and alignment by proton impact

The cross sections of X-ray production from L-subshells of palladium atom by proton impact have been determined by measuring the intensity of the L X-ray lines. We obtained the alignment parameter by measuring the degree of the polarization of the L1-line excited by 0.2–0.5 MeV protons. The experimental cross sections agree well with the theoretical predictions of the ECPSSR model. The experimental alignment parameter differs markedly from that calculated in terms of the Hartree-Slater model, making allowance for the Coster-Kronig (CK) transitions in case used the values of the ionization cross section from the theory and the CK transition rates from Krauses compilation. In our experiment semiempirical value of the corrections to the L-subshell CK transitions for Pd has been derived from the results of measuring L-line intensities. The semiempirical correction factor improves the agreement of the theory with experimental data.

Enhanced laser induced K X-rays generation during microchannel formation inside the object positioned in air

The increasing of yield of X-rays more than two times from femtosecond laser plasma produced in the target microchannel positioned in air compared to the case from fresh target’s surface was registered and the angular dependence of output of X-rays was firstly observed.

HIGH-RESOLUTION PIXE INSTRUMENTATION SURVEY. PART II

Abstract High resolution PIXE facilities (X-ray crystal spectrometers working on ion beams of accelerators) and their applications in chemical analysis and in basic research are surveyed.