G. P. Pokhil

Ion irradiation in liquid of μm3 region for cell surgery

We present here a cell surgery scheme involving selective inactivation or disruption of cellular structures. Energetic ions are injected into a cell through a tapered glass capillary like a microinjection method. A slight but essential difference from microinjection is that a thin window is prepared at the outlet so that no liquid material can flow in or back through the outlet while still allowing energetic ions to penetrate into the cell. An ∼MeV He ion beam from such a capillary having 10μm outlet diameter inactivated a selected volume (∼μm3) of fluorescent molecules located in a HeLa cell nucleus.

Focusing of charged particle beams with various glass-made optics

We have developed methods to focus slow highly charged ions, MeV ions, and muon beams with various glass-made beam optics. (1) A focusing effect for an Ar8 + beam of 8 keV through a cm-long tapered capillary was obtained with a density enhancement of the transmitted beam compared with that of the input beam, which increases from 1 to 6 as the input current decreases from 30 pA to 0.8 pA. To study the stability of the transmitted beams through a glass capillary, we have measured the transmission of an 104 keV Ar8+ beam through a gap between a pair of parallel glass plates, and observed a precisely vibrational output current. (2) For 4 MeV He2+ beam, a 100 times density enhanced beam by a cm-long tapered capillary with a closed outlet was utilized to irradiate a cell in liquid. The range of the beam was controlled by the closed outlet with accuracy of ~1 μm. (3) Using 40 cm-long tapered glass tubes, a density enhancement of a factor of 2 was observed for both positive and negative muon beams with an energy of 13 MeV.

Oscillations of the charge in oxide at silicon surface as an origin of the process leading to the long-range effect

A model of the excitation of the periodical stress pulses in the silicon-oxide system leading to generation of moving discrete breathers (local nonlinear wave disturbances of the atomic system) has been suggested. The latter can provide transportation of energy through the bulk of a sample at the external effect on its surface (the long-range effect). Several scenarios of evolving alternating electrical fields in oxide resulting (due to its local piezoelectricity) in corresponding changes of stresses have been considered.

Monte Carlo simulation of ion-beam channeling in YBa2Cu3O7

Abstract A Monte Carlo program (UPIC) for the simulation of ion channeling in crystals with complex structure is described. The program is applied to simulate the channeling of 1.5 MeV He+ and 1 MeV D+ near the [001] axis of YBa2Cu3O7 assuming strongly correlated atomic displacements along the [001] Cu-O rows in the superconducting state. The values for the abrupt change in the half-width of the channeling dip observed in experiments [R.P. Sharma et al., Phys. Rev. B 38 (1988) 9287] at the temperature of the superconducting transition, Tc, are reproduced in the simulations with correlation coefficients of 0.8–0.9. The increase in the minimum channeling yield at Tc found in measurements [T. Haga et al., Phys. Rev. B 41 (1990) 826] can be qualitatively explained by the increase in dechanneling rate due to correlations.

Investigation of contactless electron transmission through dielectric channels

The effect of the contactless transmission (guiding) of 10 keV electrons through cylindrical dielectric channels and planar channels formed by glass plates is studied. The capture and propagation of an electron beam along the channel axis, usual in these cases, are observed in the experiments with two plates. The deviation of the reflection angle from the specular angle and its dependence on the plate length and beamcurrent value under beam reflection from a single plate are investigated.

Measurement of the polarization bremsstrahlung of relativistic electrons in polycrystalline targets

The spectra of the collimated polarization bremsstrahlung of 7-MeV electrons intersecting Al, Cu, and Ni polycrystalline films have been measured. Detailed quantitative comparison of the experimental data with theoretical predictions has been performed. It has been shown that the model of a polycrystal as an ensemble of randomly oriented single crystals adequately describes the experimental results. This makes it possible to expect the development of a new method of diagnostics of the atomic structure of partially ordered solids.

Studying the interaction of 10-keV electrons with a dielectric surface

The grazing incidence interaction of a 10-keV electron beam with a planar surface of plexiglass is studied experimentally. Moreover, the electron passage through flat channels formed by such surfaces is investigated. The experiments reveal the presence of a guiding effect of the electron passage as in the case of a glass surface. However, there are some features, such as the existence of an initial elevation angle for the case of negative inclination angles of the plate. The formation of self-consistent charge on the surface of the plexiglass and its drain when the current is turned off occur more slowly than on the glass surface. This fact points to the difference in the surface conductivity of insulators.

Investigation of the guiding effect of 10-keV electrons using planar dielectric surfaces

The effect of guiding a 10-keV electron beam using dielectric plates is studied. It is shown that the electron beam after interaction with the insulator surface is deflected by this surface in different ways depending on a variety of grounding schemes of the front and back sides of plexiglass and aluminum-oxide plates. The dependence of the deflection of the beam from the plexiglass plates at different angle positions on the incident electron-beam current value is studied.

Model of ion beam guiding using a flat capillary

This work is devoted to the further development of the theoretical model of double guiding of an ion beam using a flat capillary, which has given greater insight into the structure of the charge distribution created on the capillary wall during ion transmission. It is established that in the improved model the shape of a beam trace, similar to the one obtained in an experiment, which varies with the change in the angle of the capillary rotation, is observed on a screen.

Suppression of density effect in the polarization bremsstrahlung for relativistic charged particles crossing a thin target

Abstract The peculiarities of polarization bremsstrahlung emitted when a relativistic charged particle penetrates a thin layer of an amorphous medium are considered. In particular, suppression of the density effect, which otherwise limits the emission, is predicted. The physical nature of this suppression is analogous to that taking place in ionization energy losses of a relativistic particle crossing a thin target.