V. P. Efremov

Radiation dynamics of fast heavy ions interacting with matter

The study of heavy ion stopping dynamics using associated K-shell projectile and target radiation was the focus of the reported experiments. Ar, Ca, Ti, and Ni projectile ions with the initial energies of 5.9 and 11.4 MeV/u were slowed down in quartz and arogels. Characteristic radiation of projectiles and target atoms induced in close collisions was registered. The variation of the projectile ion line Doppler shift due to the ion deceleration measured along the ion beam trajectory was used to determine the ion velocity dynamics. The dependence of the ion velocity on the trajectory coordinate was measured over 70–90% of the ion beam path with a spatial resolution of 50–70 μm. The choice of SiO 2 aerogel with low mean densities of 0.04–0.15 g/cm 3 as a target material, made it possible to stretch the ion stopping range by more than 20–50 times in comparison with solid quartz. It allowed for resolving the dynamics of the ion stopping process. Experimentally, it has been proven that the fine porous nano-structure of aerogels does not affect the ion energy loss and charge state distribution. The strong increase of the ion stopping range in aerogels made it possible to resolve fast ion radiation dynamics. The analysis of the projectile Kα-satellites structure allows supposing that ions propagate in solid in highly exicted states. This can provide an experimental explanation for so called gas-solid effect.

Dynamics of fiber fuse propagation

The dynamics of the fiber fuse effect, including the process of bubble formation in the fiber core, was investigated for the first time. Bubbles in the core were observed not later than 20-70 /spl mu/s after the passing of the plasma leading edge.

Investigation of the projectile ion velocity inside the interaction media by the x-ray spectromicroscopy method

A method for space resolved measurements of the fast heavy ion velocity during the interaction with matter are presented. The main idea is based upon the fact that the characteristic radiation from ions traveling in the stopping media undergoes the Doppler shift, which varies along the ion beam trajectory due to the ion deceleration. High spectrally (λ/Δλ=1000–3000) and spatially (up to 30–100 μm) resolved x-ray K-shell spectra of Ca projectile ions as well as of the ionized stopping media have been obtained using focusing spectrometers with spatial resolution (FSSR). Spherically bent crystals of quartz and mica with small curvature radii R=150 mm and large apertures (15×50 mm) have been used as dispersive elements. Fast Ca+6 ions with energies of 5.9 and 11.4 MeV/u were stopped in quartz, SiO2 aerogels and CaF2 targets. High spectral and spatial resolution of the spectra allowed measuring the velocity of heavy projectile ions at different points along the beam trajectory. A method based on the utilizatio...

Detonation-like mode of the destruction of optical fibers under intense laser radiation

A “fast,” detonation-like mode of the propagation of an optical discharge with velocities up to 3 km/s is observed in a silica optical fiber at the laser radiation intensity in the core up to 40 W/μm2.

X-ray Spectroscopic Observations of a Superdense Plasma in Nanoparticles Irradiated by Superintense Femtosecond Laser Radiation

The interaction of femtosecond laser pulses with SiO2 aerogel targets has been analyzed by x-ray spectroscopic methods. The use of an aerogel target with transparent grains makes it possible to considerably reduce the requirements on laser-pulse contrasts for which heating occurs without the formation of a preplasma. A nanoplasma with a density sevenfold higher than the solid-state density has been detected.

Optical strength of polymer materials subjected to laser ablation-induced destruction

Laser ablation-induced destruction of polymethyl methacrylate, epoxy compound, and styrosyl is studied experimentally. The values of the threshold energy density of this destruction are measured for each sample at the laboratory laser ablation station. Methods for estimating and predicting the optical strength of polymer materials are developed on the basis of a statistical model of laser ablation-induced destruction.

Dynamics of interaction of a high-current electron beam with polymeric materials

The fracture dynamics of transparent polymeric materials under the impact of shockwaves induced by the energy release due to a high-power electron beam has been studied in polymethyl methacrylate (plexiglas), polystyrene, and epoxy samples by high frame-rate imaging. A qualitatively different character of fracture has been observed in polystyrene as compared to plexiglas and epoxy. The causes of the difference are discussed.

Study of the energy release region of a heavy-ion flux in nanomaterials by x-ray spectroscopy of multicharged ions

X-ray spectroscopic data are reported on the state of a silicon aerogel medium (SiO2) irradiated by a Ni ion flux with an energy of 4.7 MeV/nucleon. Radiation from the electron transitions to the K shell in multicharged Si ions is detected with spatial resolution along the direction of the beam propagation in the medium. Calculations performed for the ionization state and population of the levels excited in the silicon atoms of the target provide the estimate Te = 70–120 eV for the medium electron temperature in the ion tack region. Two-dimensional hydrodynamic calculations provide the estimate Te = 60–116 eV for the same conditions and densities of 0.5–2.5 g/cm3 of the excited target medium.

Measuring the mechanical recoil impulse of a polymeric target upon impact of a high power electron beam

A method for measuring the mechanical recoil impulse of a target produced by the relativistic electron beam of the Calamary accelerator is described. A detector based on a piezoelectric sensor is used in measurements. Results of measurements are presented for the mechanical recoil impulse produced by the relativistic electron beam with an energy as high as 300 keV, a current of up to 30 kA, and a duration of ~100 ns that is incident on an epoxy target. The energy flux density on the target surface is varied in the range of 1–10 GW/cm2. The maximum measured impulse value is 0.32 N · s at an energy flux density of 10 GW/cm2 (an energy fluence of 810 J/cm2).

New method of the polymeric material properties experimental investigation under powerful energy flux impact

Investigation of the polymeric material properties under powerfull energy flux impact is relevant as for basic research (mathematical modeling of polymeric materials behavior in extreme conditions, testing the state equations), as for practical applications (for testing of protective coatings for space research and laboratory facilities). This paper presents the results of experimental studies of the interaction of polymeric materials with a relativistic electron beam produced by a high-current electron accelerator Calamary. Calamary facility provides a wide range of electron beam parameters: diameter 10-15 mm, the voltage on the diode up to 300 kV, the current through the diode up to 30 kA. New method of beam-target interaction area measurement was developed. The original method for the mechanical kick impulse measuring based on piezoelectric vibration sensor was presented. The dependence of the kick impulse from the power flux was obtained.