V. Kim

Numerical modeling of heavy ion induced stress waves in solid targets

The target is cylinder with a length = 7 mm and radius = 5 mm. One face of the cylinder is irradiated with a uranium beam having a particle energy of 400 MeV/u. The beam pulse consists of two bunches, each having a full width at half maximum (FWHM) of 80 ns and the total pule duration is 500 ns. The beam focal spot size (FWHM of the Gaussian power distribution in transverse direction) is as sumed to be 0.5 mm. Two different values for beam intensity, N are used.

High energy density physics problems related to liquid jet lithium target for Super-FRS fast extraction scheme

The new international facility for antiproton and ion research (FAIR), at Darmstadt, Germany, will accelerate beams of all stable isotopes from protons up to uranium with unprecedented intensities (of the order of 10 12 ions per spill). Planned future experiments include production of exotic nuclei by fragmentation/fission of projectile ions of different species with energies up to 1.5 GeV/u at the proposed super conducting fragment separator, Super-FRS. In such experiments, the production target must survive multiple irradiations over an extended period of time, which in case of such beam intensities is highly questionable. Previous work showed that with full intensity of the uranium beam, a solid graphite target will be destroyed after being irradiated once, unless the beam focal spot is made very large that will result in extremely poor transmission and resolution of the secondary isotopes. An alternative to a solid target could be a windowless liquid jet target. We have carried out three-dimensional numerical simulations to study the problem of target heating and propagation of pressure in a liquid Li target. These first calculations have shown that a liquid lithium target may survive the full uranium beam intensity for a reasonable size focal spot.

Electroconductivity and pressure–temperature states of step shocked C60 fullerite

A study of electrophysical and thermodynamic properties of C60 single crystals under step shock loading has been carried out. The increase and the following reduction in specific electroconductivity of C60 fullerite single crystals at step shock compression up to pressure 30 GPa have been measured. The equations of state for face centred cubic (fcc) C60 fullerite as well as for two-dimensional polymer C60 and for three-dimensional polymer C60 (3D-C60) were constructed. The pressure–temperature states of C60 fullerite were calculated at step shock compression up to pressure 30 GPa and temperature 550 K. The X-ray diffraction studies of shock-recovered samples reveal a mixture of fcc C60 and a X-ray amorphous component of fullerite C60. The start of the formation of the X-ray amorphous component occurs at a pressure P m≈ 19.8 GPa and a temperature T m≈ 520 K. At pressures exceeding P m and temperatures exceeding T m, the shock compressed fullerite consist of a two-phase mixture of fcc C60 fullerite and an X-ray amorphous component presumably consisting of the nucleators of polymer 3D-C60 fullerite. The decrease in electroconductivity of fullerite can be explained by the percolation effect caused by the change of pressure, size and number of polymeric phase nuclei.

NUMERICAL MODELLING OF DEEP IMPACT EXPERIMENT

The Deep Impact active space experiment has been done to study a hypervelocity collision of a metal impactor with the nucleus of the comet 9P/Temple 1. In this work we present results of numerical modeling in comparison with corresponding experimental data. The modeling has been done with the use of 3D “finite‐size particle in cell” method. The computational setup corresponded to impact angle of 30 degree with respect to the horizon for different materials forming the surface of the comet nuclei, i.e. ice and sand. Conclusions are made for the possible composition of the comet.

Volume dependence of AlH3 band gap at high pressures

The volume dependence of the band gap for aluminum hydride (alane) is compared at high static and dynamic pressures. Room temperature high pressure isotherm data and multiple-shock conductivity data were used for the reconstruction of the volume dependence of the alane band gap in the pressure range 50–75 GPa. The traditional exponential relationship for the temperature dependence of semiconductor conductivity with the power law volume dependence of the aluminum hydride band gap is suggested in the regions of volumes 11.5–12.5 cm3/mol, pressures 50–75 GPa and temperatures 1270–1370 K.

Proposed high energy density physics research using intense particle beams at fair and CERN: The HEDgeHOB collaboration

We present results of our theoretical investigations that have been carried out over the past years to assess the potential of intense heavy ion beams that will be generated at the future FAIR facility, at Darmstadt, to study the physics of high energy density (HED) states in matter. It has been found that three different experimental schemes, namely, HIHEX, LAPLAS and Ramp Compression can be employed for this purpose.In the first scheme, HED state are induced in a sample material employing isochoric and uniform heating by an intense ion beam that is followed by isentropic expansion of the heated material. One can study the equation of state (EOS) properties of these exotic states of matter using this scheme. The second scheme involves a low- entropy compression of a test material like hydrogen or water in a multi-layered cylindrical target that is imploded by a hollow beam with an annular focal spot. This scheme generate physical conditions that are expected to exist in the interiors of the giant planets. The third scheme is suitable for a shockless compression of a sample to study material properties under dynamic conditions.

3D Computer Modeling of High‐Velocity Impact Phenomena

This research presents results of 3D modeling of impacts at different velocity and impactor geometry. Original finite‐size particle in cell method was used as a tool for modeling performed. The results of modeling were compared with experimental x‐ray photographs and experimental values of hole diameter and debris cloud dimensions. The influence of material properties models used has been investigated.