Biomedical subjects

I Kostyukov

Publications and source records attributed to I Kostyukov.

3 recordsLinked to original sources

PubMed2004

X-ray generation in strongly nonlinear plasma waves.

We show that a laser wake field in the "bubble" regime [Appl. Phys. B 74, 355 (2002)]], works as a compact high-brightness source of x-rays. The self-trapped relativistic electrons make betatron oscillations in the transverse fields of the bubble and emit a bright broadband x-ray radiation with a maximum about 50 keV. The emission is confined to a small angle of about 0.1 rad. In addition, we make simulations of x-ray generation by an external 28.5 GeV electron bunch injected into the bubble. gamma quanta with up to GeV energies are observed in the simulation in good agreement with analytical results. The energy conversion is efficient, leading to a significant stopping of the electron bunch over 5 mm interaction distance.

Journal Article↗

PubMed2003

Self-compression of laser pulses in plasma.

We study self-compression of weakly relativistically intense laser pulses in subcritical plasmas using one- (1D) and three-dimensional (3D) direct particle-in-cell (PIC) simulations. The self-compression works in the density window from 1/4 critical to slightly below critical density, where the Raman instability is prohibited. An analytical model is developed to describe the self-compression. The model admits pulsing Gaussian solutions and a long-lived running soliton solution. The 1D PIC results agree well with the analytical model, and compressions by an order of magnitude are observed. In the 3D geometry, the longitudinal self-compression competes with the transverse self-focusing/filamentation. To damp the filamentation we use a periodic plasma-vacuum structure. The 3D PIC simulations suggest that a 30 fs long laser pulse is efficiently compressed to 5 fs.

Journal Article↗

PubMed2003

Collisional versus collisionless resonant and autoresonant heating in laser-cluster interaction.

When a hot cluster expands, a transient matching between the plasma frequency and the laser frequency has been predicted, observed, and analyzed recently. The associate energy transfer to the electrons has been described as an enhanced collisional absorption. However, for hot plasmas the collision frequency is small and a collisionless resonant heating is more efficient. We set up and solve the problem of resonant collisional and collisionless cluster heating taking into account cluster expansion, laser pulse duration and pulse chirping. Moreover, we identify an efficient autoresonant mechanism of collisionless heating with a chirped laser pulse when the crossing between the plasmon frequency and the laser frequency is degenerate and the time derivatives of these two frequencies are equal at the crossing time. Transition between collisional regime of cluster heating and collisionless one is discussed.

Journal Article↗