21 research outputs found
Optical Probing of Ultrafast Laser-Induced Solid-to-Overdense-Plasma Transitions
Understanding the target dynamics during its interaction with a relativistic
ultrashort laser pulse is a challenging fundamental multi-physics problem
involving at least atomic and solid-state physics, plasma physics, and laser
physics. Already, the properties of the so-called pre-plasma formed as the
laser pulse's rising edge ionizes the target are complicated to access in
experiments and modeling, and many aspects of this laser-induced transition
from solid to overdense plasma over picosecond time scales are still open
questions. At the same time, applications like laser-driven ion acceleration
require precise knowledge and control of the pre-plasma because the efficiency
of the acceleration process itself crucially depends on the target properties
at the arrival of the relativistic intensity peak of the pulse. By capturing
the dynamics of the initial stage of the interaction, we report on a detailed
visualization of the pre-plasma formation and evolution. Nanometer-thin
diamond-like carbon foils are shown to transition from solid to plasma during
the laser rising edge with intensities < 10^16 W/cm^2. Single-shot
near-infrared probe transmission measurements evidence sub-picosecond dynamics
of an expanding plasma with densities above 10^23 cm^-3 (about 100 times the
critical plasma density). The complementarity of a solid-state interaction
model and a kinetic plasma description provides deep insight into the interplay
of ionization, collisions, and expansion
Structure formation in Multiple Dark Matter cosmologies with long-range scalar interactions
(Abridged) An interaction between Cold Dark Matter (CDM) and a classical
scalar field playing the role of the cosmic dark energy (DE) might provide
long-range dark interactions without conflicting with solar system bounds.
Although presently available observations allow to constrain such interactions
to a few percent of the gravitational strength, some recent studies have shown
that if CDM is composed by two different particle species having opposite
couplings to the DE field, such tight constraints can be considerably relaxed,
allowing for long-range scalar forces of order gravity without significantly
affecting observations both at the background and at the linear perturbations
level. In the present work, we extend the investigation of such Multiple Dark
Matter scenarios to the nonlinear regime of structure formation, by presenting
the first N-body simulations ever performed for these cosmologies. Our results
highlight some characteristic footprints of long-range scalar forces that arise
only in the nonlinear regime for specific models that would be otherwise
practically indistinguishable from the standard LCDM scenario both in the
background and in the growth of linear density perturbations. Among these
effects, the formation of "mirror" cosmic structures in the two CDM species,
the suppression of the nonlinear matter power spectrum at k > 1 h/Mpc, and the
fragmentation of collapsed halos, represent peculiar features that might
provide a direct way to constrain this class of cosmological models.Comment: 11 pages, 4 figures. Submitted to MNRA
High contrast, 86 fs, 35 mJ pulses from a diode-pumped, Yb:glass, double-chirped-pulse amplification laser system
Modeling of the 3D spatio-temporal thermal profile of joule-class Yb-based laser amplifiers
54 J pulses with 18 nm bandwidth from a diode-pumped chirped-pulse amplification laser system
Optical Probing of Ultrafast Laser-Induced Solid-to-Overdense-Plasma Transitions
Understanding the target dynamics during its interaction with a relativistic ultrashort laser pulse is a challenging fundamental multi-physics problem involving at least atomic and solid-state physics, plasma physics, and laser physics. Already, the properties of the so-called pre-plasma formed as the laser pulse's rising edge ionizes the target are complicated to access in experiments and modeling, and many aspects of this laser-induced transition from solid to overdense plasma over picosecond time scales are still open questions. At the same time, applications like laser-driven ion acceleration require precise knowledge and control of the pre-plasma because the efficiency of the acceleration process itself crucially depends on the target properties at the arrival of the relativistic intensity peak of the pulse. By capturing the dynamics of the initial stage of the interaction, we report on a detailed visualization of the pre-plasma formation and evolution. Nanometer-thin diamond-like carbon foils are shown to transition from solid to plasma during the laser rising edge with intensities < 10^16 W/cm^2. Single-shot near-infrared probe transmission measurements evidence sub-picosecond dynamics of an expanding plasma with densities above 10^23 cm^-3 (about 100 times the critical plasma density). The complementarity of a solid-state interaction model and a kinetic plasma description provides deep insight into the interplay of ionization, collisions, and expansion