Acceleration of particles from the interaction of ultraintense laser pulses up to 5×10^{21} W cm^{-2} with thin foils is investigated experimentally. The electron beam parameters varied with ...decreasing spot size, not just laser intensity, resulting in reduced temperatures and divergence. In particular, the temperature saturated due to insufficient acceleration length in the tightly focused spot. These dependencies affected the sheath-accelerated protons, which showed poorer spot-size scaling than widely used scaling laws. It is therefore shown that maximizing laser intensity by using very small foci has reducing returns for some applications.
Using particle-in-cell simulations of relativistic laser plasma wakes in the presence of an external magnetic field, we demonstrate that there exists a parameter window where the dynamics of the ...magnetized wake channel are largely independent of the laser wavelength λlas. One condition for this manifestation of “limited similarity” is that the electron density ne is highly subcritical, so that the plasma does not affect the laser. The freedom to choose a convenient laser wavelength can be useful in experiments and simulations. In simulations, an up-scaled wavelength (and, thus, a coarser mesh and larger time steps) reduces the computational effort, while limited similarity ensures that the overall structure and evolutionary phases of the wake channel are preserved. In our demonstrative example, we begin with a terrawatt⋅picosecond pulse from a CO2 laser with λlas=10μm, whose field reaches a relativistic amplitude at the center of a sub-millimeter-sized focal spot. The laser is shot into a sparse deuterium gas ( ne∼1013cm−3) in the presence of a tesla-scale magnetic field. Limited similarity is demonstrated in 2D for 4μm≤λlas≤40μm and is expected to extend to shorter wavelengths. Assuming that this limited similarity also holds in 3D, increasing the wavelength to 40μm enables us to simulate the after-glow dynamics of the wake channel all the way into the nanosecond regime.
Burst Intensification by Singularity Emitting Radiation (BISER) is proposed. Singularities in multi-stream flows of emitting media cause constructive interference of emitted travelling waves, forming ...extremely localized sources of bright coherent emission. Here we for the first time demonstrate this extreme localization of BISER by direct observation of nano-scale coherent x-ray sources in a laser plasma. The energy emitted into the spectral range from 60 to 100 eV is up to ~100 nJ, corresponding to ~10
photons. Simulations reveal that these sources emit trains of attosecond x-ray pulses. Our findings establish a new class of bright laboratory sources of electromagnetic radiation. Furthermore, being applicable to travelling waves of any nature (e.g. electromagnetic, gravitational or acoustic), BISER provides a novel framework for creating new emitters and for interpreting observations in many fields of science.
We propose the experiments on the collision of laser light and high intensity electromagnetic pulses generated by relativistic flying mirrors, with electron bunches produced by a conventional ...accelerator and with laser wake field accelerated electrons for studying extreme field limits in the nonlinear interaction of electromagnetic waves. The regimes of dominant radiation reaction, which completely changes the electromagnetic wave–matter interaction, will be revealed in the laser plasma experiments. This will result in a new powerful source of ultra short high brightness gamma-ray pulses. A possibility of the demonstration of the electron–positron pair creation in vacuum in a multi-photon processes can be realized. This will allow modeling under terrestrial laboratory conditions neutron star magnetospheres, cosmological gamma ray bursts and the Leptonic Era of the Universe.
We have observed simultaneously both the fast proton generation and terahertz (THz) radiation in the laser pulse interaction with a 5-μm thick titanium target. In order to control the proton ...acceleration and THz radiation, we have changed the duration of the amplified spontaneous emission (ASE) preceding the main pulse generated by the high-intensity Ti:sapphire laser. A fast proton beam with the maximal energy of ∼ 490 keV has been realized by reducing the duration of the ASE. Simultaneously, an intense emission of THz radiation is observed for various ASE durations. We propose the antenna mechanism for the THz radiation, according to which the fast electrons moving along the target surface emit the low-frequency electromagnetic wave.
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