Exotic dense-matter states pumped by a relativistic laser plasma in the radiation-dominated regime.

In high-spectral resolution experiments with the petawatt Vulcan laser, strong x-ray radiation of KK hollow atoms (atoms without n = 1 electrons) from thin Al foils was observed at pulse intensities of 3 × 10(20) W/cm(2). The observations of spectra from these exotic states of matter are supported by detailed kinetics calculations, and are consistent with a picture in which an intense polychromatic x-ray field, formed from Thomson scattering and bremsstrahlung in the electrostatic fields at the target surface, drives the KK hollow atom production. We estimate that this x-ray field has an intensity of >5 × 10(18) W/cm(2) and is in the 3 keV range.

Scattered light diagnostics of overdense plasma cavity in solid targets irradiated by an ultraintense laser pulse.

The light scattered backward from a target illuminated by ultraintense laser pulses carries important information about the nonlinear laser-plasma interaction. We analyze the usefulness of this information by plasma corona analysis with the help of an analytical model we developed, and particle-in-cell simulation. The spectrum of scattered light is shown to be shifted, to be broadened, and to be modulated, in comparison with the initial laser spectrum, and the spectral shift is an indicator of laser pulse contrast ratio.

Boosted high-harmonics pulse from a double-sided relativistic mirror.

An ultrabright high-power x- and gamma-radiation source is proposed. A high-density thin plasma slab, accelerating in the radiation pressure dominant regime by an ultraintense electromagnetic wave, reflects a counterpropagating relativistically strong electromagnetic wave, producing extremely time-compressed and intensified radiation. The reflected light contains relativistic harmonics generated at the plasma slab, all upshifted with the same factor as the fundamental mode of the incident light. The theory of an arbitrarily moving thin plasma slab reflectivity is presented.

Direct spectroscopic observation of multiple-charged-ion acceleration by an intense femtosecond-pulse laser.

We have observed evidence of the emission of energetic He-and H-like ions of fluorine more than 1 MeV produced via the optical field ionization (OFI) from a solid target irradiated by an intense I=(2-4)x10(18) W/cm(2) (60 fs, lambda=800 nm), obliquely incident p-polarized pulse laser. The measured blue wing of He(alpha), He(beta), and Ly(alpha) lines of fluorine shows a feature of the Doppler-shifted spectrum due to the self-similar ion expansion dominated by superthermal electrons with the temperature T(h) approximately 100 keV. Using a collisional particle-in-cell simulation, which incorporates the nonlocal-thermodynamic-equilibrium ionization including OFI, we have obtained the plasma temperature, line shape, and maximal energy of accelerated ions, which agree well with those determined from the experimental spectra. The red wing of ion spectra gives the temperature of bulk plasma electrons.