The laminarity of high-current multi-MeV proton beams produced by irradiating thin metallic foils with ultraintense lasers has been measured. For proton energies $>10\mathrm{MeV}$, the transverse and longitudinal emittance are, respectively, $<0.004\mathrm{mm}\mathrm{mrad}$ and $<{10}^{-4}\mathrm{eV}\mathrm{s}$, i.e., at least 100-fold and may be as much as ${10}^4$-fold better than conventional accelerator beams. The fast acceleration being electrostatic from an initially cold surface, only collisions with the accelerating fast electrons appear to limit the beam laminarity. The ion beam source size is measured to be $<15\mu \mathrm{m}$ (FWHM) for proton energies $>10\mathrm{MeV}$.

The generation of extremely bright coherent X-ray pulses in the femtosecond and attosecond regime is currently one of the most exciting frontiers of physics–allowing, for the first time, measurements with unprecedented temporal resolution^1,2,3,4,5,6. Harmonics from laser–solid target interactions have been identified as a means of achieving fields as high as the Schwinger limit^2,7 (E=1.3×10¹⁶ V m⁻¹) and as a highly promising route to high-efficiency attosecond (10⁻¹⁸ s) pulses⁸ owing to their intrinsically phase-locked nature. The key steps to attain these goals are achieving high conversion efficiencies and a slow decay of harmonic efficiency to high orders by driving harmonic production to the relativistic limit¹. Here we present the first experimental demonstration of high harmonic generation in the relativistic limit, obtained on the Vulcan Petawatt laser⁹. High conversion efficiencies (η>10⁻⁶ per harmonic) and bright emission (>10²² photons s⁻¹ mm⁻² mrad⁻² (0.1% bandwidth)) are observed at wavelengths <4 nm (the `water-window' region of particular interest for bio-microscopy).

Collimated jets of carbon and fluorine ions up to $5\mathrm{M}\mathrm{e}\mathrm{V}/\mathrm{\text{nucleon}}$ ($\sim 100\mathrm{M}\mathrm{e}\mathrm{V}$) are observed from the rear surface of thin foils irradiated with laser intensities of up to $5\times {10}^{19}\mathrm{W}/{\mathrm{c}\mathrm{m}}^2$. The normally dominant proton acceleration could be surpressed by removing the hydrocarbon contaminants by resistive heating. This inhibits screening effects and permits effective energy transfer and acceleration of other ion species. The acceleration dynamics and the spatiotemporal distributions of the accelerating $E$ fields at the rear surface of the target are inferred from the detailed spectra.

We report the generation of stable and tunable electron bunches with very low absolute energy spread ($\Delta E\approx 5\mathrm{MeV}$) accelerated in laser wakefields via injection and trapping at a sharp downward density jump produced by a shock front in a supersonic gas flow. The peak of the highly stable and reproducible electron energy spectrum was tuned over more than 1 order of magnitude, containing a charge of 1–100 pC and a charge per energy interval of more than $10\mathrm{pC}/\mathrm{MeV}$. Laser-plasma electron acceleration with Ti:sapphire lasers using this novel injection mechanism provides high-quality electron bunches tailored for applications.

${\mathrm{Al}}_x{\mathrm{Ga}}_{\text{1−x}}\mathrm{N}$ alloys were grown on $c$ -plane sapphire by plasma-induced molecular beam epitaxy. The Al content $x$ was varied over the whole composition range $\text{(0⩽x⩽1).}$ The molar Al fraction was deduced from x-ray diffraction and for comparison by elastic recoil detection analysis. The composition of the alloys calculated from the lattice parameter $c$ underestimates $x$ . This is due to a deformation of the unit cell. The exact Al mole fraction and the biaxial strain of the alloys can be calculated by an additional determination of $a$ , using asymmetric reflections. The results obtained by x-ray diffraction and elastic recoil detection provide evidence for the validity of Vegard’s law in the AlGaN system. In addition, the deviation of the band gap from a linear dependence on $x$ was investigated. We found a downward bowing with a bowing parameter $\text{b=1.3\hspace{0.17em}}\mathrm{eV}.$