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 MeV, the transverse and longitudinal emittance are, respectively, <0.004 mm mrad and <10(-4) eV 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 microm (FWHM) for proton energies >10 MeV.

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Waveguide slot array antennas can have high gain, since the power distribution network (waveguide) has low loss, enabling a large aperture size. Rapid response to requirements for frequency, gain, and skew angle inspired a search for an alternative to conventional, commercial slot array acquisition. The solution to this requirement is high-resolution 3-D printing of modified slot arrays combined with metal plating. Modification of the structure included removal of wall material in regions where these openings would not cause radiation, opening the structure to enable metal plating while not affecting gain. A 3-D-printed slot array requires no further assembly, unlike conventional waveguide-based arrays that require soldering or brazing, block machining, or plate assembled, brazed structures. Stereolithography 3-D printing of plastic slot array antennas, modified to enable metal plating, has been used to produce a 30 dBi realized gain slot array at 21 GHz for under $1000 USD in a few weeks. Metal plated, 3-D printed plastic slot arrays are also very lightweight in comparison with conventional metal structures. Performance of 3-D printed, metal plated slot arrays has been shown to be identical to conventional metal structures at frequencies up to 22 GHz.

The PLEIADES ͑Picosecond Laser-Electron InterAction for the Dynamical Evaluation of Structures͒ facility has produced first light at 70 keV. This milestone offers a new opportunity to develop laser-driven, compact, tunable x-ray sources for critical applications such as diagnostics for the National Ignition Facility and time-resolved material studies. The electron beam was focused to 50 m rms, at 57 MeV, with 260 pC of charge, a relative energy spread of 0.2%, and a normalized emittance of 5 mm mrad horizontally and 13 mm mrad vertically. The scattered 820 nm laser pulse had an energy of 180 mJ and a duration of 54 fs. Initial x rays were captured with a cooled charge-coupled device using a cesium iodide scintillator; the peak photon energy was approximately 78 keV, with a total x-ray flux of 1.3ϫ10 6 photons/shot, and the observed angular distribution found to agree very well with three-dimensional codes. Simple K-edge radiography of a tantalum foil showed good agreement with the theoretical divergence-angle dependence of the x-ray energy. Optimization of the x-ray dose is currently under way, with the goal of reaching 10 8 photons/shot and a peak brightness approaching 10 20 photons/mm 2 /mrad 2 /s/0.1% bandwidth.

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