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MASSIM, the Milli-Arc-Second Structure Imager, is a mission that has been proposed for study within the context of NASA's Astrophysics Strategic Mission Concept Studies program. It uses a set of achromatic diffractive-refractive Fresnel lenses on an optics spacecraft to focus 5-11 keV X-rays onto detectors on a second spacecraft flying in formation 1000 km away. It will have a point-source sensitivity comparable with that of the current generation of major X-ray observatories (Chandra, XMM-Newton) but an angular resolution some three orders of magnitude better. MASSIM is optimized for the study of jets and other phenomena that occur in the immediate vicinity of black holes and neutron stars. It can also be used for studying other astrophysical phenomena on the milli-arc-second scale, such as those involving proto-stars, the surfaces and surroundings of nearby active stars and interacting winds. We describe the MASSIM mission concept, scientific objectives and the trade-offs within the X-ray optics design. The anticipated performance of the mission and possible future developments using the diffractive-refractive optics approach to imaging at X-ray and gamma-ray energies are discussed.

Starting from FCI2 simulations showing good multi-keV conversion efficiencies of a preformed plasm from thin foils heated by two laser pulses, experiments have been performed with titanium and copper on the Omega laser facility at University of Rochester. The advantages of using this method are efficiencies close to gas targets due to the under-dense plasma created by the pre-pulse and X-ray emissions available at high photon energies that cannot be reached with gas targets. Optimum parameters (laser intensities, delay between the two pulses and thickness of the foil) for titanium and copper foils were estimated from simulations. An increase in the multi-keV conversion efficiency (above 4 keV) by a factor of 2, compared to the case without pre-pulse, is clearly shown on titanium targets. X-ray emission was measured by different diagnostics in good agreement and close to simulations results.

We report on an extensive series of experiments using 2ω light on a variety of gaseous targets at the HELEN laser facility at AWE. The aims of the experiments were to investigate laser-plasma interactions and hot electron generation for 2ω light, and to test schemes for efficiently producing multi-keV X-rays. The experiments were diagnosed by an extensive suite of optical and x-ray instrumentation, including streaked SRS and SBS spectrographs, hard X-ray and Dante measurements. The targets used to data have been filled with C 5 H 12 , CO 2 and Kr. These three targets give very different backscatter, including almost no backscatter from the Kr targets, showing that plasma composition can also be used to minimize backscatter losses. These data also indicate that is possible to produce or quench hot electron production by varying the plasma composition, even near quarter critical density.

Recent experiments at the HELEN laser at AWE have focused on investigations into the performance of a series of scaled NOVA halfraum targets. These were varied from scale 1 to scale 0.1, and used a single beam at 0.53 μm to irradiate the target. The aim of these experiments was to investigate performance limitations for higher temperature small hohlraums. Target diagnostics included time-resolved X-ray power measurements, full aperture measurements of stimulated Raman and Brillouin backscatter, and time-integrated soft and hard X-ray spectrographs. Analyses of the results from this campaign are presented with particular emphasis on the conditions present in the smallest scale targets, including comparison with calculated performance.

We describe a proposal for an added capability of fast timing to the European x-ray astronomy mission XEUS. The scientific value of fast timing observations for the investigation of compact objects is recognized and has been demonstrated through observations by the Rossi x-ray Timing Explorer. We propose to make use of the huge collecting area of XEUS for timing studies with unparalleled photon statistics and time resolution. We describe the sceintifc motivation, e.g. to probe strong gravity fields around collapsed objects and to constrain the equation of state of dense matter in neutron stars. We discuss options for the implementation of detectors which coudl be small silicon drift detectors out of focus.

X-ray sources in the 3-7 keV energy regime can be produced by laser-irradiating mid- and high-Z gas-filled targets with high-powered lasers. A series of experiments have been performed using underdense targets that are supersonically heated with approximately 35 kJ of 0.35 micrometers laser light. These targets were cylindrical Be enclosures that were filled with 1-2 atms of Xe or Ar gas. L-shell x-ray emission is emitted from the plasma and detected by Bragg crystal spectrometers and x-ray diodes. Absolute flux measurements show conversion efficiencies of approximately 10 percent in the multi-kilovolt x-ray emission. These sources can be used as bright x-ray backlighters or for material testing.